path: root/net
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authorEric Dumazet <edumazet@google.com>2013-02-21 12:18:52 +0000
committerDavid S. Miller <davem@davemloft.net>2013-02-21 18:15:58 -0500
commit08dcdbf6a7b9d14c2302c5bd0c5390ddf122f664 (patch)
treefc1d00005fda323296b93064416d255b81fdab73 /net
parent0ab8a9f5fa94ac625c1f19acc48db299416c6d49 (diff)
ipv6: use a stronger hash for tcp
It looks like its possible to open thousands of TCP IPv6 sessions on a server, all landing in a single slot of TCP hash table. Incoming packets have to lookup sockets in a very long list. We should hash all bits from foreign IPv6 addresses, using a salt and hash mix, not a simple XOR. inet6_ehashfn() can also separately use the ports, instead of xoring them. Reported-by: Neal Cardwell <ncardwell@google.com> Signed-off-by: Eric Dumazet <edumazet@google.com> Cc: Yuchung Cheng <ycheng@google.com> Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'net')
1 files changed, 7 insertions, 2 deletions
diff --git a/net/ipv4/af_inet.c b/net/ipv4/af_inet.c
index e225a4e5b57..9cbcb94a4c6 100644
--- a/net/ipv4/af_inet.c
+++ b/net/ipv4/af_inet.c
@@ -248,8 +248,12 @@ EXPORT_SYMBOL(inet_listen);
u32 inet_ehash_secret __read_mostly;
+u32 ipv6_hash_secret __read_mostly;
- * inet_ehash_secret must be set exactly once
+ * inet_ehash_secret must be set exactly once, and to a non nul value
+ * ipv6_hash_secret must be set exactly once.
void build_ehash_secret(void)
@@ -259,7 +263,8 @@ void build_ehash_secret(void)
get_random_bytes(&rnd, sizeof(rnd));
} while (rnd == 0);
- cmpxchg(&inet_ehash_secret, 0, rnd);
+ if (cmpxchg(&inet_ehash_secret, 0, rnd) == 0)
+ get_random_bytes(&ipv6_hash_secret, sizeof(ipv6_hash_secret));