From: "James Harper" <james.harper@bendigoit.com.au>
To: Ian Campbell <Ian.Campbell@citrix.com>,
Jan Beulich <JBeulich@novell.com>
Cc: Jeremy Fitzhardinge <jeremy@goop.org>, xen-devel@lists.xensource.com
Subject: RE: [PATCH 4/6] xen/netback: Always pull throughPKT_PROT_LEN bytes into the linear part of an skb.
Date: Wed, 24 Feb 2010 20:23:12 +1100 [thread overview]
Message-ID: <AEC6C66638C05B468B556EA548C1A77D01899565@trantor> (raw)
In-Reply-To: <1267001738.24360.283.camel@localhost.localdomain>
>
> On Wed, 2010-02-24 at 08:28 +0000, Jan Beulich wrote:
> > Could you point out what problem this addresses?
>
> It ensures that at least the TCP/IP headers will be pulled into the
> linear part of the SKB. At least skb_checksum_setup relies on this and
I
> think it is a more generic assumption in at least some parts of the
> network stack as well. The next patch increases PKT_PROT_LEN to
include
> the TCP options as well since we have observed cases where Windows
> guests with PV drivers can generate a frame with a split at the point.
>
My PV drivers couldn't always be relied on to do this, because Windows
couldn't be relied on to do it either. I just coalesced the first buffer
to some minimum value depending on the header type. If you are doing TCP
checksum offload then you have to tell Windows that you support IP
checksum offload too - Linux doesn't support that so you have to lie to
Windows about it and calculate the IP checksum in the PV drivers, and if
you are doing that you have to have your own copy of the header anyway
so it turns out not to be a big deal.
James
next prev parent reply other threads:[~2010-02-24 9:23 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2010-02-23 16:46 [GIT] netback fixes from XCP kernel tree Ian Campbell
2010-02-23 16:47 ` [PATCH 1/6] xen: netback: remove unused xen_network_done code Ian Campbell
2010-02-23 16:47 ` [PATCH 2/6] xen: netback: factor disconnect from backend into new function Ian Campbell
2010-02-23 16:47 ` [PATCH 3/6] xen: netback: wait for hotplug scripts to complete before signalling connected to frontend Ian Campbell
2010-02-23 16:47 ` [PATCH 4/6] xen/netback: Always pull through PKT_PROT_LEN bytes into the linear part of an skb Ian Campbell
2010-02-24 8:28 ` Jan Beulich
2010-02-24 8:55 ` Ian Campbell
2010-02-24 9:23 ` James Harper [this message]
2010-02-24 9:56 ` [PATCH 4/6] xen/netback: Always pull throughPKT_PROT_LEN " Ian Campbell
2010-02-23 16:47 ` [PATCH 5/6] xen/netback: try to pull a minimum of 72 bytes into the skb data area Ian Campbell
2010-02-23 17:04 ` Ian Campbell
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