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 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. >> >> @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] <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
