1 files changed, 59 insertions, 6 deletions

diff --git a/net/ipv4/route.c b/net/ipv4/route.c
index 76ca4e75f785..54297d3a0559 100644
--- a/net/ipv4/route.c
+++ b/net/ipv4/route.c
@@ -1651,6 +1651,48 @@ out:
 	return err;
 }
 
+#ifdef CONFIG_IP_ROUTE_MULTIPATH
+
+/* To make ICMP packets follow the right flow, the multipath hash is
+ * calculated from the inner IP addresses in reverse order.
+ */
+static int ip_multipath_icmp_hash(struct sk_buff *skb)
+{
+	const struct iphdr *outer_iph = ip_hdr(skb);
+	struct icmphdr _icmph;
+	const struct icmphdr *icmph;
+	struct iphdr _inner_iph;
+	const struct iphdr *inner_iph;
+
+	if (unlikely((outer_iph->frag_off & htons(IP_OFFSET)) != 0))
+		goto standard_hash;
+
+	icmph = skb_header_pointer(skb, outer_iph->ihl * 4, sizeof(_icmph),
+				   &_icmph);
+	if (!icmph)
+		goto standard_hash;
+
+	if (icmph->type != ICMP_DEST_UNREACH &&
+	    icmph->type != ICMP_REDIRECT &&
+	    icmph->type != ICMP_TIME_EXCEEDED &&
+	    icmph->type != ICMP_PARAMETERPROB) {
+		goto standard_hash;
+	}
+
+	inner_iph = skb_header_pointer(skb,
+				       outer_iph->ihl * 4 + sizeof(_icmph),
+				       sizeof(_inner_iph), &_inner_iph);
+	if (!inner_iph)
+		goto standard_hash;
+
+	return fib_multipath_hash(inner_iph->daddr, inner_iph->saddr);
+
+standard_hash:
+	return fib_multipath_hash(outer_iph->saddr, outer_iph->daddr);
+}
+
+#endif /* CONFIG_IP_ROUTE_MULTIPATH */
+
 static int ip_mkroute_input(struct sk_buff *skb,
 			    struct fib_result *res,
 			    const struct flowi4 *fl4,
@@ -1658,8 +1700,15 @@ static int ip_mkroute_input(struct sk_buff *skb,
 			    __be32 daddr, __be32 saddr, u32 tos)
 {
 #ifdef CONFIG_IP_ROUTE_MULTIPATH
-	if (res->fi && res->fi->fib_nhs > 1)
-		fib_select_multipath(res);
+	if (res->fi && res->fi->fib_nhs > 1) {
+		int h;
+
+		if (unlikely(ip_hdr(skb)->protocol == IPPROTO_ICMP))
+			h = ip_multipath_icmp_hash(skb);
+		else
+			h = fib_multipath_hash(saddr, daddr);
+		fib_select_multipath(res, h);
+	}
 #endif
 
 	/* create a routing cache entry */
@@ -2026,7 +2075,8 @@ add:
  * Major route resolver routine.
  */
 
-struct rtable *__ip_route_output_key(struct net *net, struct flowi4 *fl4)
+struct rtable *__ip_route_output_key_hash(struct net *net, struct flowi4 *fl4,
+					  int mp_hash)
 {
 	struct net_device *dev_out = NULL;
 	__u8 tos = RT_FL_TOS(fl4);
@@ -2189,8 +2239,11 @@ struct rtable *__ip_route_output_key(struct net *net, struct flowi4 *fl4)
 	}
 
 #ifdef CONFIG_IP_ROUTE_MULTIPATH
-	if (res.fi->fib_nhs > 1 && fl4->flowi4_oif == 0)
-		fib_select_multipath(&res);
+	if (res.fi->fib_nhs > 1 && fl4->flowi4_oif == 0) {
+		if (mp_hash < 0)
+			mp_hash = fib_multipath_hash(fl4->saddr, fl4->daddr);
+		fib_select_multipath(&res, mp_hash);
+	}
 	else
 #endif
 	if (!res.prefixlen &&
@@ -2212,7 +2265,7 @@ out:
 	rcu_read_unlock();
 	return rth;
 }
-EXPORT_SYMBOL_GPL(__ip_route_output_key);
+EXPORT_SYMBOL_GPL(__ip_route_output_key_hash);
 
 static struct dst_entry *ipv4_blackhole_dst_check(struct dst_entry *dst, u32 cookie)
 {