Hi all, I’ve faced condition in flow lookup where OVS crashes with segmentation violation because of insufficient stack limit size for ovs-vswitchd daemon. Below is the reproducer:
# ---> # Ensure there is a default LimitSTACK in ovs-vswitchd.service file with which OVS is run (should be 2M): grep LimitSTACK /usr/lib/systemd/system/ovs-vswitchd.service # create 2 LRs and connect them via ls ovn-nbctl lr-add lr1 ovn-nbctl lr-add lr2 ovn-nbctl lrp-add lr1 lrp1 00:00:00:00:00:01 10.0.0.1/24 ovn-nbctl lrp-add lr2 lrp2 00:00:00:00:00:02 10.0.0.2/24 ovn-nbctl ls-add ls ovn-nbctl lsp-add ls ls-lrp1 -- lsp-set-type ls-lrp1 router -- lsp-set-addresses ls-lrp1 router -- lsp-set-options ls-lrp1 router-port=lrp1 ovn-nbctl lsp-add ls ls-lrp2 -- lsp-set-type ls-lrp2 router -- lsp-set-addresses ls-lrp2 router -- lsp-set-options ls-lrp2 router-port=lrp2 # create route to same cidr looping routing ovn-nbctl lr-route-add lr1 1.1.1.1/32 10.0.0.2 ovn-nbctl lr-route-add lr2 1.1.1.1/32 10.0.0.1 # create vif lport and configure it ovn-nbctl lsp-add ls lp1 -- lsp-set-addresses lp1 00:00:00:00:00:f1 ovs-vsctl add-port br-int lp1 -- set int lp1 type=internal external_ids:iface-id=lp1 ip li set lp1 addr 00:00:00:00:00:f1 ip a add 10.0.0.200/24 dev lp1 ip li set lp1 up ip r add 1.1.1.1/32 via 10.0.0.1 ping 1.1.1.1 -c1 # <--- This problem was first described in [1] and continued in [2]. I’m wonder whether [2] was discussed somewhere in another place or had no resolution. OVS crash reproduces on different versions: 2.13, 2.17, 3.1. Default stack limit shipped with OVS looks not enough to reach 'Recursion too deep'. In my tests for this reproducer it is needed at least 2293K to work properly. I understand, that such configuration should be validated and avoided from the CMS side, but I think that there should be no possibility so easily bring system to crashed state. Should the default OVS StackLimit in systemd.unit be increased? Or, maybe, OVN should document the need to increase OVS stack limit manually by users? Or, should OVN supply systemd drop-in unit to override default OVS StackLimit? 1: https://bugzilla.redhat.com/show_bug.cgi?id=1821185#c3 2: https://mail.openvswitch.org/pipermail/ovs-dev/2020-April/369776.html Regards, Vladislav Odintsov
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