curl/lib/url.c

/***************************************************************************
 *                                  _   _ ____  _
 *  Project                     ___| | | |  _ \| |
 *                             / __| | | | |_) | |
 *                            | (__| |_| |  _ <| |___
 *                             \___|\___/|_| \_\_____|
 *
 * Copyright (C) Daniel Stenberg, <daniel@haxx.se>, et al.
 *
 * This software is licensed as described in the file COPYING, which
 * you should have received as part of this distribution. The terms
 * are also available at https://curl.se/docs/copyright.html.
 *
 * You may opt to use, copy, modify, merge, publish, distribute and/or sell
 * copies of the Software, and permit persons to whom the Software is
 * furnished to do so, under the terms of the COPYING file.
 *
 * This software is distributed on an "AS IS" basis, WITHOUT WARRANTY OF ANY
 * KIND, either express or implied.
 *
 * SPDX-License-Identifier: curl
 *
 ***************************************************************************/

#include "curl_setup.h"

#ifdef HAVE_NETINET_IN_H
#include <netinet/in.h>
#endif
#ifdef HAVE_NETDB_H
#include <netdb.h>
#endif
#ifdef HAVE_ARPA_INET_H
#include <arpa/inet.h>
#endif
#ifdef HAVE_NET_IF_H
#include <net/if.h>
#endif
#ifdef HAVE_IPHLPAPI_H
#include <Iphlpapi.h>
#endif
#ifdef HAVE_SYS_IOCTL_H
#include <sys/ioctl.h>
#endif
#ifdef HAVE_SYS_PARAM_H
#include <sys/param.h>
#endif

#ifdef __VMS
#include <in.h>
#include <inet.h>
#endif

#ifdef HAVE_SYS_UN_H
#include <sys/un.h>
#endif

#ifndef HAVE_SOCKET
#error "We cannot compile without socket() support!"
#endif

#include <limits.h>

#include "doh.h"
#include "urldata.h"
#include "netrc.h"
#include "formdata.h"
#include "mime.h"
#include "vtls/vtls.h"
#include "hostip.h"
#include "transfer.h"
#include "sendf.h"
#include "progress.h"
#include "cookie.h"
#include "strcase.h"
#include "strerror.h"
#include "escape.h"
#include "strtok.h"
#include "share.h"
#include "content_encoding.h"
#include "http_digest.h"
#include "http_negotiate.h"
#include "select.h"
#include "multiif.h"
#include "easyif.h"
#include "speedcheck.h"
#include "warnless.h"
#include "getinfo.h"
#include "urlapi-int.h"
#include "system_win32.h"
#include "hsts.h"
#include "noproxy.h"
#include "cfilters.h"
#include "idn.h"

/* And now for the protocols */
#include "ftp.h"
#include "dict.h"
#include "telnet.h"
#include "tftp.h"
#include "http.h"
#include "http2.h"
#include "file.h"
#include "curl_ldap.h"
#include "vssh/ssh.h"
#include "imap.h"
#include "url.h"
#include "connect.h"
#include "inet_ntop.h"
#include "http_ntlm.h"
#include "curl_rtmp.h"
#include "gopher.h"
#include "mqtt.h"
#include "http_proxy.h"
#include "conncache.h"
#include "multihandle.h"
#include "strdup.h"
#include "setopt.h"
#include "altsvc.h"
#include "dynbuf.h"
#include "headers.h"

/* The last 3 #include files should be in this order */
#include "curl_printf.h"
#include "curl_memory.h"
#include "memdebug.h"

#ifndef ARRAYSIZE
#define ARRAYSIZE(A) (sizeof(A)/sizeof((A)[0]))
#endif

#ifdef USE_NGHTTP2
static void data_priority_cleanup(struct Curl_easy *data);
#else
#define data_priority_cleanup(x)
#endif

/* Some parts of the code (e.g. chunked encoding) assume this buffer has at
 * more than just a few bytes to play with. Do not let it become too small or
 * bad things will happen.
 */
#if READBUFFER_SIZE < READBUFFER_MIN
# error READBUFFER_SIZE is too small
#endif

#ifdef USE_UNIX_SOCKETS
#define UNIX_SOCKET_PREFIX "localhost"
#endif

/* Reject URLs exceeding this length */
#define MAX_URL_LEN 0xffff

/*
* get_protocol_family()
*
* This is used to return the protocol family for a given protocol.
*
* Parameters:
*
* 'h'  [in]  - struct Curl_handler pointer.
*
* Returns the family as a single bit protocol identifier.
*/
static curl_prot_t get_protocol_family(const struct Curl_handler *h)
{
  DEBUGASSERT(h);
  DEBUGASSERT(h->family);
  return h->family;
}

void Curl_freeset(struct Curl_easy *data)
{
  /* Free all dynamic strings stored in the data->set substructure. */
  enum dupstring i;
  enum dupblob j;

  for(i = (enum dupstring)0; i < STRING_LAST; i++) {
    Curl_safefree(data->set.str[i]);
  }

  for(j = (enum dupblob)0; j < BLOB_LAST; j++) {
    Curl_safefree(data->set.blobs[j]);
  }

  if(data->state.referer_alloc) {
    Curl_safefree(data->state.referer);
    data->state.referer_alloc = FALSE;
  }
  data->state.referer = NULL;
  if(data->state.url_alloc) {
    Curl_safefree(data->state.url);
    data->state.url_alloc = FALSE;
  }
  data->state.url = NULL;

  Curl_mime_cleanpart(&data->set.mimepost);

#ifndef CURL_DISABLE_COOKIES
  curl_slist_free_all(data->state.cookielist);
  data->state.cookielist = NULL;
#endif
}

/* free the URL pieces */
static void up_free(struct Curl_easy *data)
{
  struct urlpieces *up = &data->state.up;
  Curl_safefree(up->scheme);
  Curl_safefree(up->hostname);
  Curl_safefree(up->port);
  Curl_safefree(up->user);
  Curl_safefree(up->password);
  Curl_safefree(up->options);
  Curl_safefree(up->path);
  Curl_safefree(up->query);
  curl_url_cleanup(data->state.uh);
  data->state.uh = NULL;
}

/*
 * This is the internal function curl_easy_cleanup() calls. This should
 * cleanup and free all resources associated with this sessionhandle.
 *
 * We ignore SIGPIPE when this is called from curl_easy_cleanup.
 */

CURLcode Curl_close(struct Curl_easy **datap)
{
  struct Curl_easy *data;

  if(!datap || !*datap)
    return CURLE_OK;

  data = *datap;
  *datap = NULL;

  /* Detach connection if any is left. This should not be normal, but can be
     the case for example with CONNECT_ONLY + recv/send (test 556) */
  Curl_detach_connection(data);
  if(!data->state.internal) {
    if(data->multi)
      /* This handle is still part of a multi handle, take care of this first
         and detach this handle from there. */
      curl_multi_remove_handle(data->multi, data);

    if(data->multi_easy) {
      /* when curl_easy_perform() is used, it creates its own multi handle to
         use and this is the one */
      curl_multi_cleanup(data->multi_easy);
      data->multi_easy = NULL;
    }
  }

  Curl_expire_clear(data); /* shut off any timers left */

  data->magic = 0; /* force a clear AFTER the possibly enforced removal from
                      the multi handle, since that function uses the magic
                      field! */

  if(data->state.rangestringalloc)
    free(data->state.range);

  /* freed here just in case DONE was not called */
  Curl_req_free(&data->req, data);

  /* Close down all open SSL info and sessions */
  Curl_ssl_close_all(data);
  Curl_safefree(data->state.first_host);
  Curl_ssl_free_certinfo(data);

  if(data->state.referer_alloc) {
    Curl_safefree(data->state.referer);
    data->state.referer_alloc = FALSE;
  }
  data->state.referer = NULL;

  up_free(data);
  Curl_dyn_free(&data->state.headerb);
  Curl_flush_cookies(data, TRUE);
#ifndef CURL_DISABLE_ALTSVC
  Curl_altsvc_save(data, data->asi, data->set.str[STRING_ALTSVC]);
  Curl_altsvc_cleanup(&data->asi);
#endif
#ifndef CURL_DISABLE_HSTS
  Curl_hsts_save(data, data->hsts, data->set.str[STRING_HSTS]);
  if(!data->share || !data->share->hsts)
    Curl_hsts_cleanup(&data->hsts);
  curl_slist_free_all(data->state.hstslist); /* clean up list */
#endif
#if !defined(CURL_DISABLE_HTTP) && !defined(CURL_DISABLE_DIGEST_AUTH)
  Curl_http_auth_cleanup_digest(data);
#endif
  Curl_safefree(data->info.contenttype);
  Curl_safefree(data->info.wouldredirect);

  /* this destroys the channel and we cannot use it anymore after this */
  Curl_resolver_cancel(data);
  Curl_resolver_cleanup(data->state.async.resolver);

  data_priority_cleanup(data);

  /* No longer a dirty share, if it exists */
  if(data->share) {
    Curl_share_lock(data, CURL_LOCK_DATA_SHARE, CURL_LOCK_ACCESS_SINGLE);
    data->share->dirty--;
    Curl_share_unlock(data, CURL_LOCK_DATA_SHARE);
  }

#ifndef CURL_DISABLE_PROXY
  Curl_safefree(data->state.aptr.proxyuserpwd);
#endif
  Curl_safefree(data->state.aptr.uagent);
  Curl_safefree(data->state.aptr.userpwd);
  Curl_safefree(data->state.aptr.accept_encoding);
  Curl_safefree(data->state.aptr.te);
  Curl_safefree(data->state.aptr.rangeline);
  Curl_safefree(data->state.aptr.ref);
  Curl_safefree(data->state.aptr.host);
#ifndef CURL_DISABLE_COOKIES
  Curl_safefree(data->state.aptr.cookiehost);
#endif
#ifndef CURL_DISABLE_RTSP
  Curl_safefree(data->state.aptr.rtsp_transport);
#endif
  Curl_safefree(data->state.aptr.user);
  Curl_safefree(data->state.aptr.passwd);
#ifndef CURL_DISABLE_PROXY
  Curl_safefree(data->state.aptr.proxyuser);
  Curl_safefree(data->state.aptr.proxypasswd);
#endif

#if !defined(CURL_DISABLE_HTTP) && !defined(CURL_DISABLE_FORM_API)
  Curl_mime_cleanpart(data->state.formp);
  Curl_safefree(data->state.formp);
#endif

  /* destruct wildcard structures if it is needed */
  Curl_wildcard_dtor(&data->wildcard);
  Curl_freeset(data);
  Curl_headers_cleanup(data);
  free(data);
  return CURLE_OK;
}

/*
 * Initialize the UserDefined fields within a Curl_easy.
 * This may be safely called on a new or existing Curl_easy.
 */
CURLcode Curl_init_userdefined(struct Curl_easy *data)
{
  struct UserDefined *set = &data->set;
  CURLcode result = CURLE_OK;

  set->out = stdout; /* default output to stdout */
  set->in_set = stdin;  /* default input from stdin */
  set->err  = stderr;  /* default stderr to stderr */

  /* use fwrite as default function to store output */
  set->fwrite_func = (curl_write_callback)fwrite;

  /* use fread as default function to read input */
  set->fread_func_set = (curl_read_callback)fread;
  set->is_fread_set = 0;

  set->seek_client = ZERO_NULL;

  set->filesize = -1;        /* we do not know the size */
  set->postfieldsize = -1;   /* unknown size */
  set->maxredirs = 30;       /* sensible default */

  set->method = HTTPREQ_GET; /* Default HTTP request */
#ifndef CURL_DISABLE_RTSP
  set->rtspreq = RTSPREQ_OPTIONS; /* Default RTSP request */
#endif
#ifndef CURL_DISABLE_FTP
  set->ftp_use_epsv = TRUE;   /* FTP defaults to EPSV operations */
  set->ftp_use_eprt = TRUE;   /* FTP defaults to EPRT operations */
  set->ftp_use_pret = FALSE;  /* mainly useful for drftpd servers */
  set->ftp_filemethod = FTPFILE_MULTICWD;
  set->ftp_skip_ip = TRUE;    /* skip PASV IP by default */
#endif
  set->dns_cache_timeout = 60; /* Timeout every 60 seconds by default */

  /* Set the default size of the SSL session ID cache */
  set->general_ssl.max_ssl_sessions = 5;
  /* Timeout every 24 hours by default */
  set->general_ssl.ca_cache_timeout = 24 * 60 * 60;

  set->httpauth = CURLAUTH_BASIC;  /* defaults to basic */

#ifndef CURL_DISABLE_PROXY
  set->proxyport = 0;
  set->proxytype = CURLPROXY_HTTP; /* defaults to HTTP proxy */
  set->proxyauth = CURLAUTH_BASIC; /* defaults to basic */
  /* SOCKS5 proxy auth defaults to username/password + GSS-API */
  set->socks5auth = CURLAUTH_BASIC | CURLAUTH_GSSAPI;
#endif

  /* make libcurl quiet by default: */
  set->hide_progress = TRUE;  /* CURLOPT_NOPROGRESS changes these */

  Curl_mime_initpart(&set->mimepost);

  Curl_ssl_easy_config_init(data);
#ifndef CURL_DISABLE_DOH
  set->doh_verifyhost = TRUE;
  set->doh_verifypeer = TRUE;
#endif
#ifdef USE_SSH
  /* defaults to any auth type */
  set->ssh_auth_types = CURLSSH_AUTH_DEFAULT;
  set->new_directory_perms = 0755; /* Default permissions */
#endif

  set->new_file_perms = 0644;    /* Default permissions */
  set->allowed_protocols = (curl_prot_t) CURLPROTO_ALL;
  set->redir_protocols = CURLPROTO_REDIR;

#if defined(HAVE_GSSAPI) || defined(USE_WINDOWS_SSPI)
  /*
   * disallow unprotected protection negotiation NEC reference implementation
   * seem not to follow rfc1961 section 4.3/4.4
   */
  set->socks5_gssapi_nec = FALSE;
#endif

  /* Set the default CA cert bundle/path detected/specified at build time.
   *
   * If Schannel or SecureTransport is the selected SSL backend then these
   * locations are ignored. We allow setting CA location for schannel and
   * securetransport when explicitly specified by the user via
   *  CURLOPT_CAINFO / --cacert.
   */
  if(Curl_ssl_backend() != CURLSSLBACKEND_SCHANNEL &&
     Curl_ssl_backend() != CURLSSLBACKEND_SECURETRANSPORT) {
#if defined(CURL_CA_BUNDLE)
    result = Curl_setstropt(&set->str[STRING_SSL_CAFILE], CURL_CA_BUNDLE);
    if(result)
      return result;
#ifndef CURL_DISABLE_PROXY
    result = Curl_setstropt(&set->str[STRING_SSL_CAFILE_PROXY],
                            CURL_CA_BUNDLE);
    if(result)
      return result;
#endif
#endif
#if defined(CURL_CA_PATH)
    result = Curl_setstropt(&set->str[STRING_SSL_CAPATH], CURL_CA_PATH);
    if(result)
      return result;
#ifndef CURL_DISABLE_PROXY
    result = Curl_setstropt(&set->str[STRING_SSL_CAPATH_PROXY], CURL_CA_PATH);
    if(result)
      return result;
#endif
#endif
  }

#ifndef CURL_DISABLE_FTP
  set->wildcard_enabled = FALSE;
  set->chunk_bgn      = ZERO_NULL;
  set->chunk_end      = ZERO_NULL;
  set->fnmatch = ZERO_NULL;
#endif
  set->tcp_keepalive = FALSE;
  set->tcp_keepintvl = 60;
  set->tcp_keepidle = 60;
  set->tcp_keepcnt = 9;
  set->tcp_fastopen = FALSE;
  set->tcp_nodelay = TRUE;
  set->ssl_enable_alpn = TRUE;
  set->expect_100_timeout = 1000L; /* Wait for a second by default. */
  set->sep_headers = TRUE; /* separated header lists by default */
  set->buffer_size = READBUFFER_SIZE;
  set->upload_buffer_size = UPLOADBUFFER_DEFAULT;
  set->happy_eyeballs_timeout = CURL_HET_DEFAULT;
  set->upkeep_interval_ms = CURL_UPKEEP_INTERVAL_DEFAULT;
  set->maxconnects = DEFAULT_CONNCACHE_SIZE; /* for easy handles */
  set->maxage_conn = 118;
  set->maxlifetime_conn = 0;
  set->http09_allowed = FALSE;
#ifdef USE_HTTP2
  set->httpwant = CURL_HTTP_VERSION_2TLS
#else
  set->httpwant = CURL_HTTP_VERSION_1_1
#endif
    ;
#if defined(USE_HTTP2) || defined(USE_HTTP3)
  memset(&set->priority, 0, sizeof(set->priority));
#endif
  set->quick_exit = 0L;
  return result;
}

/**
 * Curl_open()
 *
 * @param curl is a pointer to a sessionhandle pointer that gets set by this
 * function.
 * @return CURLcode
 */

CURLcode Curl_open(struct Curl_easy **curl)
{
  CURLcode result;
  struct Curl_easy *data;

  /* Very simple start-up: alloc the struct, init it with zeroes and return */
  data = calloc(1, sizeof(struct Curl_easy));
  if(!data) {
    /* this is a very serious error */
    DEBUGF(fprintf(stderr, "Error: calloc of Curl_easy failed\n"));
    return CURLE_OUT_OF_MEMORY;
  }

  data->magic = CURLEASY_MAGIC_NUMBER;

  Curl_req_init(&data->req);

  result = Curl_resolver_init(data, &data->state.async.resolver);
  if(result) {
    DEBUGF(fprintf(stderr, "Error: resolver_init failed\n"));
    Curl_req_free(&data->req, data);
    free(data);
    return result;
  }

  result = Curl_init_userdefined(data);
  if(!result) {
    Curl_dyn_init(&data->state.headerb, CURL_MAX_HTTP_HEADER);
    Curl_initinfo(data);

    /* most recent connection is not yet defined */
    data->state.lastconnect_id = -1;
    data->state.recent_conn_id = -1;
    /* and not assigned an id yet */
    data->id = -1;
    data->mid = -1;
#ifndef CURL_DISABLE_DOH
    data->set.dohfor_mid = -1;
#endif

    data->progress.flags |= PGRS_HIDE;
    data->state.current_speed = -1; /* init to negative == impossible */
#ifndef CURL_DISABLE_HTTP
    Curl_llist_init(&data->state.httphdrs, NULL);
#endif
  }

  if(result) {
    Curl_resolver_cleanup(data->state.async.resolver);
    Curl_dyn_free(&data->state.headerb);
    Curl_freeset(data);
    Curl_req_free(&data->req, data);
    free(data);
    data = NULL;
  }
  else
    *curl = data;
  return result;
}

void Curl_conn_free(struct Curl_easy *data, struct connectdata *conn)
{
  size_t i;

  DEBUGASSERT(conn);

  for(i = 0; i < ARRAYSIZE(conn->cfilter); ++i) {
    Curl_conn_cf_discard_all(data, conn, (int)i);
  }

  Curl_free_idnconverted_hostname(&conn->host);
  Curl_free_idnconverted_hostname(&conn->conn_to_host);
#ifndef CURL_DISABLE_PROXY
  Curl_free_idnconverted_hostname(&conn->http_proxy.host);
  Curl_free_idnconverted_hostname(&conn->socks_proxy.host);
  Curl_safefree(conn->http_proxy.user);
  Curl_safefree(conn->socks_proxy.user);
  Curl_safefree(conn->http_proxy.passwd);
  Curl_safefree(conn->socks_proxy.passwd);
  Curl_safefree(conn->http_proxy.host.rawalloc); /* http proxy name buffer */
  Curl_safefree(conn->socks_proxy.host.rawalloc); /* socks proxy name buffer */
#endif
  Curl_safefree(conn->user);
  Curl_safefree(conn->passwd);
  Curl_safefree(conn->sasl_authzid);
  Curl_safefree(conn->options);
  Curl_safefree(conn->oauth_bearer);
  Curl_safefree(conn->host.rawalloc); /* hostname buffer */
  Curl_safefree(conn->conn_to_host.rawalloc); /* hostname buffer */
  Curl_safefree(conn->hostname_resolve);
  Curl_safefree(conn->secondaryhostname);
  Curl_safefree(conn->localdev);
  Curl_ssl_conn_config_cleanup(conn);

#ifdef USE_UNIX_SOCKETS
  Curl_safefree(conn->unix_domain_socket);
#endif
  Curl_safefree(conn->destination);

  free(conn); /* free all the connection oriented data */
}

/*
 * Disconnects the given connection. Note the connection may not be the
 * primary connection, like when freeing room in the connection pool or
 * killing of a dead old connection.
 *
 * A connection needs an easy handle when closing down. We support this passed
 * in separately since the connection to get closed here is often already
 * disassociated from an easy handle.
 *
 * This function MUST NOT reset state in the Curl_easy struct if that
 * is not strictly bound to the life-time of *this* particular connection.
 */
bool Curl_on_disconnect(struct Curl_easy *data,
                        struct connectdata *conn, bool aborted)
{
  /* there must be a connection to close */
  DEBUGASSERT(conn);

  /* it must be removed from the connection pool */
  DEBUGASSERT(!conn->bits.in_cpool);

  /* there must be an associated transfer */
  DEBUGASSERT(data);

  /* the transfer must be detached from the connection */
  DEBUGASSERT(!data->conn);

  DEBUGF(infof(data, "Curl_disconnect(conn #%" FMT_OFF_T ", aborted=%d)",
         conn->connection_id, aborted));

  if(conn->dns_entry)
    Curl_resolv_unlink(data, &conn->dns_entry);

  /* Cleanup NTLM connection-related data */
  Curl_http_auth_cleanup_ntlm(conn);

  /* Cleanup NEGOTIATE connection-related data */
  Curl_http_auth_cleanup_negotiate(conn);

  if(conn->connect_only)
    /* treat the connection as aborted in CONNECT_ONLY situations */
    aborted = TRUE;

  return aborted;
}

/*
 * Curl_xfer_may_multiplex()
 *
 * Return a TRUE, iff the transfer can be done over an (appropriate)
 * multiplexed connection.
 */
static bool Curl_xfer_may_multiplex(const struct Curl_easy *data,
                                    const struct connectdata *conn)
{
  /* If an HTTP protocol and multiplexing is enabled */
  if((conn->handler->protocol & PROTO_FAMILY_HTTP) &&
     (!conn->bits.protoconnstart || !conn->bits.close)) {

    if(Curl_multiplex_wanted(data->multi) &&
       (data->state.httpwant >= CURL_HTTP_VERSION_2))
      /* allows HTTP/2 or newer */
      return TRUE;
  }
  return FALSE;
}

#ifndef CURL_DISABLE_PROXY
static bool
proxy_info_matches(const struct proxy_info *data,
                   const struct proxy_info *needle)
{
  if((data->proxytype == needle->proxytype) &&
     (data->port == needle->port) &&
     strcasecompare(data->host.name, needle->host.name))
    return TRUE;

  return FALSE;
}

static bool
socks_proxy_info_matches(const struct proxy_info *data,
                         const struct proxy_info *needle)
{
  if(!proxy_info_matches(data, needle))
    return FALSE;

  /* the user information is case-sensitive
     or at least it is not defined as case-insensitive
     see https://datatracker.ietf.org/doc/html/rfc3986#section-3.2.1 */

  /* curl_strequal does a case insensitive comparison,
     so do not use it here! */
  if(Curl_timestrcmp(data->user, needle->user) ||
     Curl_timestrcmp(data->passwd, needle->passwd))
    return FALSE;
  return TRUE;
}
#else
/* disabled, will not get called */
#define proxy_info_matches(x,y) FALSE
#define socks_proxy_info_matches(x,y) FALSE
#endif

/* A connection has to have been idle for a shorter time than 'maxage_conn'
   (the success rate is just too low after this), or created less than
   'maxlifetime_conn' ago, to be subject for reuse. */

static bool conn_maxage(struct Curl_easy *data,
                        struct connectdata *conn,
                        struct curltime now)
{
  timediff_t idletime, lifetime;

  idletime = Curl_timediff(now, conn->lastused);
  idletime /= 1000; /* integer seconds is fine */

  if(idletime > data->set.maxage_conn) {
    infof(data, "Too old connection (%" FMT_TIMEDIFF_T
          " seconds idle), disconnect it", idletime);
    return TRUE;
  }

  lifetime = Curl_timediff(now, conn->created);
  lifetime /= 1000; /* integer seconds is fine */

  if(data->set.maxlifetime_conn && lifetime > data->set.maxlifetime_conn) {
    infof(data,
          "Too old connection (%" FMT_TIMEDIFF_T
          " seconds since creation), disconnect it", lifetime);
    return TRUE;
  }


  return FALSE;
}

/*
 * Return TRUE iff the given connection is considered dead.
 */
bool Curl_conn_seems_dead(struct connectdata *conn,
                          struct Curl_easy *data,
                          struct curltime *pnow)
{
  DEBUGASSERT(!data->conn);
  if(!CONN_INUSE(conn)) {
    /* The check for a dead socket makes sense only if the connection is not in
       use */
    bool dead;
    struct curltime now;
    if(!pnow) {
      now = Curl_now();
      pnow = &now;
    }

    if(conn_maxage(data, conn, *pnow)) {
      /* avoid check if already too old */
      dead = TRUE;
    }
    else if(conn->handler->connection_check) {
      /* The protocol has a special method for checking the state of the
         connection. Use it to check if the connection is dead. */
      unsigned int state;

      /* briefly attach the connection to this transfer for the purpose of
         checking it */
      Curl_attach_connection(data, conn);

      state = conn->handler->connection_check(data, conn, CONNCHECK_ISDEAD);
      dead = (state & CONNRESULT_DEAD);
      /* detach the connection again */
      Curl_detach_connection(data);

    }
    else {
      bool input_pending = FALSE;

      Curl_attach_connection(data, conn);
      dead = !Curl_conn_is_alive(data, conn, &input_pending);
      if(input_pending) {
        /* For reuse, we want a "clean" connection state. The includes
         * that we expect - in general - no waiting input data. Input
         * waiting might be a TLS Notify Close, for example. We reject
         * that.
         * For protocols where data from other end may arrive at
         * any time (HTTP/2 PING for example), the protocol handler needs
         * to install its own `connection_check` callback.
         */
        DEBUGF(infof(data, "connection has input pending, not reusable"));
        dead = TRUE;
      }
      Curl_detach_connection(data);
    }

    if(dead) {
      /* remove connection from cpool */
      infof(data, "Connection %" FMT_OFF_T " seems to be dead",
            conn->connection_id);
      return TRUE;
    }
  }
  return FALSE;
}

CURLcode Curl_conn_upkeep(struct Curl_easy *data,
                          struct connectdata *conn,
                          struct curltime *now)
{
  CURLcode result = CURLE_OK;
  if(Curl_timediff(*now, conn->keepalive) <= data->set.upkeep_interval_ms)
    return result;

  /* briefly attach for action */
  Curl_attach_connection(data, conn);
  if(conn->handler->connection_check) {
    /* Do a protocol-specific keepalive check on the connection. */
    unsigned int rc;
    rc = conn->handler->connection_check(data, conn, CONNCHECK_KEEPALIVE);
    if(rc & CONNRESULT_DEAD)
      result = CURLE_RECV_ERROR;
  }
  else {
    /* Do the generic action on the FIRSTSOCKET filter chain */
    result = Curl_conn_keep_alive(data, conn, FIRSTSOCKET);
  }
  Curl_detach_connection(data);

  conn->keepalive = *now;
  return result;
}

#ifdef USE_SSH
static bool ssh_config_matches(struct connectdata *one,
                               struct connectdata *two)
{
  return (Curl_safecmp(one->proto.sshc.rsa, two->proto.sshc.rsa) &&
          Curl_safecmp(one->proto.sshc.rsa_pub, two->proto.sshc.rsa_pub));
}
#else
#define ssh_config_matches(x,y) FALSE
#endif

struct url_conn_match {
  struct connectdata *found;
  struct Curl_easy *data;
  struct connectdata *needle;
  BIT(may_multiplex);
  BIT(want_ntlm_http);
  BIT(want_proxy_ntlm_http);

  BIT(wait_pipe);
  BIT(force_reuse);
  BIT(seen_pending_conn);
  BIT(seen_single_use_conn);
  BIT(seen_multiplex_conn);
};

static bool url_match_conn(struct connectdata *conn, void *userdata)
{
  struct url_conn_match *match = userdata;
  struct Curl_easy *data = match->data;
  struct connectdata *needle = match->needle;

  /* Check if `conn` can be used for transfer `data` */

  if(conn->connect_only || conn->bits.close)
    /* connect-only or to-be-closed connections will not be reused */
    return FALSE;

  if(data->set.ipver != CURL_IPRESOLVE_WHATEVER
     && data->set.ipver != conn->ip_version) {
    /* skip because the connection is not via the requested IP version */
    return FALSE;
  }

  if(needle->localdev || needle->localport) {
    /* If we are bound to a specific local end (IP+port), we must not
       reuse a random other one, although if we did not ask for a
       particular one we can reuse one that was bound.

       This comparison is a bit rough and too strict. Since the input
       parameters can be specified in numerous ways and still end up the
       same it would take a lot of processing to make it really accurate.
       Instead, this matching will assume that reuses of bound connections
       will most likely also reuse the exact same binding parameters and
       missing out a few edge cases should not hurt anyone very much.
    */
    if((conn->localport != needle->localport) ||
       (conn->localportrange != needle->localportrange) ||
       (needle->localdev &&
        (!conn->localdev || strcmp(conn->localdev, needle->localdev))))
      return FALSE;
  }

  if(needle->bits.conn_to_host != conn->bits.conn_to_host)
    /* do not mix connections that use the "connect to host" feature and
     * connections that do not use this feature */
    return FALSE;

  if(needle->bits.conn_to_port != conn->bits.conn_to_port)
    /* do not mix connections that use the "connect to port" feature and
     * connections that do not use this feature */
    return FALSE;

  if(!Curl_conn_is_connected(conn, FIRSTSOCKET) ||
     conn->bits.asks_multiplex) {
    /* Not yet connected, or not yet decided if it multiplexes. The later
     * happens for HTTP/2 Upgrade: requests that need a response. */
    if(match->may_multiplex) {
      match->seen_pending_conn = TRUE;
      /* Do not pick a connection that has not connected yet */
      infof(data, "Connection #%" FMT_OFF_T
            " is not open enough, cannot reuse", conn->connection_id);
    }
    /* Do not pick a connection that has not connected yet */
    return FALSE;
  }
  /* `conn` is connected. If it has transfers, can we add ours to it? */

  if(CONN_INUSE(conn)) {
    if(!conn->bits.multiplex) {
      /* conn busy and conn cannot take more transfers */
      match->seen_single_use_conn = TRUE;
      return FALSE;
    }
    match->seen_multiplex_conn = TRUE;
    if(!match->may_multiplex)
      /* conn busy and transfer cannot be multiplexed */
      return FALSE;
    else {
      /* transfer and conn multiplex. Are they on the same multi? */
      struct Curl_llist_node *e = Curl_llist_head(&conn->easyq);
      struct Curl_easy *entry = Curl_node_elem(e);
      if(entry->multi != data->multi)
        return FALSE;
    }
  }
  /* `conn` is connected and we could add the transfer to it, if
   * all the other criteria do match. */

  /* Does `conn` use the correct protocol? */
#ifdef USE_UNIX_SOCKETS
  if(needle->unix_domain_socket) {
    if(!conn->unix_domain_socket)
      return FALSE;
    if(strcmp(needle->unix_domain_socket, conn->unix_domain_socket))
      return FALSE;
    if(needle->bits.abstract_unix_socket != conn->bits.abstract_unix_socket)
      return FALSE;
  }
  else if(conn->unix_domain_socket)
    return FALSE;
#endif

  if((needle->handler->flags&PROTOPT_SSL) !=
     (conn->handler->flags&PROTOPT_SSL))
    /* do not do mixed SSL and non-SSL connections */
    if(get_protocol_family(conn->handler) !=
       needle->handler->protocol || !conn->bits.tls_upgraded)
      /* except protocols that have been upgraded via TLS */
      return FALSE;

#ifndef CURL_DISABLE_PROXY
  if(needle->bits.httpproxy != conn->bits.httpproxy ||
     needle->bits.socksproxy != conn->bits.socksproxy)
    return FALSE;

  if(needle->bits.socksproxy &&
    !socks_proxy_info_matches(&needle->socks_proxy,
                              &conn->socks_proxy))
    return FALSE;

  if(needle->bits.httpproxy) {
    if(needle->bits.tunnel_proxy != conn->bits.tunnel_proxy)
      return FALSE;

    if(!proxy_info_matches(&needle->http_proxy, &conn->http_proxy))
      return FALSE;

    if(IS_HTTPS_PROXY(needle->http_proxy.proxytype)) {
      /* https proxies come in different types, http/1.1, h2, ... */
      if(needle->http_proxy.proxytype != conn->http_proxy.proxytype)
        return FALSE;
      /* match SSL config to proxy */
      if(!Curl_ssl_conn_config_match(data, conn, TRUE)) {
        DEBUGF(infof(data,
          "Connection #%" FMT_OFF_T
          " has different SSL proxy parameters, cannot reuse",
          conn->connection_id));
        return FALSE;
      }
      /* the SSL config to the server, which may apply here is checked
       * further below */
    }
  }
#endif

  if(match->may_multiplex &&
     (data->state.httpwant == CURL_HTTP_VERSION_2_0) &&
     (needle->handler->protocol & CURLPROTO_HTTP) &&
     !conn->httpversion) {
    if(data->set.pipewait) {
      infof(data, "Server upgrade does not support multiplex yet, wait");
      match->found = NULL;
      match->wait_pipe = TRUE;
      return TRUE; /* stop searching, we want to wait */
    }
    infof(data, "Server upgrade cannot be used");
    return FALSE;
  }

  if(!(needle->handler->flags & PROTOPT_CREDSPERREQUEST)) {
    /* This protocol requires credentials per connection,
       so verify that we are using the same name and password as well */
    if(Curl_timestrcmp(needle->user, conn->user) ||
       Curl_timestrcmp(needle->passwd, conn->passwd) ||
       Curl_timestrcmp(needle->sasl_authzid, conn->sasl_authzid) ||
       Curl_timestrcmp(needle->oauth_bearer, conn->oauth_bearer)) {
      /* one of them was different */
      return FALSE;
    }
  }

  /* GSS delegation differences do not actually affect every connection
     and auth method, but this check takes precaution before efficiency */
  if(needle->gssapi_delegation != conn->gssapi_delegation)
    return FALSE;

  /* If looking for HTTP and the HTTP version we want is less
   * than the HTTP version of conn, continue looking */
  if((needle->handler->protocol & PROTO_FAMILY_HTTP) &&
     (((conn->httpversion >= 20) &&
       (data->state.httpwant < CURL_HTTP_VERSION_2_0))
      || ((conn->httpversion >= 30) &&
          (data->state.httpwant < CURL_HTTP_VERSION_3))))
    return FALSE;
#ifdef USE_SSH
  else if(get_protocol_family(needle->handler) & PROTO_FAMILY_SSH) {
    if(!ssh_config_matches(needle, conn))
      return FALSE;
  }
#endif
#ifndef CURL_DISABLE_FTP
  else if(get_protocol_family(needle->handler) & PROTO_FAMILY_FTP) {
    /* Also match ACCOUNT, ALTERNATIVE-TO-USER, USE_SSL and CCC options */
    if(Curl_timestrcmp(needle->proto.ftpc.account,
                       conn->proto.ftpc.account) ||
       Curl_timestrcmp(needle->proto.ftpc.alternative_to_user,
                       conn->proto.ftpc.alternative_to_user) ||
       (needle->proto.ftpc.use_ssl != conn->proto.ftpc.use_ssl) ||
       (needle->proto.ftpc.ccc != conn->proto.ftpc.ccc))
      return FALSE;
  }
#endif

  /* Additional match requirements if talking TLS OR
   * not talking to an HTTP proxy OR using a tunnel through a proxy */
  if((needle->handler->flags&PROTOPT_SSL)
#ifndef CURL_DISABLE_PROXY
     || !needle->bits.httpproxy || needle->bits.tunnel_proxy
#endif
    ) {
    /* Talking the same protocol scheme or a TLS upgraded protocol in the
     * same protocol family? */
    if(!strcasecompare(needle->handler->scheme, conn->handler->scheme) &&
       (get_protocol_family(conn->handler) !=
        needle->handler->protocol || !conn->bits.tls_upgraded))
      return FALSE;

    /* If needle has "conn_to_*" set, conn must match this */
    if((needle->bits.conn_to_host && !strcasecompare(
        needle->conn_to_host.name, conn->conn_to_host.name)) ||
       (needle->bits.conn_to_port &&
         needle->conn_to_port != conn->conn_to_port))
      return FALSE;

    /* hostname and port must match */
    if(!strcasecompare(needle->host.name, conn->host.name) ||
       needle->remote_port != conn->remote_port)
      return FALSE;

    /* If talking TLS, conn needs to use the same SSL options. */
    if((needle->handler->flags & PROTOPT_SSL) &&
       !Curl_ssl_conn_config_match(data, conn, FALSE)) {
      DEBUGF(infof(data,
                   "Connection #%" FMT_OFF_T
                   " has different SSL parameters, cannot reuse",
                   conn->connection_id));
      return FALSE;
    }
  }

#if defined(USE_NTLM)
  /* If we are looking for an HTTP+NTLM connection, check if this is
     already authenticating with the right credentials. If not, keep
     looking so that we can reuse NTLM connections if
     possible. (Especially we must not reuse the same connection if
     partway through a handshake!) */
  if(match->want_ntlm_http) {
    if(Curl_timestrcmp(needle->user, conn->user) ||
       Curl_timestrcmp(needle->passwd, conn->passwd)) {

      /* we prefer a credential match, but this is at least a connection
         that can be reused and "upgraded" to NTLM */
      if(conn->http_ntlm_state == NTLMSTATE_NONE)
        match->found = conn;
      return FALSE;
    }
  }
  else if(conn->http_ntlm_state != NTLMSTATE_NONE) {
    /* Connection is using NTLM auth but we do not want NTLM */
    return FALSE;
  }

#ifndef CURL_DISABLE_PROXY
  /* Same for Proxy NTLM authentication */
  if(match->want_proxy_ntlm_http) {
    /* Both conn->http_proxy.user and conn->http_proxy.passwd can be
     * NULL */
    if(!conn->http_proxy.user || !conn->http_proxy.passwd)
      return FALSE;

    if(Curl_timestrcmp(needle->http_proxy.user,
                       conn->http_proxy.user) ||
       Curl_timestrcmp(needle->http_proxy.passwd,
                       conn->http_proxy.passwd))
      return FALSE;
  }
  else if(conn->proxy_ntlm_state != NTLMSTATE_NONE) {
    /* Proxy connection is using NTLM auth but we do not want NTLM */
    return FALSE;
  }
#endif
  if(match->want_ntlm_http || match->want_proxy_ntlm_http) {
    /* Credentials are already checked, we may use this connection.
     * With NTLM being weird as it is, we MUST use a
     * connection where it has already been fully negotiated.
     * If it has not, we keep on looking for a better one. */
    match->found = conn;

    if((match->want_ntlm_http &&
       (conn->http_ntlm_state != NTLMSTATE_NONE)) ||
        (match->want_proxy_ntlm_http &&
         (conn->proxy_ntlm_state != NTLMSTATE_NONE))) {
      /* We must use this connection, no other */
      match->force_reuse = TRUE;
      return TRUE;
    }
    /* Continue look up for a better connection */
    return FALSE;
  }
#endif

  if(CONN_INUSE(conn)) {
    DEBUGASSERT(match->may_multiplex);
    DEBUGASSERT(conn->bits.multiplex);
    /* If multiplexed, make sure we do not go over concurrency limit */
    if(CONN_INUSE(conn) >=
            Curl_multi_max_concurrent_streams(data->multi)) {
      infof(data, "client side MAX_CONCURRENT_STREAMS reached"
            ", skip (%zu)", CONN_INUSE(conn));
      return FALSE;
    }
    if(CONN_INUSE(conn) >=
            Curl_conn_get_max_concurrent(data, conn, FIRSTSOCKET)) {
      infof(data, "MAX_CONCURRENT_STREAMS reached, skip (%zu)",
            CONN_INUSE(conn));
      return FALSE;
    }
    /* When not multiplexed, we have a match here! */
    infof(data, "Multiplexed connection found");
  }
  else if(Curl_conn_seems_dead(conn, data, NULL)) {
    /* removed and disconnect. Do not treat as aborted. */
    Curl_cpool_disconnect(data, conn, FALSE);
    return FALSE;
  }

  /* We have found a connection. Let's stop searching. */
  match->found = conn;
  return TRUE;
}

static bool url_match_result(bool result, void *userdata)
{
  struct url_conn_match *match = userdata;
  (void)result;
  if(match->found) {
    /* Attach it now while still under lock, so the connection does
     * no longer appear idle and can be reaped. */
    Curl_attach_connection(match->data, match->found);
    return TRUE;
  }
  else if(match->seen_single_use_conn && !match->seen_multiplex_conn) {
    /* We've seen a single-use, existing connection to the destination and
     * no multiplexed one. It seems safe to assume that the server does
     * not support multiplexing. */
    match->wait_pipe = FALSE;
  }
  else if(match->seen_pending_conn && match->data->set.pipewait) {
    infof(match->data,
          "Found pending candidate for reuse and CURLOPT_PIPEWAIT is set");
    match->wait_pipe = TRUE;
  }
  match->force_reuse = FALSE;
  return FALSE;
}

/*
 * Given one filled in connection struct (named needle), this function should
 * detect if there already is one that has all the significant details
 * exactly the same and thus should be used instead.
 *
 * If there is a match, this function returns TRUE - and has marked the
 * connection as 'in-use'. It must later be called with ConnectionDone() to
 * return back to 'idle' (unused) state.
 *
 * The force_reuse flag is set if the connection must be used.
 */
static bool
ConnectionExists(struct Curl_easy *data,
                 struct connectdata *needle,
                 struct connectdata **usethis,
                 bool *force_reuse,
                 bool *waitpipe)
{
  struct url_conn_match match;
  bool result;

  memset(&match, 0, sizeof(match));
  match.data = data;
  match.needle = needle;
  match.may_multiplex = Curl_xfer_may_multiplex(data, needle);

#ifdef USE_NTLM
  match.want_ntlm_http = ((data->state.authhost.want & CURLAUTH_NTLM) &&
                          (needle->handler->protocol & PROTO_FAMILY_HTTP));
#ifndef CURL_DISABLE_PROXY
  match.want_proxy_ntlm_http =
    (needle->bits.proxy_user_passwd &&
     (data->state.authproxy.want & CURLAUTH_NTLM) &&
     (needle->handler->protocol & PROTO_FAMILY_HTTP));
#endif
#endif

  /* Find a connection in the pool that matches what "data + needle"
   * requires. If a suitable candidate is found, it is attached to "data". */
  result = Curl_cpool_find(data, needle->destination, needle->destination_len,
                           url_match_conn, url_match_result, &match);

  /* wait_pipe is TRUE if we encounter a bundle that is undecided. There
   * is no matching connection then, yet. */
  *usethis = match.found;
  *force_reuse = match.force_reuse;
  *waitpipe = match.wait_pipe;
  return result;
}

/*
 * verboseconnect() displays verbose information after a connect
 */
#ifndef CURL_DISABLE_VERBOSE_STRINGS
void Curl_verboseconnect(struct Curl_easy *data,
                         struct connectdata *conn, int sockindex)
{
  if(data->set.verbose && sockindex == SECONDARYSOCKET)
    infof(data, "Connected 2nd connection to %s port %u",
          conn->secondary.remote_ip, conn->secondary.remote_port);
  else
    infof(data, "Connected to %s (%s) port %u",
          CURL_CONN_HOST_DISPNAME(conn), conn->primary.remote_ip,
          conn->primary.remote_port);
#if !defined(CURL_DISABLE_HTTP)
    if(conn->handler->protocol & PROTO_FAMILY_HTTP) {
      switch(conn->alpn) {
      case CURL_HTTP_VERSION_3:
        infof(data, "using HTTP/3");
        break;
      case CURL_HTTP_VERSION_2:
        infof(data, "using HTTP/2");
        break;
      default:
        infof(data, "using HTTP/1.x");
        break;
      }
    }
#endif
}
#endif

/*
 * Allocate and initialize a new connectdata object.
 */
static struct connectdata *allocate_conn(struct Curl_easy *data)
{
  struct connectdata *conn = calloc(1, sizeof(struct connectdata));
  if(!conn)
    return NULL;

  /* and we setup a few fields in case we end up actually using this struct */

  conn->sock[FIRSTSOCKET] = CURL_SOCKET_BAD;     /* no file descriptor */
  conn->sock[SECONDARYSOCKET] = CURL_SOCKET_BAD; /* no file descriptor */
  conn->sockfd = CURL_SOCKET_BAD;
  conn->writesockfd = CURL_SOCKET_BAD;
  conn->connection_id = -1;    /* no ID */
  conn->primary.remote_port = -1; /* unknown at this point */
  conn->remote_port = -1; /* unknown at this point */

  /* Default protocol-independent behavior does not support persistent
     connections, so we set this to force-close. Protocols that support
     this need to set this to FALSE in their "curl_do" functions. */
  connclose(conn, "Default to force-close");

  /* Store creation time to help future close decision making */
  conn->created = Curl_now();

  /* Store current time to give a baseline to keepalive connection times. */
  conn->keepalive = conn->created;

#ifndef CURL_DISABLE_PROXY
  conn->http_proxy.proxytype = data->set.proxytype;
  conn->socks_proxy.proxytype = CURLPROXY_SOCKS4;

  /* note that these two proxy bits are now just on what looks to be
     requested, they may be altered down the road */
  conn->bits.proxy = (data->set.str[STRING_PROXY] &&
                      *data->set.str[STRING_PROXY]) ? TRUE : FALSE;
  conn->bits.httpproxy = (conn->bits.proxy &&
                          (conn->http_proxy.proxytype == CURLPROXY_HTTP ||
                           conn->http_proxy.proxytype == CURLPROXY_HTTP_1_0 ||
                           IS_HTTPS_PROXY(conn->http_proxy.proxytype))) ?
    TRUE : FALSE;
  conn->bits.socksproxy = (conn->bits.proxy &&
                           !conn->bits.httpproxy) ? TRUE : FALSE;

  if(data->set.str[STRING_PRE_PROXY] && *data->set.str[STRING_PRE_PROXY]) {
    conn->bits.proxy = TRUE;
    conn->bits.socksproxy = TRUE;
  }

  conn->bits.proxy_user_passwd =
    (data->state.aptr.proxyuser) ? TRUE : FALSE;
  conn->bits.tunnel_proxy = data->set.tunnel_thru_httpproxy;
#endif /* CURL_DISABLE_PROXY */

#ifndef CURL_DISABLE_FTP
  conn->bits.ftp_use_epsv = data->set.ftp_use_epsv;
  conn->bits.ftp_use_eprt = data->set.ftp_use_eprt;
#endif
  conn->ip_version = data->set.ipver;
  conn->connect_only = data->set.connect_only;
  conn->transport = TRNSPRT_TCP; /* most of them are TCP streams */

  /* Initialize the easy handle list */
  Curl_llist_init(&conn->easyq, NULL);

#ifdef HAVE_GSSAPI
  conn->data_prot = PROT_CLEAR;
#endif

  /* Store the local bind parameters that will be used for this connection */
  if(data->set.str[STRING_DEVICE]) {
    conn->localdev = strdup(data->set.str[STRING_DEVICE]);
    if(!conn->localdev)
      goto error;
  }
#ifndef CURL_DISABLE_BINDLOCAL
  conn->localportrange = data->set.localportrange;
  conn->localport = data->set.localport;
#endif

  /* the close socket stuff needs to be copied to the connection struct as
     it may live on without (this specific) Curl_easy */
  conn->fclosesocket = data->set.fclosesocket;
  conn->closesocket_client = data->set.closesocket_client;
  conn->lastused = conn->created;
  conn->gssapi_delegation = data->set.gssapi_delegation;

  return conn;
error:

  free(conn->localdev);
  free(conn);
  return NULL;
}

const struct Curl_handler *Curl_get_scheme_handler(const char *scheme)
{
  return Curl_getn_scheme_handler(scheme, strlen(scheme));
}

/* returns the handler if the given scheme is built-in */
const struct Curl_handler *Curl_getn_scheme_handler(const char *scheme,
                                                    size_t len)
{
  /* table generated by schemetable.c:
     1. gcc schemetable.c && ./a.out
     2. check how small the table gets
     3. tweak the hash algorithm, then rerun from 1
     4. when the table is good enough
     5. copy the table into this source code
     6. make sure this function uses the same hash function that worked for
     schemetable.c
     7. if needed, adjust the #ifdefs in schemetable.c and rerun
     */
  static const struct Curl_handler * const protocols[67] = {
#ifndef CURL_DISABLE_FILE
    &Curl_handler_file,
#else
    NULL,
#endif
    NULL, NULL,
#if defined(USE_SSL) && !defined(CURL_DISABLE_GOPHER)
    &Curl_handler_gophers,
#else
    NULL,
#endif
    NULL,
#ifdef USE_LIBRTMP
    &Curl_handler_rtmpe,
#else
    NULL,
#endif
#ifndef CURL_DISABLE_SMTP
    &Curl_handler_smtp,
#else
    NULL,
#endif
#if defined(USE_SSH)
    &Curl_handler_sftp,
#else
    NULL,
#endif
#if !defined(CURL_DISABLE_SMB) && defined(USE_CURL_NTLM_CORE) && \
  (SIZEOF_CURL_OFF_T > 4)
    &Curl_handler_smb,
#else
    NULL,
#endif
#if defined(USE_SSL) && !defined(CURL_DISABLE_SMTP)
    &Curl_handler_smtps,
#else
    NULL,
#endif
#ifndef CURL_DISABLE_TELNET
    &Curl_handler_telnet,
#else
    NULL,
#endif
#ifndef CURL_DISABLE_GOPHER
    &Curl_handler_gopher,
#else
    NULL,
#endif
#ifndef CURL_DISABLE_TFTP
    &Curl_handler_tftp,
#else
    NULL,
#endif
    NULL, NULL, NULL,
#if defined(USE_SSL) && !defined(CURL_DISABLE_FTP)
    &Curl_handler_ftps,
#else
    NULL,
#endif
#ifndef CURL_DISABLE_HTTP
    &Curl_handler_http,
#else
    NULL,
#endif
#ifndef CURL_DISABLE_IMAP
    &Curl_handler_imap,
#else
    NULL,
#endif
#ifdef USE_LIBRTMP
    &Curl_handler_rtmps,
#else
    NULL,
#endif
#ifdef USE_LIBRTMP
    &Curl_handler_rtmpt,
#else
    NULL,
#endif
    NULL, NULL, NULL,
#if !defined(CURL_DISABLE_LDAP) && \
  !defined(CURL_DISABLE_LDAPS) && \
  ((defined(USE_OPENLDAP) && defined(USE_SSL)) || \
   (!defined(USE_OPENLDAP) && defined(HAVE_LDAP_SSL)))
    &Curl_handler_ldaps,
#else
    NULL,
#endif
#if defined(USE_WEBSOCKETS) && \
  defined(USE_SSL) && !defined(CURL_DISABLE_HTTP)
    &Curl_handler_wss,
#else
    NULL,
#endif
#if defined(USE_SSL) && !defined(CURL_DISABLE_HTTP)
    &Curl_handler_https,
#else
    NULL,
#endif
    NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL,
#ifndef CURL_DISABLE_RTSP
    &Curl_handler_rtsp,
#else
    NULL,
#endif
#if defined(USE_SSL) && !defined(CURL_DISABLE_SMB) && \
  defined(USE_CURL_NTLM_CORE) && (SIZEOF_CURL_OFF_T > 4)
    &Curl_handler_smbs,
#else
    NULL,
#endif
#if defined(USE_SSH) && !defined(USE_WOLFSSH)
    &Curl_handler_scp,
#else
    NULL,
#endif
    NULL, NULL, NULL,
#ifndef CURL_DISABLE_POP3
    &Curl_handler_pop3,
#else
    NULL,
#endif
    NULL, NULL,
#ifdef USE_LIBRTMP
    &Curl_handler_rtmp,
#else
    NULL,
#endif
    NULL, NULL, NULL,
#ifdef USE_LIBRTMP
    &Curl_handler_rtmpte,
#else
    NULL,
#endif
    NULL, NULL, NULL,
#ifndef CURL_DISABLE_DICT
    &Curl_handler_dict,
#else
    NULL,
#endif
    NULL, NULL, NULL,
#ifndef CURL_DISABLE_MQTT
    &Curl_handler_mqtt,
#else
    NULL,
#endif
#if defined(USE_SSL) && !defined(CURL_DISABLE_POP3)
    &Curl_handler_pop3s,
#else
    NULL,
#endif
#if defined(USE_SSL) && !defined(CURL_DISABLE_IMAP)
    &Curl_handler_imaps,
#else
    NULL,
#endif
    NULL,
#if defined(USE_WEBSOCKETS) && !defined(CURL_DISABLE_HTTP)
    &Curl_handler_ws,
#else
    NULL,
#endif
    NULL,
#ifdef USE_LIBRTMP
    &Curl_handler_rtmpts,
#else
    NULL,
#endif
#ifndef CURL_DISABLE_LDAP
    &Curl_handler_ldap,
#else
    NULL,
#endif
    NULL, NULL,
#ifndef CURL_DISABLE_FTP
    &Curl_handler_ftp,
#else
    NULL,
#endif
  };

  if(len && (len <= 7)) {
    const char *s = scheme;
    size_t l = len;
    const struct Curl_handler *h;
    unsigned int c = 978;
    while(l) {
      c <<= 5;
      c += (unsigned int)Curl_raw_tolower(*s);
      s++;
      l--;
    }

    h = protocols[c % 67];
    if(h && strncasecompare(scheme, h->scheme, len) && !h->scheme[len])
      return h;
  }
  return NULL;
}

static CURLcode findprotocol(struct Curl_easy *data,
                             struct connectdata *conn,
                             const char *protostr)
{
  const struct Curl_handler *p = Curl_get_scheme_handler(protostr);

  if(p && /* Protocol found in table. Check if allowed */
     (data->set.allowed_protocols & p->protocol)) {

    /* it is allowed for "normal" request, now do an extra check if this is
       the result of a redirect */
    if(data->state.this_is_a_follow &&
       !(data->set.redir_protocols & p->protocol))
      /* nope, get out */
      ;
    else {
      /* Perform setup complement if some. */
      conn->handler = conn->given = p;
      /* 'port' and 'remote_port' are set in setup_connection_internals() */
      return CURLE_OK;
    }
  }

  /* The protocol was not found in the table, but we do not have to assign it
     to anything since it is already assigned to a dummy-struct in the
     create_conn() function when the connectdata struct is allocated. */
  failf(data, "Protocol \"%s\" %s%s", protostr,
        p ? "disabled" : "not supported",
        data->state.this_is_a_follow ? " (in redirect)":"");

  return CURLE_UNSUPPORTED_PROTOCOL;
}


CURLcode Curl_uc_to_curlcode(CURLUcode uc)
{
  switch(uc) {
  default:
    return CURLE_URL_MALFORMAT;
  case CURLUE_UNSUPPORTED_SCHEME:
    return CURLE_UNSUPPORTED_PROTOCOL;
  case CURLUE_OUT_OF_MEMORY:
    return CURLE_OUT_OF_MEMORY;
  case CURLUE_USER_NOT_ALLOWED:
    return CURLE_LOGIN_DENIED;
  }
}

#ifdef USE_IPV6
/*
 * If the URL was set with an IPv6 numerical address with a zone id part, set
 * the scope_id based on that!
 */

static void zonefrom_url(CURLU *uh, struct Curl_easy *data,
                         struct connectdata *conn)
{
  char *zoneid;
  CURLUcode uc = curl_url_get(uh, CURLUPART_ZONEID, &zoneid, 0);
#ifdef CURL_DISABLE_VERBOSE_STRINGS
  (void)data;
#endif

  if(!uc && zoneid) {
    char *endp;
    unsigned long scope = strtoul(zoneid, &endp, 10);
    if(!*endp && (scope < UINT_MAX))
      /* A plain number, use it directly as a scope id. */
      conn->scope_id = (unsigned int)scope;
#if defined(HAVE_IF_NAMETOINDEX)
    else {
#elif defined(_WIN32)
    else if(Curl_if_nametoindex) {
#endif

#if defined(HAVE_IF_NAMETOINDEX) || defined(_WIN32)
      /* Zone identifier is not numeric */
      unsigned int scopeidx = 0;
#if defined(_WIN32)
      scopeidx = Curl_if_nametoindex(zoneid);
#else
      scopeidx = if_nametoindex(zoneid);
#endif
      if(!scopeidx) {
#ifndef CURL_DISABLE_VERBOSE_STRINGS
        char buffer[STRERROR_LEN];
        infof(data, "Invalid zoneid: %s; %s", zoneid,
              Curl_strerror(errno, buffer, sizeof(buffer)));
#endif
      }
      else
        conn->scope_id = scopeidx;
    }
#endif /* HAVE_IF_NAMETOINDEX || _WIN32 */

    free(zoneid);
  }
}
#else
#define zonefrom_url(a,b,c) Curl_nop_stmt
#endif

/*
 * Parse URL and fill in the relevant members of the connection struct.
 */
static CURLcode parseurlandfillconn(struct Curl_easy *data,
                                    struct connectdata *conn)
{
  CURLcode result;
  CURLU *uh;
  CURLUcode uc;
  char *hostname;
  bool use_set_uh = (data->set.uh && !data->state.this_is_a_follow);

  up_free(data); /* cleanup previous leftovers first */

  /* parse the URL */
  if(use_set_uh) {
    uh = data->state.uh = curl_url_dup(data->set.uh);
  }
  else {
    uh = data->state.uh = curl_url();
  }

  if(!uh)
    return CURLE_OUT_OF_MEMORY;

  if(data->set.str[STRING_DEFAULT_PROTOCOL] &&
     !Curl_is_absolute_url(data->state.url, NULL, 0, TRUE)) {
    char *url = aprintf("%s://%s", data->set.str[STRING_DEFAULT_PROTOCOL],
                        data->state.url);
    if(!url)
      return CURLE_OUT_OF_MEMORY;
    if(data->state.url_alloc)
      free(data->state.url);
    data->state.url = url;
    data->state.url_alloc = TRUE;
  }

  if(!use_set_uh) {
    char *newurl;
    uc = curl_url_set(uh, CURLUPART_URL, data->state.url, (unsigned int)
                      (CURLU_GUESS_SCHEME |
                       CURLU_NON_SUPPORT_SCHEME |
                       (data->set.disallow_username_in_url ?
                        CURLU_DISALLOW_USER : 0) |
                       (data->set.path_as_is ? CURLU_PATH_AS_IS : 0)));
    if(uc) {
      failf(data, "URL rejected: %s", curl_url_strerror(uc));
      return Curl_uc_to_curlcode(uc);
    }

    /* after it was parsed, get the generated normalized version */
    uc = curl_url_get(uh, CURLUPART_URL, &newurl, 0);
    if(uc)
      return Curl_uc_to_curlcode(uc);
    if(data->state.url_alloc)
      free(data->state.url);
    data->state.url = newurl;
    data->state.url_alloc = TRUE;
  }

  uc = curl_url_get(uh, CURLUPART_SCHEME, &data->state.up.scheme, 0);
  if(uc)
    return Curl_uc_to_curlcode(uc);

  uc = curl_url_get(uh, CURLUPART_HOST, &data->state.up.hostname, 0);
  if(uc) {
    if(!strcasecompare("file", data->state.up.scheme))
      return CURLE_OUT_OF_MEMORY;
  }
  else if(strlen(data->state.up.hostname) > MAX_URL_LEN) {
    failf(data, "Too long hostname (maximum is %d)", MAX_URL_LEN);
    return CURLE_URL_MALFORMAT;
  }
  hostname = data->state.up.hostname;

  if(hostname && hostname[0] == '[') {
    /* This looks like an IPv6 address literal. See if there is an address
       scope. */
    size_t hlen;
    conn->bits.ipv6_ip = TRUE;
    /* cut off the brackets! */
    hostname++;
    hlen = strlen(hostname);
    hostname[hlen - 1] = 0;

    zonefrom_url(uh, data, conn);
  }

  /* make sure the connect struct gets its own copy of the hostname */
  conn->host.rawalloc = strdup(hostname ? hostname : "");
  if(!conn->host.rawalloc)
    return CURLE_OUT_OF_MEMORY;
  conn->host.name = conn->host.rawalloc;

  /*************************************************************
   * IDN-convert the hostnames
   *************************************************************/
  result = Curl_idnconvert_hostname(&conn->host);
  if(result)
    return result;

#ifndef CURL_DISABLE_HSTS
  /* HSTS upgrade */
  if(data->hsts && strcasecompare("http", data->state.up.scheme)) {
    /* This MUST use the IDN decoded name */
    if(Curl_hsts(data->hsts, conn->host.name, TRUE)) {
      char *url;
      Curl_safefree(data->state.up.scheme);
      uc = curl_url_set(uh, CURLUPART_SCHEME, "https", 0);
      if(uc)
        return Curl_uc_to_curlcode(uc);
      if(data->state.url_alloc)
        Curl_safefree(data->state.url);
      /* after update, get the updated version */
      uc = curl_url_get(uh, CURLUPART_URL, &url, 0);
      if(uc)
        return Curl_uc_to_curlcode(uc);
      uc = curl_url_get(uh, CURLUPART_SCHEME, &data->state.up.scheme, 0);
      if(uc) {
        free(url);
        return Curl_uc_to_curlcode(uc);
      }
      data->state.url = url;
      data->state.url_alloc = TRUE;
      infof(data, "Switched from HTTP to HTTPS due to HSTS => %s",
            data->state.url);
    }
  }
#endif

  result = findprotocol(data, conn, data->state.up.scheme);
  if(result)
    return result;

  /*
   * username and password set with their own options override the
   * credentials possibly set in the URL.
   */
  if(!data->set.str[STRING_PASSWORD]) {
    uc = curl_url_get(uh, CURLUPART_PASSWORD, &data->state.up.password, 0);
    if(!uc) {
      char *decoded;
      result = Curl_urldecode(data->state.up.password, 0, &decoded, NULL,
                              conn->handler->flags&PROTOPT_USERPWDCTRL ?
                              REJECT_ZERO : REJECT_CTRL);
      if(result)
        return result;
      conn->passwd = decoded;
      result = Curl_setstropt(&data->state.aptr.passwd, decoded);
      if(result)
        return result;
    }
    else if(uc != CURLUE_NO_PASSWORD)
      return Curl_uc_to_curlcode(uc);
  }

  if(!data->set.str[STRING_USERNAME]) {
    /* we do not use the URL API's URL decoder option here since it rejects
       control codes and we want to allow them for some schemes in the user
       and password fields */
    uc = curl_url_get(uh, CURLUPART_USER, &data->state.up.user, 0);
    if(!uc) {
      char *decoded;
      result = Curl_urldecode(data->state.up.user, 0, &decoded, NULL,
                              conn->handler->flags&PROTOPT_USERPWDCTRL ?
                              REJECT_ZERO : REJECT_CTRL);
      if(result)
        return result;
      conn->user = decoded;
      result = Curl_setstropt(&data->state.aptr.user, decoded);
    }
    else if(uc != CURLUE_NO_USER)
      return Curl_uc_to_curlcode(uc);
    else if(data->state.aptr.passwd) {
      /* no user was set but a password, set a blank user */
      result = Curl_setstropt(&data->state.aptr.user, "");
    }
    if(result)
      return result;
  }

  uc = curl_url_get(uh, CURLUPART_OPTIONS, &data->state.up.options,
                    CURLU_URLDECODE);
  if(!uc) {
    conn->options = strdup(data->state.up.options);
    if(!conn->options)
      return CURLE_OUT_OF_MEMORY;
  }
  else if(uc != CURLUE_NO_OPTIONS)
    return Curl_uc_to_curlcode(uc);

  uc = curl_url_get(uh, CURLUPART_PATH, &data->state.up.path,
                    CURLU_URLENCODE);
  if(uc)
    return Curl_uc_to_curlcode(uc);

  uc = curl_url_get(uh, CURLUPART_PORT, &data->state.up.port,
                    CURLU_DEFAULT_PORT);
  if(uc) {
    if(!strcasecompare("file", data->state.up.scheme))
      return CURLE_OUT_OF_MEMORY;
  }
  else {
    unsigned long port = strtoul(data->state.up.port, NULL, 10);
    conn->primary.remote_port = conn->remote_port =
      (data->set.use_port && data->state.allow_port) ?
      data->set.use_port : curlx_ultous(port);
  }

  (void)curl_url_get(uh, CURLUPART_QUERY, &data->state.up.query, 0);

#ifdef USE_IPV6
  if(data->set.scope_id)
    /* Override any scope that was set above.  */
    conn->scope_id = data->set.scope_id;
#endif

  return CURLE_OK;
}


/*
 * If we are doing a resumed transfer, we need to setup our stuff
 * properly.
 */
static CURLcode setup_range(struct Curl_easy *data)
{
  struct UrlState *s = &data->state;
  s->resume_from = data->set.set_resume_from;
  if(s->resume_from || data->set.str[STRING_SET_RANGE]) {
    if(s->rangestringalloc)
      free(s->range);

    if(s->resume_from)
      s->range = aprintf("%" FMT_OFF_T "-", s->resume_from);
    else
      s->range = strdup(data->set.str[STRING_SET_RANGE]);

    s->rangestringalloc = (s->range) ? TRUE : FALSE;

    if(!s->range)
      return CURLE_OUT_OF_MEMORY;

    /* tell ourselves to fetch this range */
    s->use_range = TRUE;        /* enable range download */
  }
  else
    s->use_range = FALSE; /* disable range download */

  return CURLE_OK;
}


/*
 * setup_connection_internals() -
 *
 * Setup connection internals specific to the requested protocol in the
 * Curl_easy. This is inited and setup before the connection is made but
 * is about the particular protocol that is to be used.
 *
 * This MUST get called after proxy magic has been figured out.
 */
static CURLcode setup_connection_internals(struct Curl_easy *data,
                                           struct connectdata *conn)
{
  const struct Curl_handler *p;
  const char *hostname;
  int port;
  CURLcode result;

  /* Perform setup complement if some. */
  p = conn->handler;

  if(p->setup_connection) {
    result = (*p->setup_connection)(data, conn);

    if(result)
      return result;

    p = conn->handler;              /* May have changed. */
  }

  if(conn->primary.remote_port < 0)
    /* we check for -1 here since if proxy was detected already, this
       was very likely already set to the proxy port */
    conn->primary.remote_port = p->defport;

  /* Now create the destination name */
#ifndef CURL_DISABLE_PROXY
  if(conn->bits.httpproxy && !conn->bits.tunnel_proxy) {
    hostname = conn->http_proxy.host.name;
    port = conn->primary.remote_port;
  }
  else
#endif
  {
    port = conn->remote_port;
    if(conn->bits.conn_to_host)
      hostname = conn->conn_to_host.name;
    else
      hostname = conn->host.name;
  }

#ifdef USE_IPV6
  conn->destination = aprintf("%u/%d/%s", conn->scope_id, port, hostname);
#else
  conn->destination = aprintf("%d/%s", port, hostname);
#endif
  if(!conn->destination)
    return CURLE_OUT_OF_MEMORY;

  conn->destination_len = strlen(conn->destination) + 1;
  Curl_strntolower(conn->destination, conn->destination,
                   conn->destination_len - 1);

  return CURLE_OK;
}


#ifndef CURL_DISABLE_PROXY

#ifndef CURL_DISABLE_HTTP
/****************************************************************
* Detect what (if any) proxy to use. Remember that this selects a host
* name and is not limited to HTTP proxies only.
* The returned pointer must be freed by the caller (unless NULL)
****************************************************************/
static char *detect_proxy(struct Curl_easy *data,
                          struct connectdata *conn)
{
  char *proxy = NULL;

  /* If proxy was not specified, we check for default proxy environment
   * variables, to enable i.e Lynx compliance:
   *
   * http_proxy=http://some.server.dom:port/
   * https_proxy=http://some.server.dom:port/
   * ftp_proxy=http://some.server.dom:port/
   * no_proxy=domain1.dom,host.domain2.dom
   *   (a comma-separated list of hosts which should
   *   not be proxied, or an asterisk to override
   *   all proxy variables)
   * all_proxy=http://some.server.dom:port/
   *   (seems to exist for the CERN www lib. Probably
   *   the first to check for.)
   *
   * For compatibility, the all-uppercase versions of these variables are
   * checked if the lowercase versions do not exist.
   */
  char proxy_env[20];
  char *envp = proxy_env;
#ifdef CURL_DISABLE_VERBOSE_STRINGS
  (void)data;
#endif

  msnprintf(proxy_env, sizeof(proxy_env), "%s_proxy", conn->handler->scheme);

  /* read the protocol proxy: */
  proxy = curl_getenv(proxy_env);

  /*
   * We do not try the uppercase version of HTTP_PROXY because of
   * security reasons:
   *
   * When curl is used in a webserver application
   * environment (cgi or php), this environment variable can
   * be controlled by the web server user by setting the
   * http header 'Proxy:' to some value.
   *
   * This can cause 'internal' http/ftp requests to be
   * arbitrarily redirected by any external attacker.
   */
  if(!proxy && !strcasecompare("http_proxy", proxy_env)) {
    /* There was no lowercase variable, try the uppercase version: */
    Curl_strntoupper(proxy_env, proxy_env, sizeof(proxy_env));
    proxy = curl_getenv(proxy_env);
  }

  if(!proxy) {
#ifdef USE_WEBSOCKETS
    /* websocket proxy fallbacks */
    if(strcasecompare("ws_proxy", proxy_env)) {
      proxy = curl_getenv("http_proxy");
    }
    else if(strcasecompare("wss_proxy", proxy_env)) {
      proxy = curl_getenv("https_proxy");
      if(!proxy)
        proxy = curl_getenv("HTTPS_PROXY");
    }
    if(!proxy) {
#endif
      envp = (char *)"all_proxy";
      proxy = curl_getenv(envp); /* default proxy to use */
      if(!proxy) {
        envp = (char *)"ALL_PROXY";
        proxy = curl_getenv(envp);
      }
#ifdef USE_WEBSOCKETS
    }
#endif
  }
  if(proxy)
    infof(data, "Uses proxy env variable %s == '%s'", envp, proxy);

  return proxy;
}
#endif /* CURL_DISABLE_HTTP */

/*
 * If this is supposed to use a proxy, we need to figure out the proxy
 * hostname, so that we can reuse an existing connection
 * that may exist registered to the same proxy host.
 */
static CURLcode parse_proxy(struct Curl_easy *data,
                            struct connectdata *conn, char *proxy,
                            curl_proxytype proxytype)
{
  char *portptr = NULL;
  int port = -1;
  char *proxyuser = NULL;
  char *proxypasswd = NULL;
  char *host = NULL;
  bool sockstype;
  CURLUcode uc;
  struct proxy_info *proxyinfo;
  CURLU *uhp = curl_url();
  CURLcode result = CURLE_OK;
  char *scheme = NULL;
#ifdef USE_UNIX_SOCKETS
  char *path = NULL;
  bool is_unix_proxy = FALSE;
#endif


  if(!uhp) {
    result = CURLE_OUT_OF_MEMORY;
    goto error;
  }

  /* When parsing the proxy, allowing non-supported schemes since we have
     these made up ones for proxies. Guess scheme for URLs without it. */
  uc = curl_url_set(uhp, CURLUPART_URL, proxy,
                    CURLU_NON_SUPPORT_SCHEME|CURLU_GUESS_SCHEME);
  if(!uc) {
    /* parsed okay as a URL */
    uc = curl_url_get(uhp, CURLUPART_SCHEME, &scheme, 0);
    if(uc) {
      result = CURLE_OUT_OF_MEMORY;
      goto error;
    }

    if(strcasecompare("https", scheme)) {
      if(proxytype != CURLPROXY_HTTPS2)
        proxytype = CURLPROXY_HTTPS;
      else
        proxytype = CURLPROXY_HTTPS2;
    }
    else if(strcasecompare("socks5h", scheme))
      proxytype = CURLPROXY_SOCKS5_HOSTNAME;
    else if(strcasecompare("socks5", scheme))
      proxytype = CURLPROXY_SOCKS5;
    else if(strcasecompare("socks4a", scheme))
      proxytype = CURLPROXY_SOCKS4A;
    else if(strcasecompare("socks4", scheme) ||
            strcasecompare("socks", scheme))
      proxytype = CURLPROXY_SOCKS4;
    else if(strcasecompare("http", scheme))
      ; /* leave it as HTTP or HTTP/1.0 */
    else {
      /* Any other xxx:// reject! */
      failf(data, "Unsupported proxy scheme for \'%s\'", proxy);
      result = CURLE_COULDNT_CONNECT;
      goto error;
    }
  }
  else {
    failf(data, "Unsupported proxy syntax in \'%s\': %s", proxy,
          curl_url_strerror(uc));
    result = CURLE_COULDNT_RESOLVE_PROXY;
    goto error;
  }

#ifdef USE_SSL
  if(!Curl_ssl_supports(data, SSLSUPP_HTTPS_PROXY))
#endif
    if(IS_HTTPS_PROXY(proxytype)) {
      failf(data, "Unsupported proxy \'%s\', libcurl is built without the "
            "HTTPS-proxy support.", proxy);
      result = CURLE_NOT_BUILT_IN;
      goto error;
    }

  sockstype =
    proxytype == CURLPROXY_SOCKS5_HOSTNAME ||
    proxytype == CURLPROXY_SOCKS5 ||
    proxytype == CURLPROXY_SOCKS4A ||
    proxytype == CURLPROXY_SOCKS4;

  proxyinfo = sockstype ? &conn->socks_proxy : &conn->http_proxy;
  proxyinfo->proxytype = (unsigned char)proxytype;

  /* Is there a username and password given in this proxy url? */
  uc = curl_url_get(uhp, CURLUPART_USER, &proxyuser, CURLU_URLDECODE);
  if(uc && (uc != CURLUE_NO_USER))
    goto error;
  uc = curl_url_get(uhp, CURLUPART_PASSWORD, &proxypasswd, CURLU_URLDECODE);
  if(uc && (uc != CURLUE_NO_PASSWORD))
    goto error;

  if(proxyuser || proxypasswd) {
    Curl_safefree(proxyinfo->user);
    proxyinfo->user = proxyuser;
    result = Curl_setstropt(&data->state.aptr.proxyuser, proxyuser);
    proxyuser = NULL;
    if(result)
      goto error;
    Curl_safefree(proxyinfo->passwd);
    if(!proxypasswd) {
      proxypasswd = strdup("");
      if(!proxypasswd) {
        result = CURLE_OUT_OF_MEMORY;
        goto error;
      }
    }
    proxyinfo->passwd = proxypasswd;
    result = Curl_setstropt(&data->state.aptr.proxypasswd, proxypasswd);
    proxypasswd = NULL;
    if(result)
      goto error;
    conn->bits.proxy_user_passwd = TRUE; /* enable it */
  }

  (void)curl_url_get(uhp, CURLUPART_PORT, &portptr, 0);

  if(portptr) {
    port = (int)strtol(portptr, NULL, 10);
    free(portptr);
  }
  else {
    if(data->set.proxyport)
      /* None given in the proxy string, then get the default one if it is
         given */
      port = (int)data->set.proxyport;
    else {
      if(IS_HTTPS_PROXY(proxytype))
        port = CURL_DEFAULT_HTTPS_PROXY_PORT;
      else
        port = CURL_DEFAULT_PROXY_PORT;
    }
  }
  if(port >= 0) {
    proxyinfo->port = port;
    if(conn->primary.remote_port < 0 || sockstype ||
       !conn->socks_proxy.host.rawalloc)
      conn->primary.remote_port = port;
  }

  /* now, clone the proxy hostname */
  uc = curl_url_get(uhp, CURLUPART_HOST, &host, CURLU_URLDECODE);
  if(uc) {
    result = CURLE_OUT_OF_MEMORY;
    goto error;
  }
#ifdef USE_UNIX_SOCKETS
  if(sockstype && strcasecompare(UNIX_SOCKET_PREFIX, host)) {
    uc = curl_url_get(uhp, CURLUPART_PATH, &path, CURLU_URLDECODE);
    if(uc) {
      result = CURLE_OUT_OF_MEMORY;
      goto error;
    }
    /* path will be "/", if no path was found */
    if(strcmp("/", path)) {
      is_unix_proxy = TRUE;
      free(host);
      host = aprintf(UNIX_SOCKET_PREFIX"%s", path);
      if(!host) {
        result = CURLE_OUT_OF_MEMORY;
        goto error;
      }
      Curl_safefree(proxyinfo->host.rawalloc);
      proxyinfo->host.rawalloc = host;
      proxyinfo->host.name = host;
      host = NULL;
    }
  }

  if(!is_unix_proxy) {
#endif
    Curl_safefree(proxyinfo->host.rawalloc);
    proxyinfo->host.rawalloc = host;
    if(host[0] == '[') {
      /* this is a numerical IPv6, strip off the brackets */
      size_t len = strlen(host);
      host[len-1] = 0; /* clear the trailing bracket */
      host++;
      zonefrom_url(uhp, data, conn);
    }
    proxyinfo->host.name = host;
    host = NULL;
#ifdef USE_UNIX_SOCKETS
  }
#endif

error:
  free(proxyuser);
  free(proxypasswd);
  free(host);
  free(scheme);
#ifdef USE_UNIX_SOCKETS
  free(path);
#endif
  curl_url_cleanup(uhp);
  return result;
}

/*
 * Extract the user and password from the authentication string
 */
static CURLcode parse_proxy_auth(struct Curl_easy *data,
                                 struct connectdata *conn)
{
  const char *proxyuser = data->state.aptr.proxyuser ?
    data->state.aptr.proxyuser : "";
  const char *proxypasswd = data->state.aptr.proxypasswd ?
    data->state.aptr.proxypasswd : "";
  CURLcode result = CURLE_OUT_OF_MEMORY;

  conn->http_proxy.user = strdup(proxyuser);
  if(conn->http_proxy.user) {
    conn->http_proxy.passwd = strdup(proxypasswd);
    if(conn->http_proxy.passwd)
      result = CURLE_OK;
    else
      Curl_safefree(conn->http_proxy.user);
  }
  return result;
}

/* create_conn helper to parse and init proxy values. to be called after Unix
   socket init but before any proxy vars are evaluated. */
static CURLcode create_conn_helper_init_proxy(struct Curl_easy *data,
                                              struct connectdata *conn)
{
  char *proxy = NULL;
  char *socksproxy = NULL;
  char *no_proxy = NULL;
  CURLcode result = CURLE_OK;

  /*************************************************************
   * Extract the user and password from the authentication string
   *************************************************************/
  if(conn->bits.proxy_user_passwd) {
    result = parse_proxy_auth(data, conn);
    if(result)
      goto out;
  }

  /*************************************************************
   * Detect what (if any) proxy to use
   *************************************************************/
  if(data->set.str[STRING_PROXY]) {
    proxy = strdup(data->set.str[STRING_PROXY]);
    /* if global proxy is set, this is it */
    if(!proxy) {
      failf(data, "memory shortage");
      result = CURLE_OUT_OF_MEMORY;
      goto out;
    }
  }

  if(data->set.str[STRING_PRE_PROXY]) {
    socksproxy = strdup(data->set.str[STRING_PRE_PROXY]);
    /* if global socks proxy is set, this is it */
    if(!socksproxy) {
      failf(data, "memory shortage");
      result = CURLE_OUT_OF_MEMORY;
      goto out;
    }
  }

  if(!data->set.str[STRING_NOPROXY]) {
    const char *p = "no_proxy";
    no_proxy = curl_getenv(p);
    if(!no_proxy) {
      p = "NO_PROXY";
      no_proxy = curl_getenv(p);
    }
    if(no_proxy) {
      infof(data, "Uses proxy env variable %s == '%s'", p, no_proxy);
    }
  }

  if(Curl_check_noproxy(conn->host.name, data->set.str[STRING_NOPROXY] ?
                        data->set.str[STRING_NOPROXY] : no_proxy)) {
    Curl_safefree(proxy);
    Curl_safefree(socksproxy);
  }
#ifndef CURL_DISABLE_HTTP
  else if(!proxy && !socksproxy)
    /* if the host is not in the noproxy list, detect proxy. */
    proxy = detect_proxy(data, conn);
#endif /* CURL_DISABLE_HTTP */
  Curl_safefree(no_proxy);

#ifdef USE_UNIX_SOCKETS
  /* For the time being do not mix proxy and Unix domain sockets. See #1274 */
  if(proxy && conn->unix_domain_socket) {
    free(proxy);
    proxy = NULL;
  }
#endif

  if(proxy && (!*proxy || (conn->handler->flags & PROTOPT_NONETWORK))) {
    free(proxy);  /* Do not bother with an empty proxy string or if the
                     protocol does not work with network */
    proxy = NULL;
  }
  if(socksproxy && (!*socksproxy ||
                    (conn->handler->flags & PROTOPT_NONETWORK))) {
    free(socksproxy);  /* Do not bother with an empty socks proxy string or if
                          the protocol does not work with network */
    socksproxy = NULL;
  }

  /***********************************************************************
   * If this is supposed to use a proxy, we need to figure out the proxy host
   * name, proxy type and port number, so that we can reuse an existing
   * connection that may exist registered to the same proxy host.
   ***********************************************************************/
  if(proxy || socksproxy) {
    curl_proxytype ptype = (curl_proxytype)conn->http_proxy.proxytype;
    if(proxy) {
      result = parse_proxy(data, conn, proxy, ptype);
      Curl_safefree(proxy); /* parse_proxy copies the proxy string */
      if(result)
        goto out;
    }

    if(socksproxy) {
      result = parse_proxy(data, conn, socksproxy, ptype);
      /* parse_proxy copies the socks proxy string */
      Curl_safefree(socksproxy);
      if(result)
        goto out;
    }

    if(conn->http_proxy.host.rawalloc) {
#ifdef CURL_DISABLE_HTTP
      /* asking for an HTTP proxy is a bit funny when HTTP is disabled... */
      result = CURLE_UNSUPPORTED_PROTOCOL;
      goto out;
#else
      /* force this connection's protocol to become HTTP if compatible */
      if(!(conn->handler->protocol & PROTO_FAMILY_HTTP)) {
        if((conn->handler->flags & PROTOPT_PROXY_AS_HTTP) &&
           !conn->bits.tunnel_proxy)
          conn->handler = &Curl_handler_http;
        else
          /* if not converting to HTTP over the proxy, enforce tunneling */
          conn->bits.tunnel_proxy = TRUE;
      }
      conn->bits.httpproxy = TRUE;
#endif
    }
    else {
      conn->bits.httpproxy = FALSE; /* not an HTTP proxy */
      conn->bits.tunnel_proxy = FALSE; /* no tunneling if not HTTP */
    }

    if(conn->socks_proxy.host.rawalloc) {
      if(!conn->http_proxy.host.rawalloc) {
        /* once a socks proxy */
        if(!conn->socks_proxy.user) {
          conn->socks_proxy.user = conn->http_proxy.user;
          conn->http_proxy.user = NULL;
          Curl_safefree(conn->socks_proxy.passwd);
          conn->socks_proxy.passwd = conn->http_proxy.passwd;
          conn->http_proxy.passwd = NULL;
        }
      }
      conn->bits.socksproxy = TRUE;
    }
    else
      conn->bits.socksproxy = FALSE; /* not a socks proxy */
  }
  else {
    conn->bits.socksproxy = FALSE;
    conn->bits.httpproxy = FALSE;
  }
  conn->bits.proxy = conn->bits.httpproxy || conn->bits.socksproxy;

  if(!conn->bits.proxy) {
    /* we are not using the proxy after all... */
    conn->bits.proxy = FALSE;
    conn->bits.httpproxy = FALSE;
    conn->bits.socksproxy = FALSE;
    conn->bits.proxy_user_passwd = FALSE;
    conn->bits.tunnel_proxy = FALSE;
    /* CURLPROXY_HTTPS does not have its own flag in conn->bits, yet we need
       to signal that CURLPROXY_HTTPS is not used for this connection */
    conn->http_proxy.proxytype = CURLPROXY_HTTP;
  }

out:

  free(socksproxy);
  free(proxy);
  return result;
}
#endif /* CURL_DISABLE_PROXY */

/*
 * Curl_parse_login_details()
 *
 * This is used to parse a login string for username, password and options in
 * the following formats:
 *
 *   user
 *   user:password
 *   user:password;options
 *   user;options
 *   user;options:password
 *   :password
 *   :password;options
 *   ;options
 *   ;options:password
 *
 * Parameters:
 *
 * login    [in]     - login string.
 * len      [in]     - length of the login string.
 * userp    [in/out] - address where a pointer to newly allocated memory
 *                     holding the user will be stored upon completion.
 * passwdp  [in/out] - address where a pointer to newly allocated memory
 *                     holding the password will be stored upon completion.
 * optionsp [in/out] - OPTIONAL address where a pointer to newly allocated
 *                     memory holding the options will be stored upon
 *                     completion.
 *
 * Returns CURLE_OK on success.
 */
CURLcode Curl_parse_login_details(const char *login, const size_t len,
                                  char **userp, char **passwdp,
                                  char **optionsp)
{
  char *ubuf = NULL;
  char *pbuf = NULL;
  const char *psep = NULL;
  const char *osep = NULL;
  size_t ulen;
  size_t plen;
  size_t olen;

  DEBUGASSERT(userp);
  DEBUGASSERT(passwdp);

  /* Attempt to find the password separator */
  psep = memchr(login, ':', len);

  /* Attempt to find the options separator */
  if(optionsp)
    osep = memchr(login, ';', len);

  /* Calculate the portion lengths */
  ulen = (psep ?
          (size_t)(osep && psep > osep ? osep - login : psep - login) :
          (osep ? (size_t)(osep - login) : len));
  plen = (psep ?
          (osep && osep > psep ? (size_t)(osep - psep) :
           (size_t)(login + len - psep)) - 1 : 0);
  olen = (osep ?
          (psep && psep > osep ? (size_t)(psep - osep) :
           (size_t)(login + len - osep)) - 1 : 0);

  /* Clone the user portion buffer, which can be zero length */
  ubuf = Curl_memdup0(login, ulen);
  if(!ubuf)
    goto error;

  /* Clone the password portion buffer */
  if(psep) {
    pbuf = Curl_memdup0(&psep[1], plen);
    if(!pbuf)
      goto error;
  }

  /* Allocate the options portion buffer */
  if(optionsp) {
    char *obuf = NULL;
    if(olen) {
      obuf = Curl_memdup0(&osep[1], olen);
      if(!obuf)
        goto error;
    }
    *optionsp = obuf;
  }
  *userp = ubuf;
  *passwdp = pbuf;
  return CURLE_OK;
error:
  free(ubuf);
  free(pbuf);
  return CURLE_OUT_OF_MEMORY;
}

/*************************************************************
 * Figure out the remote port number and fix it in the URL
 *
 * No matter if we use a proxy or not, we have to figure out the remote
 * port number of various reasons.
 *
 * The port number embedded in the URL is replaced, if necessary.
 *************************************************************/
static CURLcode parse_remote_port(struct Curl_easy *data,
                                  struct connectdata *conn)
{

  if(data->set.use_port && data->state.allow_port) {
    /* if set, we use this instead of the port possibly given in the URL */
    char portbuf[16];
    CURLUcode uc;
    conn->remote_port = data->set.use_port;
    msnprintf(portbuf, sizeof(portbuf), "%d", conn->remote_port);
    uc = curl_url_set(data->state.uh, CURLUPART_PORT, portbuf, 0);
    if(uc)
      return CURLE_OUT_OF_MEMORY;
  }

  return CURLE_OK;
}

/*
 * Override the login details from the URL with that in the CURLOPT_USERPWD
 * option or a .netrc file, if applicable.
 */
static CURLcode override_login(struct Curl_easy *data,
                               struct connectdata *conn)
{
  CURLUcode uc;
  char **userp = &conn->user;
  char **passwdp = &conn->passwd;
  char **optionsp = &conn->options;

  if(data->set.str[STRING_OPTIONS]) {
    free(*optionsp);
    *optionsp = strdup(data->set.str[STRING_OPTIONS]);
    if(!*optionsp)
      return CURLE_OUT_OF_MEMORY;
  }

#ifndef CURL_DISABLE_NETRC
  if(data->set.use_netrc == CURL_NETRC_REQUIRED) {
    Curl_safefree(*userp);
    Curl_safefree(*passwdp);
  }
  conn->bits.netrc = FALSE;
  if(data->set.use_netrc && !data->set.str[STRING_USERNAME]) {
    int ret;
    bool url_provided = FALSE;

    if(data->state.aptr.user) {
      /* there was a username in the URL. Use the URL decoded version */
      userp = &data->state.aptr.user;
      url_provided = TRUE;
    }

    ret = Curl_parsenetrc(conn->host.name,
                          userp, passwdp,
                          data->set.str[STRING_NETRC_FILE]);
    if(ret > 0) {
      infof(data, "Couldn't find host %s in the %s file; using defaults",
            conn->host.name,
            (data->set.str[STRING_NETRC_FILE] ?
             data->set.str[STRING_NETRC_FILE] : ".netrc"));
    }
    else if(ret < 0) {
      failf(data, ".netrc parser error");
      return CURLE_READ_ERROR;
    }
    else {
      /* set bits.netrc TRUE to remember that we got the name from a .netrc
         file, so that it is safe to use even if we followed a Location: to a
         different host or similar. */
      conn->bits.netrc = TRUE;
    }
    if(url_provided) {
      Curl_safefree(conn->user);
      conn->user = strdup(*userp);
      if(!conn->user)
        return CURLE_OUT_OF_MEMORY;
    }
    /* no user was set but a password, set a blank user */
    if(!*userp && *passwdp) {
      *userp = strdup("");
      if(!*userp)
        return CURLE_OUT_OF_MEMORY;
    }
  }
#endif

  /* for updated strings, we update them in the URL */
  if(*userp) {
    CURLcode result;
    if(data->state.aptr.user != *userp) {
      /* nothing to do then */
      result = Curl_setstropt(&data->state.aptr.user, *userp);
      if(result)
        return result;
    }
  }
  if(data->state.aptr.user) {
    uc = curl_url_set(data->state.uh, CURLUPART_USER, data->state.aptr.user,
                      CURLU_URLENCODE);
    if(uc)
      return Curl_uc_to_curlcode(uc);
    if(!*userp) {
      *userp = strdup(data->state.aptr.user);
      if(!*userp)
        return CURLE_OUT_OF_MEMORY;
    }
  }
  if(*passwdp) {
    CURLcode result = Curl_setstropt(&data->state.aptr.passwd, *passwdp);
    if(result)
      return result;
  }
  if(data->state.aptr.passwd) {
    uc = curl_url_set(data->state.uh, CURLUPART_PASSWORD,
                      data->state.aptr.passwd, CURLU_URLENCODE);
    if(uc)
      return Curl_uc_to_curlcode(uc);
    if(!*passwdp) {
      *passwdp = strdup(data->state.aptr.passwd);
      if(!*passwdp)
        return CURLE_OUT_OF_MEMORY;
    }
  }

  return CURLE_OK;
}

/*
 * Set the login details so they are available in the connection
 */
static CURLcode set_login(struct Curl_easy *data,
                          struct connectdata *conn)
{
  CURLcode result = CURLE_OK;
  const char *setuser = CURL_DEFAULT_USER;
  const char *setpasswd = CURL_DEFAULT_PASSWORD;

  /* If our protocol needs a password and we have none, use the defaults */
  if((conn->handler->flags & PROTOPT_NEEDSPWD) && !data->state.aptr.user)
    ;
  else {
    setuser = "";
    setpasswd = "";
  }
  /* Store the default user */
  if(!conn->user) {
    conn->user = strdup(setuser);
    if(!conn->user)
      return CURLE_OUT_OF_MEMORY;
  }

  /* Store the default password */
  if(!conn->passwd) {
    conn->passwd = strdup(setpasswd);
    if(!conn->passwd)
      result = CURLE_OUT_OF_MEMORY;
  }

  return result;
}

/*
 * Parses a "host:port" string to connect to.
 * The hostname and the port may be empty; in this case, NULL is returned for
 * the hostname and -1 for the port.
 */
static CURLcode parse_connect_to_host_port(struct Curl_easy *data,
                                           const char *host,
                                           char **hostname_result,
                                           int *port_result)
{
  char *host_dup;
  char *hostptr;
  char *host_portno;
  char *portptr;
  int port = -1;
  CURLcode result = CURLE_OK;

#if defined(CURL_DISABLE_VERBOSE_STRINGS)
  (void) data;
#endif

  *hostname_result = NULL;
  *port_result = -1;

  if(!host || !*host)
    return CURLE_OK;

  host_dup = strdup(host);
  if(!host_dup)
    return CURLE_OUT_OF_MEMORY;

  hostptr = host_dup;

  /* start scanning for port number at this point */
  portptr = hostptr;

  /* detect and extract RFC6874-style IPv6-addresses */
  if(*hostptr == '[') {
#ifdef USE_IPV6
    char *ptr = ++hostptr; /* advance beyond the initial bracket */
    while(*ptr && (ISXDIGIT(*ptr) || (*ptr == ':') || (*ptr == '.')))
      ptr++;
    if(*ptr == '%') {
      /* There might be a zone identifier */
      if(strncmp("%25", ptr, 3))
        infof(data, "Please URL encode %% as %%25, see RFC 6874.");
      ptr++;
      /* Allow unreserved characters as defined in RFC 3986 */
      while(*ptr && (ISALPHA(*ptr) || ISXDIGIT(*ptr) || (*ptr == '-') ||
                     (*ptr == '.') || (*ptr == '_') || (*ptr == '~')))
        ptr++;
    }
    if(*ptr == ']')
      /* yeps, it ended nicely with a bracket as well */
      *ptr++ = '\0';
    else
      infof(data, "Invalid IPv6 address format");
    portptr = ptr;
    /* Note that if this did not end with a bracket, we still advanced the
     * hostptr first, but I cannot see anything wrong with that as no host
     * name nor a numeric can legally start with a bracket.
     */
#else
    failf(data, "Use of IPv6 in *_CONNECT_TO without IPv6 support built-in");
    result = CURLE_NOT_BUILT_IN;
    goto error;
#endif
  }

  /* Get port number off server.com:1080 */
  host_portno = strchr(portptr, ':');
  if(host_portno) {
    char *endp = NULL;
    *host_portno = '\0'; /* cut off number from hostname */
    host_portno++;
    if(*host_portno) {
      long portparse = strtol(host_portno, &endp, 10);
      if((endp && *endp) || (portparse < 0) || (portparse > 65535)) {
        failf(data, "No valid port number in connect to host string (%s)",
              host_portno);
        result = CURLE_SETOPT_OPTION_SYNTAX;
        goto error;
      }
      else
        port = (int)portparse; /* we know it will fit */
    }
  }

  /* now, clone the cleaned hostname */
  DEBUGASSERT(hostptr);
  *hostname_result = strdup(hostptr);
  if(!*hostname_result) {
    result = CURLE_OUT_OF_MEMORY;
    goto error;
  }

  *port_result = port;

error:
  free(host_dup);
  return result;
}

/*
 * Parses one "connect to" string in the form:
 * "HOST:PORT:CONNECT-TO-HOST:CONNECT-TO-PORT".
 */
static CURLcode parse_connect_to_string(struct Curl_easy *data,
                                        struct connectdata *conn,
                                        const char *conn_to_host,
                                        char **host_result,
                                        int *port_result)
{
  CURLcode result = CURLE_OK;
  const char *ptr = conn_to_host;
  int host_match = FALSE;
  int port_match = FALSE;

  *host_result = NULL;
  *port_result = -1;

  if(*ptr == ':') {
    /* an empty hostname always matches */
    host_match = TRUE;
    ptr++;
  }
  else {
    /* check whether the URL's hostname matches */
    size_t hostname_to_match_len;
    char *hostname_to_match = aprintf("%s%s%s",
                                      conn->bits.ipv6_ip ? "[" : "",
                                      conn->host.name,
                                      conn->bits.ipv6_ip ? "]" : "");
    if(!hostname_to_match)
      return CURLE_OUT_OF_MEMORY;
    hostname_to_match_len = strlen(hostname_to_match);
    host_match = strncasecompare(ptr, hostname_to_match,
                                 hostname_to_match_len);
    free(hostname_to_match);
    ptr += hostname_to_match_len;

    host_match = host_match && *ptr == ':';
    ptr++;
  }

  if(host_match) {
    if(*ptr == ':') {
      /* an empty port always matches */
      port_match = TRUE;
      ptr++;
    }
    else {
      /* check whether the URL's port matches */
      char *ptr_next = strchr(ptr, ':');
      if(ptr_next) {
        char *endp = NULL;
        long port_to_match = strtol(ptr, &endp, 10);
        if((endp == ptr_next) && (port_to_match == conn->remote_port)) {
          port_match = TRUE;
          ptr = ptr_next + 1;
        }
      }
    }
  }

  if(host_match && port_match) {
    /* parse the hostname and port to connect to */
    result = parse_connect_to_host_port(data, ptr, host_result, port_result);
  }

  return result;
}

/*
 * Processes all strings in the "connect to" slist, and uses the "connect
 * to host" and "connect to port" of the first string that matches.
 */
static CURLcode parse_connect_to_slist(struct Curl_easy *data,
                                       struct connectdata *conn,
                                       struct curl_slist *conn_to_host)
{
  CURLcode result = CURLE_OK;
  char *host = NULL;
  int port = -1;

  while(conn_to_host && !host && port == -1) {
    result = parse_connect_to_string(data, conn, conn_to_host->data,
                                     &host, &port);
    if(result)
      return result;

    if(host && *host) {
      conn->conn_to_host.rawalloc = host;
      conn->conn_to_host.name = host;
      conn->bits.conn_to_host = TRUE;

      infof(data, "Connecting to hostname: %s", host);
    }
    else {
      /* no "connect to host" */
      conn->bits.conn_to_host = FALSE;
      Curl_safefree(host);
    }

    if(port >= 0) {
      conn->conn_to_port = port;
      conn->bits.conn_to_port = TRUE;
      infof(data, "Connecting to port: %d", port);
    }
    else {
      /* no "connect to port" */
      conn->bits.conn_to_port = FALSE;
      port = -1;
    }

    conn_to_host = conn_to_host->next;
  }

#ifndef CURL_DISABLE_ALTSVC
  if(data->asi && !host && (port == -1) &&
     ((conn->handler->protocol == CURLPROTO_HTTPS) ||
#ifdef DEBUGBUILD
      /* allow debug builds to circumvent the HTTPS restriction */
      getenv("CURL_ALTSVC_HTTP")
#else
      0
#endif
       )) {
    /* no connect_to match, try alt-svc! */
    enum alpnid srcalpnid;
    bool hit;
    struct altsvc *as;
    const int allowed_versions = ( ALPN_h1
#ifdef USE_HTTP2
                                   | ALPN_h2
#endif
#ifdef USE_HTTP3
                                   | ALPN_h3
#endif
      ) & data->asi->flags;

    host = conn->host.rawalloc;
#ifdef USE_HTTP2
    /* with h2 support, check that first */
    srcalpnid = ALPN_h2;
    hit = Curl_altsvc_lookup(data->asi,
                             srcalpnid, host, conn->remote_port, /* from */
                             &as /* to */,
                             allowed_versions);
    if(!hit)
#endif
    {
      srcalpnid = ALPN_h1;
      hit = Curl_altsvc_lookup(data->asi,
                               srcalpnid, host, conn->remote_port, /* from */
                               &as /* to */,
                               allowed_versions);
    }
    if(hit) {
      char *hostd = strdup((char *)as->dst.host);
      if(!hostd)
        return CURLE_OUT_OF_MEMORY;
      conn->conn_to_host.rawalloc = hostd;
      conn->conn_to_host.name = hostd;
      conn->bits.conn_to_host = TRUE;
      conn->conn_to_port = as->dst.port;
      conn->bits.conn_to_port = TRUE;
      conn->bits.altused = TRUE;
      infof(data, "Alt-svc connecting from [%s]%s:%d to [%s]%s:%d",
            Curl_alpnid2str(srcalpnid), host, conn->remote_port,
            Curl_alpnid2str(as->dst.alpnid), hostd, as->dst.port);
      if(srcalpnid != as->dst.alpnid) {
        /* protocol version switch */
        switch(as->dst.alpnid) {
        case ALPN_h1:
          conn->httpversion = 11;
          break;
        case ALPN_h2:
          conn->httpversion = 20;
          break;
        case ALPN_h3:
          conn->transport = TRNSPRT_QUIC;
          conn->httpversion = 30;
          break;
        default: /* should not be possible */
          break;
        }
      }
    }
  }
#endif

  return result;
}

#ifdef USE_UNIX_SOCKETS
static CURLcode resolve_unix(struct Curl_easy *data,
                             struct connectdata *conn,
                             char *unix_path)
{
  struct Curl_dns_entry *hostaddr = NULL;
  bool longpath = FALSE;

  DEBUGASSERT(unix_path);
  DEBUGASSERT(conn->dns_entry == NULL);

  /* Unix domain sockets are local. The host gets ignored, just use the
   * specified domain socket address. Do not cache "DNS entries". There is
   * no DNS involved and we already have the filesystem path available. */
  hostaddr = calloc(1, sizeof(struct Curl_dns_entry));
  if(!hostaddr)
    return CURLE_OUT_OF_MEMORY;

  hostaddr->addr = Curl_unix2addr(unix_path, &longpath,
                                  conn->bits.abstract_unix_socket);
  if(!hostaddr->addr) {
    if(longpath)
      /* Long paths are not supported for now */
      failf(data, "Unix socket path too long: '%s'", unix_path);
    free(hostaddr);
    return longpath ? CURLE_COULDNT_RESOLVE_HOST : CURLE_OUT_OF_MEMORY;
  }

  hostaddr->refcount = 1; /* connection is the only one holding this */
  conn->dns_entry = hostaddr;
  return CURLE_OK;
}
#endif

/*************************************************************
 * Resolve the address of the server or proxy
 *************************************************************/
static CURLcode resolve_server(struct Curl_easy *data,
                               struct connectdata *conn,
                               bool *async)
{
  struct hostname *ehost;
  timediff_t timeout_ms = Curl_timeleft(data, NULL, TRUE);
  const char *peertype = "host";
  int rc;
#ifdef USE_UNIX_SOCKETS
  char *unix_path = conn->unix_domain_socket;

#ifndef CURL_DISABLE_PROXY
  if(!unix_path && CONN_IS_PROXIED(conn) && conn->socks_proxy.host.name &&
     !strncmp(UNIX_SOCKET_PREFIX"/",
              conn->socks_proxy.host.name, sizeof(UNIX_SOCKET_PREFIX)))
    unix_path = conn->socks_proxy.host.name + sizeof(UNIX_SOCKET_PREFIX) - 1;
#endif

  if(unix_path) {
    /* TODO, this only works if previous transport is TRNSPRT_TCP. Check it? */
    conn->transport = TRNSPRT_UNIX;
    return resolve_unix(data, conn, unix_path);
  }
#endif

  DEBUGASSERT(conn->dns_entry == NULL);

#ifndef CURL_DISABLE_PROXY
  if(CONN_IS_PROXIED(conn)) {
    ehost = conn->bits.socksproxy ? &conn->socks_proxy.host :
      &conn->http_proxy.host;
    peertype = "proxy";
  }
  else
#endif
  {
    ehost = conn->bits.conn_to_host ? &conn->conn_to_host : &conn->host;
    /* If not connecting via a proxy, extract the port from the URL, if it is
     * there, thus overriding any defaults that might have been set above. */
    conn->primary.remote_port = conn->bits.conn_to_port ? conn->conn_to_port :
      conn->remote_port;
  }

  /* Resolve target host right on */
  conn->hostname_resolve = strdup(ehost->name);
  if(!conn->hostname_resolve)
    return CURLE_OUT_OF_MEMORY;

  rc = Curl_resolv_timeout(data, conn->hostname_resolve,
                           conn->primary.remote_port,
                           &conn->dns_entry, timeout_ms);
  if(rc == CURLRESOLV_PENDING)
    *async = TRUE;
  else if(rc == CURLRESOLV_TIMEDOUT) {
    failf(data, "Failed to resolve %s '%s' with timeout after %"
          FMT_TIMEDIFF_T " ms", peertype, ehost->dispname,
          Curl_timediff(Curl_now(), data->progress.t_startsingle));
    return CURLE_OPERATION_TIMEDOUT;
  }
  else if(!conn->dns_entry) {
    failf(data, "Could not resolve %s: %s", peertype, ehost->dispname);
    return CURLE_COULDNT_RESOLVE_HOST;
  }

  return CURLE_OK;
}

/*
 * Cleanup the connection `temp`, just allocated for `data`, before using the
 * previously `existing` one for `data`. All relevant info is copied over
 * and `temp` is freed.
 */
static void reuse_conn(struct Curl_easy *data,
                       struct connectdata *temp,
                       struct connectdata *existing)
{
  /* get the user+password information from the temp struct since it may
   * be new for this request even when we reuse an existing connection */
  if(temp->user) {
    /* use the new username and password though */
    Curl_safefree(existing->user);
    Curl_safefree(existing->passwd);
    existing->user = temp->user;
    existing->passwd = temp->passwd;
    temp->user = NULL;
    temp->passwd = NULL;
  }

#ifndef CURL_DISABLE_PROXY
  existing->bits.proxy_user_passwd = temp->bits.proxy_user_passwd;
  if(existing->bits.proxy_user_passwd) {
    /* use the new proxy username and proxy password though */
    Curl_safefree(existing->http_proxy.user);
    Curl_safefree(existing->socks_proxy.user);
    Curl_safefree(existing->http_proxy.passwd);
    Curl_safefree(existing->socks_proxy.passwd);
    existing->http_proxy.user = temp->http_proxy.user;
    existing->socks_proxy.user = temp->socks_proxy.user;
    existing->http_proxy.passwd = temp->http_proxy.passwd;
    existing->socks_proxy.passwd = temp->socks_proxy.passwd;
    temp->http_proxy.user = NULL;
    temp->socks_proxy.user = NULL;
    temp->http_proxy.passwd = NULL;
    temp->socks_proxy.passwd = NULL;
  }
#endif

  /* Finding a connection for reuse in the cpool matches, among other
   * things on the "remote-relevant" hostname. This is not necessarily
   * the authority of the URL, e.g. conn->host. For example:
   * - we use a proxy (not tunneling). we want to send all requests
   *   that use the same proxy on this connection.
   * - we have a "connect-to" setting that may redirect the hostname of
   *   a new request to the same remote endpoint of an existing conn.
   *   We want to reuse an existing conn to the remote endpoint.
   * Since connection reuse does not match on conn->host necessarily, we
   * switch `existing` conn to `temp` conn's host settings.
   * TODO: is this correct in the case of TLS connections that have
   *       used the original hostname in SNI to negotiate? Do we send
   *       requests for another host through the different SNI?
   */
  Curl_free_idnconverted_hostname(&existing->host);
  Curl_free_idnconverted_hostname(&existing->conn_to_host);
  Curl_safefree(existing->host.rawalloc);
  Curl_safefree(existing->conn_to_host.rawalloc);
  existing->host = temp->host;
  temp->host.rawalloc = NULL;
  temp->host.encalloc = NULL;
  existing->conn_to_host = temp->conn_to_host;
  temp->conn_to_host.rawalloc = NULL;
  existing->conn_to_port = temp->conn_to_port;
  existing->remote_port = temp->remote_port;
  Curl_safefree(existing->hostname_resolve);

  existing->hostname_resolve = temp->hostname_resolve;
  temp->hostname_resolve = NULL;

  /* reuse init */
  existing->bits.reuse = TRUE; /* yes, we are reusing here */

  Curl_conn_free(data, temp);
}

/**
 * create_conn() sets up a new connectdata struct, or reuses an already
 * existing one, and resolves hostname.
 *
 * if this function returns CURLE_OK and *async is set to TRUE, the resolve
 * response will be coming asynchronously. If *async is FALSE, the name is
 * already resolved.
 *
 * @param data The sessionhandle pointer
 * @param in_connect is set to the next connection data pointer
 * @param async is set TRUE when an async DNS resolution is pending
 * @see Curl_setup_conn()
 *
 */

static CURLcode create_conn(struct Curl_easy *data,
                            struct connectdata **in_connect,
                            bool *async)
{
  CURLcode result = CURLE_OK;
  struct connectdata *conn;
  struct connectdata *existing = NULL;
  bool reuse;
  bool connections_available = TRUE;
  bool force_reuse = FALSE;
  bool waitpipe = FALSE;

  *async = FALSE;
  *in_connect = NULL;

  /*************************************************************
   * Check input data
   *************************************************************/
  if(!data->state.url) {
    result = CURLE_URL_MALFORMAT;
    goto out;
  }

  /* First, split up the current URL in parts so that we can use the
     parts for checking against the already present connections. In order
     to not have to modify everything at once, we allocate a temporary
     connection data struct and fill in for comparison purposes. */
  conn = allocate_conn(data);

  if(!conn) {
    result = CURLE_OUT_OF_MEMORY;
    goto out;
  }

  /* We must set the return variable as soon as possible, so that our
     parent can cleanup any possible allocs we may have done before
     any failure */
  *in_connect = conn;

  result = parseurlandfillconn(data, conn);
  if(result)
    goto out;

  if(data->set.str[STRING_SASL_AUTHZID]) {
    conn->sasl_authzid = strdup(data->set.str[STRING_SASL_AUTHZID]);
    if(!conn->sasl_authzid) {
      result = CURLE_OUT_OF_MEMORY;
      goto out;
    }
  }

  if(data->set.str[STRING_BEARER]) {
    conn->oauth_bearer = strdup(data->set.str[STRING_BEARER]);
    if(!conn->oauth_bearer) {
      result = CURLE_OUT_OF_MEMORY;
      goto out;
    }
  }

#ifdef USE_UNIX_SOCKETS
  if(data->set.str[STRING_UNIX_SOCKET_PATH]) {
    conn->unix_domain_socket = strdup(data->set.str[STRING_UNIX_SOCKET_PATH]);
    if(!conn->unix_domain_socket) {
      result = CURLE_OUT_OF_MEMORY;
      goto out;
    }
    conn->bits.abstract_unix_socket = data->set.abstract_unix_socket;
  }
#endif

  /* After the Unix socket init but before the proxy vars are used, parse and
     initialize the proxy vars */
#ifndef CURL_DISABLE_PROXY
  result = create_conn_helper_init_proxy(data, conn);
  if(result)
    goto out;

  /*************************************************************
   * If the protocol is using SSL and HTTP proxy is used, we set
   * the tunnel_proxy bit.
   *************************************************************/
  if((conn->given->flags&PROTOPT_SSL) && conn->bits.httpproxy)
    conn->bits.tunnel_proxy = TRUE;
#endif

  /*************************************************************
   * Figure out the remote port number and fix it in the URL
   *************************************************************/
  result = parse_remote_port(data, conn);
  if(result)
    goto out;

  /* Check for overridden login details and set them accordingly so that
     they are known when protocol->setup_connection is called! */
  result = override_login(data, conn);
  if(result)
    goto out;

  result = set_login(data, conn); /* default credentials */
  if(result)
    goto out;

  /*************************************************************
   * Process the "connect to" linked list of hostname/port mappings.
   * Do this after the remote port number has been fixed in the URL.
   *************************************************************/
  result = parse_connect_to_slist(data, conn, data->set.connect_to);
  if(result)
    goto out;

  /*************************************************************
   * IDN-convert the proxy hostnames
   *************************************************************/
#ifndef CURL_DISABLE_PROXY
  if(conn->bits.httpproxy) {
    result = Curl_idnconvert_hostname(&conn->http_proxy.host);
    if(result)
      return result;
  }
  if(conn->bits.socksproxy) {
    result = Curl_idnconvert_hostname(&conn->socks_proxy.host);
    if(result)
      return result;
  }
#endif
  if(conn->bits.conn_to_host) {
    result = Curl_idnconvert_hostname(&conn->conn_to_host);
    if(result)
      return result;
  }

  /*************************************************************
   * Check whether the host and the "connect to host" are equal.
   * Do this after the hostnames have been IDN-converted.
   *************************************************************/
  if(conn->bits.conn_to_host &&
     strcasecompare(conn->conn_to_host.name, conn->host.name)) {
    conn->bits.conn_to_host = FALSE;
  }

  /*************************************************************
   * Check whether the port and the "connect to port" are equal.
   * Do this after the remote port number has been fixed in the URL.
   *************************************************************/
  if(conn->bits.conn_to_port && conn->conn_to_port == conn->remote_port) {
    conn->bits.conn_to_port = FALSE;
  }

#ifndef CURL_DISABLE_PROXY
  /*************************************************************
   * If the "connect to" feature is used with an HTTP proxy,
   * we set the tunnel_proxy bit.
   *************************************************************/
  if((conn->bits.conn_to_host || conn->bits.conn_to_port) &&
      conn->bits.httpproxy)
    conn->bits.tunnel_proxy = TRUE;
#endif

  /*************************************************************
   * Setup internals depending on protocol. Needs to be done after
   * we figured out what/if proxy to use.
   *************************************************************/
  result = setup_connection_internals(data, conn);
  if(result)
    goto out;

  /***********************************************************************
   * file: is a special case in that it does not need a network connection
   ***********************************************************************/
#ifndef CURL_DISABLE_FILE
  if(conn->handler->flags & PROTOPT_NONETWORK) {
    bool done;
    /* this is supposed to be the connect function so we better at least check
       that the file is present here! */
    DEBUGASSERT(conn->handler->connect_it);
    data->info.conn_scheme = conn->handler->scheme;
    /* conn_protocol can only provide "old" protocols */
    data->info.conn_protocol = (conn->handler->protocol) & CURLPROTO_MASK;
    result = conn->handler->connect_it(data, &done);

    /* Setup a "faked" transfer that will do nothing */
    if(!result) {
      Curl_attach_connection(data, conn);
      result = Curl_cpool_add_conn(data, conn);
      if(result)
        goto out;

      /*
       * Setup whatever necessary for a resumed transfer
       */
      result = setup_range(data);
      if(result) {
        DEBUGASSERT(conn->handler->done);
        /* we ignore the return code for the protocol-specific DONE */
        (void)conn->handler->done(data, result, FALSE);
        goto out;
      }
      Curl_xfer_setup_nop(data);
    }

    /* since we skip do_init() */
    Curl_init_do(data, conn);

    goto out;
  }
#endif

  /* Setup filter for network connections */
  conn->recv[FIRSTSOCKET] = Curl_cf_recv;
  conn->send[FIRSTSOCKET] = Curl_cf_send;
  conn->recv[SECONDARYSOCKET] = Curl_cf_recv;
  conn->send[SECONDARYSOCKET] = Curl_cf_send;
  conn->bits.tcp_fastopen = data->set.tcp_fastopen;

  /* Complete the easy's SSL configuration for connection cache matching */
  result = Curl_ssl_easy_config_complete(data);
  if(result)
    goto out;

  /* FIXME: do we really want to run this every time we add a transfer? */
  Curl_cpool_prune_dead(data);

  /*************************************************************
   * Check the current list of connections to see if we can
   * reuse an already existing one or if we have to create a
   * new one.
   *************************************************************/

  DEBUGASSERT(conn->user);
  DEBUGASSERT(conn->passwd);

  /* reuse_fresh is TRUE if we are told to use a new connection by force, but
     we only acknowledge this option if this is not a reused connection
     already (which happens due to follow-location or during an HTTP
     authentication phase). CONNECT_ONLY transfers also refuse reuse. */
  if((data->set.reuse_fresh && !data->state.followlocation) ||
     data->set.connect_only)
    reuse = FALSE;
  else
    reuse = ConnectionExists(data, conn, &existing, &force_reuse, &waitpipe);

  if(reuse) {
    /*
     * We already have a connection for this, we got the former connection in
     * `existing` and thus we need to cleanup the one we just
     * allocated before we can move along and use `existing`.
     */
    reuse_conn(data, conn, existing);
    conn = existing;
    *in_connect = conn;

#ifndef CURL_DISABLE_PROXY
    infof(data, "Re-using existing connection with %s %s",
          conn->bits.proxy?"proxy":"host",
          conn->socks_proxy.host.name ? conn->socks_proxy.host.dispname :
          conn->http_proxy.host.name ? conn->http_proxy.host.dispname :
          conn->host.dispname);
#else
    infof(data, "Re-using existing connection with host %s",
          conn->host.dispname);
#endif
  }
  else {
    /* We have decided that we want a new connection. However, we may not
       be able to do that if we have reached the limit of how many
       connections we are allowed to open. */

    if(conn->handler->flags & PROTOPT_ALPN) {
      /* The protocol wants it, so set the bits if enabled in the easy handle
         (default) */
      if(data->set.ssl_enable_alpn)
        conn->bits.tls_enable_alpn = TRUE;
    }

    if(waitpipe)
      /* There is a connection that *might* become usable for multiplexing
         "soon", and we wait for that */
      connections_available = FALSE;
    else {
      switch(Curl_cpool_check_limits(data, conn)) {
      case CPOOL_LIMIT_DEST:
        infof(data, "No more connections allowed to host");
        connections_available = FALSE;
        break;
      case CPOOL_LIMIT_TOTAL:
#ifndef CURL_DISABLE_DOH
        if(data->set.dohfor_mid >= 0)
          infof(data, "Allowing DoH to override max connection limit");
        else
#endif
        {
          infof(data, "No connections available in cache");
          connections_available = FALSE;
        }
        break;
      default:
        break;
      }
    }

    if(!connections_available) {
      infof(data, "No connections available.");

      Curl_conn_free(data, conn);
      *in_connect = NULL;

      result = CURLE_NO_CONNECTION_AVAILABLE;
      goto out;
    }
    else {
      /*
       * This is a brand new connection, so let's store it in the connection
       * cache of ours!
       */
      result = Curl_ssl_conn_config_init(data, conn);
      if(result) {
        DEBUGF(fprintf(stderr, "Error: init connection ssl config\n"));
        goto out;
      }

      Curl_attach_connection(data, conn);
      result = Curl_cpool_add_conn(data, conn);
      if(result)
        goto out;
    }

#if defined(USE_NTLM)
    /* If NTLM is requested in a part of this connection, make sure we do not
       assume the state is fine as this is a fresh connection and NTLM is
       connection based. */
    if((data->state.authhost.picked & CURLAUTH_NTLM) &&
       data->state.authhost.done) {
      infof(data, "NTLM picked AND auth done set, clear picked");
      data->state.authhost.picked = CURLAUTH_NONE;
      data->state.authhost.done = FALSE;
    }

    if((data->state.authproxy.picked & CURLAUTH_NTLM) &&
       data->state.authproxy.done) {
      infof(data, "NTLM-proxy picked AND auth done set, clear picked");
      data->state.authproxy.picked = CURLAUTH_NONE;
      data->state.authproxy.done = FALSE;
    }
#endif
  }

  /* Setup and init stuff before DO starts, in preparing for the transfer. */
  Curl_init_do(data, conn);

  /*
   * Setup whatever necessary for a resumed transfer
   */
  result = setup_range(data);
  if(result)
    goto out;

  /* Continue connectdata initialization here. */

  if(conn->bits.reuse) {
    /* We are reusing the connection - no need to resolve anything, and
       idnconvert_hostname() was called already in create_conn() for the reuse
       case. */
    *async = FALSE;
  }
  else {
    /*************************************************************
     * Resolve the address of the server or proxy
     *************************************************************/
    result = resolve_server(data, conn, async);
    if(result)
      goto out;
  }

  /* persist the scheme and handler the transfer is using */
  data->info.conn_scheme = conn->handler->scheme;
  /* conn_protocol can only provide "old" protocols */
  data->info.conn_protocol = (conn->handler->protocol) & CURLPROTO_MASK;
  data->info.used_proxy =
#ifdef CURL_DISABLE_PROXY
    0
#else
    conn->bits.proxy
#endif
    ;

  /* Everything general done, inform filters that they need
   * to prepare for a data transfer. */
  result = Curl_conn_ev_data_setup(data);

out:
  return result;
}

/* Curl_setup_conn() is called after the name resolve initiated in
 * create_conn() is all done.
 *
 * Curl_setup_conn() also handles reused connections
 */
CURLcode Curl_setup_conn(struct Curl_easy *data,
                         bool *protocol_done)
{
  CURLcode result = CURLE_OK;
  struct connectdata *conn = data->conn;

  Curl_pgrsTime(data, TIMER_NAMELOOKUP);

  if(conn->handler->flags & PROTOPT_NONETWORK) {
    /* nothing to setup when not using a network */
    *protocol_done = TRUE;
    return result;
  }

  /* set start time here for timeout purposes in the connect procedure, it
     is later set again for the progress meter purpose */
  conn->now = Curl_now();
  if(!conn->bits.reuse)
    result = Curl_conn_setup(data, conn, FIRSTSOCKET, conn->dns_entry,
                             CURL_CF_SSL_DEFAULT);
  if(!result)
    result = Curl_headers_init(data);

  /* not sure we need this flag to be passed around any more */
  *protocol_done = FALSE;
  return result;
}

CURLcode Curl_connect(struct Curl_easy *data,
                      bool *asyncp,
                      bool *protocol_done)
{
  CURLcode result;
  struct connectdata *conn;

  *asyncp = FALSE; /* assume synchronous resolves by default */

  /* Set the request to virgin state based on transfer settings */
  Curl_req_hard_reset(&data->req, data);

  /* call the stuff that needs to be called */
  result = create_conn(data, &conn, asyncp);

  if(!result) {
    if(CONN_INUSE(conn) > 1)
      /* multiplexed */
      *protocol_done = TRUE;
    else if(!*asyncp) {
      /* DNS resolution is done: that is either because this is a reused
         connection, in which case DNS was unnecessary, or because DNS
         really did finish already (synch resolver/fast async resolve) */
      result = Curl_setup_conn(data, protocol_done);
    }
  }

  if(result == CURLE_NO_CONNECTION_AVAILABLE) {
    return result;
  }
  else if(result && conn) {
    /* We are not allowed to return failure with memory left allocated in the
       connectdata struct, free those here */
    Curl_detach_connection(data);
    Curl_cpool_disconnect(data, conn, TRUE);
  }

  return result;
}

/*
 * Curl_init_do() inits the readwrite session. This is inited each time (in
 * the DO function before the protocol-specific DO functions are invoked) for
 * a transfer, sometimes multiple times on the same Curl_easy. Make sure
 * nothing in here depends on stuff that are setup dynamically for the
 * transfer.
 *
 * Allow this function to get called with 'conn' set to NULL.
 */

CURLcode Curl_init_do(struct Curl_easy *data, struct connectdata *conn)
{
  /* if this is a pushed stream, we need this: */
  CURLcode result;

  if(conn) {
    conn->bits.do_more = FALSE; /* by default there is no curl_do_more() to
                                   use */
    /* if the protocol used does not support wildcards, switch it off */
    if(data->state.wildcardmatch &&
       !(conn->handler->flags & PROTOPT_WILDCARD))
      data->state.wildcardmatch = FALSE;
  }

  data->state.done = FALSE; /* *_done() is not called yet */

  if(data->req.no_body)
    /* in HTTP lingo, no body means using the HEAD request... */
    data->state.httpreq = HTTPREQ_HEAD;

  result = Curl_req_start(&data->req, data);
  if(!result) {
    Curl_speedinit(data);
    Curl_pgrsSetUploadCounter(data, 0);
    Curl_pgrsSetDownloadCounter(data, 0);
  }
  return result;
}

#if defined(USE_HTTP2) || defined(USE_HTTP3)

#ifdef USE_NGHTTP2

static void priority_remove_child(struct Curl_easy *parent,
                                  struct Curl_easy *child)
{
  struct Curl_data_prio_node **pnext = &parent->set.priority.children;
  struct Curl_data_prio_node *pnode = parent->set.priority.children;

  DEBUGASSERT(child->set.priority.parent == parent);
  while(pnode && pnode->data != child) {
    pnext = &pnode->next;
    pnode = pnode->next;
  }

  DEBUGASSERT(pnode);
  if(pnode) {
    *pnext = pnode->next;
    free(pnode);
  }

  child->set.priority.parent = 0;
  child->set.priority.exclusive = FALSE;
}

CURLcode Curl_data_priority_add_child(struct Curl_easy *parent,
                                      struct Curl_easy *child,
                                      bool exclusive)
{
  if(child->set.priority.parent) {
    priority_remove_child(child->set.priority.parent, child);
  }

  if(parent) {
    struct Curl_data_prio_node **tail;
    struct Curl_data_prio_node *pnode;

    pnode = calloc(1, sizeof(*pnode));
    if(!pnode)
      return CURLE_OUT_OF_MEMORY;
    pnode->data = child;

    if(parent->set.priority.children && exclusive) {
      /* exclusive: move all existing children underneath the new child */
      struct Curl_data_prio_node *node = parent->set.priority.children;
      while(node) {
        node->data->set.priority.parent = child;
        node = node->next;
      }

      tail = &child->set.priority.children;
      while(*tail)
        tail = &(*tail)->next;

      DEBUGASSERT(!*tail);
      *tail = parent->set.priority.children;
      parent->set.priority.children = 0;
    }

    tail = &parent->set.priority.children;
    while(*tail) {
      (*tail)->data->set.priority.exclusive = FALSE;
      tail = &(*tail)->next;
    }

    DEBUGASSERT(!*tail);
    *tail = pnode;
  }

  child->set.priority.parent = parent;
  child->set.priority.exclusive = exclusive;
  return CURLE_OK;
}

#endif /* USE_NGHTTP2 */

#ifdef USE_NGHTTP2
static void data_priority_cleanup(struct Curl_easy *data)
{
  while(data->set.priority.children) {
    struct Curl_easy *tmp = data->set.priority.children->data;
    priority_remove_child(data, tmp);
    if(data->set.priority.parent)
      Curl_data_priority_add_child(data->set.priority.parent, tmp, FALSE);
  }

  if(data->set.priority.parent)
    priority_remove_child(data->set.priority.parent, data);
}
#endif

void Curl_data_priority_clear_state(struct Curl_easy *data)
{
  memset(&data->state.priority, 0, sizeof(data->state.priority));
}

#endif /* defined(USE_HTTP2) || defined(USE_HTTP3) */