Pierre Pronchery
4757b351ea
Migrate to OpenSSL 3.5 in advance of FreeBSD 15.0. OpenSSL 3.0 will be EOL after 2026-09-07. Approved by: philip (mentor) Sponsored by: Alpha-Omega Beach Cleaning Project Sponsored by: The FreeBSD Foundation Differential revision: https://reviews.freebsd.org/D51613
311 lines
12 KiB
Plaintext
311 lines
12 KiB
Plaintext
.\" -*- mode: troff; coding: utf-8 -*-
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.\" ========================================================================
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.\"
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.IX Title "BIO_S_ACCEPT 3ossl"
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.TH BIO_S_ACCEPT 3ossl 2025-07-01 3.5.1 OpenSSL
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.\" For nroff, turn off justification. Always turn off hyphenation; it makes
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.\" way too many mistakes in technical documents.
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.if n .ad l
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.nh
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.SH NAME
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BIO_s_accept, BIO_set_accept_name, BIO_set_accept_port, BIO_get_accept_name,
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BIO_get_accept_port, BIO_new_accept, BIO_set_nbio_accept, BIO_set_tfo_accept, BIO_set_accept_bios,
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BIO_get_peer_name, BIO_get_peer_port,
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BIO_get_accept_ip_family, BIO_set_accept_ip_family,
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BIO_set_bind_mode, BIO_get_bind_mode, BIO_do_accept \- accept BIO
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.SH SYNOPSIS
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.IX Header "SYNOPSIS"
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.Vb 1
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\& #include <openssl/bio.h>
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\&
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\& const BIO_METHOD *BIO_s_accept(void);
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\&
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\& long BIO_set_accept_name(BIO *b, char *name);
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\& char *BIO_get_accept_name(BIO *b);
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\&
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\& long BIO_set_accept_port(BIO *b, char *port);
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\& char *BIO_get_accept_port(BIO *b);
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\&
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\& BIO *BIO_new_accept(char *host_port);
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\&
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\& long BIO_set_nbio_accept(BIO *b, int n);
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\& long BIO_set_tfo_accept(BIO *b, int n);
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\& long BIO_set_accept_bios(BIO *b, char *bio);
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\&
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\& char *BIO_get_peer_name(BIO *b);
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\& char *BIO_get_peer_port(BIO *b);
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\& long BIO_get_accept_ip_family(BIO *b);
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\& long BIO_set_accept_ip_family(BIO *b, long family);
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\&
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\& long BIO_set_bind_mode(BIO *b, long mode);
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\& long BIO_get_bind_mode(BIO *b);
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\&
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\& int BIO_do_accept(BIO *b);
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.Ve
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.SH DESCRIPTION
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.IX Header "DESCRIPTION"
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\&\fBBIO_s_accept()\fR 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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.PP
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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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.PP
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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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.PP
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Accept BIOs support \fBBIO_puts()\fR but not \fBBIO_gets()\fR.
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.PP
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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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.PP
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Calling \fBBIO_reset()\fR on an 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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.PP
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\&\fBBIO_get_fd()\fR and \fBBIO_set_fd()\fR can be called to retrieve or set
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the accept socket. See \fBBIO_s_fd\fR\|(3)
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.PP
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\&\fBBIO_set_accept_name()\fR uses the string \fBname\fR to set the accept
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name. The name 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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The host can be "*" or empty which is interpreted as meaning
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any interface. If the host is an IPv6 address, it has to be
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enclosed in brackets, for example "[::1]:https". "port" has the
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same syntax as the port specified in \fBBIO_set_conn_port()\fR for
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connect BIOs, that is it can be a numerical port string or a
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string to lookup using \fBgetservbyname()\fR and a string table.
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.PP
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\&\fBBIO_set_accept_port()\fR uses the string \fBport\fR to set the accept
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port of BIO \fIb\fR. "port" has the same syntax as the port specified in
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\&\fBBIO_set_conn_port()\fR for connect BIOs, that is it can be a numerical
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port string or a string to lookup using \fBgetservbyname()\fR and a string
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table.
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If the given port is \f(CW0\fR then a random available port is chosen.
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It may be queried using \fBBIO_sock_info()\fR and \fBBIO_ADDR_service_string\fR\|(3).
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.PP
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\&\fBBIO_new_accept()\fR combines \fBBIO_new()\fR and \fBBIO_set_accept_name()\fR into
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a single call: that is it creates a new accept BIO with port
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\&\fBhost_port\fR.
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.PP
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\&\fBBIO_set_nbio_accept()\fR sets the accept socket to blocking mode
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(the default) if \fBn\fR is 0 or non blocking mode if \fBn\fR is 1.
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.PP
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\&\fBBIO_set_tfo_accept()\fR enables TCP Fast Open on the accept socket
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if \fBn\fR is 1 or disables TCP Fast Open if \fBn\fR is 0 (the default).
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Setting the value to 1 is equivalent to setting \fBBIO_SOCK_TFO\fR
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in \fBBIO_set_bind_mode()\fR.
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.PP
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\&\fBBIO_set_accept_bios()\fR 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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.PP
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\&\fBBIO_get_accept_ip_family()\fR returns the IP family accepted by the BIO \fIb\fR,
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which may be \fBBIO_FAMILY_IPV4\fR, \fBBIO_FAMILY_IPV6\fR, or \fBBIO_FAMILY_IPANY\fR.
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.PP
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\&\fBBIO_set_accept_ip_family()\fR sets the IP family \fIfamily\fR accepted by BIO \fIb\fR.
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The default is \fBBIO_FAMILY_IPANY\fR.
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.PP
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\&\fBBIO_set_bind_mode()\fR and \fBBIO_get_bind_mode()\fR set and retrieve
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the current bind mode. If \fBBIO_BIND_NORMAL\fR (the default) is set
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then another socket cannot be bound to the same port. If
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\&\fBBIO_BIND_REUSEADDR\fR is set then other sockets can bind to the
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same port. If \fBBIO_BIND_REUSEADDR_IF_UNUSED\fR 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 \fBBIO_BIND_REUSEADDR\fR. If \fBBIO_SOCK_TFO\fR is set, then
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the socket will be configured to accept TCP Fast Open
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connections.
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.PP
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\&\fBBIO_do_accept()\fR 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 \fBBIO_do_accept()\fR will await an incoming
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connection, or request a retry in non blocking mode.
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.SH NOTES
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.IX Header "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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.PP
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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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.PP
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If any additional BIOs have been set using \fBBIO_set_accept_bios()\fR
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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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.PP
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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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.PP
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.Vb 1
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\& connection = BIO_pop(accept);
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.Ve
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.PP
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After this call \fBconnection\fR will contain a BIO for the recently
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established connection and \fBaccept\fR 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 \fBaccept\fR can
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be freed using \fBBIO_free()\fR.
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.PP
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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 \fBBIO_pop()\fR (see above)
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and freeing up the accept BIO after the initial connection.
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.PP
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If the underlying accept socket is nonblocking and \fBBIO_do_accept()\fR is
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called to await an incoming connection it is possible for
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\&\fBBIO_should_io_special()\fR 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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.PP
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\&\fBBIO_set_accept_name()\fR, \fBBIO_get_accept_name()\fR, \fBBIO_set_accept_port()\fR,
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\&\fBBIO_get_accept_port()\fR, \fBBIO_set_nbio_accept()\fR, \fBBIO_set_accept_bios()\fR,
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\&\fBBIO_get_peer_name()\fR, \fBBIO_get_peer_port()\fR,
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\&\fBBIO_get_accept_ip_family()\fR, \fBBIO_set_accept_ip_family()\fR,
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\&\fBBIO_set_bind_mode()\fR, \fBBIO_get_bind_mode()\fR and \fBBIO_do_accept()\fR are macros.
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.SH "RETURN VALUES"
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.IX Header "RETURN VALUES"
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\&\fBBIO_do_accept()\fR,
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\&\fBBIO_set_accept_name()\fR, \fBBIO_set_accept_port()\fR, \fBBIO_set_nbio_accept()\fR,
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\&\fBBIO_set_accept_bios()\fR, \fBBIO_set_accept_ip_family()\fR, and \fBBIO_set_bind_mode()\fR
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return 1 for success and <= 0 for failure.
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.PP
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\&\fBBIO_get_accept_name()\fR returns the accept name or NULL on error.
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\&\fBBIO_get_peer_name()\fR returns the peer name or NULL on error.
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.PP
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\&\fBBIO_get_accept_port()\fR returns the accept port as a string or NULL on error.
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\&\fBBIO_get_peer_port()\fR returns the peer port as a string or NULL on error.
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\&\fBBIO_get_accept_ip_family()\fR returns the IP family or <= 0 on error.
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.PP
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\&\fBBIO_get_bind_mode()\fR returns the set of \fBBIO_BIND\fR flags, or <= 0 on failure.
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.PP
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\&\fBBIO_new_accept()\fR returns a BIO or NULL on error.
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.SH EXAMPLES
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.IX Header "EXAMPLES"
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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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.PP
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.Vb 1
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\& BIO *abio, *cbio, *cbio2;
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\&
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\& /* First call to BIO_do_accept() sets up accept BIO */
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\& abio = BIO_new_accept("4444");
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\& if (BIO_do_accept(abio) <= 0) {
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\& fprintf(stderr, "Error setting up accept\en");
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\& ERR_print_errors_fp(stderr);
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\& exit(1);
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\& }
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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\en");
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\& ERR_print_errors_fp(stderr);
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\& exit(1);
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\& }
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\& fprintf(stderr, "Connection 1 established\en");
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\&
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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\en");
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\& fprintf(stderr, "Sent out data on connection 1\en");
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\&
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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\en");
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\& ERR_print_errors_fp(stderr);
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\& exit(1);
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\& }
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\& fprintf(stderr, "Connection 2 established\en");
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\&
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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\en");
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\& fprintf(stderr, "Sent out data on connection 2\en");
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\&
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\& BIO_puts(cbio, "Connection 1: Second connection established\en");
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\&
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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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.Ve
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.SH HISTORY
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.IX Header "HISTORY"
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\&\fBBIO_set_tfo_accept()\fR was added in OpenSSL 3.2.
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.SH COPYRIGHT
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.IX Header "COPYRIGHT"
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Copyright 2000\-2022 The OpenSSL Project Authors. All Rights Reserved.
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.PP
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Licensed under the Apache License 2.0 (the "License"). You may not use
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this file except in compliance with the License. You can obtain a copy
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in the file LICENSE in the source distribution or at
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<https://www.openssl.org/source/license.html>.
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