On 9/16/21 2:50 AM, Vladislav Odintsov wrote: > 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?
I just tried with OVS v2.13.4, OVN master and it all worked fine (both on Fedora 34 and rhel 7). I don't think the problem is in user space. Regards, Dumitru _______________________________________________ dev mailing list [email protected] https://mail.openvswitch.org/mailman/listinfo/ovs-dev
