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Commit 4f2e4ad5 authored by Eric Dumazet's avatar Eric Dumazet Committed by David S. Miller
Browse files

net: mangle zero checksum in skb_checksum_help() 



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: default avatarEric Dumazet <edumazet@google.com>
Cc: Maciej Żenczykowski <maze@google.com>
Cc: Willem de Bruijn <willemb@google.com>
Acked-by: default avatarMaciej Żenczykowski <maze@google.com>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent e551c32d

net/core/dev.c

+1 −1
Original line number Diff line number Diff line
@@ -2484,7 +2484,7 @@ int skb_checksum_help(struct sk_buff *skb) 
			goto out;

	}



	*(__sum16 *)(skb->data + offset) = csum_fold(csum);

	*(__sum16 *)(skb->data + offset) = csum_fold(csum) ?: CSUM_MANGLED_0;

out_set_summed:

	skb->ip_summed = CHECKSUM_NONE;

out: