From 424848bd9895979e2758156ca99e317a3c2d5804 Mon Sep 17 00:00:00 2001 From: "David S. Miller" Date: Fri, 1 Jul 2016 16:07:50 -0400 Subject: packet: Use symmetric hash for PACKET_FANOUT_HASH. [ Upstream commit eb70db8756717b90c01ccc765fdefc4dd969fc74 ] People who use PACKET_FANOUT_HASH want a symmetric hash, meaning that they want packets going in both directions on a flow to hash to the same bucket. The core kernel SKB hash became non-symmetric when the ipv6 flow label and other entities were incorporated into the standard flow hash order to increase entropy. But there are no users of PACKET_FANOUT_HASH who want an assymetric hash, they all want a symmetric one. Therefore, use the flow dissector to compute a flat symmetric hash over only the protocol, addresses and ports. This hash does not get installed into and override the normal skb hash, so this change has no effect whatsoever on the rest of the stack. Reported-by: Eric Leblond Tested-by: Eric Leblond Signed-off-by: David S. Miller Signed-off-by: Greg Kroah-Hartman --- net/core/flow_dissector.c | 43 +++++++++++++++++++++++++++++++++++++++++++ net/packet/af_packet.c | 2 +- 2 files changed, 44 insertions(+), 1 deletion(-) (limited to 'net') diff --git a/net/core/flow_dissector.c b/net/core/flow_dissector.c index 12e700332010..4ab6ead3d8ee 100644 --- a/net/core/flow_dissector.c +++ b/net/core/flow_dissector.c @@ -662,6 +662,23 @@ void make_flow_keys_digest(struct flow_keys_digest *digest, } EXPORT_SYMBOL(make_flow_keys_digest); +static struct flow_dissector flow_keys_dissector_symmetric __read_mostly; + +u32 __skb_get_hash_symmetric(struct sk_buff *skb) +{ + struct flow_keys keys; + + __flow_hash_secret_init(); + + memset(&keys, 0, sizeof(keys)); + __skb_flow_dissect(skb, &flow_keys_dissector_symmetric, &keys, + NULL, 0, 0, 0, + FLOW_DISSECTOR_F_STOP_AT_FLOW_LABEL); + + return __flow_hash_from_keys(&keys, hashrnd); +} +EXPORT_SYMBOL_GPL(__skb_get_hash_symmetric); + /** * __skb_get_hash: calculate a flow hash * @skb: sk_buff to calculate flow hash from @@ -874,6 +891,29 @@ static const struct flow_dissector_key flow_keys_dissector_keys[] = { }, }; +static const struct flow_dissector_key flow_keys_dissector_symmetric_keys[] = { + { + .key_id = FLOW_DISSECTOR_KEY_CONTROL, + .offset = offsetof(struct flow_keys, control), + }, + { + .key_id = FLOW_DISSECTOR_KEY_BASIC, + .offset = offsetof(struct flow_keys, basic), + }, + { + .key_id = FLOW_DISSECTOR_KEY_IPV4_ADDRS, + .offset = offsetof(struct flow_keys, addrs.v4addrs), + }, + { + .key_id = FLOW_DISSECTOR_KEY_IPV6_ADDRS, + .offset = offsetof(struct flow_keys, addrs.v6addrs), + }, + { + .key_id = FLOW_DISSECTOR_KEY_PORTS, + .offset = offsetof(struct flow_keys, ports), + }, +}; + static const struct flow_dissector_key flow_keys_buf_dissector_keys[] = { { .key_id = FLOW_DISSECTOR_KEY_CONTROL, @@ -895,6 +935,9 @@ static int __init init_default_flow_dissectors(void) skb_flow_dissector_init(&flow_keys_dissector, flow_keys_dissector_keys, ARRAY_SIZE(flow_keys_dissector_keys)); + skb_flow_dissector_init(&flow_keys_dissector_symmetric, + flow_keys_dissector_symmetric_keys, + ARRAY_SIZE(flow_keys_dissector_symmetric_keys)); skb_flow_dissector_init(&flow_keys_buf_dissector, flow_keys_buf_dissector_keys, ARRAY_SIZE(flow_keys_buf_dissector_keys)); diff --git a/net/packet/af_packet.c b/net/packet/af_packet.c index 9cc7b512b472..a86f26d05bc2 100644 --- a/net/packet/af_packet.c +++ b/net/packet/af_packet.c @@ -1341,7 +1341,7 @@ static unsigned int fanout_demux_hash(struct packet_fanout *f, struct sk_buff *skb, unsigned int num) { - return reciprocal_scale(skb_get_hash(skb), num); + return reciprocal_scale(__skb_get_hash_symmetric(skb), num); } static unsigned int fanout_demux_lb(struct packet_fanout *f, -- cgit v1.2.3