PIM(4)                  NetBSD Kernel Interfaces Manual                 PIM(4)

     pim -- Protocol Independent Multicast

     options MROUTING
     options PIM

     #include <sys/types.h>
     #include <sys/socket.h>
     #include <netinet/in.h>
     #include <netinet/ip_mroute.h>
     #include <netinet/pim.h>

     getsockopt(int s, IPPROTO_IP, MRT_PIM, void *optval, socklen_t *optlen);

     setsockopt(int s, IPPROTO_IP, MRT_PIM, const void *optval,
           socklen_t optlen);

     getsockopt(int s, IPPROTO_IPV6, MRT6_PIM, void *optval,
           socklen_t *optlen);

     setsockopt(int s, IPPROTO_IPV6, MRT6_PIM, const void *optval,
           socklen_t optlen);

     PIM is the common name for two multicast routing protocols: Protocol
     Independent Multicast - Sparse Mode (PIM-SM) and Protocol Independent
     Multicast - Dense Mode (PIM-DM).

     PIM-SM is a multicast routing protocol that can use the underlying uni-
     cast routing information base or a separate multicast-capable routing
     information base.  It builds unidirectional shared trees rooted at a Ren-
     dezvous Point (RP) per group, and optionally creates shortest-path trees
     per source.

     PIM-DM is a multicast routing protocol that uses the underlying unicast
     routing information base to flood multicast datagrams to all multicast
     routers.  Prune messages are used to prevent future datagrams from propa-
     gating to routers with no group membership information.

     Both PIM-SM and PIM-DM are fairly complex protocols, though PIM-SM is
     much more complex.  To enable PIM-SM or PIM-DM multicast routing in a
     router, the user must enable multicast routing and PIM processing in the
     kernel (see SYNOPSIS about the kernel configuration options), and must
     run a PIM-SM or PIM-DM capable user-level process.  From developer's
     point of view, the programming guide described in the Programming Guide
     section should be used to control the PIM processing in the kernel.

   Programming Guide
     After a multicast routing socket is open and multicast forwarding is
     enabled in the kernel (see multicast(4)), one of the following socket
     options should be used to enable or disable PIM processing in the kernel.
     Note that those options require certain privilege (i.e., root privilege):

     /* IPv4 */
     int v = 1;        /* 1 to enable, or 0 to disable */
     setsockopt(mrouter_s4, IPPROTO_IP, MRT_PIM, (void *)&v, sizeof(v));

     /* IPv6 */
     int v = 1;        /* 1 to enable, or 0 to disable */
     setsockopt(mrouter_s6, IPPROTO_IPV6, MRT6_PIM, (void *)&v, sizeof(v));

     After PIM processing is enabled, the multicast-capable interfaces should
     be added (see multicast(4)).  In case of PIM-SM, the PIM-Register virtual
     interface must be added as well.  This can be accomplished by using the
     following options:

     /* IPv4 */
     struct vifctl vc;
     memset(&vc, 0, sizeof(vc));
     /* Assign all vifctl fields as appropriate */
     if (is_pim_register_vif)
         vc.vifc_flags |= VIFF_REGISTER;
     setsockopt(mrouter_s4, IPPROTO_IP, MRT_ADD_VIF, (void *)&vc,

     /* IPv6 */
     struct mif6ctl mc;
     memset(&mc, 0, sizeof(mc));
     /* Assign all mif6ctl fields as appropriate */
     if (is_pim_register_vif)
         mc.mif6c_flags |= MIFF_REGISTER;
     setsockopt(mrouter_s6, IPPROTO_IPV6, MRT6_ADD_MIF, (void *)&mc,

     Sending or receiving of PIM packets can be accomplished by opening first
     a ``raw socket'' (see socket(2)), with protocol value of IPPROTO_PIM:

     /* IPv4 */
     int pim_s4;
     pim_s4 = socket(AF_INET, SOCK_RAW, IPPROTO_PIM);

     /* IPv6 */
     int pim_s6;
     pim_s6 = socket(AF_INET6, SOCK_RAW, IPPROTO_PIM);

     Then, the following system calls can be used to send or receive PIM pack-
     ets: sendto(2), sendmsg(2), recvfrom(2), recvmsg(2).

     getsockopt(2), recvfrom(2), recvmsg(2), sendmsg(2), sendto(2),
     setsockopt(2), socket(2), inet(4), intro(4), ip(4), multicast(4)

     The PIM-SM protocol is specified in RFC 2362 (to be replaced by
     draft-ietf-pim-sm-v2-new-*).  The PIM-DM protocol is specified in

     The original IPv4 PIM kernel support for IRIX and SunOS-4.x was imple-
     mented by Ahmed Helmy (USC and SGI).  Later the code was ported to vari-
     ous BSD flavors and modified by George Edmond Eddy (Rusty) (ISI), Hitoshi
     Asaeda (WIDE Project), and Pavlin Radoslavov (USC/ISI and ICSI).  The
     IPv6 PIM kernel support was implemented by the KAME project
     (http://www.kame.net), and was based on the IPv4 PIM kernel support.

     This manual page was written by Pavlin Radoslavov (ICSI).

NetBSD 9.0                     September 4, 2003                    NetBSD 9.0

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