pimd: pim_ifchannel_local_membership_add should not inherit if (S,G) rpf unresolved

Problem:
S,G entry has iif = oif in FHR is LHR case.

Setup:-

R11-----R2----R4

R11 :- FHR and LHR
R2 :- RP
R4 :- LHR

Issue :-

1) shut mapped interface in R11
2) wait for 5 min
3) do FRR restart
5) No shut of mapped interface

OIL is added for local interface also where OIL is same as IIF
and duplicate traffic observed on R4 receives in Ixia

RCA:
pim_ifchannel_local_membership_add adds inherited oif from starg when iif for
SG is unavailable.
When  rpf for that SG resolves to this inherited oif from starg, iif is also in oif.
This results in dup traffic.

Fix:
If iif is not available, do not inherit from starg.

Signed-off-by: Mobashshera Rasool <mrasool@vmware.com>
(cherry picked from commit 660b04429437416d71ec22dcc8bb798fdf45bec6)

diff --git a/pimd/pim_ifchannel.c b/pimd/pim_ifchannel.c
index 1bf3a619bf69c710c53e33a1aecb8facafe624df..3b00e779cfe67825083be2b7d251eddc2061a370 100644 (file)
--- a/pimd/pim_ifchannel.c
+++ b/pimd/pim_ifchannel.c
@@ -1232,6 +1232,16 @@ int pim_ifchannel_local_membership_add(struct interface *ifp,
                                           __FILE__, __func__, child->sg_str,
                                           ifp->name, up->sg_str);
 
+                       if (!child->rpf.source_nexthop.interface) {
+                               /* when iif unknown, do not inherit */
+                               if (PIM_DEBUG_EVENTS)
+                                       zlog_debug(
+                                               "Skipped (S,G)=%s(%s) from %s: no iif",
+                                               child->sg_str, ifp->name,
+                                               up->sg_str);
+                               continue;
+                       }
+
                        ch = pim_ifchannel_find(ifp, &child->sg);
                        if (pim_upstream_evaluate_join_desired_interface(
                                    child, ch, starch)) {