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 non-blocking 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 EXAMPLE
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 2000-2018 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