Adding upstream version 9.1.upstream/9.1

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 2585 insertions, 0 deletions

diff --git a/isisd/isis_pdu.c b/isisd/isis_pdu.c
new file mode 100644
index 0000000..0cd43a7
--- /dev/null
+++ b/isisd/isis_pdu.c
@@ -0,0 +1,2585 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * IS-IS Rout(e)ing protocol - isis_pdu.c
+ *                             PDU processing
+ *
+ * Copyright (C) 2001,2002   Sampo Saaristo
+ *                           Tampere University of Technology
+ *                           Institute of Communications Engineering
+ */
+
+#include <zebra.h>
+
+#include "memory.h"
+#include "frrevent.h"
+#include "linklist.h"
+#include "log.h"
+#include "stream.h"
+#include "vty.h"
+#include "hash.h"
+#include "prefix.h"
+#include "if.h"
+#include "checksum.h"
+#include "md5.h"
+#include "lib_errors.h"
+
+#include "isisd/isis_constants.h"
+#include "isisd/isis_common.h"
+#include "isisd/isis_flags.h"
+#include "isisd/isis_adjacency.h"
+#include "isisd/isis_circuit.h"
+#include "isisd/isis_network.h"
+#include "isisd/isis_misc.h"
+#include "isisd/isis_dr.h"
+#include "isisd/isisd.h"
+#include "isisd/isis_dynhn.h"
+#include "isisd/isis_lsp.h"
+#include "isisd/isis_pdu.h"
+#include "isisd/iso_checksum.h"
+#include "isisd/isis_csm.h"
+#include "isisd/isis_events.h"
+#include "isisd/isis_te.h"
+#include "isisd/isis_mt.h"
+#include "isisd/isis_tlvs.h"
+#include "isisd/isis_errors.h"
+#include "isisd/fabricd.h"
+#include "isisd/isis_tx_queue.h"
+#include "isisd/isis_pdu_counter.h"
+#include "isisd/isis_nb.h"
+
+static int ack_lsp(struct isis_lsp_hdr *hdr, struct isis_circuit *circuit,
+		   int level)
+{
+	unsigned long lenp;
+	int retval;
+	uint16_t length;
+	uint8_t pdu_type =
+		(level == IS_LEVEL_1) ? L1_PARTIAL_SEQ_NUM : L2_PARTIAL_SEQ_NUM;
+
+	isis_circuit_stream(circuit, &circuit->snd_stream);
+
+	fill_fixed_hdr(pdu_type, circuit->snd_stream);
+
+	lenp = stream_get_endp(circuit->snd_stream);
+
+	stream_putw(circuit->snd_stream, 0); /* PDU length  */
+	stream_put(circuit->snd_stream, circuit->isis->sysid, ISIS_SYS_ID_LEN);
+	stream_putc(circuit->snd_stream, circuit->idx);
+	stream_putc(circuit->snd_stream, 9);  /* code */
+	stream_putc(circuit->snd_stream, 16); /* len */
+
+	stream_putw(circuit->snd_stream, hdr->rem_lifetime);
+	stream_put(circuit->snd_stream, hdr->lsp_id, ISIS_SYS_ID_LEN + 2);
+	stream_putl(circuit->snd_stream, hdr->seqno);
+	stream_putw(circuit->snd_stream, hdr->checksum);
+
+	length = (uint16_t)stream_get_endp(circuit->snd_stream);
+	/* Update PDU length */
+	stream_putw_at(circuit->snd_stream, lenp, length);
+
+	pdu_counter_count(circuit->area->pdu_tx_counters, pdu_type);
+	retval = circuit->tx(circuit, level);
+	if (retval != ISIS_OK)
+		flog_err(EC_ISIS_PACKET,
+			 "ISIS-Upd (%s): Send L%d LSP PSNP on %s failed",
+			 circuit->area->area_tag, level,
+			 circuit->interface->name);
+
+	return retval;
+}
+
+/*
+ *  RECEIVE SIDE
+ */
+
+struct iih_info {
+	struct isis_circuit *circuit;
+	uint8_t *ssnpa;
+	int level;
+
+	uint8_t circ_type;
+	uint8_t sys_id[ISIS_SYS_ID_LEN];
+	uint16_t holdtime;
+	uint16_t pdu_len;
+
+	uint8_t circuit_id;
+
+	uint8_t priority;
+	uint8_t dis[ISIS_SYS_ID_LEN + 1];
+
+	bool v4_usable;
+	bool v6_usable;
+
+	struct isis_tlvs *tlvs;
+};
+
+static int process_p2p_hello(struct iih_info *iih)
+{
+	struct isis_threeway_adj *tw_adj = iih->tlvs->threeway_adj;
+
+	if (tw_adj) {
+		if (tw_adj->state > ISIS_THREEWAY_DOWN) {
+			if (IS_DEBUG_ADJ_PACKETS) {
+				zlog_debug("ISIS-Adj (%s): Rcvd P2P IIH from (%s) with invalid three-way state: %d",
+					   iih->circuit->area->area_tag,
+					   iih->circuit->interface->name,
+					   tw_adj->state);
+			}
+			return ISIS_WARNING;
+		}
+
+		if (tw_adj->neighbor_set
+		    && (memcmp(tw_adj->neighbor_id, iih->circuit->isis->sysid,
+			       ISIS_SYS_ID_LEN)
+			|| tw_adj->neighbor_circuit_id
+				   != (uint32_t)iih->circuit->idx)) {
+
+			if (IS_DEBUG_ADJ_PACKETS) {
+				zlog_debug("ISIS-Adj (%s): Rcvd P2P IIH from (%s) which lists IS/Circuit different from us as neighbor.",
+					   iih->circuit->area->area_tag,
+					   iih->circuit->interface->name);
+			}
+
+			return ISIS_WARNING;
+		}
+	}
+
+	/*
+	 * My interpertation of the ISO, if no adj exists we will create one for
+	 * the circuit
+	 */
+	struct isis_adjacency *adj = iih->circuit->u.p2p.neighbor;
+	/* If an adjacency exists, check it is with the source of the hello
+	 * packets */
+	if (adj) {
+		if (memcmp(iih->sys_id, adj->sysid, ISIS_SYS_ID_LEN)) {
+			zlog_debug(
+				"hello source and adjacency do not match, set adj down");
+			isis_adj_state_change(&adj, ISIS_ADJ_DOWN,
+					      "adj do not exist");
+			return ISIS_OK;
+		}
+	}
+	if (!adj || adj->level != iih->circ_type) {
+		if (!adj) {
+			adj = isis_new_adj(iih->sys_id, NULL, iih->circ_type,
+					   iih->circuit);
+		} else {
+			adj->level = iih->circ_type;
+		}
+		iih->circuit->u.p2p.neighbor = adj;
+		/* Build lsp with the new neighbor entry when a new
+		 * adjacency is formed. Set adjacency circuit type to
+		 * IIH PDU header circuit type before lsp is regenerated
+		 * when an adjacency is up. This will result in the new
+		 * adjacency entry getting added to the lsp tlv neighbor list.
+		 */
+		adj->circuit_t = iih->circ_type;
+		isis_adj_state_change(&adj, ISIS_ADJ_INITIALIZING, NULL);
+		adj->sys_type = ISIS_SYSTYPE_UNKNOWN;
+	}
+
+	if (tw_adj)
+		adj->ext_circuit_id = tw_adj->local_circuit_id;
+
+	/* 8.2.6 Monitoring point-to-point adjacencies */
+	adj->hold_time = iih->holdtime;
+	adj->last_upd = time(NULL);
+
+	bool changed;
+	isis_tlvs_to_adj(iih->tlvs, adj, &changed);
+	changed |= tlvs_to_adj_mt_set(iih->tlvs, iih->v4_usable, iih->v6_usable,
+				      adj);
+
+	/* lets take care of the expiry */
+	EVENT_OFF(adj->t_expire);
+	event_add_timer(master, isis_adj_expire, adj, (long)adj->hold_time,
+			&adj->t_expire);
+
+	/* While fabricds initial sync is in progress, ignore hellos from other
+	 * interfaces than the one we are performing the initial sync on. */
+	if (fabricd_initial_sync_is_in_progress(iih->circuit->area)
+	    && fabricd_initial_sync_circuit(iih->circuit->area) != iih->circuit)
+		return ISIS_OK;
+
+	/* 8.2.5.2 a) a match was detected */
+	if (isis_tlvs_area_addresses_match(iih->tlvs,
+					   iih->circuit->area->area_addrs)) {
+		/* 8.2.5.2 a) 2) If the system is L1 - table 5 */
+		if (iih->circuit->area->is_type == IS_LEVEL_1) {
+			switch (iih->circ_type) {
+			case IS_LEVEL_1:
+			case IS_LEVEL_1_AND_2:
+				if (adj->adj_state != ISIS_ADJ_UP
+				    || adj->adj_usage == ISIS_ADJ_LEVEL1) {
+					isis_adj_process_threeway(adj, tw_adj,
+								  ISIS_ADJ_LEVEL1);
+				}
+				break;
+			case IS_LEVEL_2:
+				if (adj->adj_state != ISIS_ADJ_UP) {
+					/* (7) reject - wrong system type event
+					 */
+					zlog_warn("wrongSystemType");
+					return ISIS_WARNING;
+				} else if (adj->adj_usage == ISIS_ADJ_LEVEL1) {
+					/* (6) down - wrong system */
+					isis_adj_state_change(&adj,
+							      ISIS_ADJ_DOWN,
+							      "Wrong System");
+				}
+				break;
+			}
+		}
+
+		/* 8.2.5.2 a) 3) If the system is L1L2 - table 6 */
+		if (iih->circuit->area->is_type == IS_LEVEL_1_AND_2) {
+			switch (iih->circ_type) {
+			case IS_LEVEL_1:
+				if (adj->adj_state != ISIS_ADJ_UP
+				    || adj->adj_usage == ISIS_ADJ_LEVEL1) {
+					isis_adj_process_threeway(adj, tw_adj,
+								  ISIS_ADJ_LEVEL1);
+				} else if ((adj->adj_usage
+					    == ISIS_ADJ_LEVEL1AND2)
+					   || (adj->adj_usage
+					       == ISIS_ADJ_LEVEL2)) {
+					/* (8) down - wrong system */
+					isis_adj_state_change(&adj,
+							      ISIS_ADJ_DOWN,
+							      "Wrong System");
+				}
+				break;
+			case IS_LEVEL_2:
+				if (adj->adj_state != ISIS_ADJ_UP
+				    || adj->adj_usage == ISIS_ADJ_LEVEL2) {
+					isis_adj_process_threeway(adj, tw_adj,
+								  ISIS_ADJ_LEVEL2);
+				} else if ((adj->adj_usage == ISIS_ADJ_LEVEL1)
+					   || (adj->adj_usage
+					       == ISIS_ADJ_LEVEL1AND2)) {
+					/* (8) down - wrong system */
+					isis_adj_state_change(&adj,
+							      ISIS_ADJ_DOWN,
+							      "Wrong System");
+				}
+				break;
+			case IS_LEVEL_1_AND_2:
+				if (adj->adj_state != ISIS_ADJ_UP
+				    || adj->adj_usage == ISIS_ADJ_LEVEL1AND2) {
+					isis_adj_process_threeway(adj, tw_adj,
+								  ISIS_ADJ_LEVEL1AND2);
+				} else if ((adj->adj_usage == ISIS_ADJ_LEVEL1)
+					   || (adj->adj_usage
+					       == ISIS_ADJ_LEVEL2)) {
+					/* (8) down - wrong system */
+					isis_adj_state_change(&adj,
+							      ISIS_ADJ_DOWN,
+							      "Wrong System");
+				}
+				break;
+			}
+		}
+
+		/* 8.2.5.2 a) 4) If the system is L2 - table 7 */
+		if (iih->circuit->area->is_type == IS_LEVEL_2) {
+			switch (iih->circ_type) {
+			case IS_LEVEL_1:
+				if (adj->adj_state != ISIS_ADJ_UP) {
+					/* (5) reject - wrong system type event
+					 */
+					zlog_warn("wrongSystemType");
+					return ISIS_WARNING;
+				} else if ((adj->adj_usage
+					    == ISIS_ADJ_LEVEL1AND2)
+					   || (adj->adj_usage
+					       == ISIS_ADJ_LEVEL2)) {
+					/* (6) down - wrong system */
+					isis_adj_state_change(&adj,
+							      ISIS_ADJ_DOWN,
+							      "Wrong System");
+				}
+				break;
+			case IS_LEVEL_1_AND_2:
+			case IS_LEVEL_2:
+				if (adj->adj_state != ISIS_ADJ_UP
+				    || adj->adj_usage == ISIS_ADJ_LEVEL2) {
+					isis_adj_process_threeway(adj, tw_adj,
+								  ISIS_ADJ_LEVEL2);
+				} else if (adj->adj_usage
+					   == ISIS_ADJ_LEVEL1AND2) {
+					/* (6) down - wrong system */
+					isis_adj_state_change(&adj,
+							      ISIS_ADJ_DOWN,
+							      "Wrong System");
+				}
+				break;
+			}
+		}
+	}
+	/* 8.2.5.2 b) if no match was detected */
+	else if (listcount(iih->circuit->area->area_addrs) > 0) {
+		if (iih->circuit->area->is_type == IS_LEVEL_1) {
+			/* 8.2.5.2 b) 1) is_type L1 and adj is not up */
+			if (adj->adj_state != ISIS_ADJ_UP) {
+				isis_adj_state_change(&adj, ISIS_ADJ_DOWN,
+						      "Area Mismatch");
+				/* 8.2.5.2 b) 2)is_type L1 and adj is up */
+			} else {
+				isis_adj_state_change(&adj, ISIS_ADJ_DOWN,
+						      "Down - Area Mismatch");
+			}
+		}
+		/* 8.2.5.2 b 3 If the system is L2 or L1L2 - table 8 */
+		else {
+			switch (iih->circ_type) {
+			case IS_LEVEL_1:
+				if (adj->adj_state != ISIS_ADJ_UP) {
+					/* (6) reject - Area Mismatch event */
+					zlog_warn("AreaMismatch");
+					return ISIS_WARNING;
+				} else if (adj->adj_usage == ISIS_ADJ_LEVEL1) {
+					/* (7) down - area mismatch */
+					isis_adj_state_change(&adj,
+							      ISIS_ADJ_DOWN,
+							      "Area Mismatch");
+
+				} else if ((adj->adj_usage
+					    == ISIS_ADJ_LEVEL1AND2)
+					   || (adj->adj_usage
+					       == ISIS_ADJ_LEVEL2)) {
+					/* (7) down - wrong system */
+					isis_adj_state_change(&adj,
+							      ISIS_ADJ_DOWN,
+							      "Wrong System");
+				}
+				break;
+			case IS_LEVEL_1_AND_2:
+			case IS_LEVEL_2:
+				if (adj->adj_state != ISIS_ADJ_UP
+				    || adj->adj_usage == ISIS_ADJ_LEVEL2) {
+					isis_adj_process_threeway(adj, tw_adj,
+								  ISIS_ADJ_LEVEL2);
+				} else if (adj->adj_usage == ISIS_ADJ_LEVEL1) {
+					/* (7) down - wrong system */
+					isis_adj_state_change(&adj,
+							      ISIS_ADJ_DOWN,
+							      "Wrong System");
+				} else if (adj->adj_usage
+					   == ISIS_ADJ_LEVEL1AND2) {
+					if (iih->circ_type == IS_LEVEL_2) {
+						/* (7) down - wrong system */
+						isis_adj_state_change(
+							&adj, ISIS_ADJ_DOWN,
+							"Wrong System");
+					} else {
+						/* (7) down - area mismatch */
+						isis_adj_state_change(
+							&adj, ISIS_ADJ_DOWN,
+							"Area Mismatch");
+					}
+				}
+				break;
+			}
+		}
+	} else {
+		/* down - area mismatch */
+		isis_adj_state_change(&adj, ISIS_ADJ_DOWN, "Area Mismatch");
+	}
+
+	if (adj) {
+		if (adj->adj_state == ISIS_ADJ_UP && changed) {
+			lsp_regenerate_schedule(
+				adj->circuit->area,
+				isis_adj_usage2levels(adj->adj_usage), 0);
+		}
+
+		/* 8.2.5.2 c) if the action was up - comparing circuit IDs */
+		/* FIXME - Missing parts */
+
+		/* some of my own understanding of the ISO, why the heck does
+		 * it not say what should I change the system_type to...
+		 */
+		switch (adj->adj_usage) {
+		case ISIS_ADJ_LEVEL1:
+			adj->sys_type = ISIS_SYSTYPE_L1_IS;
+			break;
+		case ISIS_ADJ_LEVEL2:
+			adj->sys_type = ISIS_SYSTYPE_L2_IS;
+			break;
+		case ISIS_ADJ_LEVEL1AND2:
+			adj->sys_type = ISIS_SYSTYPE_L2_IS;
+			break;
+		case ISIS_ADJ_NONE:
+			adj->sys_type = ISIS_SYSTYPE_UNKNOWN;
+			break;
+		}
+	}
+
+	if (IS_DEBUG_ADJ_PACKETS) {
+		zlog_debug(
+			"ISIS-Adj (%s): Rcvd P2P IIH from (%s), cir type %s, cir id %hhu, length %hu",
+			iih->circuit->area->area_tag,
+			iih->circuit->interface->name,
+			circuit_t2string(iih->circuit->is_type),
+			iih->circuit->circuit_id, iih->pdu_len);
+	}
+
+	return ISIS_OK;
+}
+
+static int process_lan_hello(struct iih_info *iih)
+{
+	struct isis_adjacency *adj;
+	adj = isis_adj_lookup(iih->sys_id,
+			      iih->circuit->u.bc.adjdb[iih->level - 1]);
+	if ((adj == NULL) || (memcmp(adj->snpa, iih->ssnpa, ETH_ALEN))
+	    || (adj->level != iih->level)) {
+		if (!adj) {
+			/* Do as in 8.4.2.5 */
+			adj = isis_new_adj(iih->sys_id, iih->ssnpa, iih->level,
+					   iih->circuit);
+		} else {
+			if (iih->ssnpa) {
+				memcpy(adj->snpa, iih->ssnpa, 6);
+			} else {
+				memset(adj->snpa, ' ', 6);
+			}
+			adj->level = iih->level;
+		}
+		isis_adj_state_change(&adj, ISIS_ADJ_INITIALIZING, NULL);
+
+		if (iih->level == IS_LEVEL_1)
+			adj->sys_type = ISIS_SYSTYPE_L1_IS;
+		else
+			adj->sys_type = ISIS_SYSTYPE_L2_IS;
+		list_delete_all_node(
+			iih->circuit->u.bc.lan_neighs[iih->level - 1]);
+		isis_adj_build_neigh_list(
+			iih->circuit->u.bc.adjdb[iih->level - 1],
+			iih->circuit->u.bc.lan_neighs[iih->level - 1]);
+	}
+
+	if (adj->dis_record[iih->level - 1].dis == ISIS_IS_DIS) {
+		uint8_t *dis = (iih->level == 1)
+				       ? iih->circuit->u.bc.l1_desig_is
+				       : iih->circuit->u.bc.l2_desig_is;
+
+		if (memcmp(dis, iih->dis, ISIS_SYS_ID_LEN + 1)) {
+			event_add_event(master, isis_event_dis_status_change,
+					iih->circuit, 0, NULL);
+			memcpy(dis, iih->dis, ISIS_SYS_ID_LEN + 1);
+		}
+	}
+
+	adj->circuit_t = iih->circ_type;
+	adj->hold_time = iih->holdtime;
+	adj->last_upd = time(NULL);
+	adj->prio[iih->level - 1] = iih->priority;
+	memcpy(adj->lanid, iih->dis, ISIS_SYS_ID_LEN + 1);
+
+	bool changed;
+	isis_tlvs_to_adj(iih->tlvs, adj, &changed);
+	changed |= tlvs_to_adj_mt_set(iih->tlvs, iih->v4_usable, iih->v6_usable,
+				      adj);
+
+	/* lets take care of the expiry */
+	EVENT_OFF(adj->t_expire);
+	event_add_timer(master, isis_adj_expire, adj, (long)adj->hold_time,
+			&adj->t_expire);
+
+	/*
+	 * If the snpa for this circuit is found from LAN Neighbours TLV
+	 * we have two-way communication -> adjacency can be put to state "up"
+	 */
+	bool own_snpa_found =
+		isis_tlvs_own_snpa_found(iih->tlvs, iih->circuit->u.bc.snpa);
+
+	if (adj->adj_state != ISIS_ADJ_UP) {
+		if (own_snpa_found) {
+			isis_adj_state_change(
+				&adj, ISIS_ADJ_UP,
+				"own SNPA found in LAN Neighbours TLV");
+		}
+	} else {
+		if (!own_snpa_found) {
+			isis_adj_state_change(
+				&adj, ISIS_ADJ_INITIALIZING,
+				"own SNPA not found in LAN Neighbours TLV");
+		}
+	}
+
+	if (adj->adj_state == ISIS_ADJ_UP && changed)
+		lsp_regenerate_schedule(adj->circuit->area, iih->level, 0);
+
+	if (IS_DEBUG_ADJ_PACKETS) {
+		zlog_debug(
+			"ISIS-Adj (%s): Rcvd L%d LAN IIH from %pSY on %s, cirType %s, cirID %u, length %zd",
+			iih->circuit->area->area_tag, iih->level, iih->ssnpa,
+			iih->circuit->interface->name,
+			circuit_t2string(iih->circuit->is_type),
+			iih->circuit->circuit_id,
+			stream_get_endp(iih->circuit->rcv_stream));
+	}
+	return ISIS_OK;
+}
+
+static int pdu_len_validate(uint16_t pdu_len, struct isis_circuit *circuit)
+{
+	if (pdu_len < stream_get_getp(circuit->rcv_stream)
+	    || pdu_len > ISO_MTU(circuit)
+	    || pdu_len > stream_get_endp(circuit->rcv_stream))
+		return 1;
+
+	if (pdu_len < stream_get_endp(circuit->rcv_stream))
+		stream_set_endp(circuit->rcv_stream, pdu_len);
+	return 0;
+}
+
+static void update_rej_adj_count(struct isis_circuit *circuit)
+{
+	circuit->rej_adjacencies++;
+	if (circuit->is_type == IS_LEVEL_1)
+		circuit->area->rej_adjacencies[0]++;
+	else if (circuit->is_type == IS_LEVEL_2)
+		circuit->area->rej_adjacencies[1]++;
+	else {
+		circuit->area->rej_adjacencies[0]++;
+		circuit->area->rej_adjacencies[1]++;
+	}
+}
+
+static int process_hello(uint8_t pdu_type, struct isis_circuit *circuit,
+			 uint8_t *ssnpa)
+{
+	/* keep a copy of the raw pdu for NB notifications */
+	size_t pdu_start = stream_get_getp(circuit->rcv_stream);
+	size_t pdu_end = stream_get_endp(circuit->rcv_stream);
+	char raw_pdu[pdu_end - pdu_start];
+	bool p2p_hello = (pdu_type == P2P_HELLO);
+	int level = p2p_hello ? 0
+			      : (pdu_type == L1_LAN_HELLO) ? ISIS_LEVEL1
+							   : ISIS_LEVEL2;
+	const char *pdu_name =
+		p2p_hello
+			? "P2P IIH"
+			: (level == ISIS_LEVEL1) ? "L1 LAN IIH" : "L2 LAN IIH";
+
+	stream_get_from(raw_pdu, circuit->rcv_stream, pdu_start,
+			pdu_end - pdu_start);
+	if (IS_DEBUG_ADJ_PACKETS) {
+		zlog_debug("ISIS-Adj (%s): Rcvd %s on %s, cirType %s, cirID %u",
+			   circuit->area->area_tag, pdu_name,
+			   circuit->interface->name,
+			   circuit_t2string(circuit->is_type),
+			   circuit->circuit_id);
+		if (IS_DEBUG_PACKET_DUMP)
+			zlog_dump_data(STREAM_DATA(circuit->rcv_stream),
+				       stream_get_endp(circuit->rcv_stream));
+	}
+
+	if (p2p_hello) {
+		if (circuit->circ_type != CIRCUIT_T_P2P) {
+			zlog_warn("p2p hello on non p2p circuit");
+			update_rej_adj_count(circuit);
+#ifndef FABRICD
+			isis_notif_reject_adjacency(
+				circuit, "p2p hello on non p2p circuit",
+				raw_pdu, sizeof(raw_pdu));
+#endif /* ifndef FABRICD */
+			return ISIS_WARNING;
+		}
+	} else {
+		if (circuit->circ_type != CIRCUIT_T_BROADCAST) {
+			zlog_warn("lan hello on non broadcast circuit");
+			update_rej_adj_count(circuit);
+#ifndef FABRICD
+			isis_notif_reject_adjacency(
+				circuit, "lan hello on non broadcast circuit",
+				raw_pdu, sizeof(raw_pdu));
+#endif /* ifndef FABRICD */
+			return ISIS_WARNING;
+		}
+
+		if (circuit->ext_domain) {
+			zlog_debug(
+				"level %d LAN Hello received over circuit with externalDomain = true",
+				level);
+			update_rej_adj_count(circuit);
+#ifndef FABRICD
+			isis_notif_reject_adjacency(
+				circuit,
+				"LAN Hello received over circuit with externalDomain = true",
+				raw_pdu, sizeof(raw_pdu));
+#endif /* ifndef FABRICD */
+			return ISIS_WARNING;
+		}
+
+		if (!(circuit->is_type & level)) {
+			if (IS_DEBUG_ADJ_PACKETS) {
+				zlog_debug(
+					"ISIS-Adj (%s): Interface level mismatch, %s",
+					circuit->area->area_tag,
+					circuit->interface->name);
+			}
+			update_rej_adj_count(circuit);
+#ifndef FABRICD
+			isis_notif_reject_adjacency(circuit,
+						    "Interface level mismatch",
+						    raw_pdu, sizeof(raw_pdu));
+#endif /* ifndef FABRICD */
+			return ISIS_WARNING;
+		}
+	}
+
+	struct iih_info iih = {
+		.circuit = circuit, .ssnpa = ssnpa, .level = level};
+
+	/* Generic IIH Header */
+	iih.circ_type = stream_getc(circuit->rcv_stream) & 0x03;
+	stream_get(iih.sys_id, circuit->rcv_stream, ISIS_SYS_ID_LEN);
+	iih.holdtime = stream_getw(circuit->rcv_stream);
+	iih.pdu_len = stream_getw(circuit->rcv_stream);
+
+	if (p2p_hello) {
+		iih.circuit_id = stream_getc(circuit->rcv_stream);
+	} else {
+		iih.priority = stream_getc(circuit->rcv_stream);
+		stream_get(iih.dis, circuit->rcv_stream, ISIS_SYS_ID_LEN + 1);
+	}
+
+	if (pdu_len_validate(iih.pdu_len, circuit)) {
+		zlog_warn(
+			"ISIS-Adj (%s): Rcvd %s from (%s) with invalid pdu length %hu",
+			circuit->area->area_tag, pdu_name,
+			circuit->interface->name, iih.pdu_len);
+		update_rej_adj_count(circuit);
+#ifndef FABRICD
+		isis_notif_reject_adjacency(circuit, "Invalid PDU length",
+					    raw_pdu, sizeof(raw_pdu));
+#endif /* ifndef FABRICD */
+		return ISIS_WARNING;
+	}
+
+	if (!p2p_hello && !(level & iih.circ_type)) {
+		flog_err(EC_ISIS_PACKET,
+			 "Level %d LAN Hello with Circuit Type %d", level,
+			 iih.circ_type);
+		update_rej_adj_count(circuit);
+#ifndef FABRICD
+		isis_notif_reject_adjacency(circuit,
+					    "LAN Hello with wrong IS-level",
+					    raw_pdu, sizeof(raw_pdu));
+#endif /* ifndef FABRICD */
+		return ISIS_ERROR;
+	}
+
+	const char *error_log;
+	int retval = ISIS_WARNING;
+
+	if (isis_unpack_tlvs(STREAM_READABLE(circuit->rcv_stream),
+			     circuit->rcv_stream, &iih.tlvs, &error_log)) {
+		zlog_warn("isis_unpack_tlvs() failed: %s", error_log);
+		update_rej_adj_count(circuit);
+#ifndef FABRICD
+		isis_notif_reject_adjacency(circuit, "Failed to unpack TLVs",
+					    raw_pdu, sizeof(raw_pdu));
+#endif /* ifndef FABRICD */
+		goto out;
+	}
+
+	if (!iih.tlvs->area_addresses.count) {
+		zlog_warn("No Area addresses TLV in %s", pdu_name);
+#ifndef FABRICD
+		/* send northbound notification */
+		isis_notif_area_mismatch(circuit, raw_pdu, sizeof(raw_pdu));
+#endif /* ifndef FABRICD */
+		goto out;
+	}
+
+	if (!iih.tlvs->protocols_supported.count) {
+		zlog_warn("No supported protocols TLV in %s", pdu_name);
+		update_rej_adj_count(circuit);
+#ifndef FABRICD
+		isis_notif_reject_adjacency(circuit,
+					    "No supported protocols TLV",
+					    raw_pdu, sizeof(raw_pdu));
+#endif /* ifndef FABRICD */
+		goto out;
+	}
+
+	int auth_code = isis_tlvs_auth_is_valid(iih.tlvs, &circuit->passwd,
+						circuit->rcv_stream, false);
+	if (auth_code != ISIS_AUTH_OK) {
+		isis_event_auth_failure(circuit->area->area_tag,
+					"IIH authentication failure",
+					iih.sys_id);
+#ifndef FABRICD
+		/* send northbound notification */
+		stream_get_from(raw_pdu, circuit->rcv_stream, pdu_start,
+				pdu_end - pdu_start);
+		if (auth_code == ISIS_AUTH_FAILURE) {
+			update_rej_adj_count(circuit);
+			isis_notif_authentication_failure(circuit, raw_pdu,
+							  sizeof(raw_pdu));
+		} else { /* AUTH_TYPE_FAILURE or NO_VALIDATOR */
+			update_rej_adj_count(circuit);
+			isis_notif_authentication_type_failure(circuit, raw_pdu,
+							       sizeof(raw_pdu));
+		}
+#endif /* ifndef FABRICD */
+		goto out;
+	}
+
+	if (!memcmp(iih.sys_id, circuit->isis->sysid, ISIS_SYS_ID_LEN)) {
+		zlog_warn(
+			"ISIS-Adj (%s): Received IIH with own sysid on %s - discard",
+			circuit->area->area_tag, circuit->interface->name);
+		update_rej_adj_count(circuit);
+#ifndef FABRICD
+		isis_notif_reject_adjacency(circuit,
+					    "Received IIH with our own sysid",
+					    raw_pdu, sizeof(raw_pdu));
+#endif /* ifndef FABRICD */
+		goto out;
+	}
+
+	if (!p2p_hello
+	    && (listcount(circuit->area->area_addrs) == 0
+		|| (level == ISIS_LEVEL1
+		    && !isis_tlvs_area_addresses_match(
+			       iih.tlvs, circuit->area->area_addrs)))) {
+		if (IS_DEBUG_ADJ_PACKETS) {
+			zlog_debug(
+				"ISIS-Adj (%s): Area mismatch, level %d IIH on %s",
+				circuit->area->area_tag, level,
+				circuit->interface->name);
+		}
+#ifndef FABRICD
+		/* send northbound notification */
+		isis_notif_area_mismatch(circuit, raw_pdu, sizeof(raw_pdu));
+#endif /* ifndef FABRICD */
+		goto out;
+	}
+
+	iih.v4_usable = (fabricd_ip_addrs(circuit)
+			 && iih.tlvs->ipv4_address.count);
+
+	iih.v6_usable =
+		(listcount(circuit->ipv6_link) && iih.tlvs->ipv6_address.count);
+
+	if (!iih.v4_usable && !iih.v6_usable) {
+		if (IS_DEBUG_ADJ_PACKETS) {
+			zlog_warn(
+				"ISIS-Adj (%s): Neither IPv4 nor IPv6 considered usable. Ignoring IIH",
+				circuit->area->area_tag);
+		}
+		update_rej_adj_count(circuit);
+#ifndef FABRICD
+		isis_notif_reject_adjacency(
+			circuit, "Neither IPv4 not IPv6 considered usable",
+			raw_pdu, sizeof(raw_pdu));
+#endif /* ifndef FABRICD */
+		goto out;
+	}
+
+	retval = p2p_hello ? process_p2p_hello(&iih) : process_lan_hello(&iih);
+out:
+	isis_free_tlvs(iih.tlvs);
+
+	return retval;
+}
+
+static void lsp_flood_or_update(struct isis_lsp *lsp,
+				struct isis_circuit *circuit,
+				bool circuit_scoped)
+{
+	if (!circuit_scoped)
+		lsp_flood(lsp, circuit);
+	else
+		fabricd_update_lsp_no_flood(lsp, circuit);
+}
+
+/*
+ * Process Level 1/2 Link State
+ * ISO - 10589
+ * Section 7.3.15.1 - Action on receipt of a link state PDU
+ */
+static int process_lsp(uint8_t pdu_type, struct isis_circuit *circuit,
+		       const uint8_t *ssnpa, uint8_t max_area_addrs)
+{
+	int level;
+	bool circuit_scoped;
+	size_t pdu_start = stream_get_getp(circuit->rcv_stream);
+	size_t pdu_end = stream_get_endp(circuit->rcv_stream);
+	char raw_pdu[pdu_end - pdu_start];
+
+	stream_get_from(raw_pdu, circuit->rcv_stream, pdu_start,
+			pdu_end - pdu_start);
+
+	if (pdu_type == FS_LINK_STATE) {
+		if (!fabricd)
+			return ISIS_ERROR;
+		if (max_area_addrs != L2_CIRCUIT_FLOODING_SCOPE)
+			return ISIS_ERROR;
+		level = ISIS_LEVEL2;
+		circuit_scoped = true;
+
+		/* The stream is used verbatim for sending out new LSPDUs.
+		 * So make sure we store it as an L2 LSPDU internally.
+		 * (compare for the reverse in `send_lsp`) */
+		stream_putc_at(circuit->rcv_stream, 4, L2_LINK_STATE);
+		stream_putc_at(circuit->rcv_stream, 7, 0);
+	} else {
+		if (pdu_type == L1_LINK_STATE)
+			level = ISIS_LEVEL1;
+		else
+			level = ISIS_LEVEL2;
+		circuit_scoped = false;
+	}
+
+	if (IS_DEBUG_UPDATE_PACKETS) {
+		zlog_debug(
+			"ISIS-Upd (%s): Rcvd %sL%d LSP on %s, cirType %s, cirID %u",
+			circuit->area->area_tag,
+			circuit_scoped ? "Circuit scoped " : "", level,
+			circuit->interface->name,
+			circuit_t2string(circuit->is_type),
+			circuit->circuit_id);
+		if (IS_DEBUG_PACKET_DUMP)
+			zlog_dump_data(STREAM_DATA(circuit->rcv_stream),
+				       stream_get_endp(circuit->rcv_stream));
+	}
+
+	struct isis_lsp_hdr hdr = {};
+
+	hdr.pdu_len = stream_getw(circuit->rcv_stream);
+	hdr.rem_lifetime = stream_getw(circuit->rcv_stream);
+	stream_get(hdr.lsp_id, circuit->rcv_stream, sizeof(hdr.lsp_id));
+	hdr.seqno = stream_getl(circuit->rcv_stream);
+	hdr.checksum = stream_getw(circuit->rcv_stream);
+	hdr.lsp_bits = stream_getc(circuit->rcv_stream);
+
+#ifndef FABRICD
+	/* send northbound notification */
+	char buf[ISO_SYSID_STRLEN];
+
+	snprintfrr(buf, ISO_SYSID_STRLEN, "%pSY", hdr.lsp_id);
+	isis_notif_lsp_received(circuit, hdr.lsp_id, hdr.seqno, time(NULL),
+				buf);
+#endif /* ifndef FABRICD */
+
+	if (pdu_len_validate(hdr.pdu_len, circuit)) {
+		zlog_debug("ISIS-Upd (%s): LSP %pLS invalid LSP length %hu",
+			   circuit->area->area_tag, hdr.lsp_id, hdr.pdu_len);
+		return ISIS_WARNING;
+	}
+
+	if (IS_DEBUG_UPDATE_PACKETS) {
+		zlog_debug(
+			"ISIS-Upd (%s): Rcvd L%d LSP %pLS, seq 0x%08x, cksum 0x%04hx, lifetime %hus, len %hu, on %s",
+			circuit->area->area_tag, level, hdr.lsp_id, hdr.seqno,
+			hdr.checksum, hdr.rem_lifetime, hdr.pdu_len,
+			circuit->interface->name);
+	}
+
+	/* lsp is_type check */
+	if ((hdr.lsp_bits & IS_LEVEL_1) != IS_LEVEL_1) {
+		zlog_debug("ISIS-Upd (%s): LSP %pLS invalid LSP is type 0x%x",
+			   circuit->area->area_tag, hdr.lsp_id,
+			   hdr.lsp_bits & IS_LEVEL_1_AND_2);
+		/* continue as per RFC1122 Be liberal in what you accept, and
+		 * conservative in what you send */
+	}
+
+	/* Checksum sanity check - FIXME: move to correct place */
+	/* 12 = sysid+pdu+remtime */
+	if (iso_csum_verify(STREAM_DATA(circuit->rcv_stream) + 12,
+			    hdr.pdu_len - 12, hdr.checksum, 12)) {
+		zlog_debug(
+			"ISIS-Upd (%s): LSP %pLS invalid LSP checksum 0x%04hx",
+			circuit->area->area_tag, hdr.lsp_id, hdr.checksum);
+		return ISIS_WARNING;
+	}
+
+	/* 7.3.15.1 a) 1 - external domain circuit will discard lsps */
+	if (circuit->ext_domain) {
+		zlog_debug(
+			"ISIS-Upd (%s): LSP %pLS received at level %d over circuit with externalDomain = true",
+			circuit->area->area_tag, hdr.lsp_id, level);
+		return ISIS_WARNING;
+	}
+
+	/* 7.3.15.1 a) 2,3 - manualL2OnlyMode not implemented */
+	if (!(circuit->is_type & level)) {
+		zlog_debug(
+			"ISIS-Upd (%s): LSP %pLS received at level %d over circuit of type %s",
+			circuit->area->area_tag, hdr.lsp_id, level,
+			circuit_t2string(circuit->is_type));
+		return ISIS_WARNING;
+	}
+
+	struct isis_tlvs *tlvs = NULL;
+	int retval = ISIS_WARNING;
+	const char *error_log;
+
+	if (isis_unpack_tlvs(STREAM_READABLE(circuit->rcv_stream),
+			     circuit->rcv_stream, &tlvs, &error_log)) {
+		zlog_warn("Something went wrong unpacking the LSP: %s",
+			  error_log);
+#ifndef FABRICD
+		/* send northbound notification. Note that the tlv-type and
+		 * offset cannot correctly be set here as they are not returned
+		 * by isis_unpack_tlvs, but in there I cannot fire a
+		 * notification because I have no circuit information. So until
+		 * we change the code above to return those extra fields, we
+		 * will send dummy values which are ignored in the callback
+		 */
+		circuit->lsp_error_counter++;
+		if (circuit->is_type == IS_LEVEL_1) {
+			circuit->area->lsp_error_counter[0]++;
+		} else if (circuit->is_type == IS_LEVEL_2) {
+			circuit->area->lsp_error_counter[1]++;
+		} else {
+			circuit->area->lsp_error_counter[0]++;
+			circuit->area->lsp_error_counter[1]++;
+		}
+
+		isis_notif_lsp_error(circuit, hdr.lsp_id, raw_pdu,
+				     sizeof(raw_pdu), 0, 0);
+#endif /* ifndef FABRICD */
+		goto out;
+	}
+
+	/* 7.3.15.1 a) 4 - need to make sure IDLength matches */
+
+	/* 7.3.15.1 a) 5 - maximum area match, can be ommited since we only use
+	 * 3 */
+
+	/* 7.3.15.1 a) 7 - password check */
+	struct isis_passwd *passwd = (level == ISIS_LEVEL1)
+					     ? &circuit->area->area_passwd
+					     : &circuit->area->domain_passwd;
+	int auth_code = isis_tlvs_auth_is_valid(tlvs, passwd,
+						circuit->rcv_stream, true);
+	if (auth_code != ISIS_AUTH_OK) {
+		isis_event_auth_failure(circuit->area->area_tag,
+					"LSP authentication failure",
+					hdr.lsp_id);
+#ifndef FABRICD
+		/* send northbound notification */
+		if (auth_code == ISIS_AUTH_FAILURE) {
+			circuit->auth_failures++;
+			if (circuit->is_type == IS_LEVEL_1) {
+				circuit->area->auth_failures[0]++;
+			} else if (circuit->is_type == IS_LEVEL_2) {
+				circuit->area->auth_failures[1]++;
+			} else {
+				circuit->area->auth_failures[0]++;
+				circuit->area->auth_failures[1]++;
+			}
+			isis_notif_authentication_failure(circuit, raw_pdu,
+							  sizeof(raw_pdu));
+		} else { /* AUTH_TYPE_FAILURE or NO_VALIDATOR */
+			circuit->auth_type_failures++;
+			if (circuit->is_type == IS_LEVEL_1) {
+				circuit->area->auth_type_failures[0]++;
+			} else if (circuit->is_type == IS_LEVEL_2) {
+				circuit->area->auth_type_failures[1]++;
+			} else {
+				circuit->area->auth_type_failures[0]++;
+				circuit->area->auth_type_failures[1]++;
+			}
+			isis_notif_authentication_type_failure(circuit, raw_pdu,
+							       sizeof(raw_pdu));
+		}
+#endif /* ifndef FABRICD */
+		goto out;
+	}
+
+	/* Find the LSP in our database and compare it to this Link State header
+	 */
+	struct isis_lsp *lsp =
+		lsp_search(&circuit->area->lspdb[level - 1], hdr.lsp_id);
+	int comp = 0;
+	if (lsp)
+		comp = lsp_compare(circuit->area->area_tag, lsp, hdr.seqno,
+				   hdr.checksum, hdr.rem_lifetime);
+	if (lsp && (lsp->own_lsp))
+		goto dontcheckadj;
+
+	/* 7.3.15.1 a) 6 - Must check that we have an adjacency of the same
+	 * level  */
+	/* for broadcast circuits, snpa should be compared */
+
+	if (circuit->circ_type == CIRCUIT_T_BROADCAST) {
+		if (!isis_adj_lookup_snpa(ssnpa,
+					  circuit->u.bc.adjdb[level - 1])) {
+			zlog_debug(
+				"(%s): DS ======= LSP %pLS, seq 0x%08x, cksum 0x%04hx, lifetime %hus on %s",
+				circuit->area->area_tag, hdr.lsp_id, hdr.seqno,
+				hdr.checksum, hdr.rem_lifetime,
+				circuit->interface->name);
+			goto out; /* Silently discard */
+		}
+	}
+	/* for non broadcast, we just need to find same level adj */
+	else {
+		/* If no adj, or no sharing of level */
+		if (!circuit->u.p2p.neighbor) {
+			retval = ISIS_OK;
+			goto out;
+		} else {
+			if (((level == IS_LEVEL_1)
+			     && (circuit->u.p2p.neighbor->adj_usage
+				 == ISIS_ADJ_LEVEL2))
+			    || ((level == IS_LEVEL_2)
+				&& (circuit->u.p2p.neighbor->adj_usage
+				    == ISIS_ADJ_LEVEL1)))
+				goto out;
+		}
+	}
+
+	bool lsp_confusion;
+
+dontcheckadj:
+	/* 7.3.15.1 a) 7 - Passwords for level 1 - not implemented  */
+
+	/* 7.3.15.1 a) 8 - Passwords for level 2 - not implemented  */
+
+	/* 7.3.15.1 a) 9 - OriginatingLSPBufferSize - not implemented  FIXME: do
+	 * it */
+
+	/* 7.3.16.2 - If this is an LSP from another IS with identical seq_num
+	 * but
+	 *            wrong checksum, initiate a purge. */
+	if (lsp && (lsp->hdr.seqno == hdr.seqno)
+	    && (lsp->hdr.checksum != hdr.checksum)
+	    && hdr.rem_lifetime) {
+		zlog_warn(
+			"ISIS-Upd (%s): LSP %pLS seq 0x%08x with confused checksum received.",
+			circuit->area->area_tag, hdr.lsp_id, hdr.seqno);
+		hdr.rem_lifetime = 0;
+		lsp_confusion = true;
+	} else
+		lsp_confusion = false;
+
+	/* 7.3.15.1 b) - If the remaining life time is 0, we perform 7.3.16.4 */
+	if (hdr.rem_lifetime == 0) {
+		if (!lsp) {
+			/* 7.3.16.4 a) 1) No LSP in db -> send an ack, but don't
+			 * save */
+			/* only needed on explicit update, eg - p2p */
+			if (circuit->circ_type == CIRCUIT_T_P2P)
+				ack_lsp(&hdr, circuit, level);
+			goto out; /* FIXME: do we need a purge? */
+		} else {
+			if (memcmp(hdr.lsp_id, circuit->isis->sysid,
+				   ISIS_SYS_ID_LEN)) {
+				/* LSP by some other system -> do 7.3.16.4 b) */
+				/* 7.3.16.4 b) 1)  */
+				if (comp == LSP_NEWER) {
+					lsp_update(lsp, &hdr, tlvs,
+						   circuit->rcv_stream,
+						   circuit->area, level,
+						   lsp_confusion);
+					if (lsp_confusion)
+						isis_free_tlvs(tlvs);
+					tlvs = NULL;
+					/* ii */
+					lsp_flood_or_update(lsp, NULL,
+							    circuit_scoped);
+					/* v */
+					ISIS_FLAGS_CLEAR_ALL(
+						lsp->SSNflags); /* FIXME:
+								   OTHER
+								   than c
+								   */
+
+					/* For the case of lsp confusion, flood
+					 * the purge back to its
+					 * originator so that it can react.
+					 * Otherwise, don't reflood
+					 * through incoming circuit as usual */
+					if (!lsp_confusion) {
+						isis_tx_queue_del(
+							circuit->tx_queue,
+							lsp);
+
+						/* iv */
+						if (circuit->circ_type
+						    != CIRCUIT_T_BROADCAST)
+							ISIS_SET_FLAG(
+								lsp->SSNflags,
+								circuit);
+					}
+				} /* 7.3.16.4 b) 2) */
+				else if (comp == LSP_EQUAL) {
+					/* i */
+					isis_tx_queue_del(circuit->tx_queue,
+							  lsp);
+					/* ii */
+					if (circuit->circ_type
+					    != CIRCUIT_T_BROADCAST)
+						ISIS_SET_FLAG(lsp->SSNflags,
+							      circuit);
+				} /* 7.3.16.4 b) 3) */
+				else {
+					isis_tx_queue_add(circuit->tx_queue,
+							  lsp, TX_LSP_NORMAL);
+					ISIS_CLEAR_FLAG(lsp->SSNflags, circuit);
+				}
+			} else if (lsp->hdr.rem_lifetime != 0) {
+				/* our own LSP -> 7.3.16.4 c) */
+				if (comp == LSP_NEWER) {
+#ifndef FABRICD
+					if (lsp->hdr.seqno < hdr.seqno) {
+						/* send northbound
+						 * notification */
+						circuit->area
+							->lsp_seqno_skipped_counter++;
+						isis_notif_seqno_skipped(
+							circuit, hdr.lsp_id);
+					}
+#endif /* ifndef FABRICD */
+					lsp_inc_seqno(lsp, hdr.seqno);
+					lsp_flood_or_update(lsp, NULL,
+							    circuit_scoped);
+				} else {
+					isis_tx_queue_add(circuit->tx_queue,
+							  lsp, TX_LSP_NORMAL);
+					ISIS_CLEAR_FLAG(lsp->SSNflags, circuit);
+				}
+				if (IS_DEBUG_UPDATE_PACKETS)
+					zlog_debug(
+						"ISIS-Upd (%s): (1) re-originating LSP %pLS new seq 0x%08x",
+						circuit->area->area_tag,
+						hdr.lsp_id, lsp->hdr.seqno);
+			} else {
+				/* our own LSP with 0 remaining life time */
+#ifndef FABRICD
+				/* send northbound notification */
+				isis_notif_own_lsp_purge(circuit, hdr.lsp_id);
+#endif /* ifndef FABRICD */
+			}
+		}
+		goto out;
+	}
+	/* 7.3.15.1 c) - If this is our own lsp and we don't have it initiate a
+	 * purge */
+	if (memcmp(hdr.lsp_id, circuit->isis->sysid, ISIS_SYS_ID_LEN) == 0) {
+		if (!lsp) {
+			/* 7.3.16.4: initiate a purge */
+			lsp_purge_non_exist(level, &hdr, circuit->area);
+			retval = ISIS_OK;
+			goto out;
+		}
+		/* 7.3.15.1 d) - If this is our own lsp and we have it */
+
+		/* In 7.3.16.1, If an Intermediate system R somewhere in the
+		 * domain
+		 * has information that the current sequence number for source S
+		 * is
+		 * "greater" than that held by S, ... */
+
+		if (comp == LSP_NEWER) {
+			/* 7.3.16.1  */
+			lsp_inc_seqno(lsp, hdr.seqno);
+#ifndef FABRICD
+			/* send northbound notification */
+			circuit->area->lsp_seqno_skipped_counter++;
+			isis_notif_seqno_skipped(circuit, hdr.lsp_id);
+#endif /* ifndef FABRICD */
+			if (IS_DEBUG_UPDATE_PACKETS) {
+				zlog_debug(
+					"ISIS-Upd (%s): (2) re-originating LSP %pLS new seq 0x%08x",
+					circuit->area->area_tag, hdr.lsp_id,
+					lsp->hdr.seqno);
+			}
+			lsp_flood(lsp, NULL);
+		} else if (comp == LSP_EQUAL) {
+			isis_tx_queue_del(circuit->tx_queue, lsp);
+			if (circuit->circ_type != CIRCUIT_T_BROADCAST)
+				ISIS_SET_FLAG(lsp->SSNflags, circuit);
+		} else {
+			isis_tx_queue_add(circuit->tx_queue, lsp,
+					  TX_LSP_NORMAL);
+			ISIS_CLEAR_FLAG(lsp->SSNflags, circuit);
+		}
+	} else {
+		/* 7.3.15.1 e) - This lsp originated on another system */
+
+		/* 7.3.15.1 e) 1) LSP newer than the one in db or no LSP in db
+		 */
+		if ((!lsp || comp == LSP_NEWER)) {
+			/*
+			 * If this lsp is a frag, need to see if we have zero
+			 * lsp present
+			 */
+			struct isis_lsp *lsp0 = NULL;
+			if (LSP_FRAGMENT(hdr.lsp_id) != 0) {
+				uint8_t lspid[ISIS_SYS_ID_LEN + 2];
+				memcpy(lspid, hdr.lsp_id, ISIS_SYS_ID_LEN + 1);
+				LSP_FRAGMENT(lspid) = 0;
+				lsp0 = lsp_search(
+					&circuit->area->lspdb[level - 1], lspid);
+				if (!lsp0) {
+					zlog_debug(
+						"Got lsp frag, while zero lsp not in database");
+					goto out;
+				}
+			}
+			/* i */
+			if (!lsp) {
+				lsp = lsp_new_from_recv(
+					&hdr, tlvs, circuit->rcv_stream, lsp0,
+					circuit->area, level);
+				tlvs = NULL;
+				lsp_insert(&circuit->area->lspdb[level - 1],
+					   lsp);
+			} else /* exists, so we overwrite */
+			{
+				lsp_update(lsp, &hdr, tlvs, circuit->rcv_stream,
+					   circuit->area, level, false);
+				tlvs = NULL;
+			}
+			lsp_flood_or_update(lsp, circuit, circuit_scoped);
+
+			/* iv */
+			if (circuit->circ_type != CIRCUIT_T_BROADCAST)
+				ISIS_SET_FLAG(lsp->SSNflags, circuit);
+			/* FIXME: v) */
+		}
+		/* 7.3.15.1 e) 2) LSP equal to the one in db */
+		else if (comp == LSP_EQUAL) {
+			isis_tx_queue_del(circuit->tx_queue, lsp);
+			lsp_update(lsp, &hdr, tlvs, circuit->rcv_stream,
+				   circuit->area, level, false);
+			tlvs = NULL;
+			if (circuit->circ_type != CIRCUIT_T_BROADCAST)
+				ISIS_SET_FLAG(lsp->SSNflags, circuit);
+		}
+		/* 7.3.15.1 e) 3) LSP older than the one in db */
+		else {
+			isis_tx_queue_add(circuit->tx_queue, lsp,
+					  TX_LSP_NORMAL);
+			ISIS_CLEAR_FLAG(lsp->SSNflags, circuit);
+		}
+	}
+
+	retval = ISIS_OK;
+
+out:
+	fabricd_trigger_csnp(circuit->area, circuit_scoped);
+
+	isis_free_tlvs(tlvs);
+	return retval;
+}
+
+/*
+ * Process Sequence Numbers
+ * ISO - 10589
+ * Section 7.3.15.2 - Action on receipt of a sequence numbers PDU
+ */
+
+static int process_snp(uint8_t pdu_type, struct isis_circuit *circuit,
+		       const uint8_t *ssnpa)
+{
+#ifndef FABRICD
+	size_t pdu_start = stream_get_getp(circuit->rcv_stream);
+	size_t pdu_end = stream_get_endp(circuit->rcv_stream);
+	char raw_pdu[pdu_end - pdu_start];
+#endif /* ifndef FABRICD */
+
+	bool is_csnp = (pdu_type == L1_COMPLETE_SEQ_NUM
+			|| pdu_type == L2_COMPLETE_SEQ_NUM);
+	char typechar = is_csnp ? 'C' : 'P';
+	int level = (pdu_type == L1_COMPLETE_SEQ_NUM
+		     || pdu_type == L1_PARTIAL_SEQ_NUM)
+			    ? ISIS_LEVEL1
+			    : ISIS_LEVEL2;
+
+	uint16_t pdu_len = stream_getw(circuit->rcv_stream);
+	uint8_t rem_sys_id[ISIS_SYS_ID_LEN];
+
+	stream_get(rem_sys_id, circuit->rcv_stream, ISIS_SYS_ID_LEN);
+	stream_forward_getp(circuit->rcv_stream, 1); /* Circuit ID - unused */
+
+	uint8_t start_lsp_id[ISIS_SYS_ID_LEN + 2] = {};
+	uint8_t stop_lsp_id[ISIS_SYS_ID_LEN + 2] = {};
+
+	if (is_csnp) {
+		stream_get(start_lsp_id, circuit->rcv_stream,
+			   ISIS_SYS_ID_LEN + 2);
+		stream_get(stop_lsp_id, circuit->rcv_stream,
+			   ISIS_SYS_ID_LEN + 2);
+	}
+
+	if (pdu_len_validate(pdu_len, circuit)) {
+		zlog_warn("Received a CSNP with bogus length %d", pdu_len);
+		return ISIS_WARNING;
+	}
+
+	if (IS_DEBUG_SNP_PACKETS) {
+		zlog_debug(
+			"ISIS-Snp (%s): Rcvd L%d %cSNP on %s, cirType %s, cirID %u",
+			circuit->area->area_tag, level, typechar,
+			circuit->interface->name,
+			circuit_t2string(circuit->is_type),
+			circuit->circuit_id);
+		if (IS_DEBUG_PACKET_DUMP)
+			zlog_dump_data(STREAM_DATA(circuit->rcv_stream),
+				       stream_get_endp(circuit->rcv_stream));
+	}
+
+	/* 7.3.15.2 a) 1 - external domain circuit will discard snp pdu */
+	if (circuit->ext_domain) {
+
+		zlog_debug(
+			"ISIS-Snp (%s): Rcvd L%d %cSNP on %s, skipping: circuit externalDomain = true",
+			circuit->area->area_tag, level, typechar,
+			circuit->interface->name);
+
+		return ISIS_OK;
+	}
+
+	/* 7.3.15.2 a) 2,3 - manualL2OnlyMode not implemented */
+	if (!(circuit->is_type & level)) {
+		zlog_debug(
+			"ISIS-Snp (%s): Rcvd L%d %cSNP on %s, skipping: circuit type %s does not match level %d",
+			circuit->area->area_tag, level, typechar,
+			circuit->interface->name,
+			circuit_t2string(circuit->is_type), level);
+
+		return ISIS_OK;
+	}
+
+	/* 7.3.15.2 a) 4 - not applicable for CSNP  only PSNPs on broadcast */
+	if (!is_csnp && (circuit->circ_type == CIRCUIT_T_BROADCAST)
+	    && !circuit->u.bc.is_dr[level - 1]) {
+		zlog_debug(
+			"ISIS-Snp (%s): Rcvd L%d %cSNP from %pSY on %s, skipping: we are not the DIS",
+			circuit->area->area_tag, level, typechar, ssnpa,
+			circuit->interface->name);
+
+		return ISIS_OK;
+	}
+
+	/* 7.3.15.2 a) 5 - need to make sure IDLength matches - already checked
+	 */
+
+	/* 7.3.15.2 a) 6 - maximum area match, can be ommited since we only use
+	 * 3
+	 * - already checked */
+
+	/* 7.3.15.2 a) 7 - Must check that we have an adjacency of the same
+	 * level  */
+	/* for broadcast circuits, snpa should be compared */
+	/* FIXME : Do we need to check SNPA? */
+	if (circuit->circ_type == CIRCUIT_T_BROADCAST) {
+		if (!isis_adj_lookup(rem_sys_id,
+				     circuit->u.bc.adjdb[level - 1]))
+			return ISIS_OK; /* Silently discard */
+	} else {
+		if (!fabricd && !circuit->u.p2p.neighbor) {
+			zlog_warn("no p2p neighbor on circuit %s",
+				  circuit->interface->name);
+			return ISIS_OK; /* Silently discard */
+		}
+	}
+
+	struct isis_tlvs *tlvs;
+	int retval = ISIS_WARNING;
+	const char *error_log;
+
+	if (isis_unpack_tlvs(STREAM_READABLE(circuit->rcv_stream),
+			     circuit->rcv_stream, &tlvs, &error_log)) {
+		zlog_warn("Something went wrong unpacking the SNP: %s",
+			  error_log);
+		goto out;
+	}
+
+	struct isis_passwd *passwd = (level == IS_LEVEL_1)
+					     ? &circuit->area->area_passwd
+					     : &circuit->area->domain_passwd;
+
+	if (CHECK_FLAG(passwd->snp_auth, SNP_AUTH_RECV)) {
+		int auth_code = isis_tlvs_auth_is_valid(
+			tlvs, passwd, circuit->rcv_stream, false);
+		if (auth_code != ISIS_AUTH_OK) {
+			isis_event_auth_failure(circuit->area->area_tag,
+						"SNP authentication failure",
+						rem_sys_id);
+#ifndef FABRICD
+			/* send northbound notification */
+			stream_get_from(raw_pdu, circuit->rcv_stream, pdu_start,
+					pdu_end - pdu_start);
+			if (auth_code == ISIS_AUTH_FAILURE) {
+				circuit->auth_failures++;
+				if (circuit->is_type == IS_LEVEL_1) {
+					circuit->area->auth_failures[0]++;
+				} else if (circuit->is_type == IS_LEVEL_2) {
+					circuit->area->auth_failures[1]++;
+				} else {
+					circuit->area->auth_failures[0]++;
+					circuit->area->auth_failures[1]++;
+				}
+				isis_notif_authentication_failure(
+					circuit, raw_pdu, sizeof(raw_pdu));
+			} else { /* AUTH_TYPE_FAILURE or NO_VALIDATOR */
+				circuit->auth_type_failures++;
+				if (circuit->is_type == IS_LEVEL_1) {
+					circuit->area->auth_type_failures[0]++;
+				} else if (circuit->is_type == IS_LEVEL_2) {
+					circuit->area->auth_type_failures[1]++;
+				} else {
+					circuit->area->auth_type_failures[0]++;
+					circuit->area->auth_type_failures[1]++;
+				}
+				isis_notif_authentication_type_failure(
+					circuit, raw_pdu, sizeof(raw_pdu));
+			}
+#endif /* ifndef FABRICD */
+			goto out;
+		}
+	}
+
+	struct isis_lsp_entry *entry_head =
+		(struct isis_lsp_entry *)tlvs->lsp_entries.head;
+
+	/* debug isis snp-packets */
+	if (IS_DEBUG_SNP_PACKETS) {
+		zlog_debug("ISIS-Snp (%s): Rcvd L%d %cSNP from %pSY on %s",
+			   circuit->area->area_tag, level, typechar, ssnpa,
+			   circuit->interface->name);
+		for (struct isis_lsp_entry *entry = entry_head; entry;
+		     entry = entry->next) {
+			zlog_debug(
+				"ISIS-Snp (%s):         %cSNP entry %pLS, seq 0x%08x, cksum 0x%04hx, lifetime %hus",
+				circuit->area->area_tag, typechar, entry->id,
+				entry->seqno, entry->checksum,
+				entry->rem_lifetime);
+		}
+	}
+
+	bool resync_needed = false;
+
+	/* 7.3.15.2 b) Actions on LSP_ENTRIES reported */
+	for (struct isis_lsp_entry *entry = entry_head; entry;
+	     entry = entry->next) {
+		struct isis_lsp *lsp =
+			lsp_search(&circuit->area->lspdb[level - 1], entry->id);
+		bool own_lsp = !memcmp(entry->id, circuit->isis->sysid,
+				       ISIS_SYS_ID_LEN);
+		if (lsp) {
+			/* 7.3.15.2 b) 1) is this LSP newer */
+			int cmp = lsp_compare(circuit->area->area_tag, lsp,
+					      entry->seqno, entry->checksum,
+					      entry->rem_lifetime);
+			/* 7.3.15.2 b) 2) if it equals, clear SRM on p2p */
+			if (cmp == LSP_EQUAL) {
+				/* if (circuit->circ_type !=
+				 * CIRCUIT_T_BROADCAST) */
+				isis_tx_queue_del(circuit->tx_queue, lsp);
+			}
+			/* 7.3.15.2 b) 3) if it is older, clear SSN and set SRM
+			   */
+			else if (cmp == LSP_OLDER) {
+				ISIS_CLEAR_FLAG(lsp->SSNflags, circuit);
+				isis_tx_queue_add(circuit->tx_queue, lsp,
+						  TX_LSP_NORMAL);
+			}
+			/* 7.3.15.2 b) 4) if it is newer, set SSN and clear SRM
+			   on p2p */
+			else {
+				if (own_lsp) {
+					lsp_inc_seqno(lsp, entry->seqno);
+					isis_tx_queue_add(circuit->tx_queue, lsp,
+							TX_LSP_NORMAL);
+				} else {
+					ISIS_SET_FLAG(lsp->SSNflags, circuit);
+					/* if (circuit->circ_type !=
+					 * CIRCUIT_T_BROADCAST) */
+					isis_tx_queue_del(circuit->tx_queue, lsp);
+					resync_needed = true;
+				}
+			}
+		} else {
+			/* 7.3.15.2 b) 5) if it was not found, and all of those
+			 * are not 0,
+			 * insert it and set SSN on it */
+			if (entry->rem_lifetime && entry->checksum
+			    && entry->seqno
+			    && memcmp(entry->id, circuit->isis->sysid,
+				      ISIS_SYS_ID_LEN)) {
+				struct isis_lsp *lsp0 = NULL;
+
+				if (LSP_FRAGMENT(entry->id)) {
+					uint8_t lspid[ISIS_SYS_ID_LEN + 2];
+
+					memcpy(lspid, entry->id,
+					       ISIS_SYS_ID_LEN + 1);
+					LSP_FRAGMENT(lspid) = 0;
+					lsp0 = lsp_search(
+						  &circuit->area->lspdb[level - 1],
+						  lspid);
+					if (!lsp0) {
+						zlog_debug("Got lsp frag in snp, while zero not in database");
+						continue;
+					}
+				}
+				lsp = lsp_new(circuit->area, entry->id,
+						entry->rem_lifetime, 0, 0,
+						entry->checksum, lsp0, level);
+				lsp_insert(&circuit->area->lspdb[level - 1],
+					   lsp);
+
+				lsp_set_all_srmflags(lsp, false);
+				ISIS_SET_FLAG(lsp->SSNflags, circuit);
+				resync_needed = true;
+			}
+		}
+	}
+
+	/* 7.3.15.2 c) on CSNP set SRM for all in range which were not reported
+	 */
+	if (is_csnp) {
+		/*
+		 * Build a list from our own LSP db bounded with
+		 * start_lsp_id and stop_lsp_id
+		 */
+		struct list *lsp_list = list_new();
+		lsp_build_list_nonzero_ht(&circuit->area->lspdb[level - 1],
+					  start_lsp_id, stop_lsp_id, lsp_list);
+
+		/* Fixme: Find a better solution */
+		struct listnode *node, *nnode;
+		struct isis_lsp *lsp;
+		for (struct isis_lsp_entry *entry = entry_head; entry;
+		     entry = entry->next) {
+			for (ALL_LIST_ELEMENTS(lsp_list, node, nnode, lsp)) {
+				if (lsp_id_cmp(lsp->hdr.lsp_id, entry->id)
+				    == 0) {
+					list_delete_node(lsp_list, node);
+					break;
+				}
+			}
+		}
+
+		/* on remaining LSPs we set SRM (neighbor knew not of) */
+		for (ALL_LIST_ELEMENTS_RO(lsp_list, node, lsp)) {
+			isis_tx_queue_add(circuit->tx_queue, lsp, TX_LSP_NORMAL);
+			resync_needed = true;
+		}
+
+		/* lets free it */
+		list_delete(&lsp_list);
+	}
+
+	if (fabricd_initial_sync_is_complete(circuit->area) && resync_needed)
+		zlog_warn("OpenFabric: Needed to resync LSPDB using CSNP!");
+
+	retval = ISIS_OK;
+out:
+	isis_free_tlvs(tlvs);
+	return retval;
+}
+
+static int pdu_size(uint8_t pdu_type, uint8_t *size)
+{
+	switch (pdu_type) {
+	case L1_LAN_HELLO:
+	case L2_LAN_HELLO:
+		*size = ISIS_LANHELLO_HDRLEN;
+		break;
+	case P2P_HELLO:
+		*size = ISIS_P2PHELLO_HDRLEN;
+		break;
+	case L1_LINK_STATE:
+	case L2_LINK_STATE:
+	case FS_LINK_STATE:
+		*size = ISIS_LSP_HDR_LEN;
+		break;
+	case L1_COMPLETE_SEQ_NUM:
+	case L2_COMPLETE_SEQ_NUM:
+		*size = ISIS_CSNP_HDRLEN;
+		break;
+	case L1_PARTIAL_SEQ_NUM:
+	case L2_PARTIAL_SEQ_NUM:
+		*size = ISIS_PSNP_HDRLEN;
+		break;
+	default:
+		return 1;
+	}
+	*size += ISIS_FIXED_HDR_LEN;
+	return 0;
+}
+
+/*
+ * PDU Dispatcher
+ */
+
+int isis_handle_pdu(struct isis_circuit *circuit, uint8_t *ssnpa)
+{
+	int retval = ISIS_OK;
+	size_t pdu_start = stream_get_getp(circuit->rcv_stream);
+	size_t pdu_end = stream_get_endp(circuit->rcv_stream);
+	char raw_pdu[pdu_end - pdu_start];
+
+	stream_get_from(raw_pdu, circuit->rcv_stream, pdu_start,
+			pdu_end - pdu_start);
+
+	/* Verify that at least the 8 bytes fixed header have been received */
+	if (stream_get_endp(circuit->rcv_stream) < ISIS_FIXED_HDR_LEN) {
+		flog_err(EC_ISIS_PACKET, "PDU is too short to be IS-IS.");
+		return ISIS_ERROR;
+	}
+
+	uint8_t idrp = stream_getc(circuit->rcv_stream);
+	uint8_t length = stream_getc(circuit->rcv_stream);
+	uint8_t version1 = stream_getc(circuit->rcv_stream);
+	uint8_t id_len = stream_getc(circuit->rcv_stream);
+	uint8_t pdu_type = stream_getc(circuit->rcv_stream)
+			   & 0x1f; /* bits 6-8 are reserved */
+	uint8_t version2 = stream_getc(circuit->rcv_stream);
+
+	stream_forward_getp(circuit->rcv_stream, 1); /* reserved */
+	uint8_t max_area_addrs = stream_getc(circuit->rcv_stream);
+
+	pdu_counter_count(circuit->area->pdu_rx_counters, pdu_type);
+
+	if (idrp == ISO9542_ESIS) {
+		flog_err(EC_LIB_DEVELOPMENT,
+			 "No support for ES-IS packet IDRP=%hhx", idrp);
+		pdu_counter_count_drop(circuit->area, pdu_type);
+		return ISIS_ERROR;
+	}
+
+	if (idrp != ISO10589_ISIS) {
+		flog_err(EC_ISIS_PACKET, "Not an IS-IS packet IDRP=%hhx",
+			 idrp);
+		pdu_counter_count_drop(circuit->area, pdu_type);
+		return ISIS_ERROR;
+	}
+
+	if (version1 != 1) {
+		zlog_warn("Unsupported ISIS version %hhu", version1);
+#ifndef FABRICD
+		/* send northbound notification */
+		isis_notif_version_skew(circuit, version1, raw_pdu,
+					sizeof(raw_pdu));
+#endif /* ifndef FABRICD */
+		pdu_counter_count_drop(circuit->area, pdu_type);
+		return ISIS_WARNING;
+	}
+
+	if (id_len != 0 && id_len != ISIS_SYS_ID_LEN) {
+		flog_err(
+			EC_ISIS_PACKET,
+			"IDFieldLengthMismatch: ID Length field in a received PDU  %hhu, while the parameter for this IS is %u",
+			id_len, ISIS_SYS_ID_LEN);
+		circuit->id_len_mismatches++;
+		if (circuit->is_type == IS_LEVEL_1) {
+			circuit->area->id_len_mismatches[0]++;
+		} else if (circuit->is_type == IS_LEVEL_2) {
+			circuit->area->id_len_mismatches[1]++;
+		} else {
+			circuit->area->id_len_mismatches[0]++;
+			circuit->area->id_len_mismatches[1]++;
+		}
+
+#ifndef FABRICD
+		/* send northbound notification */
+		isis_notif_id_len_mismatch(circuit, id_len, raw_pdu,
+					   sizeof(raw_pdu));
+#endif /* ifndef FABRICD */
+		pdu_counter_count_drop(circuit->area, pdu_type);
+		return ISIS_ERROR;
+	}
+
+	uint8_t expected_length;
+	if (pdu_size(pdu_type, &expected_length)) {
+		zlog_warn("Unsupported ISIS PDU %hhu", pdu_type);
+		pdu_counter_count_drop(circuit->area, pdu_type);
+		return ISIS_WARNING;
+	}
+
+	if (length != expected_length) {
+		flog_err(EC_ISIS_PACKET,
+			 "Expected fixed header length = %hhu but got %hhu",
+			 expected_length, length);
+		pdu_counter_count_drop(circuit->area, pdu_type);
+		return ISIS_ERROR;
+	}
+
+	if (stream_get_endp(circuit->rcv_stream) < length) {
+		flog_err(
+			EC_ISIS_PACKET,
+			"PDU is too short to contain fixed header of given PDU type.");
+		pdu_counter_count_drop(circuit->area, pdu_type);
+		return ISIS_ERROR;
+	}
+
+	if (version2 != 1) {
+		zlog_warn("Unsupported ISIS PDU version %hhu", version2);
+#ifndef FABRICD
+		/* send northbound notification */
+		isis_notif_version_skew(circuit, version2, raw_pdu,
+					sizeof(raw_pdu));
+#endif /* ifndef FABRICD */
+		pdu_counter_count_drop(circuit->area, pdu_type);
+		return ISIS_WARNING;
+	}
+
+	if (circuit->is_passive) {
+		zlog_warn("Received ISIS PDU on passive circuit %s",
+			  circuit->interface->name);
+		pdu_counter_count_drop(circuit->area, pdu_type);
+		return ISIS_WARNING;
+	}
+
+	/* either 3 or 0 */
+	if (pdu_type != FS_LINK_STATE /* FS PDU doesn't contain max area addr
+					 field */
+	    && max_area_addrs != 0
+	    && max_area_addrs != circuit->isis->max_area_addrs) {
+		flog_err(
+			EC_ISIS_PACKET,
+			"maximumAreaAddressesMismatch: maximumAreaAdresses in a received PDU %hhu while the parameter for this IS is %u",
+			max_area_addrs, circuit->isis->max_area_addrs);
+		circuit->max_area_addr_mismatches++;
+#ifndef FABRICD
+		/* send northbound notification */
+		isis_notif_max_area_addr_mismatch(circuit, max_area_addrs,
+						  raw_pdu, sizeof(raw_pdu));
+#endif /* ifndef FABRICD */
+		pdu_counter_count_drop(circuit->area, pdu_type);
+		return ISIS_ERROR;
+	}
+
+	switch (pdu_type) {
+	case L1_LAN_HELLO:
+	case L2_LAN_HELLO:
+	case P2P_HELLO:
+		if (fabricd && pdu_type != P2P_HELLO) {
+			pdu_counter_count_drop(circuit->area, pdu_type);
+			return ISIS_ERROR;
+		}
+
+		retval = process_hello(pdu_type, circuit, ssnpa);
+		break;
+	case L1_LINK_STATE:
+	case L2_LINK_STATE:
+	case FS_LINK_STATE:
+		if (fabricd && pdu_type != L2_LINK_STATE &&
+		    pdu_type != FS_LINK_STATE) {
+			pdu_counter_count_drop(circuit->area, pdu_type);
+			return ISIS_ERROR;
+		}
+
+		retval = process_lsp(pdu_type, circuit, ssnpa, max_area_addrs);
+		break;
+	case L1_COMPLETE_SEQ_NUM:
+	case L2_COMPLETE_SEQ_NUM:
+	case L1_PARTIAL_SEQ_NUM:
+	case L2_PARTIAL_SEQ_NUM:
+		retval = process_snp(pdu_type, circuit, ssnpa);
+		break;
+	default:
+		pdu_counter_count_drop(circuit->area, pdu_type);
+		return ISIS_ERROR;
+	}
+
+	if (retval != ISIS_OK)
+		pdu_counter_count_drop(circuit->area, pdu_type);
+
+	return retval;
+}
+
+void isis_receive(struct event *thread)
+{
+	struct isis_circuit *circuit;
+	uint8_t ssnpa[ETH_ALEN];
+
+	/*
+	 * Get the circuit
+	 */
+	circuit = EVENT_ARG(thread);
+	assert(circuit);
+
+	circuit->t_read = NULL;
+
+	isis_circuit_stream(circuit, &circuit->rcv_stream);
+
+#if ISIS_METHOD != ISIS_METHOD_BPF
+	int retval;
+
+	retval = circuit->rx(circuit, ssnpa);
+
+	if (retval == ISIS_OK)
+		isis_handle_pdu(circuit, ssnpa);
+#else // ISIS_METHOD != ISIS_METHOD_BPF
+	circuit->rx(circuit, ssnpa);
+#endif
+
+	/*
+	 * prepare for next packet.
+	 */
+	if (!circuit->is_passive)
+		isis_circuit_prepare(circuit);
+}
+
+/*
+ * SEND SIDE
+ */
+void fill_fixed_hdr(uint8_t pdu_type, struct stream *stream)
+{
+	uint8_t length;
+
+	if (pdu_size(pdu_type, &length))
+		assert(!"Unknown PDU Type");
+
+	stream_putc(stream, ISO10589_ISIS); /* IDRP */
+	stream_putc(stream, length);	/* Length of fixed header */
+	stream_putc(stream, 1); /* Version/Protocol ID Extension 1 */
+	stream_putc(stream, 0); /* ID Length, 0 => 6 */
+	stream_putc(stream, pdu_type);
+	stream_putc(stream, 1); /* Subversion */
+	stream_putc(stream, 0); /* Reserved */
+	stream_putc(stream, 0); /* Max Area Addresses 0 => 3 */
+}
+
+static uint8_t hello_pdu_type(struct isis_circuit *circuit, int level)
+{
+	if (circuit->circ_type == CIRCUIT_T_BROADCAST)
+		return (level == IS_LEVEL_1) ? L1_LAN_HELLO : L2_LAN_HELLO;
+	else
+		return P2P_HELLO;
+}
+
+static void put_hello_hdr(struct isis_circuit *circuit, int level,
+			  size_t *len_pointer)
+{
+	uint8_t pdu_type = hello_pdu_type(circuit, level);
+
+	isis_circuit_stream(circuit, &circuit->snd_stream);
+	fill_fixed_hdr(pdu_type, circuit->snd_stream);
+
+	stream_putc(circuit->snd_stream, circuit->is_type);
+	stream_put(circuit->snd_stream, circuit->isis->sysid, ISIS_SYS_ID_LEN);
+
+	uint32_t holdtime = circuit->hello_multiplier[level - 1]
+			    * circuit->hello_interval[level - 1];
+
+	if (holdtime > 0xffff)
+		holdtime = 0xffff;
+
+	stream_putw(circuit->snd_stream, holdtime);
+	*len_pointer = stream_get_endp(circuit->snd_stream);
+	stream_putw(circuit->snd_stream, 0); /* length is filled in later */
+
+	if (circuit->circ_type == CIRCUIT_T_BROADCAST) {
+		uint8_t *desig_is = (level == IS_LEVEL_1)
+					    ? circuit->u.bc.l1_desig_is
+					    : circuit->u.bc.l2_desig_is;
+		stream_putc(circuit->snd_stream, circuit->priority[level - 1]);
+		stream_put(circuit->snd_stream, desig_is, ISIS_SYS_ID_LEN + 1);
+	} else {
+		stream_putc(circuit->snd_stream, circuit->circuit_id);
+	}
+}
+
+int send_hello(struct isis_circuit *circuit, int level)
+{
+	size_t len_pointer;
+	int retval;
+
+	if (circuit->is_passive)
+		return ISIS_OK;
+
+	if (circuit->interface->mtu == 0) {
+		zlog_warn("circuit has zero MTU");
+		return ISIS_WARNING;
+	}
+
+	put_hello_hdr(circuit, level, &len_pointer);
+
+	struct isis_tlvs *tlvs = isis_alloc_tlvs();
+
+	isis_tlvs_add_auth(tlvs, &circuit->passwd);
+
+	if (!listcount(circuit->area->area_addrs)) {
+		isis_free_tlvs(tlvs);
+		return ISIS_WARNING;
+	}
+
+	isis_tlvs_add_area_addresses(tlvs, circuit->area->area_addrs);
+
+	if (circuit->circ_type == CIRCUIT_T_BROADCAST) {
+		isis_tlvs_add_lan_neighbors(
+			tlvs, circuit->u.bc.lan_neighs[level - 1]);
+	} else if (circuit->circ_type == CIRCUIT_T_P2P
+		   && !circuit->disable_threeway_adj) {
+		uint32_t ext_circuit_id = circuit->idx;
+		if (circuit->u.p2p.neighbor) {
+			uint8_t threeway_state;
+
+			if (fabricd_initial_sync_is_in_progress(circuit->area)
+			    && fabricd_initial_sync_circuit(circuit->area) != circuit)
+				threeway_state = ISIS_THREEWAY_DOWN;
+			else
+				threeway_state = circuit->u.p2p.neighbor->threeway_state;
+			isis_tlvs_add_threeway_adj(tlvs,
+					threeway_state,
+					ext_circuit_id,
+					circuit->u.p2p.neighbor->sysid,
+					circuit->u.p2p.neighbor->ext_circuit_id);
+		} else {
+			isis_tlvs_add_threeway_adj(tlvs,
+					ISIS_THREEWAY_DOWN,
+					ext_circuit_id,
+					NULL, 0);
+		}
+	}
+
+	isis_tlvs_set_protocols_supported(tlvs, &circuit->nlpids);
+
+	/*
+	 * MT Supported TLV
+	 *
+	 * TLV gets included if no topology is enabled on the interface,
+	 * if one topology other than #0 is enabled, or if multiple topologies
+	 * are enabled.
+	 */
+	struct isis_circuit_mt_setting **mt_settings;
+	unsigned int mt_count;
+
+	mt_settings = circuit_mt_settings(circuit, &mt_count);
+	if (mt_count == 0 && area_is_mt(circuit->area)) {
+		tlvs->mt_router_info_empty = true;
+	} else if ((mt_count == 1
+		    && mt_settings[0]->mtid != ISIS_MT_IPV4_UNICAST)
+		   || (mt_count > 1)) {
+		for (unsigned int i = 0; i < mt_count; i++)
+			isis_tlvs_add_mt_router_info(tlvs, mt_settings[i]->mtid,
+						     false, false);
+	}
+
+	if (circuit->ip_router) {
+		struct list *circuit_ip_addrs = fabricd_ip_addrs(circuit);
+
+		if (circuit_ip_addrs)
+			isis_tlvs_add_ipv4_addresses(tlvs, circuit_ip_addrs);
+	}
+
+	if (circuit->ipv6_router)
+		isis_tlvs_add_ipv6_addresses(tlvs, circuit->ipv6_link);
+
+	/* RFC6119 section 4 define TLV 233 to provide Global IPv6 address */
+	if (circuit->ipv6_router)
+		isis_tlvs_add_global_ipv6_addresses(tlvs,
+						    circuit->ipv6_non_link);
+
+	bool should_pad_hello =
+		circuit->pad_hellos == ISIS_HELLO_PADDING_ALWAYS ||
+		(circuit->pad_hellos ==
+			 ISIS_HELLO_PADDING_DURING_ADJACENCY_FORMATION &&
+		 circuit->upadjcount[0] + circuit->upadjcount[1] == 0);
+
+	if (isis_pack_tlvs(tlvs, circuit->snd_stream, len_pointer,
+			   should_pad_hello, false)) {
+		isis_free_tlvs(tlvs);
+		return ISIS_WARNING; /* XXX: Maybe Log TLV structure? */
+	}
+
+	if (IS_DEBUG_ADJ_PACKETS) {
+		if (circuit->circ_type == CIRCUIT_T_BROADCAST) {
+			zlog_debug(
+				"ISIS-Adj (%s): Sending L%d LAN IIH on %s, length %zd",
+				circuit->area->area_tag, level,
+				circuit->interface->name,
+				stream_get_endp(circuit->snd_stream));
+		} else {
+			zlog_debug(
+				"ISIS-Adj (%s): Sending P2P IIH on %s, length %zd",
+				circuit->area->area_tag,
+				circuit->interface->name,
+				stream_get_endp(circuit->snd_stream));
+		}
+		if (IS_DEBUG_PACKET_DUMP)
+			zlog_dump_data(STREAM_DATA(circuit->snd_stream),
+				       stream_get_endp(circuit->snd_stream));
+	}
+
+	isis_free_tlvs(tlvs);
+
+	pdu_counter_count(circuit->area->pdu_tx_counters,
+			  hello_pdu_type(circuit, level));
+	retval = circuit->tx(circuit, level);
+	if (retval != ISIS_OK)
+		flog_err(EC_ISIS_PACKET,
+			 "ISIS-Adj (%s): Send L%d IIH on %s failed",
+			 circuit->area->area_tag, level,
+			 circuit->interface->name);
+
+	return retval;
+}
+
+static void send_hello_cb(struct event *thread)
+{
+	struct isis_circuit_arg *arg = EVENT_ARG(thread);
+	assert(arg);
+
+	struct isis_circuit *circuit = arg->circuit;
+	int level = arg->level;
+
+	assert(circuit);
+
+	if (circuit->circ_type == CIRCUIT_T_P2P) {
+		circuit->u.p2p.t_send_p2p_hello = NULL;
+		send_hello(circuit, 1);
+		send_hello_sched(circuit, ISIS_LEVEL1,
+				 1000 * circuit->hello_interval[1]);
+		return;
+	}
+
+	if (circuit->circ_type != CIRCUIT_T_BROADCAST) {
+		zlog_warn("ISIS-Hello (%s): Trying to send hello on unknown circuit type %d",
+			  circuit->area->area_tag, circuit->circ_type);
+		return;
+	}
+
+	circuit->u.bc.t_send_lan_hello[level - 1] = NULL;
+	if (!(circuit->is_type & level)) {
+		zlog_warn("ISIS-Hello (%s): Trying to send L%d IIH in L%d-only circuit",
+			  circuit->area->area_tag, level, 3 - level);
+		return;
+	}
+
+	if (circuit->u.bc.run_dr_elect[level - 1])
+		isis_dr_elect(circuit, level);
+
+	send_hello(circuit, level);
+
+	/* set next timer thread */
+	send_hello_sched(circuit, level, 1000 * circuit->hello_interval[level - 1]);
+}
+
+static void _send_hello_sched(struct isis_circuit *circuit,
+			      struct event **threadp, int level, long delay)
+{
+	if (*threadp) {
+		if (event_timer_remain_msec(*threadp) < (unsigned long)delay)
+			return;
+
+		EVENT_OFF(*threadp);
+	}
+
+	event_add_timer_msec(master, send_hello_cb,
+			     &circuit->level_arg[level - 1],
+			     isis_jitter(delay, IIH_JITTER), threadp);
+}
+
+void send_hello_sched(struct isis_circuit *circuit, int level, long delay)
+{
+	if (circuit->circ_type == CIRCUIT_T_P2P) {
+		_send_hello_sched(circuit, &circuit->u.p2p.t_send_p2p_hello,
+				  ISIS_LEVEL1, delay);
+		return;
+	}
+
+	if (circuit->circ_type != CIRCUIT_T_BROADCAST) {
+		zlog_warn("%s: encountered unknown circuit type %d on %s",
+			  __func__, circuit->circ_type,
+			  circuit->interface->name);
+		return;
+	}
+
+	for (int loop_level = ISIS_LEVEL1; loop_level <= ISIS_LEVEL2; loop_level++) {
+		if (!(loop_level & level))
+			continue;
+
+		_send_hello_sched(
+			circuit,
+			&circuit->u.bc.t_send_lan_hello[loop_level - 1],
+			loop_level,
+			delay
+		);
+	}
+}
+
+
+/*
+ * Count the maximum number of lsps that can be accommodated by a given size.
+ */
+#define LSP_ENTRIES_LEN (10 + ISIS_SYS_ID_LEN)
+static uint16_t get_max_lsp_count(uint16_t size)
+{
+	uint16_t tlv_count;
+	uint16_t lsp_count;
+	uint16_t remaining_size;
+
+	/* First count the full size TLVs */
+	tlv_count = size / MAX_LSP_ENTRIES_TLV_SIZE;
+	lsp_count = tlv_count * (MAX_LSP_ENTRIES_TLV_SIZE / LSP_ENTRIES_LEN);
+
+	/* The last TLV, if any */
+	remaining_size = size % MAX_LSP_ENTRIES_TLV_SIZE;
+	if (remaining_size - 2 >= LSP_ENTRIES_LEN)
+		lsp_count += (remaining_size - 2) / LSP_ENTRIES_LEN;
+
+	return lsp_count;
+}
+
+int send_csnp(struct isis_circuit *circuit, int level)
+{
+	if (lspdb_count(&circuit->area->lspdb[level - 1]) == 0)
+		return ISIS_OK;
+
+	uint8_t pdu_type = (level == ISIS_LEVEL1) ? L1_COMPLETE_SEQ_NUM
+						  : L2_COMPLETE_SEQ_NUM;
+
+	isis_circuit_stream(circuit, &circuit->snd_stream);
+	fill_fixed_hdr(pdu_type, circuit->snd_stream);
+
+	size_t len_pointer = stream_get_endp(circuit->snd_stream);
+
+	stream_putw(circuit->snd_stream, 0);
+	stream_put(circuit->snd_stream, circuit->isis->sysid, ISIS_SYS_ID_LEN);
+	/* with zero circuit id - ref 9.10, 9.11 */
+	stream_putc(circuit->snd_stream, 0);
+
+	size_t start_pointer = stream_get_endp(circuit->snd_stream);
+	stream_put(circuit->snd_stream, 0, ISIS_SYS_ID_LEN + 2);
+	size_t end_pointer = stream_get_endp(circuit->snd_stream);
+	stream_put(circuit->snd_stream, 0, ISIS_SYS_ID_LEN + 2);
+
+	struct isis_passwd *passwd = (level == ISIS_LEVEL1)
+					     ? &circuit->area->area_passwd
+					     : &circuit->area->domain_passwd;
+
+	struct isis_tlvs *tlvs = isis_alloc_tlvs();
+
+	if (CHECK_FLAG(passwd->snp_auth, SNP_AUTH_SEND))
+		isis_tlvs_add_auth(tlvs, passwd);
+
+	size_t tlv_start = stream_get_endp(circuit->snd_stream);
+	if (isis_pack_tlvs(tlvs, circuit->snd_stream, len_pointer, false,
+			   false)) {
+		isis_free_tlvs(tlvs);
+		return ISIS_WARNING;
+	}
+	isis_free_tlvs(tlvs);
+
+	uint16_t num_lsps =
+		get_max_lsp_count(STREAM_WRITEABLE(circuit->snd_stream));
+
+	uint8_t start[ISIS_SYS_ID_LEN + 2];
+	memset(start, 0x00, ISIS_SYS_ID_LEN + 2);
+	uint8_t stop[ISIS_SYS_ID_LEN + 2];
+	memset(stop, 0xff, ISIS_SYS_ID_LEN + 2);
+
+	bool loop = true;
+	while (loop) {
+		tlvs = isis_alloc_tlvs();
+		if (CHECK_FLAG(passwd->snp_auth, SNP_AUTH_SEND))
+			isis_tlvs_add_auth(tlvs, passwd);
+
+		struct isis_lsp *last_lsp;
+		isis_tlvs_add_csnp_entries(tlvs, start, stop, num_lsps,
+					   &circuit->area->lspdb[level - 1],
+					   &last_lsp);
+		/*
+		 * Update the stop lsp_id before encoding this CSNP.
+		 */
+		if (tlvs->lsp_entries.count < num_lsps) {
+			memset(stop, 0xff, ISIS_SYS_ID_LEN + 2);
+		} else {
+			memcpy(stop, last_lsp->hdr.lsp_id, sizeof(stop));
+		}
+
+		memcpy(STREAM_DATA(circuit->snd_stream) + start_pointer, start,
+		       ISIS_SYS_ID_LEN + 2);
+		memcpy(STREAM_DATA(circuit->snd_stream) + end_pointer, stop,
+		       ISIS_SYS_ID_LEN + 2);
+		stream_set_endp(circuit->snd_stream, tlv_start);
+		if (isis_pack_tlvs(tlvs, circuit->snd_stream, len_pointer,
+				   false, false)) {
+			isis_free_tlvs(tlvs);
+			return ISIS_WARNING;
+		}
+
+		if (IS_DEBUG_SNP_PACKETS) {
+			zlog_debug(
+				"ISIS-Snp (%s): Sending L%d CSNP on %s, length %zd",
+				circuit->area->area_tag, level,
+				circuit->interface->name,
+				stream_get_endp(circuit->snd_stream));
+			log_multiline(LOG_DEBUG, "              ", "%s",
+				      isis_format_tlvs(tlvs, NULL));
+			if (IS_DEBUG_PACKET_DUMP)
+				zlog_dump_data(
+					STREAM_DATA(circuit->snd_stream),
+					stream_get_endp(circuit->snd_stream));
+		}
+
+		pdu_counter_count(circuit->area->pdu_tx_counters, pdu_type);
+		int retval = circuit->tx(circuit, level);
+		if (retval != ISIS_OK) {
+			flog_err(EC_ISIS_PACKET,
+				 "ISIS-Snp (%s): Send L%d CSNP on %s failed",
+				 circuit->area->area_tag, level,
+				 circuit->interface->name);
+			isis_free_tlvs(tlvs);
+			return retval;
+		}
+
+		/*
+		 * Start lsp_id of the next CSNP should be one plus the
+		 * stop lsp_id in this current CSNP.
+		 */
+		memcpy(start, stop, ISIS_SYS_ID_LEN + 2);
+		loop = false;
+		for (int i = ISIS_SYS_ID_LEN + 1; i >= 0; --i) {
+			if (start[i] < (uint8_t)0xff) {
+				start[i] += 1;
+				loop = true;
+				break;
+			}
+		}
+		memset(stop, 0xff, ISIS_SYS_ID_LEN + 2);
+		isis_free_tlvs(tlvs);
+	}
+
+	return ISIS_OK;
+}
+
+void send_l1_csnp(struct event *thread)
+{
+	struct isis_circuit *circuit;
+
+	circuit = EVENT_ARG(thread);
+	assert(circuit);
+
+	circuit->t_send_csnp[0] = NULL;
+
+	if ((circuit->circ_type == CIRCUIT_T_BROADCAST
+	     && circuit->u.bc.is_dr[0])
+	     || circuit->circ_type == CIRCUIT_T_P2P) {
+		send_csnp(circuit, 1);
+	}
+	/* set next timer thread */
+	event_add_timer(master, send_l1_csnp, circuit,
+			isis_jitter(circuit->csnp_interval[0], CSNP_JITTER),
+			&circuit->t_send_csnp[0]);
+}
+
+void send_l2_csnp(struct event *thread)
+{
+	struct isis_circuit *circuit;
+
+	circuit = EVENT_ARG(thread);
+	assert(circuit);
+
+	circuit->t_send_csnp[1] = NULL;
+
+	if ((circuit->circ_type == CIRCUIT_T_BROADCAST
+	     && circuit->u.bc.is_dr[1])
+             || circuit->circ_type == CIRCUIT_T_P2P) {
+		send_csnp(circuit, 2);
+	}
+	/* set next timer thread */
+	event_add_timer(master, send_l2_csnp, circuit,
+			isis_jitter(circuit->csnp_interval[1], CSNP_JITTER),
+			&circuit->t_send_csnp[1]);
+}
+
+/*
+ *  7.3.15.4 action on expiration of partial SNP interval
+ *  level 1
+ */
+static int send_psnp(int level, struct isis_circuit *circuit)
+{
+	if (circuit->circ_type == CIRCUIT_T_BROADCAST
+	    && circuit->u.bc.is_dr[level - 1])
+		return ISIS_OK;
+
+	if (lspdb_count(&circuit->area->lspdb[level - 1]) == 0)
+		return ISIS_OK;
+
+	if (!circuit->snd_stream)
+		return ISIS_ERROR;
+
+	uint8_t pdu_type = (level == ISIS_LEVEL1) ? L1_PARTIAL_SEQ_NUM
+						  : L2_PARTIAL_SEQ_NUM;
+
+	isis_circuit_stream(circuit, &circuit->snd_stream);
+	fill_fixed_hdr(pdu_type, circuit->snd_stream);
+
+	size_t len_pointer = stream_get_endp(circuit->snd_stream);
+	stream_putw(circuit->snd_stream, 0); /* length is filled in later */
+	stream_put(circuit->snd_stream, circuit->isis->sysid, ISIS_SYS_ID_LEN);
+	stream_putc(circuit->snd_stream, circuit->idx);
+
+	struct isis_passwd *passwd = (level == ISIS_LEVEL1)
+					     ? &circuit->area->area_passwd
+					     : &circuit->area->domain_passwd;
+
+	struct isis_tlvs *tlvs = isis_alloc_tlvs();
+
+	if (CHECK_FLAG(passwd->snp_auth, SNP_AUTH_SEND))
+		isis_tlvs_add_auth(tlvs, passwd);
+
+	size_t tlv_start = stream_get_endp(circuit->snd_stream);
+	if (isis_pack_tlvs(tlvs, circuit->snd_stream, len_pointer, false,
+			   false)) {
+		isis_free_tlvs(tlvs);
+		return ISIS_WARNING;
+	}
+	isis_free_tlvs(tlvs);
+
+	uint16_t num_lsps =
+		get_max_lsp_count(STREAM_WRITEABLE(circuit->snd_stream));
+
+	while (1) {
+		struct isis_lsp *lsp;
+
+		tlvs = isis_alloc_tlvs();
+		if (CHECK_FLAG(passwd->snp_auth, SNP_AUTH_SEND))
+			isis_tlvs_add_auth(tlvs, passwd);
+
+		frr_each (lspdb, &circuit->area->lspdb[level - 1], lsp) {
+			if (ISIS_CHECK_FLAG(lsp->SSNflags, circuit))
+				isis_tlvs_add_lsp_entry(tlvs, lsp);
+
+			if (tlvs->lsp_entries.count == num_lsps)
+				break;
+		}
+
+		if (!tlvs->lsp_entries.count) {
+			isis_free_tlvs(tlvs);
+			return ISIS_OK;
+		}
+
+		stream_set_endp(circuit->snd_stream, tlv_start);
+		if (isis_pack_tlvs(tlvs, circuit->snd_stream, len_pointer,
+				   false, false)) {
+			isis_free_tlvs(tlvs);
+			return ISIS_WARNING;
+		}
+
+		if (IS_DEBUG_SNP_PACKETS) {
+			zlog_debug(
+				"ISIS-Snp (%s): Sending L%d PSNP on %s, length %zd",
+				circuit->area->area_tag, level,
+				circuit->interface->name,
+				stream_get_endp(circuit->snd_stream));
+			log_multiline(LOG_DEBUG, "              ", "%s",
+				      isis_format_tlvs(tlvs, NULL));
+			if (IS_DEBUG_PACKET_DUMP)
+				zlog_dump_data(
+					STREAM_DATA(circuit->snd_stream),
+					stream_get_endp(circuit->snd_stream));
+		}
+
+		pdu_counter_count(circuit->area->pdu_tx_counters, pdu_type);
+		int retval = circuit->tx(circuit, level);
+		if (retval != ISIS_OK) {
+			flog_err(EC_ISIS_PACKET,
+				 "ISIS-Snp (%s): Send L%d PSNP on %s failed",
+				 circuit->area->area_tag, level,
+				 circuit->interface->name);
+			isis_free_tlvs(tlvs);
+			return retval;
+		}
+
+		/*
+		 * sending succeeded, we can clear SSN flags of this circuit
+		 * for the LSPs in list
+		 */
+		struct isis_lsp_entry *entry_head;
+		entry_head = (struct isis_lsp_entry *)tlvs->lsp_entries.head;
+		for (struct isis_lsp_entry *entry = entry_head; entry;
+		     entry = entry->next)
+			ISIS_CLEAR_FLAG(entry->lsp->SSNflags, circuit);
+		isis_free_tlvs(tlvs);
+	}
+
+	return ISIS_OK;
+}
+
+void send_l1_psnp(struct event *thread)
+{
+
+	struct isis_circuit *circuit;
+
+	circuit = EVENT_ARG(thread);
+	assert(circuit);
+
+	circuit->t_send_psnp[0] = NULL;
+
+	send_psnp(1, circuit);
+	/* set next timer thread */
+	event_add_timer(master, send_l1_psnp, circuit,
+			isis_jitter(circuit->psnp_interval[0], PSNP_JITTER),
+			&circuit->t_send_psnp[0]);
+}
+
+/*
+ *  7.3.15.4 action on expiration of partial SNP interval
+ *  level 2
+ */
+void send_l2_psnp(struct event *thread)
+{
+	struct isis_circuit *circuit;
+
+	circuit = EVENT_ARG(thread);
+	assert(circuit);
+
+	circuit->t_send_psnp[1] = NULL;
+
+	send_psnp(2, circuit);
+
+	/* set next timer thread */
+	event_add_timer(master, send_l2_psnp, circuit,
+			isis_jitter(circuit->psnp_interval[1], PSNP_JITTER),
+			&circuit->t_send_psnp[1]);
+}
+
+/*
+ * ISO 10589 - 7.3.14.3
+ */
+void send_lsp(struct isis_circuit *circuit, struct isis_lsp *lsp,
+	      enum isis_tx_type tx_type)
+{
+	int clear_srm = 1;
+	int retval = ISIS_OK;
+
+	if (circuit->state != C_STATE_UP || circuit->is_passive == 1)
+		goto out;
+
+	/*
+	 * Do not send if levels do not match
+	 */
+	if (!(lsp->level & circuit->is_type))
+		goto out;
+
+	/*
+	 * Do not send if we do not have adjacencies in state up on the circuit
+	 */
+	if (circuit->upadjcount[lsp->level - 1] == 0)
+		goto out;
+
+	/* stream_copy will assert and stop program execution if LSP is larger
+	 * than
+	 * the circuit's MTU. So handle and log this case here. */
+	if (stream_get_endp(lsp->pdu) > stream_get_size(circuit->snd_stream)) {
+		flog_err(
+			EC_ISIS_PACKET,
+			"ISIS-Upd (%s): Can't send L%d LSP %pLS, seq 0x%08x, cksum 0x%04hx, lifetime %hus on %s. LSP Size is %zu while interface stream size is %zu.",
+			circuit->area->area_tag, lsp->level, lsp->hdr.lsp_id,
+			lsp->hdr.seqno, lsp->hdr.checksum,
+			lsp->hdr.rem_lifetime, circuit->interface->name,
+			stream_get_endp(lsp->pdu),
+			stream_get_size(circuit->snd_stream));
+#ifndef FABRICD
+		/* send a northbound notification */
+		isis_notif_lsp_too_large(circuit, stream_get_endp(lsp->pdu),
+					 lsp->hdr.lsp_id);
+#endif /* ifndef FABRICD */
+		if (IS_DEBUG_PACKET_DUMP)
+			zlog_dump_data(STREAM_DATA(lsp->pdu),
+				       stream_get_endp(lsp->pdu));
+		retval = ISIS_ERROR;
+		goto out;
+	}
+
+	/* copy our lsp to the send buffer */
+	stream_copy(circuit->snd_stream, lsp->pdu);
+
+	if (tx_type == TX_LSP_CIRCUIT_SCOPED) {
+		stream_putc_at(circuit->snd_stream, 4, FS_LINK_STATE);
+		stream_putc_at(circuit->snd_stream, 7,
+			       L2_CIRCUIT_FLOODING_SCOPE);
+	}
+
+	if (IS_DEBUG_UPDATE_PACKETS) {
+		zlog_debug(
+			"ISIS-Upd (%s): Sending %sL%d LSP %pLS, seq 0x%08x, cksum 0x%04hx, lifetime %hus on %s",
+			circuit->area->area_tag,
+			(tx_type == TX_LSP_CIRCUIT_SCOPED) ? "Circuit scoped "
+							   : "",
+			lsp->level, lsp->hdr.lsp_id, lsp->hdr.seqno,
+			lsp->hdr.checksum, lsp->hdr.rem_lifetime,
+			circuit->interface->name);
+		if (IS_DEBUG_PACKET_DUMP)
+			zlog_dump_data(STREAM_DATA(circuit->snd_stream),
+				       stream_get_endp(circuit->snd_stream));
+	}
+
+	uint8_t pdu_type = (tx_type == TX_LSP_CIRCUIT_SCOPED) ? FS_LINK_STATE
+			 : (lsp->level == ISIS_LEVEL1) ? L1_LINK_STATE
+						       : L2_LINK_STATE;
+
+	clear_srm = 0;
+	pdu_counter_count(circuit->area->pdu_tx_counters, pdu_type);
+	retval = circuit->tx(circuit, lsp->level);
+	if (retval != ISIS_OK) {
+		flog_err(EC_ISIS_PACKET,
+			 "ISIS-Upd (%s): Send L%d LSP on %s failed %s",
+			 circuit->area->area_tag, lsp->level,
+			 circuit->interface->name,
+			 (retval == ISIS_WARNING) ? "temporarily"
+						  : "permanently");
+	}
+
+out:
+	if (clear_srm
+	    || (retval == ISIS_OK && circuit->circ_type == CIRCUIT_T_BROADCAST)
+	    || (retval != ISIS_OK && retval != ISIS_WARNING)) {
+		/* SRM flag will trigger retransmission. We will not retransmit
+		 * if we
+		 * encountered a fatal error.
+		 * On success, they should only be cleared if it's a broadcast
+		 * circuit.
+		 * On a P2P circuit, we will wait for the ack from the neighbor
+		 * to clear
+		 * the fag.
+		 */
+		isis_tx_queue_del(circuit->tx_queue, lsp);
+	}
+}
+
+void isis_log_pdu_drops(struct isis_area *area, const char *pdu_type)
+{
+	uint64_t total_drops = 0;
+
+	for (int i = 0; i < PDU_COUNTER_SIZE; i++) {
+		if (!area->pdu_drop_counters[i])
+			continue;
+		total_drops += area->pdu_drop_counters[i];
+	}
+
+	zlog_info("PDU drop detected of type: %s. %" PRIu64
+		  " Total Drops; %" PRIu64 " L1 IIH drops;  %" PRIu64
+		  " L2 IIH drops; %" PRIu64 " P2P IIH drops; %" PRIu64
+		  " L1 LSP drops; %" PRIu64 " L2 LSP drops; %" PRIu64
+		  " FS LSP drops; %" PRIu64 " L1 CSNP drops; %" PRIu64
+		  " L2 CSNP drops; %" PRIu64 " L1 PSNP drops; %" PRIu64
+		  " L2 PSNP drops.",
+		  pdu_type, total_drops,
+		  pdu_counter_get_count(area->pdu_drop_counters, L1_LAN_HELLO),
+		  pdu_counter_get_count(area->pdu_drop_counters, L2_LAN_HELLO),
+		  pdu_counter_get_count(area->pdu_drop_counters, P2P_HELLO),
+		  pdu_counter_get_count(area->pdu_drop_counters, L1_LINK_STATE),
+		  pdu_counter_get_count(area->pdu_drop_counters, L2_LINK_STATE),
+		  pdu_counter_get_count(area->pdu_drop_counters, FS_LINK_STATE),
+		  pdu_counter_get_count(area->pdu_drop_counters,
+					L1_COMPLETE_SEQ_NUM),
+		  pdu_counter_get_count(area->pdu_drop_counters,
+					L2_COMPLETE_SEQ_NUM),
+		  pdu_counter_get_count(area->pdu_drop_counters,
+					L1_PARTIAL_SEQ_NUM),
+		  pdu_counter_get_count(area->pdu_drop_counters,
+					L2_PARTIAL_SEQ_NUM));
+}