pimd: provide a mechanism to pin the IIF for an SG entry

In the case of vxlan origination entries IIF is set to -
1. lo for single VTEPs
2. MLAG-ISL for VTEPs multihomed via MLAG.

This commit creates the necessary infrastructure by -
1. allowing the IIF to be set statically (without RPF lookup)
2. and by preventing next-hop-tracking registration

PS: Note that I have skipped additional checks in pim_upstream_del
intentionally i.e. an attempt will be made to remove nexthop-tracking
for the upstream entry (with STATIC_IIF) which will fail because of the
up-entry not being in the nh's hash table. Ideally we should maintain
a nh pointer in the up-entry to prevent this unnecessary processing.
In the abscence of that I wanted to avoid spraying STATIC_IIF checks
all over.

Signed-off-by: Anuradha Karuppiah <anuradhak@cumulusnetworks.com>

3 files changed, 38 insertions, 2 deletions

diff --git a/pimd/pim_rpf.c b/pimd/pim_rpf.c
index 8cc8b7481..afe3886aa 100644
--- a/pimd/pim_rpf.c
+++ b/pimd/pim_rpf.c
@@ -204,6 +204,9 @@ enum pim_rpf_result pim_rpf_update(struct pim_instance *pim,
 	struct prefix src, grp;
 	bool neigh_needed = true;
 
+	if (PIM_UPSTREAM_FLAG_TEST_STATIC_IIF(up->flags))
+		return PIM_RPF_OK;
+
 	if (up->upstream_addr.s_addr == INADDR_ANY) {
 		zlog_debug("%s: RP is not configured yet for %s",
 			__PRETTY_FUNCTION__, up->sg_str);
diff --git a/pimd/pim_upstream.c b/pimd/pim_upstream.c
index 85f58555e..050e87ab2 100644
--- a/pimd/pim_upstream.c
+++ b/pimd/pim_upstream.c
@@ -647,6 +647,23 @@ int pim_upstream_compare(void *arg1, void *arg2)
 	return 0;
 }
 
+void pim_upstream_fill_static_iif(struct pim_upstream *up,
+				struct interface *incoming)
+{
+	up->rpf.source_nexthop.interface = incoming;
+
+	/* reset other parameters to matched a connected incoming interface */
+	up->rpf.source_nexthop.mrib_nexthop_addr.family = AF_INET;
+	up->rpf.source_nexthop.mrib_nexthop_addr.u.prefix4.s_addr =
+		PIM_NET_INADDR_ANY;
+	up->rpf.source_nexthop.mrib_metric_preference =
+		ZEBRA_CONNECT_DISTANCE_DEFAULT;
+	up->rpf.source_nexthop.mrib_route_metric = 0;
+	up->rpf.rpf_addr.family = AF_INET;
+	up->rpf.rpf_addr.u.prefix4.s_addr = PIM_NET_INADDR_ANY;
+
+}
+
 static struct pim_upstream *pim_upstream_new(struct pim_instance *pim,
 					     struct prefix_sg *sg,
 					     struct interface *incoming,
@@ -712,13 +729,19 @@ static struct pim_upstream *pim_upstream_new(struct pim_instance *pim,
 	if (up->sg.src.s_addr != INADDR_ANY)
 		wheel_add_item(pim->upstream_sg_wheel, up);
 
-	if (up->upstream_addr.s_addr == INADDR_ANY)
+	if (PIM_UPSTREAM_FLAG_TEST_STATIC_IIF(up->flags)) {
+		pim_upstream_fill_static_iif(up, incoming);
+		pim_ifp = up->rpf.source_nexthop.interface->info;
+		assert(pim_ifp);
+		up->channel_oil = pim_channel_oil_add(pim,
+				&up->sg, pim_ifp->mroute_vif_index);
+	} else if (up->upstream_addr.s_addr == INADDR_ANY) {
 		/* Create a dummmy channel oil with incoming ineterface MAXVIFS,
 		 * since RP is not configured
 		 */
 		up->channel_oil = pim_channel_oil_add(pim, &up->sg, MAXVIFS);
 
-	else {
+	} else {
 		rpf_result = pim_rpf_update(pim, up, NULL, 1);
 		if (rpf_result == PIM_RPF_FAILURE) {
 			if (PIM_DEBUG_TRACE)
diff --git a/pimd/pim_upstream.h b/pimd/pim_upstream.h
index 5eb230a76..c0bd9137d 100644
--- a/pimd/pim_upstream.h
+++ b/pimd/pim_upstream.h
@@ -43,6 +43,11 @@
  * lack of BUM traffic.
  */
 #define PIM_UPSTREAM_FLAG_MASK_DISABLE_KAT_EXPIRY      (1 << 9)
+/* for pim vxlan we need to pin the IIF to lo or MLAG-ISL on the
+ * originating VTEP. This flag allows that by setting IIF to the
+ * value specified and preventing next-hop-tracking on the entry
+ */
+#define PIM_UPSTREAM_FLAG_MASK_STATIC_IIF              (1 << 10)
 #define PIM_UPSTREAM_FLAG_ALL 0xFFFFFFFF
 
 #define PIM_UPSTREAM_FLAG_TEST_DR_JOIN_DESIRED(flags) ((flags) & PIM_UPSTREAM_FLAG_MASK_DR_JOIN_DESIRED)
@@ -55,6 +60,7 @@
 #define PIM_UPSTREAM_FLAG_TEST_SEND_SG_RPT_PRUNE(flags) ((flags) & PIM_UPSTREAM_FLAG_MASK_SEND_SG_RPT_PRUNE)
 #define PIM_UPSTREAM_FLAG_TEST_SRC_LHR(flags) ((flags) & PIM_UPSTREAM_FLAG_MASK_SRC_LHR)
 #define PIM_UPSTREAM_FLAG_TEST_DISABLE_KAT_EXPIRY(flags) ((flags) & PIM_UPSTREAM_FLAG_MASK_DISABLE_KAT_EXPIRY)
+#define PIM_UPSTREAM_FLAG_TEST_STATIC_IIF(flags) ((flags) & PIM_UPSTREAM_FLAG_MASK_STATIC_IIF)
 
 #define PIM_UPSTREAM_FLAG_SET_DR_JOIN_DESIRED(flags) ((flags) |= PIM_UPSTREAM_FLAG_MASK_DR_JOIN_DESIRED)
 #define PIM_UPSTREAM_FLAG_SET_DR_JOIN_DESIRED_UPDATED(flags) ((flags) |= PIM_UPSTREAM_FLAG_MASK_DR_JOIN_DESIRED_UPDATED)
@@ -66,6 +72,7 @@
 #define PIM_UPSTREAM_FLAG_SET_SEND_SG_RPT_PRUNE(flags) ((flags) |= PIM_UPSTREAM_FLAG_MASK_SEND_SG_RPT_PRUNE)
 #define PIM_UPSTREAM_FLAG_SET_SRC_LHR(flags) ((flags) |= PIM_UPSTREAM_FLAG_MASK_SRC_LHR)
 #define PIM_UPSTREAM_FLAG_SET_DISABLE_KAT_EXPIRY(flags) ((flags) |= PIM_UPSTREAM_FLAG_MASK_DISABLE_KAT_EXPIRY)
+#define PIM_UPSTREAM_FLAG_SET_STATIC_IIF(flags) ((flags) |= PIM_UPSTREAM_FLAG_MASK_STATIC_IIF)
 
 #define PIM_UPSTREAM_FLAG_UNSET_DR_JOIN_DESIRED(flags) ((flags) &= ~PIM_UPSTREAM_FLAG_MASK_DR_JOIN_DESIRED)
 #define PIM_UPSTREAM_FLAG_UNSET_DR_JOIN_DESIRED_UPDATED(flags) ((flags) &= ~PIM_UPSTREAM_FLAG_MASK_DR_JOIN_DESIRED_UPDATED)
@@ -77,6 +84,7 @@
 #define PIM_UPSTREAM_FLAG_UNSET_SEND_SG_RPT_PRUNE(flags) ((flags) &= ~PIM_UPSTREAM_FLAG_MASK_SEND_SG_RPT_PRUNE)
 #define PIM_UPSTREAM_FLAG_UNSET_SRC_LHR(flags) ((flags) &= ~PIM_UPSTREAM_FLAG_MASK_SRC_LHR)
 #define PIM_UPSTREAM_FLAG_UNSET_DISABLE_KAT_EXPIRY(flags) ((flags) &= ~PIM_UPSTREAM_FLAG_MASK_DISABLE_KAT_EXPIRY)
+#define PIM_UPSTREAM_FLAG_UNSET_STATIC_IIF(flags) ((flags) &= ~PIM_UPSTREAM_FLAG_MASK_STATIC_IIF)
 
 enum pim_upstream_state {
 	PIM_UPSTREAM_NOTJOINED,
@@ -256,4 +264,6 @@ unsigned int pim_upstream_hash_key(void *arg);
 bool pim_upstream_equal(const void *arg1, const void *arg2);
 struct pim_upstream *pim_upstream_keep_alive_timer_proc(
 		struct pim_upstream *up);
+void pim_upstream_fill_static_iif(struct pim_upstream *up,
+				struct interface *incoming);
 #endif /* PIM_UPSTREAM_H */