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