IPV6_ROUTER_ALERT(2const)                            IPV6_ROUTER_ALERT(2const)

NAME
       IPV6_ROUTER_ALERT - pass forwarded packets containing a router alert
       hop-by-hop to this 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_ROUTER_ALERT,
                      const int *val, sizeof(int));

DESCRIPTION
       Pass forwarded packets containing a router alert hop-by-hop option to
       this socket.

       Allowed only for SOCK_RAW sockets.

       The tapped packets are not forwarded by the kernel, it is the user's
       responsibility to send them out again.

       A positive integer indicates a router alert option value to intercept.
       Packets carrying a router alert option with a value field containing
       this integer will be delivered to the socket.  A negative integer
       disables delivery of packets with router alert options to this socket.

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

SEE ALSO
       IPPROTO_IPV6(2const), setsockopt(2), cmsg(3), ipv6(7)

Linux man-pages 6.17              2025-12-02         IPV6_ROUTER_ALERT(2const)