netdev - [PATCH] net: l2tp: fix reversed udp6 checksum flags

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Message-Id: <9A325D67-FED1-4AF6-8ED0-6C93FFE8DC67@gmail.com>
Date:	Fri, 29 Apr 2016 01:29:43 +0800
From:	Wang Shanker <shankerwangmiao@...il.com>
To:	netdev@...r.kernel.org
Cc:	James Chapman <jchapman@...alix.com>,
	Tom Herbert <therbert@...gle.com>,
	"David S. Miller" <davem@...emloft.net>
Subject: [PATCH] net: l2tp: fix reversed udp6 checksum flags

This patch fixes a bug which causes the behavior of whether to ignore
udp6 checksum of udp6 encapsulated l2tp tunnel contrary to what
userspace program requests.

When the flag `L2TP_ATTR_UDP_ZERO_CSUM6_RX` is set by userspace, it is
expected that udp6 checksums of received packets of the l2tp tunnel
to create should be ignored. In `l2tp_netlink.c`:
`l2tp_nl_cmd_tunnel_create()`, `cfg.udp6_zero_rx_checksums` is set
according to the flag, and then passed to `l2tp_core.c`:
`l2tp_tunnel_create()` and then `l2tp_tunnel_sock_create()`. In
`l2tp_tunnel_sock_create()`, `udp_conf.use_udp6_rx_checksums` is set
the same to `cfg.udp6_zero_rx_checksums`. However, if we want the
checksum to be ignored, `udp_conf.use_udp6_rx_checksums` should be set
to `false`, i.e. be set to the contrary. Similarly, the same should be
done to `udp_conf.use_udp6_tx_checksums`.

Signed-off-by: Miao Wang <shankerwangmiao@...il.com>
---
 net/l2tp/l2tp_core.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/net/l2tp/l2tp_core.c b/net/l2tp/l2tp_core.c
index afca2eb..6edfa99 100644
--- a/net/l2tp/l2tp_core.c
+++ b/net/l2tp/l2tp_core.c
@@ -1376,9 +1376,9 @@ static int l2tp_tunnel_sock_create(struct net *net,
 			memcpy(&udp_conf.peer_ip6, cfg->peer_ip6,
 			       sizeof(udp_conf.peer_ip6));
 			udp_conf.use_udp6_tx_checksums =
-			    cfg->udp6_zero_tx_checksums;
+			  ! cfg->udp6_zero_tx_checksums;
 			udp_conf.use_udp6_rx_checksums =
-			    cfg->udp6_zero_rx_checksums;
+			  ! cfg->udp6_zero_rx_checksums;
 		} else
 #endif
 		{
-- 
2.5.2

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