net: mangle zero checksum in skb_checksum_help()
authorEric Dumazet <edumazet@google.com>
Sat, 29 Oct 2016 18:02:36 +0000 (11:02 -0700)
committerBen Hutchings <ben@decadent.org.uk>
Thu, 16 Mar 2017 02:18:53 +0000 (02:18 +0000)
commitf8c5af060edec5c5d8277b162a49cd53c780b247
tree213f2b84d5ade41f4513da76a58d6155150377fa
parent5a479261c906d2ddfdcbddaa2a1d97e7578d4241
net: mangle zero checksum in skb_checksum_help()

[ Upstream commit 4f2e4ad56a65f3b7d64c258e373cb71e8d2499f4 ]

Sending zero checksum is ok for TCP, but not for UDP.

UDPv6 receiver should by default drop a frame with a 0 checksum,
and UDPv4 would not verify the checksum and might accept a corrupted
packet.

Simply replace such checksum by 0xffff, regardless of transport.

This error was caught on SIT tunnels, but seems generic.

Signed-off-by: Eric Dumazet <edumazet@google.com>
Cc: Maciej ┼╗enczykowski <maze@google.com>
Cc: Willem de Bruijn <willemb@google.com>
Acked-by: Maciej ┼╗enczykowski <maze@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
net/core/dev.c