udp checksum issue in netpoll mode.

udp checksum issue in netpoll mode.

[Aubrey Li]

I think we discussed this issue before.

The current checksum function doesn't consider the kind of packet
which is padded to reach a specific minimum length. I believe that's
the problem caused my test case failed. Is this issue fixed? Or is it
acceptable if I make a patch not calculating this kind of packet?

Thanks,
-Aubrey
===============================================
static __sum16 checksum_udp(struct sk_buff *skb, struct udphdr *uh,
                            unsigned short ulen, __be32 saddr, __be32 daddr)
{
        __wsum psum;

        if (uh->check == 0 || skb->ip_summed == CHECKSUM_UNNECESSARY)
                return 0;

        psum = csum_tcpudp_nofold(saddr, daddr, ulen, IPPROTO_UDP, 0);
        if (skb->ip_summed == CHECKSUM_COMPLETE &&
            !csum_fold(csum_add(psum, skb->csum)))
                return 0;

        skb->csum = psum;

        return __skb_checksum_complete(skb);
}
===============================================

Re: udp checksum issue in netpoll mode.

[Stephen Hemminger]

Aubrey Li wrote:
> I think we discussed this issue before.
>
> The current checksum function doesn't consider the kind of packet
> which is padded to reach a specific minimum length. I believe that's
> the problem caused my test case failed. Is this issue fixed? Or is it
> acceptable if I make a patch not calculating this kind of packet?
>
> Thanks,
> -Aubrey
The caller should be trimming the packet and updating the hardware checksum
value (like the normal UDP path).

Re: udp checksum issue in netpoll mode.

[Aubrey Li]

On 4/12/07, Stephen Hemminger <shemminger@linux-foundation.org> wrote:
> Aubrey Li wrote:
> > I think we discussed this issue before.
> >
> > The current checksum function doesn't consider the kind of packet
> > which is padded to reach a specific minimum length. I believe that's
> > the problem caused my test case failed. Is this issue fixed? Or is it
> > acceptable if I make a patch not calculating this kind of packet?
> >
> > Thanks,
> > -Aubrey
> The caller should be trimming the packet and updating the hardware checksum
> value (like the normal UDP path).
>
OK, the following patch fixed the problem.

Signed-off-by: Aubrey.Li <aubreylee@gmail.com>
---
 net/core/netpoll.c |    7 +++++++
 1 files changed, 7 insertions(+), 0 deletions(-)

diff --git a/net/core/netpoll.c b/net/core/netpoll.c
index 823215d..522e441 100644
--- a/net/core/netpoll.c
+++ b/net/core/netpoll.c
@@ -471,6 +471,13 @@ int __netpoll_rx(struct sk_buff *skb)
 	if (skb->len < len || len < iph->ihl*4)
 		goto out;

+	/*
+	 * Our transport medium may have padded the buffer out.
+	 * Now We trim to the true length of the frame.
+	 */
+	if (pskb_trim_rcsum(skb, len))
+		goto out;
+
 	if (iph->protocol != IPPROTO_UDP)
 		goto out;

-- 
1.5.1