From 95e31a6081294d9c05fec92166361ec03023f340 Mon Sep 17 00:00:00 2001 From: Adriano Marto Reis Date: Sat, 30 Sep 2023 15:49:40 +1000 Subject: [PATCH] pimd: Indicating the rp in the msdp sa message Indicating the configured PIM Rendezvous Point (RP) in the MSDP SA message The RFC-3618, section 12.2.1, describes the fields included in the MSDP SA message. The "RP address" field is "the address of the RP in the domain the source has become active in". In the most common case, we will establish an MSDP connection from RP to RP. However, there are cases where we want to establish a MSDP connection from an interface/address that is not the RP. Section 3 of RFC-3618 describes that scenario as "intermediate MSDP peer". Moreover, the RP could be another router in the PIM domain - not the one establishing the MSDP connection. The current implementation could be problematic even with a single router per PIM domain. Consider the following scenario: * There are two PIM domains, each one with a single router. * The two routers are connected via two independent networks. Let's say that is to provide redundancy. * The routers are configured to establish two MSDP connections, one on each network (redundancy again). * A multicast source becomes active on the router 1. It will be communicated to router 2 via two independent MSDP SA messages, one per MSDP connection. * Without these changes, each MSDP SA message will indicate a different RP. * Both RP addresses will pass the RPF check, and both MSDP sources will be accepted. * If the router has clients interested in that multicast group, it will send PIM Join messages to both RPs and start receiving the multicast traffic from both. With the changes included in this commit, the multicast source available in router 1 would still be communicated to router 2 twice. But both MSDP SA messages would indicate the same RP, and one of them would be discarded due to failure in the RPF-check failure. Also, the changes allow us to define the RP that will be included in the MSDP SA message, and it could be one of the interfaces used to establish the MSDP connection, some other interface on the router, a loopback interface, or another router in the PIM domain. These changes should not create compatibility issues. As I mentioned, we usually establish MSDP connections from RP to RP. In this case, the result will be the same. We would still indicate the address used to establish the MSDP connection if the RP is not set - I wonder if that should even be a valid configuration. Signed-off-by: Adriano Marto Reis --- pimd/pim_msdp.c | 10 ++++++++++ pimd/pim_msdp_packet.c | 18 +++++++++++++++--- 2 files changed, 25 insertions(+), 3 deletions(-) diff --git a/pimd/pim_msdp.c b/pimd/pim_msdp.c index b1b6958fe166..623c14bb0391 100644 --- a/pimd/pim_msdp.c +++ b/pimd/pim_msdp.c @@ -374,6 +374,8 @@ void pim_msdp_sa_ref(struct pim_instance *pim, struct pim_msdp_peer *mp, pim_sgaddr *sg, struct in_addr rp) { struct pim_msdp_sa *sa; + struct rp_info *rp_info; + struct prefix grp; sa = pim_msdp_sa_add(pim, sg, rp); if (!sa) { @@ -406,6 +408,14 @@ void pim_msdp_sa_ref(struct pim_instance *pim, struct pim_msdp_peer *mp, sa->sg_str); } /* send an immediate SA update to peers */ + pim_addr_to_prefix(&grp, sa->sg.grp); + rp_info = pim_rp_find_match_group(pim, &grp); + if (rp_info) { + sa->rp = rp_info->rp.rpf_addr; + } else + { + sa->rp = pim->msdp.originator_id; + } sa->rp = pim->msdp.originator_id; pim_msdp_pkt_sa_tx_one(sa); } diff --git a/pimd/pim_msdp_packet.c b/pimd/pim_msdp_packet.c index a414736cccf1..4324a96bef89 100644 --- a/pimd/pim_msdp_packet.c +++ b/pimd/pim_msdp_packet.c @@ -14,7 +14,9 @@ #include "pimd.h" #include "pim_instance.h" +#include "pim_rp.h" #include "pim_str.h" +#include "pim_util.h" #include "pim_errors.h" #include "pim_msdp.h" @@ -387,6 +389,9 @@ static void pim_msdp_pkt_sa_gen(struct pim_instance *pim, { struct listnode *sanode; struct pim_msdp_sa *sa; + struct rp_info *rp_info; + struct prefix group_all; + struct in_addr rp; int sa_count; int local_cnt = pim->msdp.local_cnt; @@ -395,8 +400,15 @@ static void pim_msdp_pkt_sa_gen(struct pim_instance *pim, zlog_debug(" sa gen %d", local_cnt); } - local_cnt = pim_msdp_pkt_sa_fill_hdr(pim, local_cnt, - pim->msdp.originator_id); + rp = pim->msdp.originator_id; + if (pim_get_all_mcast_group(&group_all)) { + rp_info = pim_rp_find_match_group(pim, &group_all); + if (rp_info) { + rp = rp_info->rp.rpf_addr; + } + } + + local_cnt = pim_msdp_pkt_sa_fill_hdr(pim, local_cnt, rp); for (ALL_LIST_ELEMENTS_RO(pim->msdp.sa_list, sanode, sa)) { if (!(sa->flags & PIM_MSDP_SAF_LOCAL)) { @@ -418,7 +430,7 @@ static void pim_msdp_pkt_sa_gen(struct pim_instance *pim, local_cnt); } local_cnt = pim_msdp_pkt_sa_fill_hdr( - pim, local_cnt, pim->msdp.originator_id); + pim, local_cnt, rp); } }