@@ -194,6 +194,8 @@ int udp_lib_get_port(struct sock *sk, unsigned short snum,
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 @@ static inline __be16 udp_flow_src_port(struct net *net, struct sk_buff *skb,
}
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
@@ -2525,6 +2525,16 @@ void __init udp_table_init(struct udp_table *table, const char *name)
}
}
+u32 udp_flow_hashrnd(void)
+{
+ static u32 hashrnd __read_mostly;
+
+ net_get_random_once(&hashrnd, sizeof(hashrnd));
+
+ return hashrnd;
+}
+EXPORT_SYMBOL(udp_flow_hashrnd);
+
void __init udp_init(void)
{
unsigned long limit;
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> --- include/net/udp.h | 21 +++++++++++++++------ net/ipv4/udp.c | 10 ++++++++++ 2 files changed, 25 insertions(+), 6 deletions(-)