.\" Copyright, the authors of the Linux man-pages project
.\"
.\" SPDX-License-Identifier: Linux-man-pages-copyleft
.\"
.TH IP_BIND_ADDRESS_NO_PORT 2const 2025-11-25 "Linux man-pages 6.17"
.SH NAME
IP_BIND_ADDRESS_NO_PORT
\-
don't reserve an ephemeral port
.SH LIBRARY
Standard C library
.RI ( libc ,\~ \-lc )
.SH SYNOPSIS
.nf
.BR "#include <netinet/in.h>" "  /* Definition of " IP* " constants */"
.B #include <sys/socket.h>
.P
.BI int\~setsockopt(int\~ sockfd ,\~IPPROTO_IP,\~IP_BIND_ADDRESS_NO_PORT,
.BI "               const\~int\~*" enable ,\~sizeof(int));
.fi
.SH DESCRIPTION
Inform the kernel to not reserve an ephemeral port when using
.BR bind (2)
with a port number of 0.
The port will later be automatically chosen at
.BR connect (2)
time,
in a way that allows sharing a source port as long as the 4-tuple is unique.
.SH ERRORS
See
.BR IPPROTO_IP (2const).
See
.BR setsockopt (2).
See
.BR ip (7).
.SH HISTORY
Linux 4.2.
.\" commit 90c337da1524863838658078ec34241f45d8394d
.SH SEE ALSO
.BR IPPROTO_IP (2const),
.BR setsockopt (2),
.BR ip (7)