From f88d0cfe7a26c56693c74bd1ec515c7d5f1623f2 Mon Sep 17 00:00:00 2001
From: Michael Tuexen <tuexen@FreeBSD.org>
Date: Wed, 25 May 2016 22:16:11 +0000
Subject: [PATCH] When sending in ICMP response to an SCTP packet, * include
 the SCTP common header, if possible * include the first 8 bytes of the INIT
 chunk, if possible This provides the necesary information for the receiver of
 the ICMP packet to process it.

MFC after:	1 week
---
 sys/netinet/ip_icmp.c | 29 +++++++++++++++++++++++++++++
 1 file changed, 29 insertions(+)

diff --git a/sys/netinet/ip_icmp.c b/sys/netinet/ip_icmp.c
index 39a28b87b45c..867c5e8f76e8 100644
--- a/sys/netinet/ip_icmp.c
+++ b/sys/netinet/ip_icmp.c
@@ -61,6 +61,7 @@ __FBSDID("$FreeBSD$");
 #include <netinet/ip_icmp.h>
 #include <netinet/ip_var.h>
 #include <netinet/ip_options.h>
+#include <netinet/sctp.h>
 #include <netinet/tcp.h>
 #include <netinet/tcp_var.h>
 #include <netinet/tcpip.h>
@@ -249,6 +250,34 @@ icmp_error(struct mbuf *n, int type, int code, uint32_t dest, int mtu)
 			goto freeit;
 		icmpelen = max(tcphlen, min(V_icmp_quotelen,
 		    ntohs(oip->ip_len) - oiphlen));
+	} else if (oip->ip_p == IPPROTO_SCTP) {
+		struct sctphdr *sh;
+		struct sctp_chunkhdr *ch;
+
+		if (ntohs(oip->ip_len) < oiphlen + sizeof(struct sctphdr))
+			goto stdreply;
+		if (oiphlen + sizeof(struct sctphdr) > n->m_len &&
+		    n->m_next == NULL)
+			goto stdreply;
+		if (n->m_len < oiphlen + sizeof(struct sctphdr) &&
+		    (n = m_pullup(n, oiphlen + sizeof(struct sctphdr))) == NULL)
+			goto freeit;
+		icmpelen = max(sizeof(struct sctphdr),
+		    min(V_icmp_quotelen, ntohs(oip->ip_len) - oiphlen));
+		sh = (struct sctphdr *)((caddr_t)oip + oiphlen);
+		if (ntohl(sh->v_tag) == 0 &&
+		    ntohs(oip->ip_len) >= oiphlen + sizeof(struct sctphdr) + 8 &&
+		    (n->m_len >= oiphlen + sizeof(struct sctphdr) + 8 ||
+		     n->m_next != NULL)) {
+			if (n->m_len < oiphlen + sizeof(struct sctphdr) + 8 &&
+			    (n = m_pullup(n, oiphlen + sizeof(struct sctphdr) + 8)) == NULL)
+				goto freeit;
+			ch = (struct sctp_chunkhdr *)(sh + 1);
+			if (ch->chunk_type == SCTP_INITIATION) {
+				icmpelen = max(sizeof(struct sctphdr) + 8,
+				    min(V_icmp_quotelen, ntohs(oip->ip_len) - oiphlen));
+			}
+		}
 	} else
 stdreply:	icmpelen = max(8, min(V_icmp_quotelen, ntohs(oip->ip_len) - oiphlen));