Instead of only using the 32 low order bits of the local address, use all of them. Xor net_hash_mix(net) with the 32 high order bits of the local address so that we can use __jhash_mix() three times. If we were hashing 4 extra bytes, we would need one __jhash_final() which is a bit expensive. Using net_hash_mix() at the beginning allows beter register allocation. We no longer use a cascade of two jhash and inet6_ehash_secret, this was dubious/weak. $ scripts/bloat-o-meter -t vmlinux.0 vmlinux add/remove: 0/0 grow/shrink: 0/1 up/down: 0/-27 (-27) Function old new delta inet6_ehashfn 330 303 -27 Total: Before=24855320, After=24855293, chg -0.00% Signed-off-by: Eric Dumazet --- net/ipv6/inet6_hashtables.c | 34 +++++++++++++++++++++++++++++----- 1 file changed, 29 insertions(+), 5 deletions(-) diff --git a/net/ipv6/inet6_hashtables.c b/net/ipv6/inet6_hashtables.c index 72bc68fef48abc2c423c688b47154256828555e4..bf3c9bbb2107c05f18ca296cfb7a54d2d0ed558a 100644 --- a/net/ipv6/inet6_hashtables.c +++ b/net/ipv6/inet6_hashtables.c @@ -35,13 +35,37 @@ u32 inet6_ehashfn(const struct net *net, const struct in6_addr *laddr, const u16 lport, const struct in6_addr *faddr, const __be16 fport) { - u32 lhash, fhash; + u32 a, b, c; + + /* + * Please look at jhash() implementation for reference. + * Hash laddr + faddr + lport/fport + net_hash_mix. + * Notes: + * We combine laddr[0] (high order 32 bits of local address) + * with net_hash_mix() to avoid using __jhash_final(a, b, c). + * + * We do not include JHASH_INITVAL + 36 contribution + * to initial values of a, b, c. + */ + + a = b = c = tcp_ipv6_hash_secret; + + a += (__force u32)laddr->s6_addr32[0] ^ net_hash_mix(net); + b += (__force u32)laddr->s6_addr32[1]; + c += (__force u32)laddr->s6_addr32[2]; + __jhash_mix(a, b, c); + + a += (__force u32)laddr->s6_addr32[3]; + b += (__force u32)faddr->s6_addr32[0]; + c += (__force u32)faddr->s6_addr32[1]; + __jhash_mix(a, b, c); - lhash = (__force u32)laddr->s6_addr32[3]; - fhash = __ipv6_addr_jhash(faddr, tcp_ipv6_hash_secret); + a += (__force u32)faddr->s6_addr32[2]; + b += (__force u32)faddr->s6_addr32[3]; + c += ((u32)lport << 16) + (__force u32)fport; + __jhash_mix(a, b, c); - return lport + __inet6_ehashfn(lhash, 0, fhash, fport, - inet6_ehash_secret + net_hash_mix(net)); + return c; } EXPORT_SYMBOL_GPL(inet6_ehashfn); -- 2.53.0.473.g4a7958ca14-goog