Hi Dumitru, thanks for your reply.
Regards, Vladislav Odintsov > On 15 Sep 2021, at 11:24, Dumitru Ceara <[email protected]> wrote: > > Hi Vladislav, > > On 9/13/21 6:14 PM, Vladislav Odintsov wrote: >> Hi Numan, >> >> I’ve checked with OVS 2.16.0 and OVN master. The problem persists. >> Symptoms are the same. >> >> # grep ct_zero_snat /var/log/openvswitch/ovs-vswitchd.log >> 2021-09-13T16:10:01.792Z|00019|ofproto_dpif|INFO|system@ovs-system: Datapath >> supports ct_zero_snat > > This shouldn't be related to the problem we fixed with ct_zero_snat. > >> >> Regards, >> Vladislav Odintsov >> >>> On 13 Sep 2021, at 17:54, Numan Siddique <[email protected]> wrote: >>> >>> On Mon, Sep 13, 2021 at 8:10 AM Vladislav Odintsov <[email protected] >>> <mailto:[email protected]>> wrote: >>>> >>>> Hi, >>>> >>>> we’ve encountered a next problem with stateful ACLs. >>>> >>>> Suppose, we have one logical switch (ls1) and attached to it a VIF type >>>> logical ports (lsp1, lsp2). >>>> Each logical port has a linux VM besides it. >>>> >>>> Logical ports reside in port group (pg1) and two ACLs are created within >>>> this PG: >>>> to-lport outport == @pg1 && ip4 && ip4.dst == 0.0.0.0/0 allow-related >>>> from-lport outport == @pg1 && ip4 && ip4.src == 0.0.0.0/0 allow-related >>>> >>>> When we have a high-connection rate service between VMs, the tcp >>>> source/dest ports may be reused before the connection is deleted from >>>> LSP’s-related conntrack zones on the host. >>>> Let’s use curl with passing --local-port argument to have each time same >>>> source port. >>>> >>>> Run it from VM to another VM (172.31.0.18 -> 172.31.0.17): >>>> curl --local-port 44444 http://172.31.0.17/ >>>> >>>> Check connections in client’s and server’s vif zones (client - zone=20, >>>> server - zone=1): >>>> run while true script to check connections state per-second, while running >>>> new connection with same source/dest 5-tuple: >>>> >>>> while true; do date; grep -e 'zone=1 ' -e zone=20 /proc/net/nf_conntrack; >>>> sleep 0.2; done >>>> >>>> Right after we’ve succesfully run curl, the connection is getting >>>> time-closed and next time-wait states: >>>> >>>> Mon Sep 13 14:34:39 MSK 2021 >>>> ipv4 2 tcp 6 59 CLOSE_WAIT src=172.31.0.18 dst=172.31.0.17 >>>> sport=44444 dport=80 src=172.31.0.17 dst=172.31.0.18 sport=80 dport=44444 >>>> [ASSURED] mark=0 zone=1 use=2 >>>> ipv4 2 tcp 6 59 CLOSE_WAIT src=172.31.0.18 dst=172.31.0.17 >>>> sport=44444 dport=80 src=172.31.0.17 dst=172.31.0.18 sport=80 dport=44444 >>>> [ASSURED] mark=0 zone=20 use=2 >>>> Mon Sep 13 14:34:39 MSK 2021 >>>> ipv4 2 tcp 6 119 TIME_WAIT src=172.31.0.18 dst=172.31.0.17 >>>> sport=44444 dport=80 src=172.31.0.17 dst=172.31.0.18 sport=80 dport=44444 >>>> [ASSURED] mark=0 zone=1 use=2 >>>> ipv4 2 tcp 6 119 TIME_WAIT src=172.31.0.18 dst=172.31.0.17 >>>> sport=44444 dport=80 src=172.31.0.17 dst=172.31.0.18 sport=80 dport=44444 >>>> [ASSURED] mark=0 zone=20 use=2 >>>> >>>> And it remains in time-wait state for nf_conntrack_time_wait_timeout (120 >>>> seconds for centos 7). >>>> >>>> Everything is okay for now. >>>> While we have installed connections in TW state in zone 1 and 20, lets run >>>> this curl (source port 44444) again: >>>> 1st SYN packet is lost. It didn’t get to destination VM. In conntrack we >>>> have: >>>> >>>> Mon Sep 13 14:34:41 MSK 2021 >>>> ipv4 2 tcp 6 118 TIME_WAIT src=172.31.0.18 dst=172.31.0.17 >>>> sport=44444 dport=80 src=172.31.0.17 dst=172.31.0.18 sport=80 dport=44444 >>>> [ASSURED] mark=0 zone=1 use=2 >>>> >>>> We see that TW connection was dropped in source vif’s zone (20). >>>> >>>> Next, after one second TCP sends retry and connection in destination >>>> (server’s) zone is dropped and a new connection is created in source zone >>>> (client’s): >>>> >>>> Mon Sep 13 14:34:41 MSK 2021 >>>> ipv4 2 tcp 6 120 SYN_SENT src=172.31.0.18 dst=172.31.0.17 >>>> sport=44444 dport=80 [UNREPLIED] src=172.31.0.17 dst=172.31.0.18 sport=80 >>>> dport=44444 mark=0 zone=20 use=2 >>>> >>>> Server VM still didn’t get this SYN packet. It got dropped. >>>> >>>> Then, after 2 seconds TCP sends retry again and connection is working well: >>>> >>>> Mon Sep 13 14:34:44 MSK 2021 >>>> ipv4 2 tcp 6 59 CLOSE_WAIT src=172.31.0.18 dst=172.31.0.17 >>>> sport=44444 dport=80 src=172.31.0.17 dst=172.31.0.18 sport=80 dport=44444 >>>> [ASSURED] mark=0 zone=1 use=2 >>>> ipv4 2 tcp 6 59 CLOSE_WAIT src=172.31.0.18 dst=172.31.0.17 >>>> sport=44444 dport=80 src=172.31.0.17 dst=172.31.0.18 sport=80 dport=44444 >>>> [ASSURED] mark=0 zone=20 use=2 >>>> Mon Sep 13 14:34:44 MSK 2021 >>>> ipv4 2 tcp 6 119 TIME_WAIT src=172.31.0.18 dst=172.31.0.17 >>>> sport=44444 dport=80 src=172.31.0.17 dst=172.31.0.18 sport=80 dport=44444 >>>> [ASSURED] mark=0 zone=1 use=2 >>>> ipv4 2 tcp 6 119 TIME_WAIT src=172.31.0.18 dst=172.31.0.17 >>>> sport=44444 dport=80 src=172.31.0.17 dst=172.31.0.18 sport=80 dport=44444 >>>> [ASSURED] mark=0 zone=20 use=2 >>>> >>>> I guess, that it could happen: >>>> 1. Run curl with an empty conntrack zones. Everything is good, we’ve got >>>> http response, closed the connection. There’s one TW entry in client’s and >>>> one in server’s zonntrack zones. >>>> 2. Run curl with same source port within nf_conntrack_time_wait_timeout >>>> seconds. >>>> 2.1. OVS gets packet from VM, sends it to client’s conntrack zone=20. It >>>> matches pre-existed conntrack entry in tw state from previous curl run. TW >>>> connection in conntrack is deleted. A copy of a packet is returned to OVS >>>> and recirculated packet has ct.inv (?) and !ct.trk states and got dropped >>>> (I’m NOT sure, it’s just an assumption!) >>>> 3. After one second client VM resends TCP SYN. >>>> 3.1. OVS gets packet, sends through client’s conntrack zone=20, a new >>>> connection is added, packet has ct.trk and ct.new states set. Packet goes >>>> to recirculation. >>>> 3.2. OVS sends packet to server’s conntrack zone=1. It matches pre-existed >>>> conntrack entry in tw state from previous run. Conntrack removes this >>>> entry. Packet is returned to OVS with ct.inv (?) and !ct.trk. Packet got >>>> dropped. >>>> 4. Client’s VM again sends TCP SYN after 2 more seconds left. >>>> 4.1 OVS gets packet from client’s VIF, sends to client’s conntrack >>>> zone=20, it matches pre-existed SYN_SENT conntrack entry state, packets is >>>> returned to OVS with ct.new, ct.trk flags set. >>> >>> >>>> 4.2 OVS sends packet to server’s conntrack zone=1. Conntrack table for >>>> zone=1 is empty, it adds new entry, returns packet to OVS with ct.trk and >>>> ct.new flags set. >>>> 4.3 OVS sends packet to server’s VIF, next traffic operates normally. >>>> >>>> So, with such behaviour connection establishment sometimes takes up to >>>> three seconds (2 TCP SYN retries) and makes troubles in overlay services. >>>> (Application timeouts and service outages). >>>> >>>> I’ve checked how conntrack works inside VMs with such traffic and it looks >>>> like if conntrack gets a packet within a TW connection it recreates a new >>>> conntrack entry. No tuning inside VMs was performed. As a server I used >>>> apache with default config from CentOS distribution. > > I don't have a centos 7 at hand but I do have a rhel 7 > (3.10.0-1160.36.2.el7.x86_64) and I didn't manage to hit the issue you > reported here (using OVS and OVN upstream master). The SYN matching the > conntrack entry in state TIME_WAIT moves the entry to NEW and seems to > be forwarded just fine, the session afterwards go to ESTABLISHED. > > Wed Sep 15 04:18:35 AM EDT 2021 > conntrack v1.4.5 (conntrack-tools): 7 flow entries have been shown. > tcp 6 431930 ESTABLISHED src=42.42.42.2 dst=42.42.42.3 sport=4141 > dport=4242 src=42.42.42.3 dst=42.42.42.2 sport=4242 dport=4141 [ASSURED] > mark=0 secctx=system_u:object_r:unlabeled_t:s0 zone=6 use=1 > tcp 6 431930 ESTABLISHED src=42.42.42.2 dst=42.42.42.3 sport=4141 > dport=4242 src=42.42.42.3 dst=42.42.42.2 sport=4242 dport=4141 [ASSURED] > mark=0 secctx=system_u:object_r:unlabeled_t:s0 zone=3 use=1 > -- > Wed Sep 15 04:18:36 AM EDT 2021 > conntrack v1.4.5 (conntrack-tools): 7 flow entries have been shown. > tcp 6 119 TIME_WAIT src=42.42.42.2 dst=42.42.42.3 sport=4141 > dport=4242 src=42.42.42.3 dst=42.42.42.2 sport=4242 dport=4141 [ASSURED] > mark=0 secctx=system_u:object_r:unlabeled_t:s0 zone=6 use=1 > tcp 6 119 TIME_WAIT src=42.42.42.2 dst=42.42.42.3 sport=4141 > dport=4242 src=42.42.42.3 dst=42.42.42.2 sport=4242 dport=4141 [ASSURED] > mark=0 secctx=system_u:object_r:unlabeled_t:s0 zone=3 use=1 > -- > Wed Sep 15 04:18:38 AM EDT 2021 > conntrack v1.4.5 (conntrack-tools): 7 flow entries have been shown. > tcp 6 431999 ESTABLISHED src=42.42.42.2 dst=42.42.42.3 sport=4141 > dport=4242 src=42.42.42.3 dst=42.42.42.2 sport=4242 dport=4141 [ASSURED] > mark=0 secctx=system_u:object_r:unlabeled_t:s0 zone=6 use=1 > tcp 6 431999 ESTABLISHED src=42.42.42.2 dst=42.42.42.3 sport=4141 > dport=4242 src=42.42.42.3 dst=42.42.42.2 sport=4242 dport=4141 [ASSURED] > mark=0 secctx=system_u:object_r:unlabeled_t:s0 zone=3 use=1 > -- > > DP flows just after the second session is initiated also seem to confirm > that everything is fine: > > # ovs-appctl dpctl/dump-flows | grep -oE "ct_state(.*),ct_label" > ct_state(+new-est-rel-rpl-inv+trk),ct_label > ct_state(-new+est-rel-rpl-inv+trk),ct_label > ct_state(-new+est-rel+rpl-inv+trk),ct_label > ct_state(+new-est-rel-rpl-inv+trk),ct_label > ct_state(-new+est-rel+rpl-inv+trk),ct_label > ct_state(-new+est-rel-rpl-inv+trk),ct_label > > I also tried it out on a Fedora 34 with 5.13.14-200.fc34.x86_64, still > works fine. > > What kernel and openvswitch module versions do you use? > On my box there is CentOS 7.5 with kernel 3.10.0-862.14.4.el7 and OOT kernel module. I’ve tested two versions, in both the problem was hit: openvswitch-kmod-2.13.4-1.el7_5.x86_64 openvswitch-kmod-2.16.0-1.el7_5.x86_64 Do you think the problem could be related to kernel (conntrack) and kernel must be upgraded here? Or, maybe I should try master OVS, as you did? > Regards, > Dumitru > >>>> >>>> @Numan, @Han, @Mark, can you please take a look at this and give any >>>> suggestions/thoughts how this can be fixed. >>>> The problem is actual with OVS 2.13.4 and latest OVN master branch, >>>> however we’ve met it on 20.06.3 with same OVS and it’s very important for >>>> us. >>> >>> Hi Vladislav, >>> >>> From what I understand this commit should help your use case - >>> https://github.com/ovn-org/ovn/commit/58683a4271e6a885f2f2aea27f3df88e69a5c388 >>> >>> <https://github.com/ovn-org/ovn/commit/58683a4271e6a885f2f2aea27f3df88e69a5c388> >>> >>> Looks to me like there's a tuple collision. And you would need the >>> latest OVS (ovs 2.16) along with the latest OVN having the above >>> commit. >>> >>> @Dumitru Ceara please correct me If I'm wrong. >>> >>> Thanks >>> Numan >>> >>>> >>>> Thanks. >>>> >>>> >>>> Regards, >>>> Vladislav Odintsov >>>> _______________________________________________ > > _______________________________________________ > dev mailing list > [email protected] <mailto:[email protected]> > https://mail.openvswitch.org/mailman/listinfo/ovs-dev > <https://mail.openvswitch.org/mailman/listinfo/ovs-dev> _______________________________________________ dev mailing list [email protected] https://mail.openvswitch.org/mailman/listinfo/ovs-dev
