Re: [PATCH] tcp: splice as many packets as possible at once

From: David Miller
Date: Mon Jan 19 2009 - 15:59:54 EST

From: Herbert Xu <herbert@xxxxxxxxxxxxxxxxxxx>
Date: Mon, 19 Jan 2009 21:19:24 +1100

> On Sun, Jan 18, 2009 at 10:19:08PM -0800, David Miller wrote:
> >
> > Actually, I see, the myri10ge driver does put up to
> > 64 bytes of the initial packet into the linear area.
> > If the IPV4 + TCP headers are less than this, you will
> > hit the corruption case even with the myri10ge driver.
> I thought splice only mapped the payload areas, no?

And the difference between 64 and IPV4+TCP header len becomes the
payload, don't you see? :-)

myri10ge just pulls min(64, skb->len) bytes from the SKB frags into
the linear area, unconditionally. So a small number of payload bytes
can in fact end up there.

Otherwise Willy could never have triggered this bug.
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