[PATCH] net: let flow have same hash in two directions

[PATCH] net: let flow have same hash in two directions

[zhang kai]

using same source and destination ip/port for flow hash calculation
within the two directions.

Signed-off-by: zhang kai <zhangkaiheb@126.com>
---
 net/core/flow_dissector.c | 18 +++++++++---------
 1 file changed, 9 insertions(+), 9 deletions(-)

diff --git a/net/core/flow_dissector.c b/net/core/flow_dissector.c
index 3ed7c98a9..dfc18f212 100644
--- a/net/core/flow_dissector.c
+++ b/net/core/flow_dissector.c
@@ -1504,7 +1504,7 @@ __be32 flow_get_u32_dst(const struct flow_keys *flow)
 }
 EXPORT_SYMBOL(flow_get_u32_dst);
 
-/* Sort the source and destination IP (and the ports if the IP are the same),
+/* Sort the source and destination IP and the ports,
  * to have consistent hash within the two directions
  */
 static inline void __flow_hash_consistentify(struct flow_keys *keys)
@@ -1515,11 +1515,11 @@ static inline void __flow_hash_consistentify(struct flow_keys *keys)
 	case FLOW_DISSECTOR_KEY_IPV4_ADDRS:
 		addr_diff = (__force u32)keys->addrs.v4addrs.dst -
 			    (__force u32)keys->addrs.v4addrs.src;
-		if ((addr_diff < 0) ||
-		    (addr_diff == 0 &&
-		     ((__force u16)keys->ports.dst <
-		      (__force u16)keys->ports.src))) {
+		if (addr_diff < 0)
 			swap(keys->addrs.v4addrs.src, keys->addrs.v4addrs.dst);
+
+		if ((__force u16)keys->ports.dst <
+		    (__force u16)keys->ports.src) {
 			swap(keys->ports.src, keys->ports.dst);
 		}
 		break;
@@ -1527,13 +1527,13 @@ static inline void __flow_hash_consistentify(struct flow_keys *keys)
 		addr_diff = memcmp(&keys->addrs.v6addrs.dst,
 				   &keys->addrs.v6addrs.src,
 				   sizeof(keys->addrs.v6addrs.dst));
-		if ((addr_diff < 0) ||
-		    (addr_diff == 0 &&
-		     ((__force u16)keys->ports.dst <
-		      (__force u16)keys->ports.src))) {
+		if (addr_diff < 0) {
 			for (i = 0; i < 4; i++)
 				swap(keys->addrs.v6addrs.src.s6_addr32[i],
 				     keys->addrs.v6addrs.dst.s6_addr32[i]);
+		}
+		if ((__force u16)keys->ports.dst <
+		    (__force u16)keys->ports.src) {
 			swap(keys->ports.src, keys->ports.dst);
 		}
 		break;
-- 
2.17.1

Re: [PATCH] net: let flow have same hash in two directions

[patchwork-bot+netdevbpf]

Hello:

This patch was applied to netdev/net.git (refs/heads/master):

On Wed, 28 Jul 2021 18:54:18 +0800 you wrote:
> using same source and destination ip/port for flow hash calculation
> within the two directions.
> 
> Signed-off-by: zhang kai <zhangkaiheb@126.com>
> ---
>  net/core/flow_dissector.c | 18 +++++++++---------
>  1 file changed, 9 insertions(+), 9 deletions(-)

Here is the summary with links:
  - net: let flow have same hash in two directions
    https://git.kernel.org/netdev/net/c/1e60cebf8294

You are awesome, thank you!
--
Deet-doot-dot, I am a bot.
https://korg.docs.kernel.org/patchwork/pwbot.html

Re: [PATCH] net: let flow have same hash in two directions

[Jakub Kicinski]

On Wed, 28 Jul 2021 18:54:18 +0800 zhang kai wrote:
> using same source and destination ip/port for flow hash calculation
> within the two directions.

Did you observe the hash being different, or just found this by code
inspection? AFAICT the existing code was fine, and probably slightly
faster.