[ovs-discuss] Enable sFlow on br-tun cause OVS 2.5.0 crashed

[张东亚]

Hi List,

Recently we are testing sFlow on OVS 2.5.0, since OVS decide whether do
sample based on ingress bridge, we then enable sFlow on br-tun, and
encounter following crash:

#0  0x0000000000434ca8 in dpif_sflow_received (ds=0x4266100,
packet=packet at entry=0x7f3cb3fc8e18, flow=flow at entry=0x7f3cb3fd8810,
odp_in_port=<optimized out>, cookie=cookie at entry=0x7f3cb3fc3440,
    sflow_actions=0x7f3cb3fc36c0) at ofproto/ofproto-dpif-sflow.c:1292
#1  0x00000000004366c0 in process_upcall (udpif=udpif at entry=0x23bb570,
upcall=upcall at entry=0x7f3cb3fe1210,
odp_actions=odp_actions at entry=0x7f3cb3fe1280,
wc=wc at entry=0x7f3cb3fe12c0)
    at ofproto/ofproto-dpif-upcall.c:1236
#2  0x0000000000437087 in recv_upcalls (handler=<error reading variable:
Unhandled dwarf expression opcode 0xfa>, handler=<error reading variable:
Unhandled dwarf expression opcode 0xfa>)
    at ofproto/ofproto-dpif-upcall.c:778
#3  0x000000000043752a in udpif_upcall_handler (arg=0x24a3490) at
ofproto/ofproto-dpif-upcall.c:696
#4  0x00000000004bbc54 in ovsthread_wrapper (aux_=<optimized out>) at
lib/ovs-thread.c:340
#5  0x00007f3cb9f96e0e in start_thread () from
/lib/x86_64-linux-gnu/libpthread.so.0
#6  0x00007f3cba2940fd in clone () from /lib/x86_64-linux-gnu/libc.so.6


After navigate the code, we think the following commit cause the crash:

7321bda384c366ae36bbca445f235a65d8f2b1f8

Extend sFlow agent to report tunnel and MPLS structures

It seems that in the following code assume in vsp have a value, however for
tunnel port, in vsp will always be NULL since there is only on
vxlan_sys_4789 datapath port.


if (flow->tunnel.ip_dst) {
memset(&tnlInElem, 0, sizeof(tnlInElem));
tnlInElem.tag = SFLFLOW_EX_IPV4_TUNNEL_INGRESS;
tnlInProto = dpif_sflow_tunnel_proto(in_dsp->tunnel_type);   // BUG: in_dsp
will be NULL...
dpif_sflow_tunnel_v4(tnlInProto,
    &flow->tunnel,
    &tnlInElem.flowType.ipv4);
SFLADD_ELEMENT(&fs, &tnlInElem);
if (flow->tunnel.tun_id) {
   memset(&vniInElem, 0, sizeof(vniInElem));
   vniInElem.tag = SFLFLOW_EX_VNI_INGRESS;
   vniInElem.flowType.tunnel_vni.vni
= ntohll(flow->tunnel.tun_id);
   SFLADD_ELEMENT(&fs, &vniInElem);
}
    }

Does anyone encounter the same value? I am wondering how we can get tunnel
types from the datapath information.

I will try to find a fix later.
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