Messages in this thread | | | From | Vlad Buslov <> | Subject | Re: [PATCH net-next v2] net: openvswitch: fix uAPI incompatibility with existing user space | Date | Thu, 12 May 2022 13:08:14 +0300 |
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On Thu 12 May 2022 at 12:19, Eelco Chaudron <echaudro@redhat.com> wrote: > On 7 Apr 2022, at 12:22, Ilya Maximets wrote: > >> On 4/7/22 10:02, Vlad Buslov wrote: >>> On Mon 14 Mar 2022 at 20:40, Ilya Maximets <i.maximets@ovn.org> wrote: >>>> On 3/14/22 19:33, Roi Dayan wrote: >>>>> >>>>> >>>>> On 2022-03-10 8:44 PM, Aaron Conole wrote: >>>>>> Ilya Maximets <i.maximets@ovn.org> writes: >>>>>> >>>>>>> Few years ago OVS user space made a strange choice in the commit [1] >>>>>>> to define types only valid for the user space inside the copy of a >>>>>>> kernel uAPI header. '#ifndef __KERNEL__' and another attribute was >>>>>>> added later. >>>>>>> >>>>>>> This leads to the inevitable clash between user space and kernel types >>>>>>> when the kernel uAPI is extended. The issue was unveiled with the >>>>>>> addition of a new type for IPv6 extension header in kernel uAPI. >>>>>>> >>>>>>> When kernel provides the OVS_KEY_ATTR_IPV6_EXTHDRS attribute to the >>>>>>> older user space application, application tries to parse it as >>>>>>> OVS_KEY_ATTR_PACKET_TYPE and discards the whole netlink message as >>>>>>> malformed. Since OVS_KEY_ATTR_IPV6_EXTHDRS is supplied along with >>>>>>> every IPv6 packet that goes to the user space, IPv6 support is fully >>>>>>> broken. >>>>>>> >>>>>>> Fixing that by bringing these user space attributes to the kernel >>>>>>> uAPI to avoid the clash. Strictly speaking this is not the problem >>>>>>> of the kernel uAPI, but changing it is the only way to avoid breakage >>>>>>> of the older user space applications at this point. >>>>>>> >>>>>>> These 2 types are explicitly rejected now since they should not be >>>>>>> passed to the kernel. Additionally, OVS_KEY_ATTR_TUNNEL_INFO moved >>>>>>> out from the '#ifdef __KERNEL__' as there is no good reason to hide >>>>>>> it from the userspace. And it's also explicitly rejected now, because >>>>>>> it's for in-kernel use only. >>>>>>> >>>>>>> Comments with warnings were added to avoid the problem coming back. >>>>>>> >>>>>>> (1 << type) converted to (1ULL << type) to avoid integer overflow on >>>>>>> OVS_KEY_ATTR_IPV6_EXTHDRS, since it equals 32 now. >>>>>>> >>>>>>> [1] beb75a40fdc2 ("userspace: Switching of L3 packets in L2 pipeline") >>>>>>> >>>>>>> Fixes: 28a3f0601727 ("net: openvswitch: IPv6: Add IPv6 extension header support") >>>>>>> Link: https://lore.kernel.org/netdev/3adf00c7-fe65-3ef4-b6d7-6d8a0cad8a5f@nvidia.com >>>>>>> Link: https://github.com/openvswitch/ovs/commit/beb75a40fdc295bfd6521b0068b4cd12f6de507c >>>>>>> Reported-by: Roi Dayan <roid@nvidia.com> >>>>>>> Signed-off-by: Ilya Maximets <i.maximets@ovn.org> >>>>>>> --- >>>>>> >>>>>> Acked-by: Aaron Conole <aconole@redhat.com> >>>>>> >>>>> >>>>> >>>>> >>>>> I got to check traffic with the fix and I do get some traffic >>>>> but something is broken. I didn't investigate much but the quick >>>>> test shows me rules are not offloaded and dumping ovs rules gives >>>>> error like this >>>>> >>>>> recirc_id(0),in_port(enp8s0f0_1),ct_state(-trk),eth(),eth_type(0x86dd),ipv6(frag=no)(bad >>>>> key length 2, expected -1)(00 00/(bad mask length 2, expected -1)(00 00), >>>>> packets:2453, bytes:211594, used:0.004s, flags:S., actions:ct,recirc(0x2) >>>> >>>> Such a dump is expected, because kernel parses fields that current >>>> userspace doesn't understand, and at the same time OVS by design is >>>> using kernel provided key/mask while installing datapath rules, IIRC. >>>> It should be possible to make these dumps a bit more friendly though. >>>> >>>> For the offloading not working, see my comment in the v2 patch email >>>> I sent (top email of this thread). In short, it's a problem in user >>>> space and it can not be fixed from the kernel side, unless we revert >>>> IPv6 extension header support and never add any new types, which is >>>> unreasonable. I didn't test any actual offloading, but I had a >>>> successful run of 'make check-offloads' with my quick'n'dirty fix from >>>> the top email. >>> >>> Hi Ilya, >>> >>> I can confirm that with latest OvS master IPv6 rules offload still fails >>> without your pastebin code applied. >>> >>>> >>>> Since we're here: >>>> >>>> Toms, do you plan to submit user space patches for this feature? >>> >>> I see there is a patch from you that is supposed to fix compatibility >>> issues caused by this change in OvS d96d14b14733 ("openvswitch.h: Align >>> uAPI definition with the kernel."), but it doesn't fix offload for me >>> without pastebin patch. >> >> Yes. OVS commit d96d14b14733 is intended to only fix the uAPI. >> Issue with offload is an OVS bug that should be fixed separately. >> The fix will also need to be backported to OVS stable branches. >> >>> Do you plan to merge that code into OvS or you >>> require some help from our side? >> >> I could do that, but I don't really have enough time. So, if you >> can work on that fix, it would be great. Note that comments inside >> the OVS's lib/odp-util.c:parse_key_and_mask_to_match() was blindly >> copied from the userspace datapath and are incorrect for the general >> case, so has to be fixed alongside the logic of that function. > > Tom or Vlad, are you working on this? Asking, as the release of a kernel with > Tom’s “net: openvswitch: IPv6: Add IPv6 extension header support” patch will > break OVS. > > //Eelco
Hi Eelco,
My simple fix for OvS was rejected and I don't have time to rework it at the moment.
Regards, Vlad
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