IP_MULTICAST_IF(2const) — Linux manual page

IP_MULTICAST_IF(2const)                           IP_MULTICAST_IF(2const)

NAME         top

       IP_MULTICAST_IF - local device for a multicast socket

LIBRARY         top

       Standard C library (libc, -lc)

SYNOPSIS         top

       #include <netinet/in.h>  /* Definition of IP* constants */
       #include <sys/socket.h>

       int setsockopt(int sockfd, IPPROTO_IP, IP_MULTICAST_IF,
                      const void val[size], size_t size);
       int getsockopt(int sockfd, IPPROTO_IP, IP_MULTICAST_IF,
                      struct in_addr *val, sizeof(struct in_addr));

DESCRIPTION         top

       Set the local device for a multicast socket.

       The argument for setsockopt(2) is an ip_mreqn(2type) or (since
       Linux 3.5) ip_mreq(2type) structure, or an in_addr(2type)
       structure.  (The kernel determines which structure is being passed
       based on the size passed in size.)

ERRORS         top

       See IPPROTO_IP(2const).  See setsockopt(2).  See ip(7).

HISTORY         top

       Linux 1.2.

SEE ALSO         top

       IPPROTO_IP(2const), in_addr(2type), ip_mreqn(2type),
       setsockopt(2), ip(7)

COLOPHON         top

       This page is part of the man-pages (Linux kernel and C library
       user-space interface documentation) project.  Information about
       the project can be found at 
       ⟨https://www.kernel.org/doc/man-pages/⟩.  If you have a bug report
       for this manual page, see
       ⟨https://git.kernel.org/pub/scm/docs/man-pages/man-pages.git/tree/CONTRIBUTING⟩.
       This page was obtained from the tarball man-pages-6.18.tar.gz
       fetched from
       ⟨https://mirrors.edge.kernel.org/pub/linux/docs/man-pages/⟩ on
       2026-05-24.  If you discover any rendering problems in this HTML
       version of the page, or you believe there is a better or more up-
       to-date source for the page, or you have corrections or
       improvements to the information in this COLOPHON (which is not
       part of the original manual page), send a mail to
       man-pages@man7.org

Linux man-pages 6.18            2025-11-25        IP_MULTICAST_IF(2const)

Pages that refer to this page: ip_mreqn(2type),  IPPROTO_IP(2const)

HTML rendering created 2026-05-24 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH.