[ovs-discuss] failure to modify flow

Salem Sol salems at nvidia.com
Wed Jan 13 14:37:13 UTC 2021


While I was running OVS-DPDK with Geneve traffic I hit a problem where in the first flow OVS does not know which port to forward the packet to, so it sends it to all the ports on the bridge leading to the creation of this datapath rule:

skb_priority(0/0),tunnel(tun_id=0x5,src=,dst=,ttl=64/0,tp_src=43419/0,tp_dst=6081/0,flags(-df-csum+key)),skb_mark(0/0),ct_state(0/0),ct_zone(0/0),ct_mark(0/0),ct_label(0/0),recirc_id(0),dp_hash(0/0),in_port(genev_sys_6081),packet_type(ns=0,id=0),eth(src=e4:0b:07:08:00:03,dst=e4:0b:08:08:00:02),eth_type(0x0800),ipv4(src=,dst=,proto=6,tos=0/0,ttl=64/0,frag=no),tcp(src=19016/0,dst=19016/0),tcp_flags(0/0), packets:208, bytes:23738, used:4.756s, flags:SFPR., dp:ovs, actions: enp8s0f0_0,ovs-sriov1,enp8s0f0_0, dp-extra-info:miniflow_bits(10,2)

after OVS learns the correct port to forward to it issues a flow modification that fails:

2021-01-12T11:41:42.733Z|00001|dpif(revalidator13)|WARN|netdev at ovs-netdev: failed to put[modify] (No such file or directory) ufid:9844be55-8c6d-4ef0-9bb8-622b13aa0c7b skb_priority(0/0),tunnel(tun_id=0x5,src=,dst=,ttl=64/0,tp_src=50367/0,tp_dst=6081/0,flags(-df-csum+key)),skb_mark(0/0),ct_state(0/0),ct_zone(0/0),ct_mark(0/0),ct_label(0/0),recirc_id(0),dp_hash(0/0),in_port(3),packet_type(ns=0,id=0),eth(src=e4:0b:08:08:00:02,dst=e4:0b:07:08:00:03),eth_type(0x0800),ipv4(src=,dst=,proto=1,tos=0/0,ttl=64/0,frag=no),icmp(type=8/0,code=0/0), actions:4

This behavior was already discussed in [1]
There is a proposed fix the this discussion that was never applied, in the discussion they mention that the fix is not complete "(The following patch is not actually the real fix because the code should still look at the key if no ufid was provided.)"

So my questions are:

  1.  What are the risks of changing the procedure of searching for the flows moving to look for the flow using UFID and not netdev_key?
  2.  Why this fix was not applied or merged to the master branch?

[1] https://lists.linuxfoundation.org/pipermail/ovs-dev/2018-September/352579.html

Salem Sol
SW. Engineer - Mellanox Cloud Acceleration
Mobile: +972 (74) 7238453

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