[ovs-dev] [PATCH v2 1/3] conntrack: Do not create new connections from ICMP errors.

Fri Dec 23 02:55:15 UTC 2016

On 12/22/16, 6:36 PM, "Daniele Di Proietto" <diproiettod at vmware.com> wrote:

    ICMP error packets (e.g. destination unreachable messages) are
    considered 'related' to another connection and are treated as part of
    that.

    However:

    * We shouldn't create new entries in the connection table if the
      original connection is not found.  This is consistent with what the
      kernel does.
    * We certainly shouldn't call valid_new() on the packet, because
      valid_new() assumes the packet l4 type (might be TCP, UDP or ICMP)
      to be consistent with the conn_key nw_proto type.

    Found by inspection.

    Fixes: a489b16854b5("conntrack: New userspace connection tracker.")
    Signed-off-by: Daniele Di Proietto <diproiettod at vmware.com>
    ---
    v2: Handle ICMP error for non existing connection in else branch without
        restructuring the whole code flow.
    ---
     lib/conntrack.c         |  6 +++++-
     tests/system-traffic.at | 27 ++++++++++++++++-----------
     2 files changed, 21 insertions(+), 12 deletions(-)

Acked-by: Darrell Ball <dlu998 at gmail.com>

    diff --git a/lib/conntrack.c b/lib/conntrack.c
    index 7c50a28..9bea3d9 100644
    --- a/lib/conntrack.c
    +++ b/lib/conntrack.c
    @@ -247,7 +247,11 @@ process_one(struct conntrack *ct, struct dp_packet *pkt,
                 }
             }
         } else {
    -        conn = conn_not_found(ct, pkt, ctx, &state, commit, now);
    +        if (ctx->related) {
    +            state |= CS_INVALID;
    +        } else {
    +            conn = conn_not_found(ct, pkt, ctx, &state, commit, now);
    +        }
         }

         write_ct_md(pkt, state, zone, conn ? conn->mark : 0,
    diff --git a/tests/system-traffic.at b/tests/system-traffic.at
    index 9ea6d6b..a5023d3 100644
    --- a/tests/system-traffic.at
    +++ b/tests/system-traffic.at
    @@ -1331,12 +1331,8 @@ ADD_VETH(p1, at_ns1, br0, "172.16.0.2/24")

     dnl Allow any traffic from ns0->ns1. Only allow nd, return traffic from ns1->ns0.
     AT_DATA([flows.txt], [dnl
    -priority=1,action=drop
    -priority=10,arp,action=normal
    -priority=100,in_port=1,udp,ct_state=-trk,action=ct(commit,table=0)
    -priority=100,in_port=1,ip,ct_state=+trk,actions=controller
    -priority=100,in_port=2,ip,ct_state=-trk,action=ct(table=0)
    -priority=100,in_port=2,ip,ct_state=+trk+rel+rpl,action=controller
    +table=0,ip,action=ct(commit,table=1)
    +table=1,ip,action=controller
     ])

     AT_CHECK([ovs-ofctl --bundle replace-flows br0 flows.txt])
    @@ -1345,22 +1341,31 @@ AT_CAPTURE_FILE([ofctl_monitor.log])
     AT_CHECK([ovs-ofctl monitor br0 65534 invalid_ttl --detach --no-chdir --pidfile 2> ofctl_monitor.log])

     dnl 1. Send an ICMP port unreach reply for port 8738, without any previous request
    -AT_CHECK([ovs-ofctl -O OpenFlow13 packet-out br0 2 ct\(table=0\) 'f64c473528c9c6f54ecb72db080045c0003d2e8700004001f355ac100004ac1000030303553f0000000045000021317040004011b138ac100003ac10000411112222000d20966369616f0a'])
    +AT_CHECK([ovs-ofctl -O OpenFlow13 packet-out br0 2 resubmit\(,0\) 'f64c473528c9c6f54ecb72db080045c0003d2e8700004001f351ac100004ac1000030303da490000000045000021317040004011b138ac100003ac10000411112222000d20966369616f0a'])

     dnl 2. Send and UDP packet to port 5555
    -AT_CHECK([ovs-ofctl -O OpenFlow13 packet-out br0 1 ct\(commit,table=0\) 'c6f94ecb72dbe64c473528c9080045000021317040004011b138ac100001ac100002a28e15b3000d20966369616f0a'])
    +AT_CHECK([ovs-ofctl -O OpenFlow13 packet-out br0 1 resubmit\(,0\) 'c6f94ecb72dbe64c473528c9080045000021317040004011b138ac100001ac100002a28e15b3000d20966369616f0a'])

     dnl 3. Send an ICMP port unreach reply for port 5555, related to the first packet
    -AT_CHECK([ovs-ofctl -O OpenFlow13 packet-out br0 2 ct\(table=0\) 'e64c473528c9c6f94ecb72db080045c0003d2e8700004001f355ac100002ac1000010303553f0000000045000021317040004011b138ac100001ac100002a28e15b3000d20966369616f0a'])
    +AT_CHECK([ovs-ofctl -O OpenFlow13 packet-out br0 2 resubmit\(,0\) 'e64c473528c9c6f94ecb72db080045c0003d2e8700004001f355ac100002ac1000010303553f0000000045000021317040004011b138ac100001ac100002a28e15b3000d20966369616f0a'])

     dnl Check this output. We only see the latter two packets, not the first.
     AT_CHECK([cat ofctl_monitor.log], [0], [dnl
    -NXT_PACKET_IN2 (xid=0x0): cookie=0x0 total_len=47 ct_state=new|trk,in_port=1 (via action) data_len=47 (unbuffered)
    +NXT_PACKET_IN2 (xid=0x0): table_id=1 cookie=0x0 total_len=75 ct_state=inv|trk,in_port=2 (via action) data_len=75 (unbuffered)
    +icmp,vlan_tci=0x0000,dl_src=c6:f5:4e:cb:72:db,dl_dst=f6:4c:47:35:28:c9,nw_src=172.16.0.4,nw_dst=172.16.0.3,nw_tos=192,nw_ecn=0,nw_ttl=64,icmp_type=3,icmp_code=3 icmp_csum:da49
    +NXT_PACKET_IN2 (xid=0x0): table_id=1 cookie=0x0 total_len=47 ct_state=new|trk,in_port=1 (via action) data_len=47 (unbuffered)
     udp,vlan_tci=0x0000,dl_src=e6:4c:47:35:28:c9,dl_dst=c6:f9:4e:cb:72:db,nw_src=172.16.0.1,nw_dst=172.16.0.2,nw_tos=0,nw_ecn=0,nw_ttl=64,tp_src=41614,tp_dst=5555 udp_csum:2096
    -NXT_PACKET_IN2 (xid=0x0): cookie=0x0 total_len=75 ct_state=rel|rpl|trk,in_port=2 (via action) data_len=75 (unbuffered)
    +NXT_PACKET_IN2 (xid=0x0): table_id=1 cookie=0x0 total_len=75 ct_state=rel|rpl|trk,in_port=2 (via action) data_len=75 (unbuffered)
     icmp,vlan_tci=0x0000,dl_src=c6:f9:4e:cb:72:db,dl_dst=e6:4c:47:35:28:c9,nw_src=172.16.0.2,nw_dst=172.16.0.1,nw_tos=192,nw_ecn=0,nw_ttl=64,icmp_type=3,icmp_code=3 icmp_csum:553f
     ])

    +AT_CHECK([ovs-appctl dpctl/dump-conntrack | FORMAT_CT(172.16.0.1)], [0], [dnl
    +udp,orig=(src=172.16.0.1,dst=172.16.0.2,sport=<cleared>,dport=<cleared>),reply=(src=172.16.0.2,dst=172.16.0.1,sport=<cleared>,dport=<cleared>)
    +])
    +
    +AT_CHECK([ovs-appctl dpctl/dump-conntrack | FORMAT_CT(172.16.0.3)], [0], [dnl
    +])
    +
     OVS_TRAFFIC_VSWITCHD_STOP
     AT_CLEANUP

    -- 
    2.10.2