Subject: [3/7] tcp: use different parts of the port_offset for index and offset

From: Willy Tarreau <[email-masked]>
Date: Mon, 2 May 2022 10:46:09 +0200

commit 9e9b70ae923baf2b5e8a0ea4fd0c8451801ac526 upstream.

Amit Klein suggests that we use different parts of port_offset for the
table's index and the port offset so that there is no direct relation
between them.

Cc: Jason A. Donenfeld <[email-masked]>
Cc: Moshe Kol <[email-masked]>
Cc: Yossi Gilad <[email-masked]>
Cc: Amit Klein <[email-masked]>
Reviewed-by: Eric Dumazet <[email-masked]>
Signed-off-by: Willy Tarreau <[email-masked]>
Signed-off-by: Jakub Kicinski <[email-masked]>
Signed-off-by: Ben Hutchings <[email-masked]>
---
 net/ipv4/inet_hashtables.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/net/ipv4/inet_hashtables.c b/net/ipv4/inet_hashtables.c
index 455a0a1aae38..8ac51e18d3d8 100644
--- a/net/ipv4/inet_hashtables.c
+++ b/net/ipv4/inet_hashtables.c
@@ -639,7 +639,7 @@ int __inet_hash_connect(struct inet_timewait_death_row *death_row,
 	net_get_random_once(table_perturb, sizeof(table_perturb));
 	index = hash_32(port_offset, INET_TABLE_PERTURB_SHIFT);
 
-	offset = READ_ONCE(table_perturb[index]) + port_offset;
+	offset = READ_ONCE(table_perturb[index]) + (port_offset >> 32);
 	offset %= remaining;
 
 	/* In first pass we try ports of @low parity.