IPV6_MULTICAST_IF(2const)                            IPV6_MULTICAST_IF(2const)

NAME
       IPV6_MULTICAST_IF - local device for a multicast socket

LIBRARY
       Standard C library (libc, -lc)

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

       int setsockopt(int sockfd, IPPROTO_IPV6, IPV6_MULTICAST_IF,
                      const int *ifindex, sizeof(int));
       int getsockopt(int sockfd, IPPROTO_IPV6, IPV6_MULTICAST_IF,
                      int *ifindex, sizeof(int));

DESCRIPTION
       Set the device for outgoing multicast packets on the socket.

       This is allowed only for SOCK_DGRAM and SOCK_RAW socket.

       The argument is a pointer to an interface index (see netdevice(7)) in
       an integer.

ERRORS
       See IPPROTO_IPV6(2const).  See setsockopt(2).  See ipv6(7).

HISTORY
       IPV6_MULTICAST_IF
              POSIX.1-2001.

SEE ALSO
       IPPROTO_IPV6(2const), setsockopt(2), ipv6(7)

Linux man-pages 6.17              2026-01-05         IPV6_MULTICAST_IF(2const)