.\" Copyright, the authors of the Linux man-pages project
.\"
.\" SPDX-License-Identifier: Linux-man-pages-copyleft
.\"
.TH IP_MULTICAST_ALL 2const 2025-11-25 "Linux man-pages 6.18"
.SH NAME
IP_MULTICAST_ALL
\-
delivery policy of multicast messages
.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_MULTICAST_ALL,
.BI "               const\~int\~*" val ,\~sizeof(int));
.fi
.SH DESCRIPTION
This option can be used to modify the delivery policy of multicast messages.
.P
If set to 1 (default),
the socket will receive messages from all the groups that have been joined
globally on the whole system.
.P
If set to 0,
it will deliver messages only from
the groups that have been explicitly joined
(for example via
.BR IP_ADD_MEMBERSHIP (2const))
on this particular socket.
.SH ERRORS
See
.BR IPPROTO_IP (2const).
See
.BR setsockopt (2).
See
.BR ip (7).
.SH HISTORY
Linux 2.6.31.
.SH SEE ALSO
.BR IPPROTO_IP (2const),
.BR setsockopt (2),
.BR ip (7)