From mboxrd@z Thu Jan 1 00:00:00 1970 From: "Michael S. Tsirkin" Subject: Re: [PATCH 1/3] ipv6: Select fragment id during UFO/GSO segmentation if not set. Date: Tue, 27 Jan 2015 18:08:08 +0200 Message-ID: <20150127160808.GA10765@redhat.com> References: <1422283026-27832-1-git-send-email-vyasevic@redhat.com> <1422283026-27832-2-git-send-email-vyasevic@redhat.com> <1422326874.31046.239.camel@decadent.org.uk> <20150127084208.GB21584@redhat.com> <1422366458.13969.11.camel@stressinduktion.org> <54C7A007.6050707@redhat.com> <1422374551.13969.35.camel@stressinduktion.org> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Cc: netdev@vger.kernel.org, Vladislav Yasevich , virtualization@lists.linux-foundation.org, edumazet@google.com, Ben Hutchings To: Hannes Frederic Sowa Return-path: Content-Disposition: inline In-Reply-To: <1422374551.13969.35.camel@stressinduktion.org> List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: virtualization-bounces@lists.linux-foundation.org Errors-To: virtualization-bounces@lists.linux-foundation.org List-Id: netdev.vger.kernel.org On Tue, Jan 27, 2015 at 05:02:31PM +0100, Hannes Frederic Sowa wrote: > 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 > > >>>> Signed-off-by: Vladislav Yasevich > > >>>> --- > > >>>> 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 I'm not sure - what will be achieved by generating the IDs guest side as opposed to host side? It's certainly harder to get hold of entropy guest-side. -- MST