[PATCH 5.4 05/11] tcp: use different parts of the port_offset for index and offset

From: Greg Kroah-Hartman
Date: Thu Jun 23 2022 - 14:23:55 EST


From: Willy Tarreau <w@xxxxxx>

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 <Jason@xxxxxxxxx>
Cc: Moshe Kol <moshe.kol@xxxxxxxxxxxxxxx>
Cc: Yossi Gilad <yossi.gilad@xxxxxxxxxxxxxxx>
Cc: Amit Klein <aksecurity@xxxxxxxxx>
Reviewed-by: Eric Dumazet <edumazet@xxxxxxxxxx>
Signed-off-by: Willy Tarreau <w@xxxxxx>
Signed-off-by: Jakub Kicinski <kuba@xxxxxxxxxx>
Cc: Ben Hutchings <ben@xxxxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
net/ipv4/inet_hashtables.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

--- a/net/ipv4/inet_hashtables.c
+++ b/net/ipv4/inet_hashtables.c
@@ -726,7 +726,7 @@ int __inet_hash_connect(struct inet_time
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.