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- #include <sys/socket.h>
- #include <netinet/in.h>
- #include <netinet/tcp.h>
- #include <netdb.h>
- #include <arpa/inet.h>
- #include <stdint.h>
- #include <string.h>
- #include <poll.h>
- #include <time.h>
- #include <ctype.h>
- #include <unistd.h>
- #include <errno.h>
- #include <pthread.h>
- #include "stdio_impl.h"
- #include "syscall.h"
- #include "lookup.h"
- static void cleanup(void *p)
- {
- struct pollfd *pfd = p;
- for (int i=0; pfd[i].fd >= -1; i++)
- if (pfd[i].fd >= 0) __syscall(SYS_close, pfd[i].fd);
- }
- static unsigned long mtime()
- {
- struct timespec ts;
- clock_gettime(CLOCK_REALTIME, &ts);
- return (unsigned long)ts.tv_sec * 1000
- + ts.tv_nsec / 1000000;
- }
- static int start_tcp(struct pollfd *pfd, int family, const void *sa, socklen_t sl, const unsigned char *q, int ql)
- {
- struct msghdr mh = {
- .msg_name = (void *)sa,
- .msg_namelen = sl,
- .msg_iovlen = 2,
- .msg_iov = (struct iovec [2]){
- { .iov_base = (uint8_t[]){ ql>>8, ql }, .iov_len = 2 },
- { .iov_base = (void *)q, .iov_len = ql } }
- };
- int r;
- int fd = socket(family, SOCK_STREAM|SOCK_CLOEXEC|SOCK_NONBLOCK, 0);
- pfd->fd = fd;
- pfd->events = POLLOUT;
- if (!setsockopt(fd, IPPROTO_TCP, TCP_FASTOPEN_CONNECT,
- &(int){1}, sizeof(int))) {
- r = sendmsg(fd, &mh, MSG_FASTOPEN|MSG_NOSIGNAL);
- if (r == ql+2) pfd->events = POLLIN;
- if (r >= 0) return r;
- if (errno == EINPROGRESS) return 0;
- }
- r = connect(fd, sa, sl);
- if (!r || errno == EINPROGRESS) return 0;
- close(fd);
- pfd->fd = -1;
- return -1;
- }
- static void step_mh(struct msghdr *mh, size_t n)
- {
- /* Adjust iovec in msghdr to skip first n bytes. */
- while (mh->msg_iovlen && n >= mh->msg_iov->iov_len) {
- n -= mh->msg_iov->iov_len;
- mh->msg_iov++;
- mh->msg_iovlen--;
- }
- if (!mh->msg_iovlen) return;
- mh->msg_iov->iov_base = (char *)mh->msg_iov->iov_base + n;
- mh->msg_iov->iov_len -= n;
- }
- /* Internal contract for __res_msend[_rc]: asize must be >=512, nqueries
- * must be sufficiently small to be safe as VLA size. In practice it's
- * either 1 or 2, anyway. */
- int __res_msend_rc(int nqueries, const unsigned char *const *queries,
- const int *qlens, unsigned char *const *answers, int *alens, int asize,
- const struct resolvconf *conf)
- {
- int fd;
- int timeout, attempts, retry_interval, servfail_retry;
- union {
- struct sockaddr_in sin;
- struct sockaddr_in6 sin6;
- } sa = {0}, ns[MAXNS] = {{0}};
- socklen_t sl = sizeof sa.sin;
- int nns = 0;
- int family = AF_INET;
- int rlen;
- int next;
- int i, j;
- int cs;
- struct pollfd pfd[nqueries+2];
- int qpos[nqueries], apos[nqueries];
- unsigned char alen_buf[nqueries][2];
- int r;
- unsigned long t0, t1, t2;
- pthread_setcancelstate(PTHREAD_CANCEL_DISABLE, &cs);
- timeout = 1000*conf->timeout;
- attempts = conf->attempts;
- for (nns=0; nns<conf->nns; nns++) {
- const struct address *iplit = &conf->ns[nns];
- if (iplit->family == AF_INET) {
- memcpy(&ns[nns].sin.sin_addr, iplit->addr, 4);
- ns[nns].sin.sin_port = htons(53);
- ns[nns].sin.sin_family = AF_INET;
- } else {
- sl = sizeof sa.sin6;
- memcpy(&ns[nns].sin6.sin6_addr, iplit->addr, 16);
- ns[nns].sin6.sin6_port = htons(53);
- ns[nns].sin6.sin6_scope_id = iplit->scopeid;
- ns[nns].sin6.sin6_family = family = AF_INET6;
- }
- }
- /* Get local address and open/bind a socket */
- fd = socket(family, SOCK_DGRAM|SOCK_CLOEXEC|SOCK_NONBLOCK, 0);
- /* Handle case where system lacks IPv6 support */
- if (fd < 0 && family == AF_INET6 && errno == EAFNOSUPPORT) {
- for (i=0; i<nns && conf->ns[nns].family == AF_INET6; i++);
- if (i==nns) {
- pthread_setcancelstate(cs, 0);
- return -1;
- }
- fd = socket(AF_INET, SOCK_DGRAM|SOCK_CLOEXEC|SOCK_NONBLOCK, 0);
- family = AF_INET;
- sl = sizeof sa.sin;
- }
- sa.sin.sin_family = family;
- if (fd < 0 || bind(fd, (void *)&sa, sl) < 0) {
- if (fd >= 0) close(fd);
- pthread_setcancelstate(cs, 0);
- return -1;
- }
- /* Past this point, there are no errors. Each individual query will
- * yield either no reply (indicated by zero length) or an answer
- * packet which is up to the caller to interpret. */
- for (i=0; i<nqueries; i++) pfd[i].fd = -1;
- pfd[nqueries].fd = fd;
- pfd[nqueries].events = POLLIN;
- pfd[nqueries+1].fd = -2;
- pthread_cleanup_push(cleanup, pfd);
- pthread_setcancelstate(cs, 0);
- /* Convert any IPv4 addresses in a mixed environment to v4-mapped */
- if (family == AF_INET6) {
- setsockopt(fd, IPPROTO_IPV6, IPV6_V6ONLY, &(int){0}, sizeof 0);
- for (i=0; i<nns; i++) {
- if (ns[i].sin.sin_family != AF_INET) continue;
- memcpy(ns[i].sin6.sin6_addr.s6_addr+12,
- &ns[i].sin.sin_addr, 4);
- memcpy(ns[i].sin6.sin6_addr.s6_addr,
- "\0\0\0\0\0\0\0\0\0\0\xff\xff", 12);
- ns[i].sin6.sin6_family = AF_INET6;
- ns[i].sin6.sin6_flowinfo = 0;
- ns[i].sin6.sin6_scope_id = 0;
- }
- }
- memset(alens, 0, sizeof *alens * nqueries);
- retry_interval = timeout / attempts;
- next = 0;
- t0 = t2 = mtime();
- t1 = t2 - retry_interval;
- for (; t2-t0 < timeout; t2=mtime()) {
- /* This is the loop exit condition: that all queries
- * have an accepted answer. */
- for (i=0; i<nqueries && alens[i]>0; i++);
- if (i==nqueries) break;
- if (t2-t1 >= retry_interval) {
- /* Query all configured namservers in parallel */
- for (i=0; i<nqueries; i++)
- if (!alens[i])
- for (j=0; j<nns; j++)
- sendto(fd, queries[i],
- qlens[i], MSG_NOSIGNAL,
- (void *)&ns[j], sl);
- t1 = t2;
- servfail_retry = 2 * nqueries;
- }
- /* Wait for a response, or until time to retry */
- if (poll(pfd, nqueries+1, t1+retry_interval-t2) <= 0) continue;
- while (next < nqueries) {
- struct msghdr mh = {
- .msg_name = (void *)&sa,
- .msg_namelen = sl,
- .msg_iovlen = 1,
- .msg_iov = (struct iovec []){
- { .iov_base = (void *)answers[next],
- .iov_len = asize }
- }
- };
- rlen = recvmsg(fd, &mh, 0);
- if (rlen < 0) break;
- /* Ignore non-identifiable packets */
- if (rlen < 4) continue;
- /* Ignore replies from addresses we didn't send to */
- for (j=0; j<nns && memcmp(ns+j, &sa, sl); j++);
- if (j==nns) continue;
- /* Find which query this answer goes with, if any */
- for (i=next; i<nqueries && (
- answers[next][0] != queries[i][0] ||
- answers[next][1] != queries[i][1] ); i++);
- if (i==nqueries) continue;
- if (alens[i]) continue;
- /* Only accept positive or negative responses;
- * retry immediately on server failure, and ignore
- * all other codes such as refusal. */
- switch (answers[next][3] & 15) {
- case 0:
- case 3:
- break;
- case 2:
- if (servfail_retry && servfail_retry--)
- sendto(fd, queries[i],
- qlens[i], MSG_NOSIGNAL,
- (void *)&ns[j], sl);
- default:
- continue;
- }
- /* Store answer in the right slot, or update next
- * available temp slot if it's already in place. */
- alens[i] = rlen;
- if (i == next)
- for (; next<nqueries && alens[next]; next++);
- else
- memcpy(answers[i], answers[next], rlen);
- /* Ignore further UDP if all slots full or TCP-mode */
- if (next == nqueries) pfd[nqueries].events = 0;
- /* If answer is truncated (TC bit), fallback to TCP */
- if ((answers[i][2] & 2) || (mh.msg_flags & MSG_TRUNC)) {
- alens[i] = -1;
- pthread_setcancelstate(PTHREAD_CANCEL_DISABLE, 0);
- r = start_tcp(pfd+i, family, ns+j, sl, queries[i], qlens[i]);
- pthread_setcancelstate(cs, 0);
- if (r >= 0) {
- qpos[i] = r;
- apos[i] = 0;
- }
- continue;
- }
- }
- for (i=0; i<nqueries; i++) if (pfd[i].revents & POLLOUT) {
- struct msghdr mh = {
- .msg_iovlen = 2,
- .msg_iov = (struct iovec [2]){
- { .iov_base = (uint8_t[]){ qlens[i]>>8, qlens[i] }, .iov_len = 2 },
- { .iov_base = (void *)queries[i], .iov_len = qlens[i] } }
- };
- step_mh(&mh, qpos[i]);
- r = sendmsg(pfd[i].fd, &mh, MSG_NOSIGNAL);
- if (r < 0) goto out;
- qpos[i] += r;
- if (qpos[i] == qlens[i]+2)
- pfd[i].events = POLLIN;
- }
- for (i=0; i<nqueries; i++) if (pfd[i].revents & POLLIN) {
- struct msghdr mh = {
- .msg_iovlen = 2,
- .msg_iov = (struct iovec [2]){
- { .iov_base = alen_buf[i], .iov_len = 2 },
- { .iov_base = answers[i], .iov_len = asize } }
- };
- step_mh(&mh, apos[i]);
- r = recvmsg(pfd[i].fd, &mh, 0);
- if (r < 0) goto out;
- apos[i] += r;
- if (apos[i] < 2) continue;
- int alen = alen_buf[i][0]*256 + alen_buf[i][1];
- if (alen < 13) goto out;
- if (apos[i] < alen+2 && apos[i] < asize+2)
- continue;
- int rcode = answers[i][3] & 15;
- if (rcode != 0 && rcode != 3)
- goto out;
- /* Storing the length here commits the accepted answer.
- * Immediately close TCP socket so as not to consume
- * resources we no longer need. */
- alens[i] = alen;
- __syscall(SYS_close, pfd[i].fd);
- pfd[i].fd = -1;
- }
- }
- out:
- pthread_cleanup_pop(1);
- /* Disregard any incomplete TCP results */
- for (i=0; i<nqueries; i++) if (alens[i]<0) alens[i] = 0;
- return 0;
- }
- int __res_msend(int nqueries, const unsigned char *const *queries,
- const int *qlens, unsigned char *const *answers, int *alens, int asize)
- {
- struct resolvconf conf;
- if (__get_resolv_conf(&conf, 0, 0) < 0) return -1;
- return __res_msend_rc(nqueries, queries, qlens, answers, alens, asize, &conf);
- }
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