On 10/20/2015 10:38 AM, Hannes Frederic Sowa wrote:
> MSG_MORE might cause the packet to get fragmented in the end when
> passed down to the flush function and the transhdrlen check alone is
> not sufficient to protect against fragmentation. Instead check if the
> socket user intends to add more data to the socket on the first packet.
>
> This broke checksum calculation for UDPv6 for NFS protocols.
>
> Fixes: 32dce968dd987 ("ipv6: Allow for partial checksums on non-ufo packets")
> Cc: Vlad Yasevich <vyasev...@gmail.com>
> Tested-by: Sabrina Dubroca <s...@quesysnail.net>
> Tested-by: Benjamin Coddington <bcodd...@redhat.com>
> Signed-off-by: Hannes Frederic Sowa <han...@stressinduktion.org>
> ---
> net/ipv6/ip6_output.c | 1 +
> 1 file changed, 1 insertion(+)
>
> diff --git a/net/ipv6/ip6_output.c b/net/ipv6/ip6_output.c
> index 61d403e..95c5780 100644
> --- a/net/ipv6/ip6_output.c
> +++ b/net/ipv6/ip6_output.c
> @@ -1317,6 +1317,7 @@ emsgsize:
> * sums only work when transhdrlen is set.
> */
> if (transhdrlen && sk->sk_protocol == IPPROTO_UDP &&
> + !(flags & MSG_MORE) &&
> length + fragheaderlen < mtu &&
> rt->dst.dev->features & NETIF_F_V6_CSUM &&
> !exthdrlen)
>
Hmm... so while this solves this problem by simply avoiding the combination of
skb #1 having CHECKSUM_PARTIAL and others having CHECKSUM_NONE, I think the
actual
problem is a bit deeper.
The above combination seems to work for me since udp6_hwcsum_outgoing() corrects
the checksum. However, my testing so far has been on nics that have
NETIF_F_V6_CSUM,
but without UFO support.
On such systems a simple test of using MSG_MORE an IPv6 udp socket sending 200
bytes
followed by 2000 bytes works correctly.
I am now wondering if this might be UFO related instead and looking for a nic
that
has UFO support.
-vlad
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