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