From 6d7270a580f08fe7ee9d17c1282d24e4393e4997 Mon Sep 17 00:00:00 2001
From: Michael Tuexen <tuexen@FreeBSD.org>
Date: Wed, 25 May 2016 15:54:21 +0000
Subject: [PATCH] Send an ICMP packet indicating destination
 unreachable/protocol unreachable if we don't handle the packet in the kernel
 and not in userspace.

MFC after:	1 week
---
 sys/netinet/raw_ip.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/sys/netinet/raw_ip.c b/sys/netinet/raw_ip.c
index 74a9d9a33a1d..59540a50c361 100644
--- a/sys/netinet/raw_ip.c
+++ b/sys/netinet/raw_ip.c
@@ -71,6 +71,7 @@ __FBSDID("$FreeBSD$");
 #include <netinet/ip.h>
 #include <netinet/ip_var.h>
 #include <netinet/ip_mroute.h>
+#include <netinet/ip_icmp.h>
 
 #ifdef IPSEC
 #include <netipsec/ipsec.h>
@@ -416,8 +417,10 @@ rip_input(struct mbuf **mp, int *offp, int proto)
 		if (inetsw[ip_protox[ip->ip_p]].pr_input == rip_input) {
 			IPSTAT_INC(ips_noproto);
 			IPSTAT_DEC(ips_delivered);
+			icmp_error(m, ICMP_UNREACH, ICMP_UNREACH_PROTOCOL, 0, 0);
+		} else {
+			m_freem(m);
 		}
-		m_freem(m);
 	}
 	return (IPPROTO_DONE);
 }