pimd: MSDP SA filtering

Implement MSDP peer incoming/outgoing SA filter.

Note
----

  Cisco extended access list has a special meaning: the first address is
  the source address to filter.

Example:

  ! The rules below filter some LAN prefix to be leaked out
  access-list filter-lan-source deny ip 192.168.0.0 0.0.255.255 224.0.0.0 0.255.255.255
  access-list filter-lan-source permit any
  router pim
   msdp peer 192.168.0.1 sa-filter filter-lan-source out

  ! The rules below filter some special management group from being
  ! learned
  access-list filter-management-group deny 230.0.0.0 0.255.255.255
  access-list filter-management-group permit any
  router pim
   msdp peer 192.168.0.1 sa-filter filter-management-group in

Signed-off-by: Rafael Zalamena <rzalamena@opensourcerouting.org>

pimd/pim_cmd.c

@@ -6486,6 +6486,69 @@ DEFPY_ATTR(no_ip_pim_msdp_peer,
 	return ret;
 }
 
+DEFPY(msdp_peer_sa_filter, msdp_peer_sa_filter_cmd,
+      "msdp peer A.B.C.D$peer sa-filter ACL_NAME$acl_name <in|out>$dir",
+      CFG_MSDP_STR
+      "Configure MSDP peer\n"
+      "MSDP Peer address\n"
+      "SA access-list filter\n"
+      "SA access-list name\n"
+      "Filter incoming SAs\n"
+      "Filter outgoing SAs\n")
+{
+	const struct lyd_node *peer_node;
+	char xpath[XPATH_MAXLEN + 24];
+
+	snprintf(xpath, sizeof(xpath), "%s/msdp-peer[peer-ip='%s']",
+		 VTY_CURR_XPATH, peer_str);
+	peer_node = yang_dnode_get(vty->candidate_config->dnode, xpath);
+	if (peer_node == NULL) {
+		vty_out(vty, "%% MSDP peer %s not yet configured\n", peer_str);
+		return CMD_SUCCESS;
+	}
+
+	if (strcmp(dir, "in") == 0)
+		nb_cli_enqueue_change(vty, "./sa-filter-in", NB_OP_MODIFY,
+				      acl_name);
+	else
+		nb_cli_enqueue_change(vty, "./sa-filter-out", NB_OP_MODIFY,
+				      acl_name);
+
+	return nb_cli_apply_changes(vty, "%s", xpath);
+}
+
+DEFPY(no_msdp_peer_sa_filter, no_ip_msdp_peer_sa_filter_cmd,
+      "no msdp peer A.B.C.D$peer sa-filter ACL_NAME <in|out>$dir",
+      NO_STR
+      CFG_MSDP_STR
+      "Configure MSDP peer\n"
+      "MSDP Peer address\n"
+      "SA access-list filter\n"
+      "SA access-list name\n"
+      "Filter incoming SAs\n"
+      "Filter outgoing SAs\n")
+{
+	const struct lyd_node *peer_node;
+	char xpath[XPATH_MAXLEN + 24];
+
+	snprintf(xpath, sizeof(xpath), "%s/msdp-peer[peer-ip='%s']",
+		 VTY_CURR_XPATH, peer_str);
+	peer_node = yang_dnode_get(vty->candidate_config->dnode, xpath);
+	if (peer_node == NULL) {
+		vty_out(vty, "%% MSDP peer %s not yet configured\n", peer_str);
+		return CMD_SUCCESS;
+	}
+
+	if (strcmp(dir, "in") == 0)
+		nb_cli_enqueue_change(vty, "./sa-filter-in", NB_OP_DESTROY,
+				      NULL);
+	else
+		nb_cli_enqueue_change(vty, "./sa-filter-out", NB_OP_DESTROY,
+				      NULL);
+
+	return nb_cli_apply_changes(vty, "%s", xpath);
+}
+
 DEFPY(pim_msdp_mesh_group_member,
       pim_msdp_mesh_group_member_cmd,
       "msdp mesh-group WORD$gname member A.B.C.D$maddr",
@@ -8259,6 +8322,8 @@ void pim_cmd_init(void)
 	install_element(PIM_NODE, &no_pim_msdp_peer_cmd);
 	install_element(PIM_NODE, &pim_msdp_timers_cmd);
 	install_element(PIM_NODE, &no_pim_msdp_timers_cmd);
+	install_element(PIM_NODE, &msdp_peer_sa_filter_cmd);
+	install_element(PIM_NODE, &no_ip_msdp_peer_sa_filter_cmd);
 	install_element(PIM_NODE, &pim_msdp_mesh_group_member_cmd);
 	install_element(PIM_NODE, &no_pim_msdp_mesh_group_member_cmd);
 	install_element(PIM_NODE, &pim_msdp_mesh_group_source_cmd);

pimd/pim_msdp.c

@@ -1317,6 +1317,15 @@ bool pim_msdp_peer_config_write(struct vty *vty, struct pim_instance *pim)
 
 		vty_out(vty, " msdp peer %pI4 source %pI4\n", &mp->peer,
 			&mp->local);
+
+		if (mp->acl_in)
+			vty_out(vty, " msdp peer %pI4 sa-filter %s in\n",
+				&mp->peer, mp->acl_in);
+
+		if (mp->acl_out)
+			vty_out(vty, " msdp peer %pI4 sa-filter %s out\n",
+				&mp->peer, mp->acl_out);
+
 		written = true;
 	}
 

pimd/pim_msdp.h

@@ -138,6 +138,11 @@ struct pim_msdp_peer {
 
 	/* timestamps */
 	int64_t uptime;
+
+	/** SA input access list name. */
+	char *acl_in;
+	/** SA output access list name. */
+	char *acl_out;
 };
 
 struct pim_msdp_mg_mbr {

pimd/pim_msdp_packet.c

@@ -6,7 +6,9 @@
 #include <zebra.h>
 
 #include <lib/log.h>
+#include <lib/filter.h>
 #include <lib/network.h>
+#include <lib/prefix.h>
 #include <lib/stream.h>
 #include "frrevent.h"
 #include <lib/vty.h>
@@ -322,8 +324,8 @@ void pim_msdp_pkt_ka_tx(struct pim_msdp_peer *mp)
 	pim_msdp_pkt_send(mp, s);
 }
 
-static void pim_msdp_pkt_sa_push_to_one_peer(struct pim_instance *pim,
+static void pim_msdp_pkt_sa_push(struct pim_instance *pim,
-					     struct pim_msdp_peer *mp)
+				 struct pim_msdp_peer *mp)
 {
 	struct stream *s;
 
@@ -338,25 +340,6 @@ static void pim_msdp_pkt_sa_push_to_one_peer(struct pim_instance *pim,
 	}
 }
 
-/* push the stream into the obuf fifo of all the peers */
-static void pim_msdp_pkt_sa_push(struct pim_instance *pim,
-				 struct pim_msdp_peer *mp)
-{
-	struct listnode *mpnode;
-
-	if (mp) {
-		pim_msdp_pkt_sa_push_to_one_peer(pim, mp);
-	} else {
-		for (ALL_LIST_ELEMENTS_RO(pim->msdp.peer_list, mpnode, mp)) {
-			if (PIM_DEBUG_MSDP_INTERNAL) {
-				zlog_debug("MSDP peer %s pim_msdp_pkt_sa_push",
-					   mp->key_str);
-			}
-			pim_msdp_pkt_sa_push_to_one_peer(pim, mp);
-		}
-	}
-}
-
 static int pim_msdp_pkt_sa_fill_hdr(struct pim_instance *pim, int local_cnt,
 				    struct in_addr rp)
 {
@@ -384,6 +367,90 @@ static void pim_msdp_pkt_sa_fill_one(struct pim_msdp_sa *sa)
 	stream_put_ipv4(sa->pim->msdp.work_obuf, sa->sg.src.s_addr);
 }
 
+static bool msdp_cisco_match(const struct filter *filter,
+			     const struct in_addr *source,
+			     const struct in_addr *group)
+{
+	const struct filter_cisco *cfilter = &filter->u.cfilter;
+	uint32_t source_addr;
+	uint32_t group_addr;
+
+	group_addr = group->s_addr & ~cfilter->mask_mask.s_addr;
+
+	if (cfilter->extended) {
+		source_addr = source->s_addr & ~cfilter->addr_mask.s_addr;
+		if (group_addr == cfilter->mask.s_addr &&
+		    source_addr == cfilter->addr.s_addr)
+			return true;
+	} else if (group_addr == cfilter->addr.s_addr)
+		return true;
+
+	return false;
+}
+
+static enum filter_type msdp_access_list_apply(struct access_list *access,
+					       const struct in_addr *source,
+					       const struct in_addr *group)
+{
+	struct filter *filter;
+	struct prefix group_prefix;
+
+	if (access == NULL)
+		return FILTER_DENY;
+
+	for (filter = access->head; filter; filter = filter->next) {
+		if (filter->cisco) {
+			if (msdp_cisco_match(filter, source, group))
+				return filter->type;
+		} else {
+			group_prefix.family = AF_INET;
+			group_prefix.prefixlen = IPV4_MAX_BITLEN;
+			group_prefix.u.prefix4.s_addr = group->s_addr;
+			if (access_list_apply(access, &group_prefix))
+				return filter->type;
+		}
+	}
+
+	return FILTER_DENY;
+}
+
+bool msdp_peer_sa_filter(const struct pim_msdp_peer *mp,
+			 const struct pim_msdp_sa *sa)
+{
+	struct access_list *acl;
+
+	/* No output filter configured, just quit. */
+	if (mp->acl_out == NULL)
+		return false;
+
+	/* Find access list and test it. */
+	acl = access_list_lookup(AFI_IP, mp->acl_out);
+	if (msdp_access_list_apply(acl, &sa->sg.src, &sa->sg.grp) == FILTER_DENY)
+		return true;
+
+	return false;
+}
+
+/** Count the number of SAs to be sent for a specific peer. */
+static size_t pim_msdp_peer_sa_count(const struct pim_instance *pim,
+				     const struct pim_msdp_peer *peer)
+{
+	const struct pim_msdp_sa *sa;
+	const struct listnode *node;
+	size_t sa_count = 0;
+
+	for (ALL_LIST_ELEMENTS_RO(pim->msdp.sa_list, node, sa)) {
+		if (!CHECK_FLAG(sa->flags, PIM_MSDP_SAF_LOCAL))
+			continue;
+		if (msdp_peer_sa_filter(peer, sa))
+			continue;
+
+		sa_count++;
+	}
+
+	return sa_count;
+}
+
 static void pim_msdp_pkt_sa_gen(struct pim_instance *pim,
 				struct pim_msdp_peer *mp)
 {
@@ -393,7 +460,7 @@ static void pim_msdp_pkt_sa_gen(struct pim_instance *pim,
 	struct prefix group_all;
 	struct in_addr rp;
 	int sa_count;
-	int local_cnt = pim->msdp.local_cnt;
+	int local_cnt = pim_msdp_peer_sa_count(pim, mp);
 
 	sa_count = 0;
 	if (PIM_DEBUG_MSDP_INTERNAL) {
@@ -418,6 +485,15 @@ static void pim_msdp_pkt_sa_gen(struct pim_instance *pim,
 			 * peers */
 			continue;
 		}
+
+		if (msdp_peer_sa_filter(mp, sa)) {
+			if (PIM_DEBUG_MSDP_EVENTS)
+				zlog_debug("MSDP peer %pI4 filter SA out %s",
+					   &mp->peer, sa->sg_str);
+
+			continue;
+		}
+
 		/* add sa into scratch pad */
 		pim_msdp_pkt_sa_fill_one(sa);
 		++sa_count;
@@ -457,15 +533,32 @@ static void pim_msdp_pkt_sa_tx_done(struct pim_instance *pim)
 
 void pim_msdp_pkt_sa_tx(struct pim_instance *pim)
 {
-	pim_msdp_pkt_sa_gen(pim, NULL /* mp */);
+	struct pim_msdp_peer *mp;
+	struct listnode *node;
+
+	for (ALL_LIST_ELEMENTS_RO(pim->msdp.peer_list, node, mp))
+		pim_msdp_pkt_sa_gen(pim, mp);
+
 	pim_msdp_pkt_sa_tx_done(pim);
 }
 
 void pim_msdp_pkt_sa_tx_one(struct pim_msdp_sa *sa)
 {
+	struct pim_msdp_peer *mp;
+	struct listnode *node;
+
 	pim_msdp_pkt_sa_fill_hdr(sa->pim, 1 /* cnt */, sa->rp);
 	pim_msdp_pkt_sa_fill_one(sa);
-	pim_msdp_pkt_sa_push(sa->pim, NULL);
+	for (ALL_LIST_ELEMENTS_RO(sa->pim->msdp.peer_list, node, mp)) {
+		if (msdp_peer_sa_filter(mp, sa)) {
+			if (PIM_DEBUG_MSDP_EVENTS)
+				zlog_debug("MSDP peer %pI4 filter SA out %s",
+					   &mp->peer, sa->sg_str);
+			continue;
+		}
+
+		pim_msdp_pkt_sa_push(sa->pim, mp);
+	}
 	pim_msdp_pkt_sa_tx_done(sa->pim);
 }
 
@@ -487,6 +580,15 @@ void pim_msdp_pkt_sa_tx_one_to_one_peer(struct pim_msdp_peer *mp,
 	/* Fills the message contents. */
 	sa.pim = mp->pim;
 	sa.sg = sg;
+
+	/* Don't push it if filtered. */
+	if (msdp_peer_sa_filter(mp, &sa)) {
+		if (PIM_DEBUG_MSDP_EVENTS)
+			zlog_debug("MSDP peer %pI4 filter SA out (%pI4, %pI4)",
+				   &mp->peer, &sa.sg.src, &sa.sg.grp);
+		return;
+	}
+
 	pim_msdp_pkt_sa_fill_one(&sa);
 
 	/* Pushes the message. */
@@ -511,6 +613,7 @@ static void pim_msdp_pkt_ka_rx(struct pim_msdp_peer *mp, int len)
 
 static void pim_msdp_pkt_sa_rx_one(struct pim_msdp_peer *mp, struct in_addr rp)
 {
+	struct access_list *acl;
 	int prefix_len;
 	pim_sgaddr sg;
 	struct listnode *peer_node;
@@ -534,6 +637,19 @@ static void pim_msdp_pkt_sa_rx_one(struct pim_msdp_peer *mp, struct in_addr rp)
 	if (PIM_DEBUG_MSDP_PACKETS) {
 		zlog_debug("  sg %pSG", &sg);
 	}
+
+	/* Filter incoming SA with configured access list. */
+	if (mp->acl_in) {
+		acl = access_list_lookup(AFI_IP, mp->acl_in);
+		if (msdp_access_list_apply(acl, &sg.src, &sg.grp) ==
+		    FILTER_DENY) {
+			if (PIM_DEBUG_MSDP_EVENTS)
+				zlog_debug("MSDP peer %pI4 filter SA in (%pI4, %pI4)",
+					   &mp->peer, &sg.src, &sg.grp);
+			return;
+		}
+	}
+
 	pim_msdp_sa_ref(mp->pim, mp, &sg, rp);
 
 	/* Forwards the SA to the peers that are not in the RPF to the RP nor in

pimd/pim_msdp_packet.h

@@ -57,5 +57,7 @@ void pim_msdp_pkt_sa_tx_one(struct pim_msdp_sa *sa);
 void pim_msdp_pkt_sa_tx_to_one_peer(struct pim_msdp_peer *mp);
 void pim_msdp_pkt_sa_tx_one_to_one_peer(struct pim_msdp_peer *mp,
 					struct in_addr rp, pim_sgaddr sg);
+bool msdp_peer_sa_filter(const struct pim_msdp_peer *mp,
+			 const struct pim_msdp_sa *sa);
 
 #endif

pimd/pim_nb.c

@@ -163,6 +163,20 @@ const struct frr_yang_module_info frr_pim_info = {
 				.modify = routing_control_plane_protocols_control_plane_protocol_pim_address_family_msdp_peer_source_ip_modify,
 			}
 		},
+		{
+			.xpath = "/frr-routing:routing/control-plane-protocols/control-plane-protocol/frr-pim:pim/address-family/msdp-peer/sa-filter-in",
+			.cbs = {
+				.modify = pim_msdp_peer_sa_filter_in_modify,
+				.destroy = pim_msdp_peer_sa_filter_in_destroy,
+			}
+		},
+		{
+			.xpath = "/frr-routing:routing/control-plane-protocols/control-plane-protocol/frr-pim:pim/address-family/msdp-peer/sa-filter-out",
+			.cbs = {
+				.modify = pim_msdp_peer_sa_filter_out_modify,
+				.destroy = pim_msdp_peer_sa_filter_out_destroy,
+			}
+		},
 		{
 			.xpath = "/frr-routing:routing/control-plane-protocols/control-plane-protocol/frr-pim:pim/address-family/mlag",
 			.cbs = {

pimd/pim_nb.h

@@ -65,6 +65,10 @@ int routing_control_plane_protocols_control_plane_protocol_pim_address_family_ms
 	struct nb_cb_destroy_args *args);
 int routing_control_plane_protocols_control_plane_protocol_pim_address_family_msdp_peer_source_ip_modify(
 	struct nb_cb_modify_args *args);
+int pim_msdp_peer_sa_filter_in_modify(struct nb_cb_modify_args *args);
+int pim_msdp_peer_sa_filter_in_destroy(struct nb_cb_destroy_args *args);
+int pim_msdp_peer_sa_filter_out_modify(struct nb_cb_modify_args *args);
+int pim_msdp_peer_sa_filter_out_destroy(struct nb_cb_destroy_args *args);
 int routing_control_plane_protocols_control_plane_protocol_pim_address_family_mlag_create(
 	struct nb_cb_create_args *args);
 int routing_control_plane_protocols_control_plane_protocol_pim_address_family_mlag_destroy(

pimd/pim_nb_config.c

@@ -1286,6 +1286,94 @@ int routing_control_plane_protocols_control_plane_protocol_pim_address_family_ms
 }
 #endif /* PIM_IPV != 6 */
 
+/*
+ * XPath:
+ * /frr-routing:routing/control-plane-protocols/control-plane-protocol/frr-pim:pim/address-family/msdp-peer/sa-filter-in
+ */
+int pim_msdp_peer_sa_filter_in_modify(struct nb_cb_modify_args *args)
+{
+	struct pim_msdp_peer *mp;
+
+	switch (args->event) {
+	case NB_EV_VALIDATE:
+	case NB_EV_PREPARE:
+	case NB_EV_ABORT:
+		/* NOTHING */
+		break;
+	case NB_EV_APPLY:
+		mp = nb_running_get_entry(args->dnode, NULL, true);
+		XFREE(MTYPE_TMP, mp->acl_in);
+		mp->acl_in = XSTRDUP(MTYPE_TMP,
+				     yang_dnode_get_string(args->dnode, NULL));
+		break;
+	}
+
+	return NB_OK;
+}
+
+int pim_msdp_peer_sa_filter_in_destroy(struct nb_cb_destroy_args *args)
+{
+	struct pim_msdp_peer *mp;
+
+	switch (args->event) {
+	case NB_EV_VALIDATE:
+	case NB_EV_PREPARE:
+	case NB_EV_ABORT:
+		/* NOTHING */
+		break;
+	case NB_EV_APPLY:
+		mp = nb_running_get_entry(args->dnode, NULL, true);
+		XFREE(MTYPE_TMP, mp->acl_in);
+		break;
+	}
+
+	return NB_OK;
+}
+
+/*
+ * XPath:
+ * /frr-routing:routing/control-plane-protocols/control-plane-protocol/frr-pim:pim/address-family/msdp-peer/sa-filter-out
+ */
+int pim_msdp_peer_sa_filter_out_modify(struct nb_cb_modify_args *args)
+{
+	struct pim_msdp_peer *mp;
+
+	switch (args->event) {
+	case NB_EV_VALIDATE:
+	case NB_EV_PREPARE:
+	case NB_EV_ABORT:
+		/* NOTHING */
+		break;
+	case NB_EV_APPLY:
+		mp = nb_running_get_entry(args->dnode, NULL, true);
+		XFREE(MTYPE_TMP, mp->acl_out);
+		mp->acl_out = XSTRDUP(MTYPE_TMP,
+				      yang_dnode_get_string(args->dnode, NULL));
+		break;
+	}
+
+	return NB_OK;
+}
+
+int pim_msdp_peer_sa_filter_out_destroy(struct nb_cb_destroy_args *args)
+{
+	struct pim_msdp_peer *mp;
+
+	switch (args->event) {
+	case NB_EV_VALIDATE:
+	case NB_EV_PREPARE:
+	case NB_EV_ABORT:
+		/* NOTHING */
+		break;
+	case NB_EV_APPLY:
+		mp = nb_running_get_entry(args->dnode, NULL, true);
+		XFREE(MTYPE_TMP, mp->acl_out);
+		break;
+	}
+
+	return NB_OK;
+}
+
 /*
  * XPath: /frr-routing:routing/control-plane-protocols/control-plane-protocol/frr-pim:pim/address-family/mlag
  */