BIO_s_accept.pod 9.4 KB

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  1. =pod
  2. =head1 NAME
  3. BIO_s_accept, BIO_set_accept_name, BIO_set_accept_port, BIO_get_accept_name,
  4. BIO_get_accept_port, BIO_new_accept, BIO_set_nbio_accept, BIO_set_tfo_accept, BIO_set_accept_bios,
  5. BIO_get_peer_name, BIO_get_peer_port,
  6. BIO_get_accept_ip_family, BIO_set_accept_ip_family,
  7. BIO_set_bind_mode, BIO_get_bind_mode, BIO_do_accept - accept BIO
  8. =head1 SYNOPSIS
  9. #include <openssl/bio.h>
  10. const BIO_METHOD *BIO_s_accept(void);
  11. long BIO_set_accept_name(BIO *b, char *name);
  12. char *BIO_get_accept_name(BIO *b);
  13. long BIO_set_accept_port(BIO *b, char *port);
  14. char *BIO_get_accept_port(BIO *b);
  15. BIO *BIO_new_accept(char *host_port);
  16. long BIO_set_nbio_accept(BIO *b, int n);
  17. long BIO_set_tfo_accept(BIO *b, int n);
  18. long BIO_set_accept_bios(BIO *b, char *bio);
  19. char *BIO_get_peer_name(BIO *b);
  20. char *BIO_get_peer_port(BIO *b);
  21. long BIO_get_accept_ip_family(BIO *b);
  22. long BIO_set_accept_ip_family(BIO *b, long family);
  23. long BIO_set_bind_mode(BIO *b, long mode);
  24. long BIO_get_bind_mode(BIO *b);
  25. int BIO_do_accept(BIO *b);
  26. =head1 DESCRIPTION
  27. BIO_s_accept() returns the accept BIO method. This is a wrapper
  28. round the platform's TCP/IP socket accept routines.
  29. Using accept BIOs, TCP/IP connections can be accepted and data
  30. transferred using only BIO routines. In this way any platform
  31. specific operations are hidden by the BIO abstraction.
  32. Read and write operations on an accept BIO will perform I/O
  33. on the underlying connection. If no connection is established
  34. and the port (see below) is set up properly then the BIO
  35. waits for an incoming connection.
  36. Accept BIOs support BIO_puts() but not BIO_gets().
  37. If the close flag is set on an accept BIO then any active
  38. connection on that chain is shutdown and the socket closed when
  39. the BIO is freed.
  40. Calling BIO_reset() on an accept BIO will close any active
  41. connection and reset the BIO into a state where it awaits another
  42. incoming connection.
  43. BIO_get_fd() and BIO_set_fd() can be called to retrieve or set
  44. the accept socket. See L<BIO_s_fd(3)>
  45. BIO_set_accept_name() uses the string B<name> to set the accept
  46. name. The name is represented as a string of the form "host:port",
  47. where "host" is the interface to use and "port" is the port.
  48. The host can be "*" or empty which is interpreted as meaning
  49. any interface. If the host is an IPv6 address, it has to be
  50. enclosed in brackets, for example "[::1]:https". "port" has the
  51. same syntax as the port specified in BIO_set_conn_port() for
  52. connect BIOs, that is it can be a numerical port string or a
  53. string to lookup using getservbyname() and a string table.
  54. BIO_set_accept_port() uses the string B<port> to set the accept
  55. port of BIO I<b>. "port" has the same syntax as the port specified in
  56. BIO_set_conn_port() for connect BIOs, that is it can be a numerical
  57. port string or a string to lookup using getservbyname() and a string
  58. table.
  59. If the given port is C<0> then a random available port is chosen.
  60. It may be queried using BIO_sock_info() and L<BIO_ADDR_service_string(3)>.
  61. BIO_new_accept() combines BIO_new() and BIO_set_accept_name() into
  62. a single call: that is it creates a new accept BIO with port
  63. B<host_port>.
  64. BIO_set_nbio_accept() sets the accept socket to blocking mode
  65. (the default) if B<n> is 0 or non blocking mode if B<n> is 1.
  66. BIO_set_tfo_accept() enables TCP Fast Open on the accept socket
  67. if B<n> is 1 or disables TCP Fast Open if B<n> is 0 (the default).
  68. Setting the value to 1 is equivalent to setting B<BIO_SOCK_TFO>
  69. in BIO_set_bind_mode().
  70. BIO_set_accept_bios() can be used to set a chain of BIOs which
  71. will be duplicated and prepended to the chain when an incoming
  72. connection is received. This is useful if, for example, a
  73. buffering or SSL BIO is required for each connection. The
  74. chain of BIOs must not be freed after this call, they will
  75. be automatically freed when the accept BIO is freed.
  76. BIO_get_accept_ip_family() returns the IP family accepted by the BIO I<b>,
  77. which may be B<BIO_FAMILY_IPV4>, B<BIO_FAMILY_IPV6>, or B<BIO_FAMILY_IPANY>.
  78. BIO_set_accept_ip_family() sets the IP family I<family> accepted by BIO I<b>.
  79. The default is B<BIO_FAMILY_IPANY>.
  80. BIO_set_bind_mode() and BIO_get_bind_mode() set and retrieve
  81. the current bind mode. If B<BIO_BIND_NORMAL> (the default) is set
  82. then another socket cannot be bound to the same port. If
  83. B<BIO_BIND_REUSEADDR> is set then other sockets can bind to the
  84. same port. If B<BIO_BIND_REUSEADDR_IF_UNUSED> is set then and
  85. attempt is first made to use BIO_BIN_NORMAL, if this fails
  86. and the port is not in use then a second attempt is made
  87. using B<BIO_BIND_REUSEADDR>. If B<BIO_SOCK_TFO> is set, then
  88. the socket will be configured to accept TCP Fast Open
  89. connections.
  90. BIO_do_accept() serves two functions. When it is first
  91. called, after the accept BIO has been setup, it will attempt
  92. to create the accept socket and bind an address to it. Second
  93. and subsequent calls to BIO_do_accept() will await an incoming
  94. connection, or request a retry in non blocking mode.
  95. =head1 NOTES
  96. When an accept BIO is at the end of a chain it will await an
  97. incoming connection before processing I/O calls. When an accept
  98. BIO is not at then end of a chain it passes I/O calls to the next
  99. BIO in the chain.
  100. When a connection is established a new socket BIO is created for
  101. the connection and appended to the chain. That is the chain is now
  102. accept->socket. This effectively means that attempting I/O on
  103. an initial accept socket will await an incoming connection then
  104. perform I/O on it.
  105. If any additional BIOs have been set using BIO_set_accept_bios()
  106. then they are placed between the socket and the accept BIO,
  107. that is the chain will be accept->otherbios->socket.
  108. If a server wishes to process multiple connections (as is normally
  109. the case) then the accept BIO must be made available for further
  110. incoming connections. This can be done by waiting for a connection and
  111. then calling:
  112. connection = BIO_pop(accept);
  113. After this call B<connection> will contain a BIO for the recently
  114. established connection and B<accept> will now be a single BIO
  115. again which can be used to await further incoming connections.
  116. If no further connections will be accepted the B<accept> can
  117. be freed using BIO_free().
  118. If only a single connection will be processed it is possible to
  119. perform I/O using the accept BIO itself. This is often undesirable
  120. however because the accept BIO will still accept additional incoming
  121. connections. This can be resolved by using BIO_pop() (see above)
  122. and freeing up the accept BIO after the initial connection.
  123. If the underlying accept socket is nonblocking and BIO_do_accept() is
  124. called to await an incoming connection it is possible for
  125. BIO_should_io_special() with the reason BIO_RR_ACCEPT. If this happens
  126. then it is an indication that an accept attempt would block: the application
  127. should take appropriate action to wait until the underlying socket has
  128. accepted a connection and retry the call.
  129. BIO_set_accept_name(), BIO_get_accept_name(), BIO_set_accept_port(),
  130. BIO_get_accept_port(), BIO_set_nbio_accept(), BIO_set_accept_bios(),
  131. BIO_get_peer_name(), BIO_get_peer_port(),
  132. BIO_get_accept_ip_family(), BIO_set_accept_ip_family(),
  133. BIO_set_bind_mode(), BIO_get_bind_mode() and BIO_do_accept() are macros.
  134. =head1 RETURN VALUES
  135. BIO_do_accept(),
  136. BIO_set_accept_name(), BIO_set_accept_port(), BIO_set_nbio_accept(),
  137. BIO_set_accept_bios(), BIO_set_accept_ip_family(), and BIO_set_bind_mode()
  138. return 1 for success and <=0 for failure.
  139. BIO_get_accept_name() returns the accept name or NULL on error.
  140. BIO_get_peer_name() returns the peer name or NULL on error.
  141. BIO_get_accept_port() returns the accept port as a string or NULL on error.
  142. BIO_get_peer_port() returns the peer port as a string or NULL on error.
  143. BIO_get_accept_ip_family() returns the IP family or <=0 on error.
  144. BIO_get_bind_mode() returns the set of B<BIO_BIND> flags, or <=0 on failure.
  145. BIO_new_accept() returns a BIO or NULL on error.
  146. =head1 EXAMPLES
  147. This example accepts two connections on port 4444, sends messages
  148. down each and finally closes both down.
  149. BIO *abio, *cbio, *cbio2;
  150. /* First call to BIO_accept() sets up accept BIO */
  151. abio = BIO_new_accept("4444");
  152. if (BIO_do_accept(abio) <= 0) {
  153. fprintf(stderr, "Error setting up accept\n");
  154. ERR_print_errors_fp(stderr);
  155. exit(1);
  156. }
  157. /* Wait for incoming connection */
  158. if (BIO_do_accept(abio) <= 0) {
  159. fprintf(stderr, "Error accepting connection\n");
  160. ERR_print_errors_fp(stderr);
  161. exit(1);
  162. }
  163. fprintf(stderr, "Connection 1 established\n");
  164. /* Retrieve BIO for connection */
  165. cbio = BIO_pop(abio);
  166. BIO_puts(cbio, "Connection 1: Sending out Data on initial connection\n");
  167. fprintf(stderr, "Sent out data on connection 1\n");
  168. /* Wait for another connection */
  169. if (BIO_do_accept(abio) <= 0) {
  170. fprintf(stderr, "Error accepting connection\n");
  171. ERR_print_errors_fp(stderr);
  172. exit(1);
  173. }
  174. fprintf(stderr, "Connection 2 established\n");
  175. /* Close accept BIO to refuse further connections */
  176. cbio2 = BIO_pop(abio);
  177. BIO_free(abio);
  178. BIO_puts(cbio2, "Connection 2: Sending out Data on second\n");
  179. fprintf(stderr, "Sent out data on connection 2\n");
  180. BIO_puts(cbio, "Connection 1: Second connection established\n");
  181. /* Close the two established connections */
  182. BIO_free(cbio);
  183. BIO_free(cbio2);
  184. =head1 HISTORY
  185. BIO_set_tfo_accept() was added in OpenSSL 3.1.
  186. =head1 COPYRIGHT
  187. Copyright 2000-2022 The OpenSSL Project Authors. All Rights Reserved.
  188. Licensed under the Apache License 2.0 (the "License"). You may not use
  189. this file except in compliance with the License. You can obtain a copy
  190. in the file LICENSE in the source distribution or at
  191. L<https://www.openssl.org/source/license.html>.
  192. =cut