doc/man3/BIO_s_accept.pod

   1 =pod
   2
   3 =head1 NAME
   4
   5 BIO_s_accept, BIO_set_accept_name, BIO_set_accept_port, BIO_get_accept_name,
   6 BIO_get_accept_port, BIO_new_accept, BIO_set_nbio_accept, BIO_set_accept_bios,
   7 BIO_get_peer_name, BIO_get_peer_port,
   8 BIO_get_accept_ip_family, BIO_set_accept_ip_family,
   9 BIO_set_bind_mode, BIO_get_bind_mode, BIO_do_accept - accept BIO
  10
  11 =head1 SYNOPSIS
  12
  13  #include <openssl/bio.h>
  14
  15  const BIO_METHOD *BIO_s_accept(void);
  16
  17  long BIO_set_accept_name(BIO *b, char *name);
  18  char *BIO_get_accept_name(BIO *b);
  19
  20  long BIO_set_accept_port(BIO *b, char *port);
  21  char *BIO_get_accept_port(BIO *b);
  22
  23  BIO *BIO_new_accept(char *host_port);
  24
  25  long BIO_set_nbio_accept(BIO *b, int n);
  26  long BIO_set_accept_bios(BIO *b, char *bio);
  27
  28  char *BIO_get_peer_name(BIO *b);
  29  char *BIO_get_peer_port(BIO *b);
  30  long BIO_get_accept_ip_family(BIO *b);
  31  long BIO_set_accept_ip_family(BIO *b, long family);
  32
  33  long BIO_set_bind_mode(BIO *b, long mode);
  34  long BIO_get_bind_mode(BIO *b);
  35
  36  int BIO_do_accept(BIO *b);
  37
  38 =head1 DESCRIPTION
  39
  40 BIO_s_accept() returns the accept BIO method. This is a wrapper
  41 round the platform's TCP/IP socket accept routines.
  42
  43 Using accept BIOs, TCP/IP connections can be accepted and data
  44 transferred using only BIO routines. In this way any platform
  45 specific operations are hidden by the BIO abstraction.
  46
  47 Read and write operations on an accept BIO will perform I/O
  48 on the underlying connection. If no connection is established
  49 and the port (see below) is set up properly then the BIO
  50 waits for an incoming connection.
  51
  52 Accept BIOs support BIO_puts() but not BIO_gets().
  53
  54 If the close flag is set on an accept BIO then any active
  55 connection on that chain is shutdown and the socket closed when
  56 the BIO is freed.
  57
  58 Calling BIO_reset() on an accept BIO will close any active
  59 connection and reset the BIO into a state where it awaits another
  60 incoming connection.
  61
  62 BIO_get_fd() and BIO_set_fd() can be called to retrieve or set
  63 the accept socket. See L<BIO_s_fd(3)>
  64
  65 BIO_set_accept_name() uses the string B<name> to set the accept
  66 name. The name is represented as a string of the form "host:port",
  67 where "host" is the interface to use and "port" is the port.
  68 The host can be "*" or empty which is interpreted as meaning
  69 any interface.  If the host is an IPv6 address, it has to be
  70 enclosed in brackets, for example "[::1]:https".  "port" has the
  71 same syntax as the port specified in BIO_set_conn_port() for
  72 connect BIOs, that is it can be a numerical port string or a
  73 string to lookup using getservbyname() and a string table.
  74
  75 BIO_set_accept_port() uses the string B<port> to set the accept
  76 port of BIO I<b>.  "port" has the same syntax as the port specified in
  77 BIO_set_conn_port() for connect BIOs, that is it can be a numerical
  78 port string or a string to lookup using getservbyname() and a string
  79 table.
  80 If the given port is C<0> then a random available port is chosen.
  81 It may be queried using BIO_sock_info() and L<BIO_ADDR_service_string(3)>.
  82
  83 BIO_new_accept() combines BIO_new() and BIO_set_accept_name() into
  84 a single call: that is it creates a new accept BIO with port
  85 B<host_port>.
  86
  87 BIO_set_nbio_accept() sets the accept socket to blocking mode
  88 (the default) if B<n> is 0 or non blocking mode if B<n> is 1.
  89
  90 BIO_set_accept_bios() can be used to set a chain of BIOs which
  91 will be duplicated and prepended to the chain when an incoming
  92 connection is received. This is useful if, for example, a
  93 buffering or SSL BIO is required for each connection. The
  94 chain of BIOs must not be freed after this call, they will
  95 be automatically freed when the accept BIO is freed.
  96
  97 BIO_set_bind_mode() and BIO_get_bind_mode() set and retrieve
  98 the current bind mode. If B<BIO_BIND_NORMAL> (the default) is set
  99 then another socket cannot be bound to the same port. If
 100 B<BIO_BIND_REUSEADDR> is set then other sockets can bind to the
 101 same port. If B<BIO_BIND_REUSEADDR_IF_UNUSED> is set then and
 102 attempt is first made to use BIO_BIN_NORMAL, if this fails
 103 and the port is not in use then a second attempt is made
 104 using B<BIO_BIND_REUSEADDR>.
 105
 106 BIO_do_accept() serves two functions. When it is first
 107 called, after the accept BIO has been setup, it will attempt
 108 to create the accept socket and bind an address to it. Second
 109 and subsequent calls to BIO_do_accept() will await an incoming
 110 connection, or request a retry in non blocking mode.
 111
 112 =head1 NOTES
 113
 114 When an accept BIO is at the end of a chain it will await an
 115 incoming connection before processing I/O calls. When an accept
 116 BIO is not at then end of a chain it passes I/O calls to the next
 117 BIO in the chain.
 118
 119 When a connection is established a new socket BIO is created for
 120 the connection and appended to the chain. That is the chain is now
 121 accept->socket. This effectively means that attempting I/O on
 122 an initial accept socket will await an incoming connection then
 123 perform I/O on it.
 124
 125 If any additional BIOs have been set using BIO_set_accept_bios()
 126 then they are placed between the socket and the accept BIO,
 127 that is the chain will be accept->otherbios->socket.
 128
 129 If a server wishes to process multiple connections (as is normally
 130 the case) then the accept BIO must be made available for further
 131 incoming connections. This can be done by waiting for a connection and
 132 then calling:
 133
 134  connection = BIO_pop(accept);
 135
 136 After this call B<connection> will contain a BIO for the recently
 137 established connection and B<accept> will now be a single BIO
 138 again which can be used to await further incoming connections.
 139 If no further connections will be accepted the B<accept> can
 140 be freed using BIO_free().
 141
 142 If only a single connection will be processed it is possible to
 143 perform I/O using the accept BIO itself. This is often undesirable
 144 however because the accept BIO will still accept additional incoming
 145 connections. This can be resolved by using BIO_pop() (see above)
 146 and freeing up the accept BIO after the initial connection.
 147
 148 If the underlying accept socket is nonblocking and BIO_do_accept() is
 149 called to await an incoming connection it is possible for
 150 BIO_should_io_special() with the reason BIO_RR_ACCEPT. If this happens
 151 then it is an indication that an accept attempt would block: the application
 152 should take appropriate action to wait until the underlying socket has
 153 accepted a connection and retry the call.
 154
 155 BIO_set_accept_name(), BIO_get_accept_name(), BIO_set_accept_port(),
 156 BIO_get_accept_port(), BIO_set_nbio_accept(), BIO_set_accept_bios(),
 157 BIO_get_peer_name(), BIO_get_peer_port(),
 158 BIO_get_accept_ip_family(), BIO_set_accept_ip_family(),
 159 BIO_set_bind_mode(), BIO_get_bind_mode() and BIO_do_accept() are macros.
 160
 161 =head1 RETURN VALUES
 162
 163 BIO_do_accept(),
 164 BIO_set_accept_name(), BIO_set_accept_port(), BIO_set_nbio_accept(),
 165 BIO_set_accept_bios(), BIO_set_accept_ip_family(), and BIO_set_bind_mode()
 166 return 1 for success and 0 or -1 for failure.
 167
 168 BIO_get_accept_name() returns the accept name or NULL on error.
 169 BIO_get_peer_name() returns the peer name or NULL on error.
 170
 171 BIO_get_accept_port() returns the accept port as a string or NULL on error.
 172 BIO_get_peer_port() returns the peer port as a string or NULL on error.
 173 BIO_get_accept_ip_family() returns the IP family or -1 on error.
 174
 175 BIO_get_bind_mode() returns the set of B<BIO_BIND> flags, or -1 on failure.
 176
 177 BIO_new_accept() returns a BIO or NULL on error.
 178
 179 =head1 EXAMPLES
 180
 181 This example accepts two connections on port 4444, sends messages
 182 down each and finally closes both down.
 183
 184  BIO *abio, *cbio, *cbio2;
 185
 186  /* First call to BIO_accept() sets up accept BIO */
 187  abio = BIO_new_accept("4444");
 188  if (BIO_do_accept(abio) <= 0) {
 189      fprintf(stderr, "Error setting up accept\n");
 190      ERR_print_errors_fp(stderr);
 191      exit(1);
 192  }
 193
 194  /* Wait for incoming connection */
 195  if (BIO_do_accept(abio) <= 0) {
 196      fprintf(stderr, "Error accepting connection\n");
 197      ERR_print_errors_fp(stderr);
 198      exit(1);
 199  }
 200  fprintf(stderr, "Connection 1 established\n");
 201
 202  /* Retrieve BIO for connection */
 203  cbio = BIO_pop(abio);
 204  BIO_puts(cbio, "Connection 1: Sending out Data on initial connection\n");
 205  fprintf(stderr, "Sent out data on connection 1\n");
 206
 207  /* Wait for another connection */
 208  if (BIO_do_accept(abio) <= 0) {
 209      fprintf(stderr, "Error accepting connection\n");
 210      ERR_print_errors_fp(stderr);
 211      exit(1);
 212  }
 213  fprintf(stderr, "Connection 2 established\n");
 214
 215  /* Close accept BIO to refuse further connections */
 216  cbio2 = BIO_pop(abio);
 217  BIO_free(abio);
 218  BIO_puts(cbio2, "Connection 2: Sending out Data on second\n");
 219  fprintf(stderr, "Sent out data on connection 2\n");
 220
 221  BIO_puts(cbio, "Connection 1: Second connection established\n");
 222
 223  /* Close the two established connections */
 224  BIO_free(cbio);
 225  BIO_free(cbio2);
 226
 227 =head1 COPYRIGHT
 228
 229 Copyright 2000-2020 The OpenSSL Project Authors. All Rights Reserved.
 230
 231 Licensed under the Apache License 2.0 (the "License").  You may not use
 232 this file except in compliance with the License.  You can obtain a copy
 233 in the file LICENSE in the source distribution or at
 234 L<https://www.openssl.org/source/license.html>.
 235
 236 =cut