ipv6: translate ICMP_TIME_EXCEEDED to ICMPV6_TIME_EXCEED

For better traceroute/mtr support for SIT and GRE tunnels,
we translate IPV4 ICMP ICMP_TIME_EXCEEDED to ICMPV6_TIME_EXCEED

We also have to translate the IPv4 source IP address of ICMP
message to IPv6 v4mapped.
Signed-off-by: NEric Dumazet <edumazet@google.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

include/linux/icmpv6.h

@@ -18,7 +18,7 @@ typedef void ip6_icmp_send_t(struct sk_buff *skb, u8 type, u8 code, __u32 info,
 			     const struct in6_addr *force_saddr);
 extern int inet6_register_icmp_sender(ip6_icmp_send_t *fn);
 extern int inet6_unregister_icmp_sender(ip6_icmp_send_t *fn);
-int ip6_err_gen_icmpv6_unreach(struct sk_buff *skb, int nhs);
+int ip6_err_gen_icmpv6_unreach(struct sk_buff *skb, int nhs, int type);
 
 #else
 

net/ipv6/icmp.c

@@ -564,8 +564,9 @@ void icmpv6_param_prob(struct sk_buff *skb, u8 code, int pos)
  *  Either an IPv4 header for SIT encap
  *         an IPv4 header + GRE header for GRE encap
  */
-int ip6_err_gen_icmpv6_unreach(struct sk_buff *skb, int nhs)
+int ip6_err_gen_icmpv6_unreach(struct sk_buff *skb, int nhs, int type)
 {
+	struct in6_addr temp_saddr;
 	struct rt6_info *rt;
 	struct sk_buff *skb2;
 
@@ -586,8 +587,13 @@ int ip6_err_gen_icmpv6_unreach(struct sk_buff *skb, int nhs)
 	if (rt && rt->dst.dev)
 		skb2->dev = rt->dst.dev;
 
-	icmpv6_send(skb2, ICMPV6_DEST_UNREACH, ICMPV6_ADDR_UNREACH, 0);
-
+	ipv6_addr_set_v4mapped(ip_hdr(skb)->saddr, &temp_saddr);
+	if (type == ICMP_TIME_EXCEEDED)
+		icmp6_send(skb2, ICMPV6_TIME_EXCEED, ICMPV6_EXC_HOPLIMIT,
+			   0, &temp_saddr);
+	else
+		icmp6_send(skb2, ICMPV6_DEST_UNREACH, ICMPV6_ADDR_UNREACH,
+			   0, &temp_saddr);
 	if (rt)
 		ip6_rt_put(rt);
 

net/ipv6/sit.c

@@ -535,11 +535,11 @@ static int ipip6_err(struct sk_buff *skb, u32 info)
 		goto out;
 	}
 
-	if (t->parms.iph.daddr == 0)
+	err = 0;
+	if (!ip6_err_gen_icmpv6_unreach(skb, iph->ihl * 4, type))
 		goto out;
 
-	err = 0;
-	if (!ip6_err_gen_icmpv6_unreach(skb, iph->ihl * 4))
+	if (t->parms.iph.daddr == 0)
 		goto out;
 
 	if (t->parms.iph.ttl == 0 && type == ICMP_TIME_EXCEEDED)