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PIM(4)			 BSD 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 In-
     dependent Multicast - Sparse Mode (PIM-SM)	and Protocol Independent Mul-
     ticast - 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 in-
     formation 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 en-
     abled in the kernel (see multicast(4)), one of the	following socket op-
     tions 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
     (, and	was based on the IPv4 PIM kernel support.

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

BSD			       September 4, 2003			   BSD


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