pimd: Implement nexthop match where if given address match any of the next hop in ecmp case

For each BSM packet, rpf check is performed. We will be accepting if the
source address match any of the next hop neighbor(in ecmp case) to reach
the Bootstrap Router.

1. pim_nexthop_match - this lookup in zebra and return true if any of the
                       next hop nbr is matching (in ecmp case).
2. pim_nexthop_match_nht_cache - this api searches the given address in local
                                 pnc and return true if any of the next hop
                                 nbr is matching (in ecmp case).

Signed-off-by: Saravanan K <saravanank@vmware.com>

2 files changed, 168 insertions, 0 deletions

diff --git a/pimd/pim_nht.c b/pimd/pim_nht.c
index 3a3a74b15..d0611a4ae 100644
--- a/pimd/pim_nht.c
+++ b/pimd/pim_nht.c
@@ -242,6 +242,169 @@ void pim_delete_tracked_nexthop(struct pim_instance *pim, struct prefix *addr,
 	}
 }
 
+/* Given a source address and a neighbor address, check if the neighbor is one
+ * of the next hop to reach the source. search from zebra route database
+ */
+bool pim_nexthop_match(struct pim_instance *pim, struct in_addr addr,
+		       struct in_addr ip_src)
+{
+	struct pim_zlookup_nexthop nexthop_tab[MULTIPATH_NUM];
+	int i = 0;
+	ifindex_t first_ifindex = 0;
+	struct interface *ifp = NULL;
+	struct pim_neighbor *nbr = NULL;
+	int num_ifindex;
+
+	if (addr.s_addr == INADDR_NONE)
+		return 0;
+
+	memset(nexthop_tab, 0,
+	       sizeof(struct pim_zlookup_nexthop) * MULTIPATH_NUM);
+	num_ifindex = zclient_lookup_nexthop(pim, nexthop_tab, MULTIPATH_NUM,
+					     addr, PIM_NEXTHOP_LOOKUP_MAX);
+	if (num_ifindex < 1) {
+		char addr_str[INET_ADDRSTRLEN];
+
+		pim_inet4_dump("<addr?>", addr, addr_str, sizeof(addr_str));
+		zlog_warn(
+			"%s %s: could not find nexthop ifindex for address %s",
+			__FILE__, __PRETTY_FUNCTION__, addr_str);
+		return 0;
+	}
+
+	while (i < num_ifindex) {
+		first_ifindex = nexthop_tab[i].ifindex;
+
+		ifp = if_lookup_by_index(first_ifindex, pim->vrf_id);
+		if (!ifp) {
+			if (PIM_DEBUG_ZEBRA) {
+				char addr_str[INET_ADDRSTRLEN];
+
+				pim_inet4_dump("<addr?>", addr, addr_str,
+					       sizeof(addr_str));
+				zlog_debug(
+					"%s %s: could not find interface for ifindex %d (address %s)",
+					__FILE__, __PRETTY_FUNCTION__,
+					first_ifindex, addr_str);
+			}
+			i++;
+			continue;
+		}
+
+		if (!ifp->info) {
+			if (PIM_DEBUG_ZEBRA) {
+				char addr_str[INET_ADDRSTRLEN];
+
+				pim_inet4_dump("<addr?>", addr, addr_str,
+					       sizeof(addr_str));
+				zlog_debug(
+					"%s: multicast not enabled on input interface %s (ifindex=%d, RPF for source %s)",
+					__PRETTY_FUNCTION__, ifp->name,
+					first_ifindex, addr_str);
+			}
+			i++;
+			continue;
+		}
+
+		if (!pim_if_connected_to_source(ifp, addr)) {
+			nbr = pim_neighbor_find(
+				ifp, nexthop_tab[i].nexthop_addr.u.prefix4);
+			if (PIM_DEBUG_PIM_TRACE_DETAIL)
+				zlog_debug("ifp name: %s, pim nbr: %p",
+					   ifp->name, nbr);
+			if (!nbr && !if_is_loopback(ifp)) {
+				i++;
+				continue;
+			}
+		}
+
+		if (nexthop_tab[i].nexthop_addr.u.prefix4.s_addr
+		    == ip_src.s_addr)
+			return 1;
+
+		i++;
+	}
+
+	return 0;
+}
+
+/* Given a source address and a neighbor address, check if the neighbor is one
+ * of the next hop to reach the source. search from pim next hop cache
+ */
+bool pim_nexthop_match_nht_cache(struct pim_instance *pim, struct in_addr addr,
+				 struct in_addr ip_src)
+{
+	struct pim_rpf rpf;
+	ifindex_t first_ifindex;
+	struct interface *ifp = NULL;
+	uint8_t nh_iter = 0;
+	struct pim_neighbor *nbr = NULL;
+	struct nexthop *nh_node = NULL;
+	struct pim_nexthop_cache *pnc = NULL;
+
+	memset(&rpf, 0, sizeof(struct pim_rpf));
+	rpf.rpf_addr.family = AF_INET;
+	rpf.rpf_addr.prefixlen = IPV4_MAX_BITLEN;
+	rpf.rpf_addr.u.prefix4 = addr;
+
+	pnc = pim_nexthop_cache_find(pim, &rpf);
+	if (!pnc || !pnc->nexthop_num)
+		return 0;
+
+	for (nh_node = pnc->nexthop; nh_node; nh_node = nh_node->next) {
+		first_ifindex = nh_node->ifindex;
+		ifp = if_lookup_by_index(first_ifindex, pim->vrf_id);
+		if (!ifp) {
+			if (PIM_DEBUG_PIM_NHT) {
+				char addr_str[INET_ADDRSTRLEN];
+
+				pim_inet4_dump("<addr?>", addr, addr_str,
+					       sizeof(addr_str));
+				zlog_debug(
+					"%s %s: could not find interface for ifindex %d (address %s(%s))",
+					__FILE__, __PRETTY_FUNCTION__,
+					first_ifindex, addr_str,
+					pim->vrf->name);
+			}
+			nh_iter++;
+			continue;
+		}
+		if (!ifp->info) {
+			if (PIM_DEBUG_PIM_NHT) {
+				char addr_str[INET_ADDRSTRLEN];
+
+				pim_inet4_dump("<addr?>", addr, addr_str,
+					       sizeof(addr_str));
+				zlog_debug(
+					"%s: multicast not enabled on input interface %s(%s) (ifindex=%d, RPF for source %s)",
+					__PRETTY_FUNCTION__, ifp->name,
+					pim->vrf->name, first_ifindex,
+					addr_str);
+			}
+			nh_iter++;
+			continue;
+		}
+
+		if (!pim_if_connected_to_source(ifp, addr)) {
+			nbr = pim_neighbor_find(ifp, nh_node->gate.ipv4);
+			if (!nbr && !if_is_loopback(ifp)) {
+				if (PIM_DEBUG_PIM_NHT)
+					zlog_debug(
+						"%s: pim nbr not found on input interface %s(%s)",
+						__PRETTY_FUNCTION__, ifp->name,
+						pim->vrf->name);
+				nh_iter++;
+				continue;
+			}
+		}
+
+		if (nh_node->gate.ipv4.s_addr == ip_src.s_addr)
+			return 1;
+	}
+
+	return 0;
+}
+
 void pim_rp_nexthop_del(struct rp_info *rp_info)
 {
 	rp_info->rp.source_nexthop.interface = NULL;
diff --git a/pimd/pim_nht.h b/pimd/pim_nht.h
index 5324aba44..e3b746b19 100644
--- a/pimd/pim_nht.h
+++ b/pimd/pim_nht.h
@@ -73,4 +73,9 @@ void pim_sendmsg_zebra_rnh(struct pim_instance *pim, struct zclient *zclient,
 int pim_ecmp_fib_lookup_if_vif_index(struct pim_instance *pim,
 				     struct prefix *src, struct prefix *grp);
 void pim_rp_nexthop_del(struct rp_info *rp_info);
+bool pim_nexthop_match(struct pim_instance *pim, struct in_addr addr,
+		       struct in_addr ip_src);
+bool pim_nexthop_match_nht_cache(struct pim_instance *pim, struct in_addr addr,
+				 struct in_addr ip_src);
+
 #endif