Adding upstream version 9.1.upstream/9.1

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

1 files changed, 780 insertions, 0 deletions

diff --git a/pimd/pim_msdp_packet.c b/pimd/pim_msdp_packet.c
new file mode 100644
index 0000000..4324a96
--- /dev/null
+++ b/pimd/pim_msdp_packet.c
@@ -0,0 +1,780 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * IP MSDP packet helper
+ * Copyright (C) 2016 Cumulus Networks, Inc.
+ */
+#include <zebra.h>
+
+#include <lib/log.h>
+#include <lib/network.h>
+#include <lib/stream.h>
+#include "frrevent.h"
+#include <lib/vty.h>
+#include <lib/lib_errors.h>
+
+#include "pimd.h"
+#include "pim_instance.h"
+#include "pim_rp.h"
+#include "pim_str.h"
+#include "pim_util.h"
+#include "pim_errors.h"
+
+#include "pim_msdp.h"
+#include "pim_msdp_packet.h"
+#include "pim_msdp_socket.h"
+
+static char *pim_msdp_pkt_type_dump(enum pim_msdp_tlv type, char *buf,
+				    int buf_size)
+{
+	switch (type) {
+	case PIM_MSDP_V4_SOURCE_ACTIVE:
+		snprintf(buf, buf_size, "%s", "SA");
+		break;
+	case PIM_MSDP_V4_SOURCE_ACTIVE_REQUEST:
+		snprintf(buf, buf_size, "%s", "SA_REQ");
+		break;
+	case PIM_MSDP_V4_SOURCE_ACTIVE_RESPONSE:
+		snprintf(buf, buf_size, "%s", "SA_RESP");
+		break;
+	case PIM_MSDP_KEEPALIVE:
+		snprintf(buf, buf_size, "%s", "KA");
+		break;
+	case PIM_MSDP_RESERVED:
+		snprintf(buf, buf_size, "%s", "RSVD");
+		break;
+	case PIM_MSDP_TRACEROUTE_PROGRESS:
+		snprintf(buf, buf_size, "%s", "TRACE_PROG");
+		break;
+	case PIM_MSDP_TRACEROUTE_REPLY:
+		snprintf(buf, buf_size, "%s", "TRACE_REPLY");
+		break;
+	default:
+		snprintf(buf, buf_size, "UNK-%d", type);
+	}
+	return buf;
+}
+
+static void pim_msdp_pkt_sa_dump_one(struct stream *s)
+{
+	pim_sgaddr sg;
+
+	/* just throw away the three reserved bytes */
+	stream_get3(s);
+	/* throw away the prefix length also */
+	stream_getc(s);
+
+	memset(&sg, 0, sizeof(sg));
+	sg.grp.s_addr = stream_get_ipv4(s);
+	sg.src.s_addr = stream_get_ipv4(s);
+
+	zlog_debug("  sg %pSG", &sg);
+}
+
+static void pim_msdp_pkt_sa_dump(struct stream *s)
+{
+	const size_t header_length = PIM_MSDP_SA_X_SIZE - PIM_MSDP_HEADER_SIZE;
+	size_t payload_length;
+	int entry_cnt;
+	int i;
+	struct in_addr rp; /* Last RP address associated with this SA */
+
+	if (header_length > STREAM_READABLE(s)) {
+		zlog_err("BUG MSDP SA bad header (readable %zu expected %zu)",
+			 STREAM_READABLE(s), header_length);
+		return;
+	}
+
+	entry_cnt = stream_getc(s);
+	rp.s_addr = stream_get_ipv4(s);
+
+	if (PIM_DEBUG_MSDP_PACKETS) {
+		char rp_str[INET_ADDRSTRLEN];
+		pim_inet4_dump("<rp?>", rp, rp_str, sizeof(rp_str));
+		zlog_debug("  entry_cnt %d rp %s", entry_cnt, rp_str);
+	}
+
+	payload_length = (size_t)entry_cnt * PIM_MSDP_SA_ONE_ENTRY_SIZE;
+	if (payload_length > STREAM_READABLE(s)) {
+		zlog_err("BUG MSDP SA bad length (readable %zu expected %zu)",
+			 STREAM_READABLE(s), payload_length);
+		return;
+	}
+
+	/* dump SAs */
+	for (i = 0; i < entry_cnt; ++i) {
+		pim_msdp_pkt_sa_dump_one(s);
+	}
+}
+
+static void pim_msdp_pkt_dump(struct pim_msdp_peer *mp, int type, int len,
+			      bool rx, struct stream *s)
+{
+	char type_str[PIM_MSDP_PKT_TYPE_STRLEN];
+
+	pim_msdp_pkt_type_dump(type, type_str, sizeof(type_str));
+
+	zlog_debug("MSDP peer %s pkt %s type %s len %d", mp->key_str,
+		   rx ? "rx" : "tx", type_str, len);
+
+	if (!s) {
+		return;
+	}
+
+	if (len < PIM_MSDP_HEADER_SIZE) {
+		zlog_err("invalid MSDP header length");
+		return;
+	}
+
+	switch (type) {
+	case PIM_MSDP_V4_SOURCE_ACTIVE:
+		pim_msdp_pkt_sa_dump(s);
+		break;
+	default:;
+	}
+}
+
+/* Check file descriptor whether connect is established. */
+static void pim_msdp_connect_check(struct pim_msdp_peer *mp)
+{
+	int status;
+	socklen_t slen;
+	int ret;
+
+	if (mp->state != PIM_MSDP_CONNECTING) {
+		/* if we are here it means we are not in a connecting or
+		 * established state
+		 * for now treat this as a fatal error */
+		pim_msdp_peer_reset_tcp_conn(mp, "invalid-state");
+		return;
+	}
+
+	PIM_MSDP_PEER_READ_OFF(mp);
+	PIM_MSDP_PEER_WRITE_OFF(mp);
+
+	/* Check file descriptor. */
+	slen = sizeof(status);
+	ret = getsockopt(mp->fd, SOL_SOCKET, SO_ERROR, (void *)&status, &slen);
+
+	/* If getsockopt is fail, this is fatal error. */
+	if (ret < 0) {
+		flog_err_sys(EC_LIB_SOCKET,
+			     "can't get sockopt for nonblocking connect");
+		pim_msdp_peer_reset_tcp_conn(mp, "connect-failed");
+		return;
+	}
+
+	/* When status is 0 then TCP connection is established. */
+	if (PIM_DEBUG_MSDP_INTERNAL) {
+		zlog_debug("MSDP peer %s pim_connect_check %s", mp->key_str,
+			   status ? "fail" : "success");
+	}
+	if (status == 0) {
+		pim_msdp_peer_established(mp);
+	} else {
+		pim_msdp_peer_reset_tcp_conn(mp, "connect-failed");
+	}
+}
+
+static void pim_msdp_pkt_delete(struct pim_msdp_peer *mp)
+{
+	stream_free(stream_fifo_pop(mp->obuf));
+}
+
+static void pim_msdp_pkt_add(struct pim_msdp_peer *mp, struct stream *s)
+{
+	stream_fifo_push(mp->obuf, s);
+}
+
+static void pim_msdp_write_proceed_actions(struct pim_msdp_peer *mp)
+{
+	if (stream_fifo_head(mp->obuf)) {
+		PIM_MSDP_PEER_WRITE_ON(mp);
+	}
+}
+
+void pim_msdp_write(struct event *thread)
+{
+	struct pim_msdp_peer *mp;
+	struct stream *s;
+	int num;
+	enum pim_msdp_tlv type;
+	int len;
+	int work_cnt = 0;
+	int work_max_cnt = 100;
+
+	mp = EVENT_ARG(thread);
+	mp->t_write = NULL;
+
+	if (PIM_DEBUG_MSDP_INTERNAL) {
+		zlog_debug("MSDP peer %s pim_msdp_write", mp->key_str);
+	}
+	if (mp->fd < 0) {
+		return;
+	}
+
+	/* check if TCP connection is established */
+	if (mp->state != PIM_MSDP_ESTABLISHED) {
+		pim_msdp_connect_check(mp);
+		return;
+	}
+
+	s = stream_fifo_head(mp->obuf);
+	if (!s) {
+		pim_msdp_write_proceed_actions(mp);
+		return;
+	}
+
+	/* Nonblocking write until TCP output buffer is full  */
+	do {
+		int writenum;
+
+		/* Number of bytes to be sent */
+		writenum = stream_get_endp(s) - stream_get_getp(s);
+
+		/* Call write() system call */
+		num = write(mp->fd, stream_pnt(s), writenum);
+		if (num < 0) {
+			/* write failed either retry needed or error */
+			if (ERRNO_IO_RETRY(errno)) {
+				if (PIM_DEBUG_MSDP_INTERNAL) {
+					zlog_debug(
+						"MSDP peer %s pim_msdp_write io retry",
+						mp->key_str);
+				}
+				break;
+			}
+
+			pim_msdp_peer_reset_tcp_conn(mp, "pkt-tx-failed");
+			return;
+		}
+
+		if (num != writenum) {
+			/* Partial write */
+			stream_forward_getp(s, num);
+			if (PIM_DEBUG_MSDP_INTERNAL) {
+				zlog_debug(
+					"MSDP peer %s pim_msdp_partial_write",
+					mp->key_str);
+			}
+			break;
+		}
+
+		/* Retrieve msdp packet type. */
+		stream_set_getp(s, 0);
+		type = stream_getc(s);
+		len = stream_getw(s);
+		switch (type) {
+		case PIM_MSDP_KEEPALIVE:
+			mp->ka_tx_cnt++;
+			break;
+		case PIM_MSDP_V4_SOURCE_ACTIVE:
+			mp->sa_tx_cnt++;
+			break;
+		case PIM_MSDP_V4_SOURCE_ACTIVE_REQUEST:
+		case PIM_MSDP_V4_SOURCE_ACTIVE_RESPONSE:
+		case PIM_MSDP_RESERVED:
+		case PIM_MSDP_TRACEROUTE_PROGRESS:
+		case PIM_MSDP_TRACEROUTE_REPLY:
+			break;
+		}
+		if (PIM_DEBUG_MSDP_PACKETS) {
+			pim_msdp_pkt_dump(mp, type, len, false /*rx*/, s);
+		}
+
+		/* packet sent delete it. */
+		pim_msdp_pkt_delete(mp);
+
+		++work_cnt;
+		/* may need to pause if we have done too much work in this
+		 * loop */
+		if (work_cnt >= work_max_cnt) {
+			break;
+		}
+	} while ((s = stream_fifo_head(mp->obuf)) != NULL);
+	pim_msdp_write_proceed_actions(mp);
+
+	if (PIM_DEBUG_MSDP_INTERNAL) {
+		zlog_debug("MSDP peer %s pim_msdp_write wrote %d packets",
+			   mp->key_str, work_cnt);
+	}
+}
+
+static void pim_msdp_pkt_send(struct pim_msdp_peer *mp, struct stream *s)
+{
+	/* Add packet to the end of list. */
+	pim_msdp_pkt_add(mp, s);
+
+	PIM_MSDP_PEER_WRITE_ON(mp);
+}
+
+void pim_msdp_pkt_ka_tx(struct pim_msdp_peer *mp)
+{
+	struct stream *s;
+
+	if (mp->state != PIM_MSDP_ESTABLISHED) {
+		/* don't tx anything unless a session is established */
+		return;
+	}
+	s = stream_new(PIM_MSDP_KA_TLV_MAX_SIZE);
+	stream_putc(s, PIM_MSDP_KEEPALIVE);
+	stream_putw(s, PIM_MSDP_KA_TLV_MAX_SIZE);
+
+	pim_msdp_pkt_send(mp, s);
+}
+
+static void pim_msdp_pkt_sa_push_to_one_peer(struct pim_instance *pim,
+					     struct pim_msdp_peer *mp)
+{
+	struct stream *s;
+
+	if (mp->state != PIM_MSDP_ESTABLISHED) {
+		/* don't tx anything unless a session is established */
+		return;
+	}
+	s = stream_dup(pim->msdp.work_obuf);
+	if (s) {
+		pim_msdp_pkt_send(mp, s);
+		mp->flags |= PIM_MSDP_PEERF_SA_JUST_SENT;
+	}
+}
+
+/* push the stream into the obuf fifo of all the peers */
+static void pim_msdp_pkt_sa_push(struct pim_instance *pim,
+				 struct pim_msdp_peer *mp)
+{
+	struct listnode *mpnode;
+
+	if (mp) {
+		pim_msdp_pkt_sa_push_to_one_peer(pim, mp);
+	} else {
+		for (ALL_LIST_ELEMENTS_RO(pim->msdp.peer_list, mpnode, mp)) {
+			if (PIM_DEBUG_MSDP_INTERNAL) {
+				zlog_debug("MSDP peer %s pim_msdp_pkt_sa_push",
+					   mp->key_str);
+			}
+			pim_msdp_pkt_sa_push_to_one_peer(pim, mp);
+		}
+	}
+}
+
+static int pim_msdp_pkt_sa_fill_hdr(struct pim_instance *pim, int local_cnt,
+				    struct in_addr rp)
+{
+	int curr_tlv_ecnt;
+
+	stream_reset(pim->msdp.work_obuf);
+	curr_tlv_ecnt = local_cnt > PIM_MSDP_SA_MAX_ENTRY_CNT
+				? PIM_MSDP_SA_MAX_ENTRY_CNT
+				: local_cnt;
+	local_cnt -= curr_tlv_ecnt;
+	stream_putc(pim->msdp.work_obuf, PIM_MSDP_V4_SOURCE_ACTIVE);
+	stream_putw(pim->msdp.work_obuf,
+		    PIM_MSDP_SA_ENTRY_CNT2SIZE(curr_tlv_ecnt));
+	stream_putc(pim->msdp.work_obuf, curr_tlv_ecnt);
+	stream_put_ipv4(pim->msdp.work_obuf, rp.s_addr);
+
+	return local_cnt;
+}
+
+static void pim_msdp_pkt_sa_fill_one(struct pim_msdp_sa *sa)
+{
+	stream_put3(sa->pim->msdp.work_obuf, 0 /* reserved */);
+	stream_putc(sa->pim->msdp.work_obuf, 32 /* sprefix len */);
+	stream_put_ipv4(sa->pim->msdp.work_obuf, sa->sg.grp.s_addr);
+	stream_put_ipv4(sa->pim->msdp.work_obuf, sa->sg.src.s_addr);
+}
+
+static void pim_msdp_pkt_sa_gen(struct pim_instance *pim,
+				struct pim_msdp_peer *mp)
+{
+	struct listnode *sanode;
+	struct pim_msdp_sa *sa;
+	struct rp_info *rp_info;
+	struct prefix group_all;
+	struct in_addr rp;
+	int sa_count;
+	int local_cnt = pim->msdp.local_cnt;
+
+	sa_count = 0;
+	if (PIM_DEBUG_MSDP_INTERNAL) {
+		zlog_debug("  sa gen  %d", local_cnt);
+	}
+
+	rp = pim->msdp.originator_id;
+	if (pim_get_all_mcast_group(&group_all)) {
+	    rp_info = pim_rp_find_match_group(pim, &group_all);
+	    if (rp_info) {
+	        rp = rp_info->rp.rpf_addr;
+	    }
+	}
+
+	local_cnt = pim_msdp_pkt_sa_fill_hdr(pim, local_cnt, rp);
+
+	for (ALL_LIST_ELEMENTS_RO(pim->msdp.sa_list, sanode, sa)) {
+		if (!(sa->flags & PIM_MSDP_SAF_LOCAL)) {
+			/* current implementation of MSDP is for anycast i.e.
+			 * full mesh. so
+			 * no re-forwarding of SAs that we learnt from other
+			 * peers */
+			continue;
+		}
+		/* add sa into scratch pad */
+		pim_msdp_pkt_sa_fill_one(sa);
+		++sa_count;
+		if (sa_count >= PIM_MSDP_SA_MAX_ENTRY_CNT) {
+			pim_msdp_pkt_sa_push(pim, mp);
+			/* reset headers */
+			sa_count = 0;
+			if (PIM_DEBUG_MSDP_INTERNAL) {
+				zlog_debug("  sa gen for remainder %d",
+					   local_cnt);
+			}
+			local_cnt = pim_msdp_pkt_sa_fill_hdr(
+				pim, local_cnt, rp);
+		}
+	}
+
+	if (sa_count) {
+		pim_msdp_pkt_sa_push(pim, mp);
+	}
+	return;
+}
+
+static void pim_msdp_pkt_sa_tx_done(struct pim_instance *pim)
+{
+	struct listnode *mpnode;
+	struct pim_msdp_peer *mp;
+
+	/* if SA were sent to the peers we restart ka timer and avoid
+	 * unnecessary ka noise */
+	for (ALL_LIST_ELEMENTS_RO(pim->msdp.peer_list, mpnode, mp)) {
+		if (mp->flags & PIM_MSDP_PEERF_SA_JUST_SENT) {
+			mp->flags &= ~PIM_MSDP_PEERF_SA_JUST_SENT;
+			pim_msdp_peer_pkt_txed(mp);
+		}
+	}
+}
+
+void pim_msdp_pkt_sa_tx(struct pim_instance *pim)
+{
+	pim_msdp_pkt_sa_gen(pim, NULL /* mp */);
+	pim_msdp_pkt_sa_tx_done(pim);
+}
+
+void pim_msdp_pkt_sa_tx_one(struct pim_msdp_sa *sa)
+{
+	pim_msdp_pkt_sa_fill_hdr(sa->pim, 1 /* cnt */, sa->rp);
+	pim_msdp_pkt_sa_fill_one(sa);
+	pim_msdp_pkt_sa_push(sa->pim, NULL);
+	pim_msdp_pkt_sa_tx_done(sa->pim);
+}
+
+/* when a connection is first established we push all SAs immediately */
+void pim_msdp_pkt_sa_tx_to_one_peer(struct pim_msdp_peer *mp)
+{
+	pim_msdp_pkt_sa_gen(mp->pim, mp);
+	pim_msdp_pkt_sa_tx_done(mp->pim);
+}
+
+void pim_msdp_pkt_sa_tx_one_to_one_peer(struct pim_msdp_peer *mp,
+					struct in_addr rp, pim_sgaddr sg)
+{
+	struct pim_msdp_sa sa;
+
+	/* Fills the SA header. */
+	pim_msdp_pkt_sa_fill_hdr(mp->pim, 1, rp);
+
+	/* Fills the message contents. */
+	sa.pim = mp->pim;
+	sa.sg = sg;
+	pim_msdp_pkt_sa_fill_one(&sa);
+
+	/* Pushes the message. */
+	pim_msdp_pkt_sa_push(sa.pim, mp);
+	pim_msdp_pkt_sa_tx_done(sa.pim);
+}
+
+static void pim_msdp_pkt_rxed_with_fatal_error(struct pim_msdp_peer *mp)
+{
+	pim_msdp_peer_reset_tcp_conn(mp, "invalid-pkt-rx");
+}
+
+static void pim_msdp_pkt_ka_rx(struct pim_msdp_peer *mp, int len)
+{
+	mp->ka_rx_cnt++;
+	if (len != PIM_MSDP_KA_TLV_MAX_SIZE) {
+		pim_msdp_pkt_rxed_with_fatal_error(mp);
+		return;
+	}
+	pim_msdp_peer_pkt_rxed(mp);
+}
+
+static void pim_msdp_pkt_sa_rx_one(struct pim_msdp_peer *mp, struct in_addr rp)
+{
+	int prefix_len;
+	pim_sgaddr sg;
+	struct listnode *peer_node;
+	struct pim_msdp_peer *peer;
+
+	/* just throw away the three reserved bytes */
+	stream_get3(mp->ibuf);
+	prefix_len = stream_getc(mp->ibuf);
+
+	memset(&sg, 0, sizeof(sg));
+	sg.grp.s_addr = stream_get_ipv4(mp->ibuf);
+	sg.src.s_addr = stream_get_ipv4(mp->ibuf);
+
+	if (prefix_len != IPV4_MAX_BITLEN) {
+		/* ignore SA update if the prefix length is not 32 */
+		flog_err(EC_PIM_MSDP_PACKET,
+			 "rxed sa update with invalid prefix length %d",
+			 prefix_len);
+		return;
+	}
+	if (PIM_DEBUG_MSDP_PACKETS) {
+		zlog_debug("  sg %pSG", &sg);
+	}
+	pim_msdp_sa_ref(mp->pim, mp, &sg, rp);
+
+	/* Forwards the SA to the peers that are not in the RPF to the RP nor in
+	 * the same mesh group as the peer from which we received the message.
+	 * If the message group is not set, i.e. "default", then we assume that
+	 * the message must be forwarded.*/
+	for (ALL_LIST_ELEMENTS_RO(mp->pim->msdp.peer_list, peer_node, peer)) {
+		/* Not a RPF peer, so skip it. */
+		if (pim_msdp_peer_rpf_check(peer, rp))
+			continue;
+		/* Don't forward inside the meshed group. */
+		if ((mp->flags & PIM_MSDP_PEERF_IN_GROUP)
+		    && strcmp(mp->mesh_group_name, peer->mesh_group_name) == 0)
+			continue;
+
+		pim_msdp_pkt_sa_tx_one_to_one_peer(peer, rp, sg);
+	}
+}
+
+static void pim_msdp_pkt_sa_rx(struct pim_msdp_peer *mp, int len)
+{
+	int entry_cnt;
+	int i;
+	struct in_addr rp; /* Last RP address associated with this SA */
+
+	mp->sa_rx_cnt++;
+
+	if (len < PIM_MSDP_SA_TLV_MIN_SIZE) {
+		pim_msdp_pkt_rxed_with_fatal_error(mp);
+		return;
+	}
+
+	entry_cnt = stream_getc(mp->ibuf);
+	/* some vendors include the actual multicast data in the tlv (at the
+	 * end). we will ignore such data. in the future we may consider pushing
+	 * it down the RPT
+	 */
+	if (len < PIM_MSDP_SA_ENTRY_CNT2SIZE(entry_cnt)) {
+		pim_msdp_pkt_rxed_with_fatal_error(mp);
+		return;
+	}
+	rp.s_addr = stream_get_ipv4(mp->ibuf);
+
+	if (PIM_DEBUG_MSDP_PACKETS) {
+		char rp_str[INET_ADDRSTRLEN];
+		pim_inet4_dump("<rp?>", rp, rp_str, sizeof(rp_str));
+		zlog_debug("  entry_cnt %d rp %s", entry_cnt, rp_str);
+	}
+
+	pim_msdp_peer_pkt_rxed(mp);
+
+	if (!pim_msdp_peer_rpf_check(mp, rp)) {
+		/* if peer-RPF check fails don't process the packet any further
+		 */
+		if (PIM_DEBUG_MSDP_PACKETS) {
+			zlog_debug("  peer RPF check failed");
+		}
+		return;
+	}
+
+	/* update SA cache */
+	for (i = 0; i < entry_cnt; ++i) {
+		pim_msdp_pkt_sa_rx_one(mp, rp);
+	}
+}
+
+static void pim_msdp_pkt_rx(struct pim_msdp_peer *mp)
+{
+	enum pim_msdp_tlv type;
+	int len;
+
+	/* re-read type and len */
+	type = stream_getc_from(mp->ibuf, 0);
+	len = stream_getw_from(mp->ibuf, 1);
+	if (len < PIM_MSDP_HEADER_SIZE) {
+		pim_msdp_pkt_rxed_with_fatal_error(mp);
+		return;
+	}
+
+	if (len > PIM_MSDP_SA_TLV_MAX_SIZE) {
+		/* if tlv size if greater than max just ignore the tlv */
+		return;
+	}
+
+	if (PIM_DEBUG_MSDP_PACKETS) {
+		pim_msdp_pkt_dump(mp, type, len, true /*rx*/, NULL /*s*/);
+	}
+
+	switch (type) {
+	case PIM_MSDP_KEEPALIVE:
+		pim_msdp_pkt_ka_rx(mp, len);
+		break;
+	case PIM_MSDP_V4_SOURCE_ACTIVE:
+		mp->sa_rx_cnt++;
+		pim_msdp_pkt_sa_rx(mp, len);
+		break;
+	case PIM_MSDP_V4_SOURCE_ACTIVE_REQUEST:
+	case PIM_MSDP_V4_SOURCE_ACTIVE_RESPONSE:
+	case PIM_MSDP_RESERVED:
+	case PIM_MSDP_TRACEROUTE_PROGRESS:
+	case PIM_MSDP_TRACEROUTE_REPLY:
+		mp->unk_rx_cnt++;
+		break;
+	}
+}
+
+/* pim msdp read utility function. */
+static int pim_msdp_read_packet(struct pim_msdp_peer *mp)
+{
+	int nbytes;
+	int readsize;
+	int old_endp;
+	int new_endp;
+
+	old_endp = stream_get_endp(mp->ibuf);
+	readsize = mp->packet_size - old_endp;
+	if (!readsize) {
+		return 0;
+	}
+
+	/* Read packet from fd */
+	nbytes = stream_read_try(mp->ibuf, mp->fd, readsize);
+	new_endp = stream_get_endp(mp->ibuf);
+	if (nbytes < 0) {
+		if (PIM_DEBUG_MSDP_INTERNAL) {
+			zlog_debug("MSDP peer %s read failed %d", mp->key_str,
+				   nbytes);
+		}
+		if (nbytes == -2) {
+			if (PIM_DEBUG_MSDP_INTERNAL) {
+				zlog_debug(
+					"MSDP peer %s pim_msdp_read io retry old_end: %d new_end: %d",
+					mp->key_str, old_endp, new_endp);
+			}
+			/* transient error retry */
+			return -1;
+		}
+		pim_msdp_pkt_rxed_with_fatal_error(mp);
+		return -1;
+	}
+
+	if (!nbytes) {
+		if (PIM_DEBUG_MSDP_INTERNAL) {
+			zlog_debug("MSDP peer %s read failed %d", mp->key_str,
+				   nbytes);
+		}
+		pim_msdp_peer_reset_tcp_conn(mp, "peer-down");
+		return -1;
+	}
+
+	/* We read partial packet. */
+	if (stream_get_endp(mp->ibuf) != mp->packet_size) {
+		if (PIM_DEBUG_MSDP_INTERNAL) {
+			zlog_debug(
+				"MSDP peer %s read partial len %d old_endp %d new_endp %d",
+				mp->key_str, mp->packet_size, old_endp,
+				new_endp);
+		}
+		return -1;
+	}
+
+	return 0;
+}
+
+void pim_msdp_read(struct event *thread)
+{
+	struct pim_msdp_peer *mp;
+	int rc;
+	uint32_t len;
+
+	mp = EVENT_ARG(thread);
+	mp->t_read = NULL;
+
+	if (PIM_DEBUG_MSDP_INTERNAL) {
+		zlog_debug("MSDP peer %s pim_msdp_read", mp->key_str);
+	}
+
+	if (mp->fd < 0) {
+		return;
+	}
+
+	/* check if TCP connection is established */
+	if (mp->state != PIM_MSDP_ESTABLISHED) {
+		pim_msdp_connect_check(mp);
+		return;
+	}
+
+	PIM_MSDP_PEER_READ_ON(mp);
+
+	if (!mp->packet_size) {
+		mp->packet_size = PIM_MSDP_HEADER_SIZE;
+	}
+
+	if (stream_get_endp(mp->ibuf) < PIM_MSDP_HEADER_SIZE) {
+		/* start by reading the TLV header */
+		rc = pim_msdp_read_packet(mp);
+		if (rc < 0)
+			return;
+
+		/* Find TLV type and len  */
+		stream_getc(mp->ibuf);
+		len = stream_getw(mp->ibuf);
+		if (len < PIM_MSDP_HEADER_SIZE) {
+			pim_msdp_pkt_rxed_with_fatal_error(mp);
+			return;
+		}
+
+		/*
+		 * Handle messages with longer than expected TLV size: resize
+		 * the stream to handle reading the whole message.
+		 *
+		 * RFC 3618 Section 12. 'Packet Formats':
+		 * > ... If an implementation receives a TLV whose length
+		 * > exceeds the maximum TLV length specified below, the TLV
+		 * > SHOULD be accepted. Any additional data, including possible
+		 * > next TLV's in the same message, SHOULD be ignored, and the
+		 * > MSDP session should not be reset. ...
+		 */
+		if (len > PIM_MSDP_SA_TLV_MAX_SIZE) {
+			/* Check if the current buffer is big enough. */
+			if (mp->ibuf->size < len) {
+				if (PIM_DEBUG_MSDP_PACKETS)
+					zlog_debug(
+						"MSDP peer %s sent TLV with unexpected large length (%d bytes)",
+						mp->key_str, len);
+
+				stream_resize_inplace(&mp->ibuf, len);
+			}
+		}
+
+		/* read complete TLV */
+		mp->packet_size = len;
+	}
+
+	rc = pim_msdp_read_packet(mp);
+	if (rc < 0)
+		return;
+
+	pim_msdp_pkt_rx(mp);
+
+	/* reset input buffers and get ready for the next packet */
+	mp->packet_size = 0;
+	stream_reset(mp->ibuf);
+}