On Di, 2015-01-27 at 09:26 -0500, Vlad Yasevich wrote:
> On 01/27/2015 08:47 AM, Hannes Frederic Sowa wrote:
> > On Di, 2015-01-27 at 10:42 +0200, Michael S. Tsirkin wrote:
> >> On Tue, Jan 27, 2015 at 02:47:54AM +0000, Ben Hutchings wrote:
> >>> On Mon, 2015-01-26 at 09:37 -0500, Vladislav Yasevich wrote:
> >>>> If the IPv6 fragment id has not been set and we perform
> >>>> fragmentation due to UFO, select a new fragment id.
> >>>> When we store the fragment id into skb_shinfo, set the bit
> >>>> in the skb so we can re-use the selected id.
> >>>> This preserves the behavior of UFO packets generated on the
> >>>> host and solves the issue of id generation for packet sockets
> >>>> and tap/macvtap devices.
> >>>>
> >>>> This patch moves ipv6_select_ident() back in to the header file.
> >>>> It also provides the helper function that sets skb_shinfo() frag
> >>>> id and sets the bit.
> >>>>
> >>>> It also makes sure that we select the fragment id when doing
> >>>> just gso validation, since it's possible for the packet to
> >>>> come from an untrusted source (VM) and be forwarded through
> >>>> a UFO enabled device which will expect the fragment id.
> >>>>
> >>>> CC: Eric Dumazet <edumazet@xxxxxxxxxx>
> >>>> Signed-off-by: Vladislav Yasevich <vyasevic@xxxxxxxxxx>
> >>>> ---
> >>>> include/linux/skbuff.h | 3 ++-
> >>>> include/net/ipv6.h | 2 ++
> >>>> net/ipv6/ip6_output.c | 4 ++--
> >>>> net/ipv6/output_core.c | 9 ++++++++-
> >>>> net/ipv6/udp_offload.c | 10 +++++++++-
> >>>> 5 files changed, 23 insertions(+), 5 deletions(-)
> >>>>
> >>>> diff --git a/include/linux/skbuff.h b/include/linux/skbuff.h
> >>>> index 85ab7d7..3ad5203 100644
> >>>> --- a/include/linux/skbuff.h
> >>>> +++ b/include/linux/skbuff.h
> >>>> @@ -605,7 +605,8 @@ struct sk_buff {
> >>>> __u8 ipvs_property:1;
> >>>> __u8 inner_protocol_type:1;
> >>>> __u8 remcsum_offload:1;
> >>>> - /* 3 or 5 bit hole */
> >>>> + __u8 ufo_fragid_set:1;
> >>> [...]
> >>>
> >>> Doesn't the flag belong in struct skb_shared_info, rather than struct
> >>> sk_buff? Otherwise this looks fine.
> >>>
> >>> Ben.
> >>
> >> Hmm we seem to be out of tx flags.
> >> Maybe ip6_frag_id == 0 should mean "not set".
> >
> > Maybe that is the best idea. Definitely the ufo_fragid_set bit should
> > move into the skb_shared_info area.
>
> That's what I originally wanted to do, but had to move and grow txflags thus
> skb_shinfo ended up growing. I wanted to avoid that, so stole an skb flag.
>
> I considered treating fragid == 0 as unset, but a 0 fragid is perfectly valid
> from the protocol perspective and could actually be generated by the id generator
> functions. This may cause us to call the id generation multiple times.
Are there plans in the long run to let virtio_net transmit auxiliary
data to the other end so we can clean all of this this up one day?
I don't like the whole situation: looking into the virtio_net headers
just adding a field for ipv6 fragmentation ids to those small structs
seems bloated, not doing it feels incorrect. :/
Thoughts?
Bye,
Hannes
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