udp: In udp_flow_src_port use random hash value if skb_get_hash fails
In the unlikely event that skb_get_hash is unable to deduce a hash
in udp_flow_src_port we use a consistent random value instead.
This is specified in GRE/UDP draft section 3.2.1:
https://tools.ietf.org/html/draft-ietf-tsvwg-gre-in-udp-encap-04
Signed-off-by: Tom Herbert <therbert@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/include/net/udp.h b/include/net/udp.h
index 07f9b70..32d8d9f 100644
--- a/include/net/udp.h
+++ b/include/net/udp.h
@@ -194,6 +194,8 @@
int (*)(const struct sock *, const struct sock *),
unsigned int hash2_nulladdr);
+u32 udp_flow_hashrnd(void);
+
static inline __be16 udp_flow_src_port(struct net *net, struct sk_buff *skb,
int min, int max, bool use_eth)
{
@@ -205,12 +207,19 @@
}
hash = skb_get_hash(skb);
- if (unlikely(!hash) && use_eth) {
- /* Can't find a normal hash, caller has indicated an Ethernet
- * packet so use that to compute a hash.
- */
- hash = jhash(skb->data, 2 * ETH_ALEN,
- (__force u32) skb->protocol);
+ if (unlikely(!hash)) {
+ if (use_eth) {
+ /* Can't find a normal hash, caller has indicated an
+ * Ethernet packet so use that to compute a hash.
+ */
+ hash = jhash(skb->data, 2 * ETH_ALEN,
+ (__force u32) skb->protocol);
+ } else {
+ /* Can't derive any sort of hash for the packet, set
+ * to some consistent random value.
+ */
+ hash = udp_flow_hashrnd();
+ }
}
/* Since this is being sent on the wire obfuscate hash a bit