From a38ed18a4ed77a31584f2692da6f40fb53cd47fe Mon Sep 17 00:00:00 2001
From: Rafael Zalamena <rzalamena@opensourcerouting.org>
Date: Tue, 10 May 2022 08:23:40 -0300
Subject: [PATCH] pimd: implement MSDP peer SA limiting

Implement a command to enable/disable per peer MSDP SA limiting.

Signed-off-by: Rafael Zalamena <rzalamena@opensourcerouting.org>
---
 pimd/pim_cmd.c       | 24 ++++++++++++++++++++++++
 pimd/pim_msdp.c      | 12 ++++++++++++
 pimd/pim_msdp.h      |  3 +++
 pimd/pim_nb_config.c |  4 ++--
 4 files changed, 41 insertions(+), 2 deletions(-)

diff --git a/pimd/pim_cmd.c b/pimd/pim_cmd.c
index f4c25ea81e..c2d88f400e 100644
--- a/pimd/pim_cmd.c
+++ b/pimd/pim_cmd.c
@@ -7578,6 +7578,29 @@ DEFPY(msdp_shutdown,
 	return nb_cli_apply_changes(vty, NULL);
 }
 
+DEFPY(msdp_peer_sa_limit, msdp_peer_sa_limit_cmd,
+      "[no] msdp peer A.B.C.D$peer sa-limit ![(1-4294967294)$sa_limit]",
+      NO_STR
+      CFG_MSDP_STR
+      "Configure MSDP peer\n"
+      "MSDP peer address\n"
+      "Limit amount of SA\n"
+      "Maximum number of SA\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;
+	}
+
+	nb_cli_enqueue_change(vty, "./sa-limit", NB_OP_MODIFY, sa_limit_str);
+	return nb_cli_apply_changes(vty, "%s", xpath);
+}
+
 static void ip_msdp_show_mesh_group(struct vty *vty, struct pim_msdp_mg *mg,
 				    struct json_object *json)
 {
@@ -8973,6 +8996,7 @@ void pim_cmd_init(void)
 	install_element(PIM_NODE, &msdp_log_neighbor_changes_cmd);
 	install_element(PIM_NODE, &msdp_log_sa_changes_cmd);
 	install_element(PIM_NODE, &msdp_shutdown_cmd);
+	install_element(PIM_NODE, &msdp_peer_sa_limit_cmd);
 
 	install_element(PIM_NODE, &pim_bsr_candidate_rp_cmd);
 	install_element(PIM_NODE, &pim_bsr_candidate_rp_group_cmd);
diff --git a/pimd/pim_msdp.c b/pimd/pim_msdp.c
index ae887b2482..bd86ca502d 100644
--- a/pimd/pim_msdp.c
+++ b/pimd/pim_msdp.c
@@ -359,6 +359,15 @@ void pim_msdp_sa_ref(struct pim_instance *pim, struct pim_msdp_peer *mp,
 	struct rp_info *rp_info;
 	struct prefix grp;
 
+	/* Check peer SA limit. */
+	if (mp && mp->sa_limit && mp->sa_cnt >= mp->sa_limit) {
+		if (pim_msdp_log_sa_events(pim))
+			zlog_debug("MSDP peer %pI4 reject SA (%pI4, %pI4): SA limit %u of %u",
+				   &mp->peer, &sg->src, &sg->grp, mp->sa_cnt, mp->sa_limit);
+
+		return;
+	}
+
 	sa = pim_msdp_sa_add(pim, sg, rp);
 	if (!sa) {
 		return;
@@ -1316,6 +1325,9 @@ bool pim_msdp_peer_config_write(struct vty *vty, struct pim_instance *pim)
 			vty_out(vty, " msdp peer %pI4 sa-filter %s out\n",
 				&mp->peer, mp->acl_out);
 
+		if (mp->sa_limit)
+			vty_out(vty, " msdp peer %pI4 sa-limit %u\n", &mp->peer, mp->sa_limit);
+
 		written = true;
 	}
 
diff --git a/pimd/pim_msdp.h b/pimd/pim_msdp.h
index d0aa83d997..15ed685b3c 100644
--- a/pimd/pim_msdp.h
+++ b/pimd/pim_msdp.h
@@ -152,6 +152,9 @@ struct pim_msdp_peer {
 	char *acl_in;
 	/** SA output access list name. */
 	char *acl_out;
+
+	/** SA maximum amount. */
+	uint32_t sa_limit;
 };
 
 struct pim_msdp_mg_mbr {
diff --git a/pimd/pim_nb_config.c b/pimd/pim_nb_config.c
index b563bf5a30..fbba045982 100644
--- a/pimd/pim_nb_config.c
+++ b/pimd/pim_nb_config.c
@@ -1595,7 +1595,7 @@ int pim_msdp_peer_sa_limit_modify(struct nb_cb_modify_args *args)
 		break;
 	case NB_EV_APPLY:
 		mp = nb_running_get_entry(args->dnode, NULL, true);
-		/* TODO: apply limitation. */
+		mp->sa_limit = yang_dnode_get_uint32(args->dnode, NULL);
 		break;
 	}
 
@@ -1614,7 +1614,7 @@ int pim_msdp_peer_sa_limit_destroy(struct nb_cb_destroy_args *args)
 		break;
 	case NB_EV_APPLY:
 		mp = nb_running_get_entry(args->dnode, NULL, true);
-		/* TODO: remove limitation. */
+		mp->sa_limit = 0;
 		break;
 	}