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 of BIO I<b>. "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. 80If the given port is C<0> then a random available port is chosen. 81It may be queried using BIO_sock_info() and L<BIO_ADDR_service_string(3)>. 82 83BIO_new_accept() combines BIO_new() and BIO_set_accept_name() into 84a single call: that is it creates a new accept BIO with port 85B<host_port>. 86 87BIO_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 90BIO_set_accept_bios() can be used to set a chain of BIOs which 91will be duplicated and prepended to the chain when an incoming 92connection is received. This is useful if, for example, a 93buffering or SSL BIO is required for each connection. The 94chain of BIOs must not be freed after this call, they will 95be automatically freed when the accept BIO is freed. 96 97BIO_get_accept_ip_family() returns the IP family accepted by the BIO I<b>, 98which may be B<BIO_FAMILY_IPV4>, B<BIO_FAMILY_IPV6>, or B<BIO_FAMILY_IPANY>. 99 100BIO_set_accept_ip_family() sets the IP family I<family> accepted by BIO I<b>. 101The default is B<BIO_FAMILY_IPANY>. 102 103BIO_set_bind_mode() and BIO_get_bind_mode() set and retrieve 104the current bind mode. If B<BIO_BIND_NORMAL> (the default) is set 105then another socket cannot be bound to the same port. If 106B<BIO_BIND_REUSEADDR> is set then other sockets can bind to the 107same port. If B<BIO_BIND_REUSEADDR_IF_UNUSED> is set then and 108attempt is first made to use BIO_BIN_NORMAL, if this fails 109and the port is not in use then a second attempt is made 110using B<BIO_BIND_REUSEADDR>. 111 112BIO_do_accept() serves two functions. When it is first 113called, after the accept BIO has been setup, it will attempt 114to create the accept socket and bind an address to it. Second 115and subsequent calls to BIO_do_accept() will await an incoming 116connection, or request a retry in non blocking mode. 117 118=head1 NOTES 119 120When an accept BIO is at the end of a chain it will await an 121incoming connection before processing I/O calls. When an accept 122BIO is not at then end of a chain it passes I/O calls to the next 123BIO in the chain. 124 125When a connection is established a new socket BIO is created for 126the connection and appended to the chain. That is the chain is now 127accept->socket. This effectively means that attempting I/O on 128an initial accept socket will await an incoming connection then 129perform I/O on it. 130 131If any additional BIOs have been set using BIO_set_accept_bios() 132then they are placed between the socket and the accept BIO, 133that is the chain will be accept->otherbios->socket. 134 135If a server wishes to process multiple connections (as is normally 136the case) then the accept BIO must be made available for further 137incoming connections. This can be done by waiting for a connection and 138then calling: 139 140 connection = BIO_pop(accept); 141 142After this call B<connection> will contain a BIO for the recently 143established connection and B<accept> will now be a single BIO 144again which can be used to await further incoming connections. 145If no further connections will be accepted the B<accept> can 146be freed using BIO_free(). 147 148If only a single connection will be processed it is possible to 149perform I/O using the accept BIO itself. This is often undesirable 150however because the accept BIO will still accept additional incoming 151connections. This can be resolved by using BIO_pop() (see above) 152and freeing up the accept BIO after the initial connection. 153 154If the underlying accept socket is nonblocking and BIO_do_accept() is 155called to await an incoming connection it is possible for 156BIO_should_io_special() with the reason BIO_RR_ACCEPT. If this happens 157then it is an indication that an accept attempt would block: the application 158should take appropriate action to wait until the underlying socket has 159accepted a connection and retry the call. 160 161BIO_set_accept_name(), BIO_get_accept_name(), BIO_set_accept_port(), 162BIO_get_accept_port(), BIO_set_nbio_accept(), BIO_set_accept_bios(), 163BIO_get_peer_name(), BIO_get_peer_port(), 164BIO_get_accept_ip_family(), BIO_set_accept_ip_family(), 165BIO_set_bind_mode(), BIO_get_bind_mode() and BIO_do_accept() are macros. 166 167=head1 RETURN VALUES 168 169BIO_do_accept(), 170BIO_set_accept_name(), BIO_set_accept_port(), BIO_set_nbio_accept(), 171BIO_set_accept_bios(), BIO_set_accept_ip_family(), and BIO_set_bind_mode() 172return 1 for success and <=0 for failure. 173 174BIO_get_accept_name() returns the accept name or NULL on error. 175BIO_get_peer_name() returns the peer name or NULL on error. 176 177BIO_get_accept_port() returns the accept port as a string or NULL on error. 178BIO_get_peer_port() returns the peer port as a string or NULL on error. 179BIO_get_accept_ip_family() returns the IP family or <=0 on error. 180 181BIO_get_bind_mode() returns the set of B<BIO_BIND> flags, or <=0 on failure. 182 183BIO_new_accept() returns a BIO or NULL on error. 184 185=head1 EXAMPLES 186 187This example accepts two connections on port 4444, sends messages 188down each and finally closes both down. 189 190 BIO *abio, *cbio, *cbio2; 191 192 /* First call to BIO_do_accept() sets up accept BIO */ 193 abio = BIO_new_accept("4444"); 194 if (BIO_do_accept(abio) <= 0) { 195 fprintf(stderr, "Error setting up accept\n"); 196 ERR_print_errors_fp(stderr); 197 exit(1); 198 } 199 200 /* Wait for incoming connection */ 201 if (BIO_do_accept(abio) <= 0) { 202 fprintf(stderr, "Error accepting connection\n"); 203 ERR_print_errors_fp(stderr); 204 exit(1); 205 } 206 fprintf(stderr, "Connection 1 established\n"); 207 208 /* Retrieve BIO for connection */ 209 cbio = BIO_pop(abio); 210 BIO_puts(cbio, "Connection 1: Sending out Data on initial connection\n"); 211 fprintf(stderr, "Sent out data on connection 1\n"); 212 213 /* Wait for another connection */ 214 if (BIO_do_accept(abio) <= 0) { 215 fprintf(stderr, "Error accepting connection\n"); 216 ERR_print_errors_fp(stderr); 217 exit(1); 218 } 219 fprintf(stderr, "Connection 2 established\n"); 220 221 /* Close accept BIO to refuse further connections */ 222 cbio2 = BIO_pop(abio); 223 BIO_free(abio); 224 BIO_puts(cbio2, "Connection 2: Sending out Data on second\n"); 225 fprintf(stderr, "Sent out data on connection 2\n"); 226 227 BIO_puts(cbio, "Connection 1: Second connection established\n"); 228 229 /* Close the two established connections */ 230 BIO_free(cbio); 231 BIO_free(cbio2); 232 233=head1 COPYRIGHT 234 235Copyright 2000-2022 The OpenSSL Project Authors. All Rights Reserved. 236 237Licensed under the Apache License 2.0 (the "License"). You may not use 238this file except in compliance with the License. You can obtain a copy 239in the file LICENSE in the source distribution or at 240L<https://www.openssl.org/source/license.html>. 241 242=cut 243