diff options
| author | Tom Herbert <therbert@google.com> | 2015-02-24 09:17:31 -0800 |
|---|---|---|
| committer | David S. Miller <davem@davemloft.net> | 2015-02-27 16:00:01 -0500 |
| commit | 723b8e460d87e957f251dc5764f4ab86af6ab44e (patch) | |
| tree | 2453607eb05e7cdf3913fedfe55599641c6a66b1 | |
| parent | fed0a159c8c5e453d79d6a73897c576efea0a8a5 (diff) | |
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>
| -rw-r--r-- | include/net/udp.h | 21 | ||||
| -rw-r--r-- | net/ipv4/udp.c | 10 |
2 files changed, 25 insertions, 6 deletions
diff --git a/include/net/udp.h b/include/net/udp.h index 07f9b70962f6..32d8d9f07f76 100644 --- a/include/net/udp.h +++ b/include/net/udp.h @@ -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 diff --git a/net/ipv4/udp.c b/net/ipv4/udp.c index 97ef1f8b7be8..0224f930c613 100644 --- a/net/ipv4/udp.c +++ b/net/ipv4/udp.c @@ -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; |