netdev - [PATCH net 1/2] udp: Copy has_conns in reuseport

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Date:   Tue, 21 Jul 2020 15:15:30 +0900
From:   Kuniyuki Iwashima <kuniyu@...zon.co.jp>
To:     "David S . Miller" <davem@...emloft.net>,
        Alexey Kuznetsov <kuznet@....inr.ac.ru>,
        Hideaki YOSHIFUJI <yoshfuji@...ux-ipv6.org>,
        "Jakub Kicinski" <kuba@...nel.org>
CC:     Willem de Bruijn <willemb@...gle.com>,
        Eric Dumazet <edumazet@...gle.com>,
        Craig Gallek <kraig@...gle.com>,
        Paolo Abeni <pabeni@...hat.com>, <netdev@...r.kernel.org>,
        Kuniyuki Iwashima <kuniyu@...zon.co.jp>,
        "Kuniyuki Iwashima" <kuni1840@...il.com>,
        Benjamin Herrenschmidt <benh@...zon.com>,
        <osa-contribution-log@...zon.com>
Subject: [PATCH net 1/2] udp: Copy has_conns in reuseport_grow().

If an unconnected socket in a UDP reuseport group connect()s, has_conns is
set to 1. Then, when a packet is received, udp[46]_lib_lookup2() scans all
sockets in udp_hslot looking for the connected socket with the highest
score.

However, when the number of sockets bound to the port exceeds max_socks,
reuseport_grow() resets has_conns to 0. It can cause udp[46]_lib_lookup2()
to return without scanning all sockets, resulting in that packets sent to
connected sockets may be distributed to unconnected sockets.

Therefore, reuseport_grow() should copy has_conns.

Fixes: acdcecc61285 ("udp: correct reuseport selection with connected sockets")
CC: Willem de Bruijn <willemb@...gle.com>
Reviewed-by: Benjamin Herrenschmidt <benh@...zon.com>
Signed-off-by: Kuniyuki Iwashima <kuniyu@...zon.co.jp>
---
 net/core/sock_reuseport.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/net/core/sock_reuseport.c b/net/core/sock_reuseport.c
index adcb3aea576d..bbdd3c7b6cb5 100644
--- a/net/core/sock_reuseport.c
+++ b/net/core/sock_reuseport.c
@@ -101,6 +101,7 @@ static struct sock_reuseport *reuseport_grow(struct sock_reuseport *reuse)
 	more_reuse->prog = reuse->prog;
 	more_reuse->reuseport_id = reuse->reuseport_id;
 	more_reuse->bind_inany = reuse->bind_inany;
+	more_reuse->has_conns = reuse->has_conns;
 
 	memcpy(more_reuse->socks, reuse->socks,
 	       reuse->num_socks * sizeof(struct sock *));
-- 
2.17.2 (Apple Git-113)