Accept BIO docs.

doc/crypto/BIO_s_accept.pod

+=pod
+
+=head1 NAME
+
+BIO_s_accept, BIO_set_nbio, BIO_set_accept_port, BIO_get_accept_port,
+BIO_set_nbio_accept, BIO_set_accept_bios, BIO_set_bind_mode,
+BIO_get_bind_mode, BIO_do_accept - accept BIO
+
+=head1 SYNOPSIS
+
+ #include <openssl/bio.h>
+
+ BIO_METHOD * BIO_s_accept(void);
+
+ #define BIO_set_accept_port(b,name) BIO_ctrl(b,BIO_C_SET_ACCEPT,0,(char *)name)
+ #define BIO_get_accept_port(b)	BIO_ptr_ctrl(b,BIO_C_GET_ACCEPT,0)
+
+ BIO *BIO_new_accept(char *host_port);
+
+ #define BIO_set_nbio_accept(b,n) BIO_ctrl(b,BIO_C_SET_ACCEPT,1,(n)?"a":NULL)
+ #define BIO_set_accept_bios(b,bio) BIO_ctrl(b,BIO_C_SET_ACCEPT,2,(char *)bio)
+
+ #define BIO_set_bind_mode(b,mode) BIO_ctrl(b,BIO_C_SET_BIND_MODE,mode,NULL)
+ #define BIO_get_bind_mode(b,mode) BIO_ctrl(b,BIO_C_GET_BIND_MODE,0,NULL)
+
+ #define BIO_BIND_NORMAL		0
+ #define BIO_BIND_REUSEADDR_IF_UNUSED	1
+ #define BIO_BIND_REUSEADDR		2
+
+ #define BIO_do_accept(b)	BIO_do_handshake(b)
+
+=head1 DESCRIPTION
+
+BIO_s_accept() returns the accept BIO method. This is a wrapper
+round the platform's TCP/IP socket accept routines.
+
+Using accept BIOs TCP/IP connections can be accepted and data
+transferred using only BIO routines. In this way any platform
+specific operations are hidden by the BIO abstraction.
+
+Read and write operations on an accept BIO will perform I/O
+on the underlying connection. If no connection is established
+and the port (see below) is set up properly then the BIO
+waits for an incoming connection.
+
+Accept BIOs support BIO_puts() but not BIO_gets().
+
+If the close flag is set on an accept BIO then any active
+connection on that chain is shutdown and the socket closed when
+the BIO is freed.
+
+Calling BIO_reset() on a accept BIO will close any active
+connection and reset the BIO into a state where it awaits another
+incoming connection.
+
+BIO_get_fd() and BIO_set_fd() can be called to retrieve or set
+the accept socket. See L<BIO_s_fd(3)|BIO_s_fd(3)>
+
+BIO_set_accept_port() uses the string B<name> to set the accept
+port. The port is represented as a string of the form "host:port",
+where "host" is the interface to use and "port" is the port.
+Either or both values can be "*" which is interpreted as meaning
+any interface or port respectively. "port" has the same syntax
+as the port specified in BIO_set_conn_port() for connect BIOs,
+that is it can be a numerical port string or a string to lookup
+using getservbyname() and a string table.
+
+BIO_new_accept() combines BIO_new() and BIO_set_accept_port() into
+a single call: that is it creates a new accept BIO with port
+B<host_port>.
+
+BIO_set_nbio_accept() sets the accept socket to blocking mode
+(the default) if B<n> is 0 or non blocking mode if B<n> is 1.
+
+BIO_set_accept_bios() can be used to set a chain of BIOs which
+will be duplicated and prepended to the chain when an incoming
+connection is received. This is useful if, for example, a 
+buffering BIO is required for each connection.
+
+BIO_set_bind_mode() and BIO_get_bind_mode() set and retrieve
+the current bind mode. If BIO_BIND_NORMAL (the default) is set
+then another socket cannot be bound to the same port. If
+BIO_BIND_REUSEADDR is set then other sockets can bind to the
+same port. If BIO_BIND_REUSEADDR_IF_UNUSED is set then and
+attempt is first made to use BIO_BIN_NORMAL, if this fails
+and the port is not in use then a second attempt is made
+using BIO_BIND_REUSEADDR.
+
+BIO_do_accept() serves two functions. When it is first
+called, after the accept BIO has been setup, it will attempt
+to create the accept socket and bind an address to it. Second
+and subsequent calls to BIO_do_accept() will await an incoming
+connection.
+
+=head1 NOTES
+
+When an accept BIO is at the end of a chain it will await an
+incoming connection before processing I/O calls. When an accept
+BIO is not at then end of a chain it passes I/O calls to the next
+BIO in the chain.
+
+When a connection is established a new socket BIO is created for
+the conection and appended to the chain. That is the chain is now
+accept->socket. This effectively means that attempting I/O on
+an initial accept socket will await an incoming connection then
+perform I/O on it.
+
+If any additional BIOs have been set using BIO_set_accept_bios()
+then they are placed between the socket and the accept BIO,
+that is the chain will be accept->otherbios->socket.
+
+If a server wishes to process multiple connections (as is normally
+the case) then the accept BIO must be made available for further
+incoming connections. This can be done by waiting for a connection and
+then calling:
+
+ connection = BIO_pop(accept);
+
+After this call B<connection> will contain a BIO for the recently
+established connection and B<accept> will now be a single BIO
+again which can be used to await further incoming connections.
+If no further connections will be accepted the B<accept> can
+be freed using BIO_free().
+
+If only a single connection will be processed it is possible to
+perform I/O using the accept BIO itself. This is often undesirable
+however because the accept BIO will still accept additional incoming
+connections. This can be resolved by using BIO_pop() (see above)
+and freeing up the accept BIO after the initial connection.
+
+=head1 RETURN VALUES
+
+TBA
+
+=head1 EXAMPLE
+
+This example accepts two connections on port 4444, sends messages
+down each and finally closes both down.
+
+ BIO *abio, *cbio, *cbio2;
+ ERR_load_crypto_strings();
+ abio = BIO_new_accept("4444");
+
+ /* First call to BIO_accept() sets up accept BIO */
+ if(BIO_do_accept(abio) <= 0) {
+	fprintf(stderr, "Error setting up accept\n");
+	ERR_print_errors_fp(stderr);
+	exit(0);		
+ }
+
+ /* Wait for incoming connection */
+ if(BIO_do_accept(abio) <= 0) {
+	fprintf(stderr, "Error accepting connection\n");
+	ERR_print_errors_fp(stderr);
+	exit(0);		
+ }
+ fprintf(stderr, "Connection 1 established\n");
+ /* Retrieve BIO for connection */
+ cbio = BIO_pop(abio);
+ BIO_puts(cbio, "Connection 1: Sending out Data on initial connection\n");
+ fprintf(stderr, "Sent out data on connection 1\n");
+ /* Wait for another connection */
+ if(BIO_do_accept(abio) <= 0) {
+	fprintf(stderr, "Error accepting connection\n");
+	ERR_print_errors_fp(stderr);
+	exit(0);		
+ }
+ fprintf(stderr, "Connection 2 established\n");
+ /* Close accept BIO to refuse further connections */
+ cbio2 = BIO_pop(abio);
+ BIO_free(abio);
+ BIO_puts(cbio2, "Connection 2: Sending out Data on second\n");
+ fprintf(stderr, "Sent out data on connection 2\n");
+
+ BIO_puts(cbio, "Connection 1: Second connection established\n");
+ /* Close the two established connections */
+ BIO_free(cbio);
+ BIO_free(cbio2);
+
+=head1 SEE ALSO
+
+TBA