.\" Copyright, the authors of the Linux man-pages project
.\"
.\" SPDX-License-Identifier: Linux-man-pages-copyleft
.\"
.TH IP_MSFILTER 2const 2025-11-25 "Linux man-pages 6.17"
.SH NAME
IP_MSFILTER
\-
multicast source filtering
.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_MSFILTER,
.BI "               const\~struct\~ip_msfilter\~*" val ,
.B "               sizeof(struct\~ip_msfilter));"
.fi
.P
.EX
struct ip_msfilter {
    struct in_addr  imsf_multiaddr;  // IP multicast group address
    struct in_addr  imsf_interface;  // IP address of local interface
    uint32_t        imsf_fmode;      // Filter\-mode
\&
    uint32_t        imsf_numsrc;     // Number of elements in .imsf_slist
    struct in_addr  imsf_slist[1];   // Array of source addresses
};
.EE
.SH DESCRIPTION
This option provides access to the advanced full-state filtering API.
.P
There are two macros,
.B MCAST_INCLUDE
and
.BR MCAST_EXCLUDE ,
which can be used to specify the filtering mode.
.P
Additionally,
the
.BR IP_MSFILTER_SIZE (n)
macro exists to determine how much memory is needed to store
.I ip_msfilter
structure with
.I n
sources in the source list.
.P
For the full description of multicast source filtering
refer to RFC 3376.
.SH ERRORS
See
.BR IPRROTO_IP (2const).
See
.BR setsockopt (2).
See
.BR ip (7).
.SH STANDARDS
Linux.
.SH HISTORY
Linux 2.4.22, Linux 2.5.68.
.SH SEE ALSO
.BR IPPROTO_IP (2const),
.BR setsockopt (2),
.BR ip (7)