From a54d9c3083a8cc8f02ce0b1427ceaa8171b37d8d Mon Sep 17 00:00:00 2001 From: Willy Tarreau Date: Wed, 26 Oct 2022 18:10:56 +0800 Subject: [PATCH] tcp: drop the hash_32() part from the index calculation stable inclusion from stable-v5.10.125 commit 7ccb026ecb997405b59d391140c25ee347891504 category: bugfix bugzilla: https://gitee.com/openeuler/kernel/issues/I5L6EY Reference: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=7ccb026ecb997405b59d391140c25ee347891504 -------------------------------- commit e8161345ddbb66e449abde10d2fdce93f867eba9 upstream. In commit 190cc82489f4 ("tcp: change source port randomizarion at connect() time"), the table_perturb[] array was introduced and an index was taken from the port_offset via hash_32(). But it turns out that hash_32() performs a multiplication while the input here comes from the output of SipHash in secure_seq, that is well distributed enough to avoid the need for yet another hash. Suggested-by: Amit Klein Reviewed-by: Eric Dumazet Signed-off-by: Willy Tarreau Signed-off-by: Jakub Kicinski Cc: Ben Hutchings Signed-off-by: Greg Kroah-Hartman Signed-off-by: Zheng Zengkai Reviewed-by: Wei Li --- 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 72716d1a06e4..31b4196ea7e1 100644 --- a/net/ipv4/inet_hashtables.c +++ b/net/ipv4/inet_hashtables.c @@ -778,7 +778,7 @@ int __inet_hash_connect(struct inet_timewait_death_row *death_row, net_get_random_once(table_perturb, INET_TABLE_PERTURB_SIZE * sizeof(*table_perturb)); - index = hash_32(port_offset, INET_TABLE_PERTURB_SHIFT); + index = port_offset & (INET_TABLE_PERTURB_SIZE - 1); offset = READ_ONCE(table_perturb[index]) + (port_offset >> 32); offset %= remaining; -- GitLab