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.
-vlad
>
> Thanks,
> Hannes
>
>
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