Messages in this thread | | | From | Eelco Chaudron <> | Subject | Re: [PATCH net-next v2] net: openvswitch: fix uAPI incompatibility with existing user space | Date | Tue, 17 May 2022 13:10:40 +0200 |
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On 12 May 2022, at 12:08, Vlad Buslov wrote:
> 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.
That’s a pity, Tom do you maybe have time as your patch left OVS in this error state?
//Eelco
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