.\" $OpenBSD: BIO_accept.3,v 1.2 2023/04/30 13:38:48 schwarze Exp $
.\"
.\" Copyright (c) 2022 Ingo Schwarze <schwarze@openbsd.org>
.\"
.\" Permission to use, copy, modify, and distribute this software for any
.\" purpose with or without fee is hereby granted, provided that the above
.\" copyright notice and this permission notice appear in all copies.
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.\" WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
.\" MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
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.Dd $Mdocdate: April 30 2023 $
.Dt BIO_ACCEPT 3
.Os
.Sh NAME
.\" mentioned in OpenSSL documentation and still used internally in LibreSSL
.Nm BIO_get_host_ip ,
.Nm BIO_get_port ,
.Nm BIO_get_accept_socket ,
.Nm BIO_accept ,
.Nm BIO_sock_error ,
.Nm BIO_sock_non_fatal_error ,
.Nm BIO_sock_should_retry ,
.\" used internally in LibreSSL and OpenSSL and not deprecated in OpenSSL
.Nm BIO_socket_nbio ,
.\" mentioned in OpenSSL documentation and not deprecated in OpenSSL
.Nm BIO_set_tcp_ndelay
.\" deprecated in OpenSSL and unused anywhere, hence intentionally undocumented
.\" .Nm BIO_gethostbyname
.\" .Nm BIO_GHBN_CTRL_CACHE_SIZE
.\" .Nm BIO_GHBN_CTRL_FLUSH
.\" .Nm BIO_GHBN_CTRL_GET_ENTRY
.\" .Nm BIO_GHBN_CTRL_HITS
.\" .Nm BIO_GHBN_CTRL_MISSES
.\" .Nm BIO_socket_ioctl
.\" does almost nothing and used very rarely, hence intentionally undocumented
.\" .Nm BIO_sock_init
.\" .Nm BIO_sock_cleanup
.Nd wrappers for socket operations
.Sh SYNOPSIS
.In openssl/bio.h
.Ft int
.Fo BIO_get_host_ip
.Fa "const char *hostname"
.Fa "unsigned char *in_addr_buffer"
.Fc
.Ft int
.Fo BIO_get_port
.Fa "const char *servname"
.Fa "unsigned short *port"
.Fc
.Ft int
.Fo BIO_get_accept_socket
.Fa "char *host_port"
.Fa "int bind_mode"
.Fc
.Ft int
.Fo BIO_accept
.Fa "int socket"
.Fa "char **addr"
.Fc
.Ft int
.Fn BIO_sock_error "int socket"
.Ft int
.Fn BIO_sock_non_fatal_error "int errnum"
.Ft int
.Fn BIO_sock_should_retry "int retval"
.Ft int
.Fn BIO_socket_nbio "int socket" "int mode"
.Ft int
.Fn BIO_set_tcp_ndelay "int socket" "int on"
.Sh DESCRIPTION
.Fn BIO_get_host_ip
looks up one IPv4 address for the given
.Fa hostname
using
.Xr getaddrinfo 3
and writes the first returned IPv4 address into
.Pf * Fa in_addr_buffer .
The caller is responsible for providing a buffer that is at least
.Fn sizeof in_addr_t
bytes long.
After a successful call, the caller needs to cast
.Fa in_addr_buffer
to
.Pq Vt in_addr_t * .
.Pp
.Fn BIO_get_port
looks up
.Fa servname
in the
.Xr services 5
database using
.Xr getaddrinfo 3
and stores the associated port number at the location specified by the
.Fa port
argument.
.Pp
.Fn BIO_get_accept_socket
creates an IPv4 TCP socket and
.Xr listen 2 Ns s
for incoming connections.
The string
.Fa host_port
is parsed.
If it contains a colon, the substring before the colon is interpreted
as a local hostname of the interface to
.Xr bind 2
to.
If the hostname is empty, consists of a single asterisk
.Pq Qq *:... ,
or if there is no colon,
.Dv INADDR_ANY
is used instead of a local hostname.
The rest of the string
.Fa host_port ,
or the whole string if it contains no colon,
is treated as a service name.
The hostname and the service name are converted to a local IP address
and port number using
.Xr getaddrinfo 3 .
If
.Fa bind_mode
is the constant
.Dv BIO_BIND_REUSEADDR ,
allowing local address reuse is attempted using
.Xr setsockopt 2
with an argument of
.Dv SO_REUSEADDR
before calling
.Xr bind 2 .
.Pp
.Fn BIO_accept
calls
.Xr accept 2
to receive one connection on the
.Fa socket .
When it receives a connection, it
.Xr free 3 Ns s
.Pf * Fa addr ,
and if it is an IPv4 connection, it allocates a new string,
writes the peer IP address in dotted decimal form, a colon,
and the decimal port number into the string, and stores a pointer
to the string in
.Pf * Fa addr .
For other address families or if
.Xr getnameinfo 3
or memory allocation fails,
.Pf * Fa addr
is set to
.Dv NULL
but
.Fn BIO_accept
succeeds anyway.
.Pp
.Fn BIO_sock_error
retrieves, clears, and returns the error status code of the
.Fa socket
by calling
.Xr getsockopt 2
with arguments
.Dv SOL_SOCKET
and
.Dv SO_ERROR .
.Pp
.Fn BIO_sock_non_fatal_error
determines whether the error status code
.Fa errnum
represents a recoverable error.
.Pp
.Fn BIO_sock_should_retry
determines whether a recoverable error occurred by inspecting both
.Xr errno 2
and
.Fa retval ,
which is supposed to usually be
the return value of a previously called function like
.Fn BIO_accept ,
.Xr BIO_read 3 ,
or
.Xr BIO_write 3 .
.Pp
If
.Fa mode
is non-zero,
.Fn BIO_socket_nbio
switches the
.Fa socket
to non-blocking mode using
.Xr fcntl 2 .
If
.Fa mode
is 0, it switches to blocking mode.
.Pp
.Fn BIO_set_tcp_ndelay
sets the
.Dv TCP_NODELAY
option on the
.Fa socket
if
.Fa on
is 1 or clears it if
.Fa on
is 0; see
.Xr tcp 4
for details.
.Sh RETURN VALUES
.Fn BIO_get_host_ip ,
.Fn BIO_get_port ,
and
.Fn BIO_socket_nbio
return 1 on success or 0 on failure.
.Pp
.Fn BIO_get_accept_socket
returns the file descriptor of the newly created listening socket or \-1 if
.Fa host_port
is
.Dv NULL ,
no service is specified, or
.Xr getaddrinfo 3 ,
.Xr socket 2 ,
.Xr bind 2 ,
.Xr listen 2 ,
or memory allocation fails.
.Pp
.Fn BIO_accept
returns the file descriptor of the received connection,
\-1 on fatal errors, that is, when
.Fa addr
is
.Dv NULL
or
.Xr accept 2
fails fatally, or \-2 when
.Xr accept 2
fails in a non-fatal way and might succeed when retried later.
.Pp
.Fn BIO_sock_error
returns an error status code like
.Dv EAGAIN ,
.Dv ECONNABORTED ,
.Dv ECONNREFUSED ,
.Dv ECONNRESET ,
.Dv ELOOP ,
.Dv EMSGSIZE ,
.Dv ENOBUFS ,
.Dv ENOTCONN ,
.Dv EPIPE ,
.Dv ETIMEDOUT ,
or others, 0 if the
.Fa socket
is not in an error state, or 1 if
.Xr getsockopt 2
fails.
.Pp
.Fn BIO_sock_non_fatal_error
returns 1 if
.Fa errnum
is
.Dv EAGAIN ,
.Dv EALREADY ,
.Dv EINPROGRESS ,
.Dv EINTR ,
or
.Dv ENOTCONN
and 0 otherwise, even if
.Fa errnum
is 0.
.Pp
.Fn BIO_sock_should_retry
returns 1 if
.Fn BIO_sock_non_fatal_error errno
is 1 and
.Fa retval
is either 0 or \-1, or 0 otherwise.
.Pp
.Fn BIO_set_tcp_ndelay
returns 0 on success or \-1 on failure.
.Sh ERRORS
If
.Fn BIO_get_host_ip ,
.Fn BIO_get_port ,
or
.Fn BIO_get_accept_socket
fail or
.Fn BIO_accept
fails fatally, the following diagnostics can be retrieved with
.Xr ERR_get_error 3 ,
.Xr ERR_GET_REASON 3 ,
and
.Xr ERR_reason_error_string 3 :
.Bl -tag -width Ds
.It Dv BIO_R_ACCEPT_ERROR Qq "accept error"
.Xr accept 2
failed fatally in
.Fn BIO_accept .
.It Dv BIO_R_BAD_HOSTNAME_LOOKUP Qq "bad hostname lookup"
.Xr getaddrinfo 3
failed or
.Fa hostname
was
.Dv NULL
in
.Fn BIO_get_host_ip ,
or
.Xr getaddrinfo 3
failed in
.Fn BIO_get_accept_socket .
.It Dv BIO_R_INVALID_ARGUMENT Qq "invalid argument"
.Xr getaddrinfo 3
failed in
.Fn BIO_get_port .
.It Dv ERR_R_MALLOC_FAILURE Qq "malloc failure"
Memory allocation failed in
.Fn BIO_get_accept_socket ,
or
.Fn BIO_accept
.Em succeeded
but was unable to allocate memory for
.Pf * Fa addr .
For
.Fn BIO_accept ,
the returned file descriptor is valid,
and communication with the peer can be attempted using it.
.It Dv BIO_R_NO_PORT_SPECIFIED Qq "no port specified"
The
.Fa servname
argument was
.Dv NULL
in
.Fn BIO_get_port ,
or
.Fa host_port
was
.Dv NULL
or ended after the first colon in
.Fn BIO_get_accept_socket .
.It Dv BIO_R_NULL_PARAMETER Qq "null parameter"
The
.Fa addr
argument was
.Dv NULL
in
.Fn BIO_accept .
.It Dv BIO_R_UNABLE_TO_BIND_SOCKET Qq "unable to bind socket"
.Xr bind 2
failed in
.Fn BIO_get_accept_socket .
.It Dv BIO_R_UNABLE_TO_CREATE_SOCKET Qq "unable to create socket"
.Xr socket 2
failed in
.Fn BIO_get_accept_socket .
.It Dv BIO_R_UNABLE_TO_LISTEN_SOCKET Qq "unable to listen socket"
.Xr listen 2
failed in
.Fn BIO_get_accept_socket .
.El
.Sh SEE ALSO
.Xr bind 2 ,
.Xr connect 2 ,
.Xr errno 2 ,
.Xr fcntl 2 ,
.Xr getsockopt 2 ,
.Xr listen 2 ,
.Xr sigaction 2 ,
.Xr socket 2 ,
.Xr BIO_new 3 ,
.Xr BIO_read 3 ,
.Xr getaddrinfo 3 ,
.Xr ip 4 ,
.Xr tcp 4
.Sh HISTORY
.Fn BIO_sock_should_retry
first appeared in SSLeay 0.6.5 and the other functions except
.Fn BIO_socket_nbio
in SSLeay 0.8.0.
They have all been available since
.Ox 2.4 .
.Pp
.Fn BIO_socket_nbio
first appeared in SSLeay 0.9.1 and has been available since
.Ox 2.6 .