Adding upstream version 9.1.upstream/9.1

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

1 files changed, 848 insertions, 0 deletions

diff --git a/pimd/pim_igmp_mtrace.c b/pimd/pim_igmp_mtrace.c
new file mode 100644
index 0000000..4d3f602
--- /dev/null
+++ b/pimd/pim_igmp_mtrace.c
@@ -0,0 +1,848 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * Multicast traceroute for FRRouting
+ * Copyright (C) 2017  Mladen Sablic
+ */
+
+/* based on draft-ietf-idmr-traceroute-ipm-07 */
+
+#include <zebra.h>
+
+#include "pimd.h"
+#include "pim_instance.h"
+#include "pim_util.h"
+#include "pim_sock.h"
+#include "pim_rp.h"
+#include "pim_oil.h"
+#include "pim_ifchannel.h"
+#include "pim_macro.h"
+#include "pim_igmp_mtrace.h"
+
+static struct in_addr mtrace_primary_address(struct interface *ifp)
+{
+	struct connected *ifc;
+	struct listnode *node;
+	struct in_addr any;
+	struct pim_interface *pim_ifp;
+
+	if (ifp->info) {
+		pim_ifp = ifp->info;
+		return pim_ifp->primary_address;
+	}
+
+	any.s_addr = INADDR_ANY;
+
+	for (ALL_LIST_ELEMENTS_RO(ifp->connected, node, ifc)) {
+		struct prefix *p = ifc->address;
+
+		if (p->family != AF_INET)
+			continue;
+
+		if (!CHECK_FLAG(ifc->flags, ZEBRA_IFA_SECONDARY))
+			return p->u.prefix4;
+		/* in case no primary found, return a secondary */
+		any = p->u.prefix4;
+	}
+	return any;
+}
+
+static bool mtrace_fwd_info_weak(struct pim_instance *pim,
+				    struct igmp_mtrace *mtracep,
+				    struct igmp_mtrace_rsp *rspp,
+				    struct interface **ifpp)
+{
+	struct pim_nexthop nexthop;
+	struct interface *ifp_in;
+	struct in_addr nh_addr;
+
+	nh_addr.s_addr = INADDR_ANY;
+
+	memset(&nexthop, 0, sizeof(nexthop));
+
+	if (!pim_nexthop_lookup(pim, &nexthop, mtracep->src_addr, 1)) {
+		if (PIM_DEBUG_MTRACE)
+			zlog_debug("mtrace not found neighbor");
+		return false;
+	}
+
+	if (PIM_DEBUG_MTRACE)
+		zlog_debug("mtrace pim_nexthop_lookup OK");
+
+	if (PIM_DEBUG_MTRACE)
+		zlog_debug("mtrace next_hop=%pPAs", &nexthop.mrib_nexthop_addr);
+
+	nh_addr = nexthop.mrib_nexthop_addr;
+
+	ifp_in = nexthop.interface;
+
+	/* return interface for forwarding mtrace packets */
+	*ifpp = ifp_in;
+
+	/* 6.2.2. 4. Fill in the Incoming Interface Address... */
+	rspp->incoming = mtrace_primary_address(ifp_in);
+	rspp->prev_hop = nh_addr;
+	rspp->in_count = htonl(MTRACE_UNKNOWN_COUNT);
+	rspp->total = htonl(MTRACE_UNKNOWN_COUNT);
+	rspp->rtg_proto = MTRACE_RTG_PROTO_PIM;
+	return true;
+}
+
+static bool mtrace_fwd_info(struct pim_instance *pim,
+			    struct igmp_mtrace *mtracep,
+			    struct igmp_mtrace_rsp *rspp,
+			    struct interface **ifpp)
+{
+	pim_sgaddr sg;
+	struct pim_upstream *up;
+	struct interface *ifp_in;
+	struct in_addr nh_addr;
+	uint32_t total;
+
+	memset(&sg, 0, sizeof(sg));
+	sg.src = mtracep->src_addr;
+	sg.grp = mtracep->grp_addr;
+
+	up = pim_upstream_find(pim, &sg);
+
+	if (!up) {
+		sg.src = PIMADDR_ANY;
+		up = pim_upstream_find(pim, &sg);
+	}
+
+	if (!up)
+		return false;
+
+	if (!up->rpf.source_nexthop.interface) {
+		if (PIM_DEBUG_TRACE)
+			zlog_debug("%s: up %s RPF is not present", __func__,
+				   up->sg_str);
+		return false;
+	}
+
+	ifp_in = up->rpf.source_nexthop.interface;
+	nh_addr = up->rpf.source_nexthop.mrib_nexthop_addr;
+	total = htonl(MTRACE_UNKNOWN_COUNT);
+
+	if (PIM_DEBUG_MTRACE)
+		zlog_debug("fwd_info: upstream next hop=%pI4", &nh_addr);
+
+	if (up->channel_oil)
+		total = up->channel_oil->cc.pktcnt;
+
+	/* return interface for forwarding mtrace packets */
+	*ifpp = ifp_in;
+
+	/* 6.2.2. 4. Fill in the Incoming Interface Address... */
+	rspp->incoming = mtrace_primary_address(ifp_in);
+	rspp->prev_hop = nh_addr;
+	rspp->in_count = htonl(MTRACE_UNKNOWN_COUNT);
+	rspp->total = total;
+	rspp->rtg_proto = MTRACE_RTG_PROTO_PIM;
+
+	/* 6.2.2. 4. Fill in ... S, and Src Mask */
+	if (!pim_addr_is_any(sg.src)) {
+		rspp->s = 1;
+		rspp->src_mask = MTRACE_SRC_MASK_SOURCE;
+	} else {
+		rspp->s = 0;
+		rspp->src_mask = MTRACE_SRC_MASK_GROUP;
+	}
+
+	return true;
+}
+
+static void mtrace_rsp_set_fwd_code(struct igmp_mtrace_rsp *mtrace_rspp,
+				    enum mtrace_fwd_code fwd_code)
+{
+	if (mtrace_rspp->fwd_code == MTRACE_FWD_CODE_NO_ERROR)
+		mtrace_rspp->fwd_code = fwd_code;
+}
+
+static void mtrace_rsp_init(struct igmp_mtrace_rsp *mtrace_rspp)
+{
+	mtrace_rspp->arrival = 0;
+	mtrace_rspp->incoming.s_addr = INADDR_ANY;
+	mtrace_rspp->outgoing.s_addr = INADDR_ANY;
+	mtrace_rspp->prev_hop.s_addr = INADDR_ANY;
+	mtrace_rspp->in_count = htonl(MTRACE_UNKNOWN_COUNT);
+	mtrace_rspp->out_count = htonl(MTRACE_UNKNOWN_COUNT);
+	mtrace_rspp->total = htonl(MTRACE_UNKNOWN_COUNT);
+	mtrace_rspp->rtg_proto = 0;
+	mtrace_rspp->fwd_ttl = 0;
+	mtrace_rspp->mbz = 0;
+	mtrace_rspp->s = 0;
+	mtrace_rspp->src_mask = 0;
+	mtrace_rspp->fwd_code = MTRACE_FWD_CODE_NO_ERROR;
+}
+
+static void mtrace_rsp_debug(uint32_t qry_id, int rsp,
+			     struct igmp_mtrace_rsp *mrspp)
+{
+	struct in_addr incoming = mrspp->incoming;
+	struct in_addr outgoing = mrspp->outgoing;
+	struct in_addr prev_hop = mrspp->prev_hop;
+
+	zlog_debug(
+		"Rx mt(%d) qid=%ud arr=%x in=%pI4 out=%pI4 prev=%pI4 proto=%d fwd=%d",
+		rsp, ntohl(qry_id), mrspp->arrival, &incoming, &outgoing,
+		&prev_hop, mrspp->rtg_proto, mrspp->fwd_code);
+}
+
+static void mtrace_debug(struct pim_interface *pim_ifp,
+			 struct igmp_mtrace *mtracep, int mtrace_len)
+{
+	struct in_addr ga, sa, da, ra;
+
+	ga = mtracep->grp_addr;
+	sa = mtracep->src_addr;
+	da = mtracep->dst_addr;
+	ra = mtracep->rsp_addr;
+
+	zlog_debug(
+		"Rx mtrace packet incoming on %pI4: hops=%d type=%d size=%d, grp=%pI4, src=%pI4, dst=%pI4 rsp=%pI4 ttl=%d qid=%ud",
+		&pim_ifp->primary_address, mtracep->hops, mtracep->type,
+		mtrace_len, &ga, &sa, &da, &ra, mtracep->rsp_ttl,
+		ntohl(mtracep->qry_id));
+	if (mtrace_len > (int)sizeof(struct igmp_mtrace)) {
+
+		int i;
+
+		int responses = mtrace_len - sizeof(struct igmp_mtrace);
+
+		if ((responses % sizeof(struct igmp_mtrace_rsp)) != 0)
+			if (PIM_DEBUG_MTRACE)
+				zlog_debug(
+					"Mtrace response block of wrong length");
+
+		responses = responses / sizeof(struct igmp_mtrace_rsp);
+
+		for (i = 0; i < responses; i++)
+			mtrace_rsp_debug(mtracep->qry_id, i, &mtracep->rsp[i]);
+	}
+}
+
+/* 5.1 Query Arrival Time */
+static uint32_t query_arrival_time(void)
+{
+	struct timeval tv;
+	uint32_t qat;
+
+	if (gettimeofday(&tv, NULL) < 0) {
+		if (PIM_DEBUG_MTRACE)
+			zlog_debug("Query arrival time lookup failed: errno=%d: %s",
+				   errno, safe_strerror(errno));
+		return 0;
+	}
+	/* not sure second offset correct, as I get different value */
+	qat = ((tv.tv_sec + 32384) << 16) + ((tv.tv_usec << 10) / 15625);
+
+	return qat;
+}
+
+static int mtrace_send_packet(struct interface *ifp,
+			      struct igmp_mtrace *mtracep,
+			      size_t mtrace_buf_len, struct in_addr dst_addr,
+			      struct in_addr group_addr)
+{
+	struct sockaddr_in to;
+	socklen_t tolen;
+	ssize_t sent;
+	int ret;
+	int fd;
+	uint8_t ttl;
+
+	memset(&to, 0, sizeof(to));
+	to.sin_family = AF_INET;
+	to.sin_addr = dst_addr;
+	tolen = sizeof(to);
+
+	if (PIM_DEBUG_MTRACE) {
+		struct in_addr if_addr;
+		struct in_addr rsp_addr = mtracep->rsp_addr;
+
+		if_addr = mtrace_primary_address(ifp);
+		zlog_debug("Sending mtrace packet to %pI4 on %pI4", &rsp_addr,
+			   &if_addr);
+	}
+
+	fd = pim_socket_raw(IPPROTO_IGMP);
+
+	if (fd < 0)
+		return -1;
+
+	ret = pim_socket_bind(fd, ifp);
+
+	if (ret < 0) {
+		ret = -1;
+		goto close_fd;
+	}
+
+	if (IPV4_CLASS_DE(ntohl(dst_addr.s_addr))) {
+		if (IPV4_MC_LINKLOCAL(ntohl(dst_addr.s_addr))) {
+			ttl = 1;
+		} else {
+			if (mtracep->type == PIM_IGMP_MTRACE_RESPONSE)
+				ttl = mtracep->rsp_ttl;
+			else
+				ttl = 64;
+		}
+		ret = setsockopt(fd, IPPROTO_IP, IP_MULTICAST_TTL, &ttl,
+				 sizeof(ttl));
+
+		if (ret < 0) {
+			if (PIM_DEBUG_MTRACE)
+				zlog_debug("Failed to set socket multicast TTL");
+			ret = -1;
+			goto close_fd;
+		}
+	}
+
+	sent = sendto(fd, (char *)mtracep, mtrace_buf_len, MSG_DONTWAIT,
+		      (struct sockaddr *)&to, tolen);
+
+	if (sent != (ssize_t)mtrace_buf_len) {
+		char dst_str[INET_ADDRSTRLEN];
+		char group_str[INET_ADDRSTRLEN];
+
+		pim_inet4_dump("<dst?>", dst_addr, dst_str, sizeof(dst_str));
+		pim_inet4_dump("<group?>", group_addr, group_str,
+			       sizeof(group_str));
+		if (sent < 0) {
+			if (PIM_DEBUG_MTRACE)
+				zlog_debug(
+					"Send mtrace request failed for %s on%s: group=%s msg_size=%zd: errno=%d:  %s",
+					dst_str, ifp->name, group_str,
+					mtrace_buf_len, errno,
+					safe_strerror(errno));
+		} else {
+			if (PIM_DEBUG_MTRACE)
+				zlog_debug(
+					"Send mtrace request failed for %s on %s: group=%s msg_size=%zd: sent=%zd",
+					dst_str, ifp->name, group_str,
+					mtrace_buf_len, sent);
+		}
+		ret = -1;
+		goto close_fd;
+	}
+	ret = 0;
+close_fd:
+	close(fd);
+	return ret;
+}
+
+static int mtrace_un_forward_packet(struct pim_instance *pim, struct ip *ip_hdr,
+				    struct interface *interface)
+{
+	struct pim_nexthop nexthop;
+	struct sockaddr_in to;
+	struct interface *if_out;
+	socklen_t tolen;
+	int ret;
+	int fd;
+	int sent;
+	uint16_t checksum;
+
+	checksum = ip_hdr->ip_sum;
+
+	ip_hdr->ip_sum = 0;
+
+	if (checksum != in_cksum(ip_hdr, ip_hdr->ip_hl * 4))
+		return -1;
+
+	if (ip_hdr->ip_ttl-- <= 1)
+		return -1;
+
+	if (interface == NULL) {
+		memset(&nexthop, 0, sizeof(nexthop));
+		if (!pim_nexthop_lookup(pim, &nexthop, ip_hdr->ip_dst, 0)) {
+			if (PIM_DEBUG_MTRACE)
+				zlog_debug(
+					"Dropping mtrace packet, no route to destination");
+			return -1;
+		}
+
+		if_out = nexthop.interface;
+	} else {
+		if_out = interface;
+	}
+
+	ip_hdr->ip_sum = in_cksum(ip_hdr, ip_hdr->ip_hl * 4);
+
+	fd = pim_socket_raw(IPPROTO_RAW);
+
+	if (fd < 0)
+		return -1;
+
+	pim_socket_ip_hdr(fd);
+
+	ret = pim_socket_bind(fd, if_out);
+
+	if (ret < 0) {
+		close(fd);
+		return -1;
+	}
+
+	memset(&to, 0, sizeof(to));
+	to.sin_family = AF_INET;
+	to.sin_addr = ip_hdr->ip_dst;
+	tolen = sizeof(to);
+
+	sent = sendto(fd, ip_hdr, ntohs(ip_hdr->ip_len), 0,
+		      (struct sockaddr *)&to, tolen);
+
+	close(fd);
+
+	if (sent < 0) {
+		if (PIM_DEBUG_MTRACE)
+			zlog_debug(
+				"Failed to forward mtrace packet: sendto errno=%d, %s",
+				errno, safe_strerror(errno));
+		return -1;
+	}
+
+	if (PIM_DEBUG_MTRACE) {
+		zlog_debug("Fwd mtrace packet len=%u to %pI4 ttl=%u",
+			   ntohs(ip_hdr->ip_len), &ip_hdr->ip_dst,
+			   ip_hdr->ip_ttl);
+	}
+
+	return 0;
+}
+
+static int mtrace_mc_forward_packet(struct pim_instance *pim, struct ip *ip_hdr)
+{
+	pim_sgaddr sg;
+	struct channel_oil *c_oil;
+	struct listnode *chnode;
+	struct listnode *chnextnode;
+	struct pim_ifchannel *ch = NULL;
+	int ret = -1;
+
+	memset(&sg, 0, sizeof(sg));
+	sg.grp = ip_hdr->ip_dst;
+
+	c_oil = pim_find_channel_oil(pim, &sg);
+
+	if (c_oil == NULL) {
+		if (PIM_DEBUG_MTRACE) {
+			zlog_debug(
+				"Dropping mtrace multicast packet len=%u to %pI4 ttl=%u",
+				ntohs(ip_hdr->ip_len),
+				&ip_hdr->ip_dst, ip_hdr->ip_ttl);
+		}
+		return -1;
+	}
+	if (c_oil->up == NULL)
+		return -1;
+	if (c_oil->up->ifchannels == NULL)
+		return -1;
+	for (ALL_LIST_ELEMENTS(c_oil->up->ifchannels, chnode, chnextnode, ch)) {
+		if (pim_macro_chisin_oiflist(ch)) {
+			int r;
+
+			r = mtrace_un_forward_packet(pim, ip_hdr,
+						     ch->interface);
+			if (r == 0)
+				ret = 0;
+		}
+	}
+	return ret;
+}
+
+
+static int mtrace_forward_packet(struct pim_instance *pim, struct ip *ip_hdr)
+{
+	if (IPV4_CLASS_DE(ntohl(ip_hdr->ip_dst.s_addr)))
+		return mtrace_mc_forward_packet(pim, ip_hdr);
+	else
+		return mtrace_un_forward_packet(pim, ip_hdr, NULL);
+}
+
+static int mtrace_send_mc_response(struct pim_instance *pim,
+				   struct igmp_mtrace *mtracep,
+				   size_t mtrace_len)
+{
+	pim_sgaddr sg;
+	struct channel_oil *c_oil;
+	struct listnode *chnode;
+	struct listnode *chnextnode;
+	struct pim_ifchannel *ch = NULL;
+	int ret = -1;
+
+	memset(&sg, 0, sizeof(sg));
+	sg.grp = mtracep->rsp_addr;
+
+	c_oil = pim_find_channel_oil(pim, &sg);
+
+	if (c_oil == NULL) {
+		if (PIM_DEBUG_MTRACE) {
+			struct in_addr rsp_addr = mtracep->rsp_addr;
+
+			zlog_debug(
+				"Dropping mtrace multicast response packet len=%u to %pI4",
+				(unsigned int)mtrace_len, &rsp_addr);
+		}
+		return -1;
+	}
+	if (c_oil->up == NULL)
+		return -1;
+	if (c_oil->up->ifchannels == NULL)
+		return -1;
+	for (ALL_LIST_ELEMENTS(c_oil->up->ifchannels, chnode, chnextnode, ch)) {
+		if (pim_macro_chisin_oiflist(ch)) {
+			int r;
+
+			r = mtrace_send_packet(ch->interface, mtracep,
+					       mtrace_len, mtracep->rsp_addr,
+					       mtracep->grp_addr);
+			if (r == 0)
+				ret = 0;
+		}
+	}
+	return ret;
+}
+
+/* 6.5 Sending Traceroute Responses */
+static int mtrace_send_response(struct pim_instance *pim,
+				struct igmp_mtrace *mtracep, size_t mtrace_len)
+{
+	struct pim_nexthop nexthop;
+
+	mtracep->type = PIM_IGMP_MTRACE_RESPONSE;
+
+	mtracep->checksum = 0;
+	mtracep->checksum = in_cksum((char *)mtracep, mtrace_len);
+
+	if (IPV4_CLASS_DE(ntohl(mtracep->rsp_addr.s_addr))) {
+		struct pim_rpf *p_rpf;
+
+		if (pim_rp_i_am_rp(pim, mtracep->rsp_addr))
+			return mtrace_send_mc_response(pim, mtracep,
+						       mtrace_len);
+
+		p_rpf = pim_rp_g(pim, mtracep->rsp_addr);
+
+		if (p_rpf == NULL) {
+			if (PIM_DEBUG_MTRACE) {
+				struct in_addr rsp_addr = mtracep->rsp_addr;
+
+				zlog_debug("mtrace no RP for %pI4", &rsp_addr);
+			}
+			return -1;
+		}
+		nexthop = p_rpf->source_nexthop;
+		if (PIM_DEBUG_MTRACE)
+			zlog_debug("mtrace response to RP");
+	} else {
+		memset(&nexthop, 0, sizeof(nexthop));
+		/* TODO: should use unicast rib lookup */
+		if (!pim_nexthop_lookup(pim, &nexthop, mtracep->rsp_addr, 1)) {
+			if (PIM_DEBUG_MTRACE)
+				zlog_debug(
+					"Dropped response qid=%ud, no route to response address",
+					mtracep->qry_id);
+			return -1;
+		}
+	}
+
+	return mtrace_send_packet(nexthop.interface, mtracep, mtrace_len,
+				  mtracep->rsp_addr, mtracep->grp_addr);
+}
+
+int igmp_mtrace_recv_qry_req(struct gm_sock *igmp, struct ip *ip_hdr,
+			     struct in_addr from, const char *from_str,
+			     char *igmp_msg, int igmp_msg_len)
+{
+	static uint32_t qry_id, qry_src;
+	char mtrace_buf[MTRACE_HDR_SIZE + MTRACE_MAX_HOPS * MTRACE_RSP_SIZE];
+	struct interface *ifp;
+	struct interface *out_ifp = NULL;
+	struct pim_interface *pim_ifp;
+	struct pim_instance *pim;
+	struct igmp_mtrace *mtracep;
+	struct igmp_mtrace_rsp *rspp;
+	struct in_addr nh_addr;
+	enum mtrace_fwd_code fwd_code = MTRACE_FWD_CODE_NO_ERROR;
+	size_t r_len;
+	int last_rsp_ind = 0;
+	size_t mtrace_len;
+	uint16_t recv_checksum;
+	uint16_t checksum;
+	bool reached_source;
+	bool fwd_info;
+
+	ifp = igmp->interface;
+	pim_ifp = ifp->info;
+	pim = pim_ifp->pim;
+
+	/*
+	 * 6. Router Behaviour
+	 * Check if mtrace packet is addressed elsewhere and forward,
+	 * if applicable
+	 */
+	if (!IPV4_CLASS_DE(ntohl(ip_hdr->ip_dst.s_addr)))
+		if (!if_address_is_local(&ip_hdr->ip_dst, AF_INET,
+					 pim->vrf->vrf_id))
+			return mtrace_forward_packet(pim, ip_hdr);
+
+	if (igmp_msg_len < (int)sizeof(struct igmp_mtrace)) {
+		if (PIM_DEBUG_MTRACE)
+			zlog_debug(
+				"Recv mtrace packet from %s on %s: too short, len=%d, min=%zu",
+				from_str, ifp->name, igmp_msg_len,
+				sizeof(struct igmp_mtrace));
+		return -1;
+	}
+
+	mtracep = (struct igmp_mtrace *)igmp_msg;
+
+	recv_checksum = mtracep->checksum;
+
+	mtracep->checksum = 0;
+
+	checksum = in_cksum(igmp_msg, igmp_msg_len);
+
+	if (recv_checksum != checksum) {
+		if (PIM_DEBUG_MTRACE)
+			zlog_debug(
+				"Recv mtrace packet from %s on %s: checksum mismatch: received=%x computed=%x",
+				from_str, ifp->name, recv_checksum, checksum);
+		return -1;
+	}
+
+	/* Collecting IGMP Rx stats */
+	igmp->igmp_stats.mtrace_req++;
+
+	if (PIM_DEBUG_MTRACE)
+		mtrace_debug(pim_ifp, mtracep, igmp_msg_len);
+
+	/* subtract header from message length */
+	r_len = igmp_msg_len - sizeof(struct igmp_mtrace);
+
+	/* Classify mtrace packet, check if it is a query */
+	if (!r_len) {
+		if (PIM_DEBUG_MTRACE)
+			zlog_debug("Received IGMP multicast traceroute query");
+
+		/* 6.1.1  Packet verification */
+		if (!pim_if_connected_to_source(ifp, mtracep->dst_addr)) {
+			if (IPV4_CLASS_DE(ntohl(ip_hdr->ip_dst.s_addr))) {
+				if (PIM_DEBUG_MTRACE)
+					zlog_debug(
+						"Dropping multicast query on wrong interface");
+				return -1;
+			}
+			/* Unicast query on wrong interface */
+			fwd_code = MTRACE_FWD_CODE_WRONG_IF;
+			if (PIM_DEBUG_MTRACE)
+				zlog_debug("Multicast query on wrong interface");
+		}
+		if (qry_id == mtracep->qry_id && qry_src == from.s_addr) {
+			if (PIM_DEBUG_MTRACE)
+				zlog_debug(
+					"Dropping multicast query with duplicate source and id");
+			return -1;
+		}
+		qry_id = mtracep->qry_id;
+		qry_src = from.s_addr;
+	}
+	/* if response fields length is equal to a whole number of responses */
+	else if ((r_len % sizeof(struct igmp_mtrace_rsp)) == 0) {
+		r_len = igmp_msg_len - sizeof(struct igmp_mtrace);
+
+		if (r_len != 0)
+			last_rsp_ind = r_len / sizeof(struct igmp_mtrace_rsp);
+		if (last_rsp_ind > MTRACE_MAX_HOPS) {
+			if (PIM_DEBUG_MTRACE)
+				zlog_debug("Mtrace request of excessive size");
+			return -1;
+		}
+	} else {
+		if (PIM_DEBUG_MTRACE)
+			zlog_debug(
+				"Recv mtrace packet from %s on %s: invalid length %d",
+				from_str, ifp->name, igmp_msg_len);
+		return -1;
+	}
+
+	/* 6.2.1 Packet Verification - drop not link-local multicast */
+	if (IPV4_CLASS_DE(ntohl(ip_hdr->ip_dst.s_addr))
+	    && !IPV4_MC_LINKLOCAL(ntohl(ip_hdr->ip_dst.s_addr))) {
+		if (PIM_DEBUG_MTRACE)
+			zlog_debug(
+				"Recv mtrace packet from %s on %s: not link-local multicast %pI4",
+				from_str, ifp->name, &ip_hdr->ip_dst);
+		return -1;
+	}
+
+	/* 6.2.2. Normal Processing */
+
+	/* 6.2.2. 1. If there is room in the current buffer? */
+
+	if (last_rsp_ind == MTRACE_MAX_HOPS) {
+		/* ...there was no room... */
+		mtracep->rsp[MTRACE_MAX_HOPS - 1].fwd_code =
+			MTRACE_FWD_CODE_NO_SPACE;
+		return mtrace_send_response(pim_ifp->pim, mtracep,
+					    igmp_msg_len);
+	}
+
+	/* ...insert new response block... */
+
+	/* calculate new mtrace lenght with extra response */
+	mtrace_len = igmp_msg_len + sizeof(struct igmp_mtrace_rsp);
+
+	/* copy received query/request */
+	memcpy(mtrace_buf, igmp_msg, igmp_msg_len);
+
+	/* repoint mtracep pointer to copy */
+	mtracep = (struct igmp_mtrace *)mtrace_buf;
+
+	/* pointer for extra response field to be filled in */
+	rspp = &mtracep->rsp[last_rsp_ind];
+
+	/* initialize extra response field */
+	mtrace_rsp_init(rspp);
+
+	/* carry over any error noted when receiving the query */
+	rspp->fwd_code = fwd_code;
+
+	/* ...and fill in Query Arrival Time... */
+	rspp->arrival = htonl(query_arrival_time());
+	rspp->outgoing = pim_ifp->primary_address;
+	rspp->out_count = htonl(MTRACE_UNKNOWN_COUNT);
+	rspp->fwd_ttl = 1;
+
+	/* 6.2.2. 2. Attempt to determine the forwarding information... */
+
+	if (mtracep->grp_addr.s_addr != INADDR_ANY)
+		fwd_info = mtrace_fwd_info(pim, mtracep, rspp, &out_ifp);
+	else
+		fwd_info = mtrace_fwd_info_weak(pim, mtracep, rspp, &out_ifp);
+
+	/* 6.2.2 3. If no forwarding information... */
+	if (!fwd_info) {
+		if (PIM_DEBUG_MTRACE)
+			zlog_debug("mtrace not found multicast state");
+		mtrace_rsp_set_fwd_code(rspp, MTRACE_FWD_CODE_NO_ROUTE);
+		/* 6.2.2. 3. forward the packet to requester */
+		return mtrace_send_response(pim, mtracep, mtrace_len);
+	}
+
+	nh_addr = rspp->prev_hop;
+
+	reached_source = false;
+
+	if (nh_addr.s_addr == INADDR_ANY) {
+		/* no pim? i.e. 7.5.3. No Previous Hop */
+		if (!out_ifp->info) {
+			if (PIM_DEBUG_MTRACE)
+				zlog_debug("mtrace not found incoming if w/ pim");
+			mtrace_rsp_set_fwd_code(rspp,
+						MTRACE_FWD_CODE_NO_MULTICAST);
+			return mtrace_send_response(pim, mtracep, mtrace_len);
+		}
+		/* reached source? i.e. 7.5.1 Arriving at source */
+		if (pim_if_connected_to_source(out_ifp, mtracep->src_addr)) {
+			reached_source = true;
+			rspp->prev_hop = mtracep->src_addr;
+		}
+		/*
+		 * 6.4 Forwarding Traceroute Requests:
+		 * Previous-hop router not known,
+		 * packet is sent to an appropriate multicast address
+		 */
+		(void)inet_aton(MCAST_ALL_ROUTERS, &nh_addr);
+	}
+
+	/* 6.2.2 8. If this router is the Rendez-vous Point */
+	if (mtracep->grp_addr.s_addr != INADDR_ANY &&
+	    pim_rp_i_am_rp(pim, mtracep->grp_addr)) {
+		mtrace_rsp_set_fwd_code(rspp, MTRACE_FWD_CODE_REACHED_RP);
+		/* 7.7.1. PIM-SM ...RP has not performed source-specific join */
+		if (rspp->src_mask == MTRACE_SRC_MASK_GROUP)
+			return mtrace_send_response(pim, mtracep, mtrace_len);
+	}
+
+	/*
+	 * 6.4 Forwarding Traceroute Requests: the number of response
+	 * blocks exceeds number of responses, so forward to the requester.
+	 */
+	if (mtracep->hops <= (last_rsp_ind + 1))
+		return mtrace_send_response(pim, mtracep, mtrace_len);
+
+	/* 7.5.1. Arriving at source: terminate trace */
+	if (reached_source)
+		return mtrace_send_response(pim, mtracep, mtrace_len);
+
+	mtracep->checksum = 0;
+
+	mtracep->checksum = in_cksum(mtrace_buf, mtrace_len);
+
+	/* 6.4 Forwarding Traceroute Requests: response blocks less than req. */
+	return mtrace_send_packet(out_ifp, mtracep, mtrace_len, nh_addr,
+				  mtracep->grp_addr);
+}
+
+/* 6.3. Traceroute responses */
+int igmp_mtrace_recv_response(struct gm_sock *igmp, struct ip *ip_hdr,
+			      struct in_addr from, const char *from_str,
+			      char *igmp_msg, int igmp_msg_len)
+{
+	static uint32_t qry_id, rsp_dst;
+	struct interface *ifp;
+	struct pim_interface *pim_ifp;
+	struct pim_instance *pim;
+	struct igmp_mtrace *mtracep;
+	uint16_t recv_checksum;
+	uint16_t checksum;
+
+	ifp = igmp->interface;
+	pim_ifp = ifp->info;
+	pim = pim_ifp->pim;
+
+	if (igmp_msg_len < (int)sizeof(struct igmp_mtrace)) {
+		if (PIM_DEBUG_MTRACE)
+			zlog_debug(
+				"Recv mtrace packet from %s on %s: too short, len=%d, min=%zu",
+				from_str, ifp->name, igmp_msg_len,
+				sizeof(struct igmp_mtrace));
+		return -1;
+	}
+
+	mtracep = (struct igmp_mtrace *)igmp_msg;
+
+	recv_checksum = mtracep->checksum;
+
+	mtracep->checksum = 0;
+
+	checksum = in_cksum(igmp_msg, igmp_msg_len);
+
+	if (recv_checksum != checksum) {
+		if (PIM_DEBUG_MTRACE)
+			zlog_debug(
+				"Recv mtrace response from %s on %s: checksum mismatch: received=%x computed=%x",
+				from_str, ifp->name, recv_checksum, checksum);
+		return -1;
+	}
+
+	mtracep->checksum = checksum;
+
+	/* Collecting IGMP Rx stats */
+	igmp->igmp_stats.mtrace_rsp++;
+
+	if (PIM_DEBUG_MTRACE)
+		mtrace_debug(pim_ifp, mtracep, igmp_msg_len);
+
+	/* Drop duplicate packets */
+	if (qry_id == mtracep->qry_id && rsp_dst == ip_hdr->ip_dst.s_addr) {
+		if (PIM_DEBUG_MTRACE)
+			zlog_debug("duplicate mtrace response packet dropped");
+		return -1;
+	}
+
+	qry_id = mtracep->qry_id;
+	rsp_dst = ip_hdr->ip_dst.s_addr;
+
+	return mtrace_forward_packet(pim, ip_hdr);
+}