Maybe a little premature again... Maybe some of the commands might help, but
from what I understand, the appctl datapath commands won't work for
datapath_type=netdev, which is what the vhost-user/ovs-dpdk sets the bridges
to. Correct me if I'm wrong, but I guess that means none of the appctl
commands in the FAQ will work for me. Bummer.
Gabe
> -----Original Message-----
> From: Gabe Black
> Sent: Friday, August 28, 2015 9:32 AM
> To: 'Ben Pfaff'
> Cc: Mooney, Sean K; b...@openvswitch.org
> Subject: RE: [ovs-discuss] millions of packets going to a flow?
>
> I saw that FAQ prior to posting. I probably should have mentioned that.
> Unfortunately the ovs-appctl does not work and complains of not finding
> /usr/var/run/openvswitch/ovs-vswitchd.pid. I tried both coping the pidfile
> and symlinking it to where ovs-appctl is looking, but it still failed with the
> same error message.
>
> Running strace when the pid file is there shows that it does finde the file,
> but
> it performs a fcntl( ..., F_GETLK, {type=F_UNLCK,...} ...) which to me makes
> me believe it might be seeing if the file/process is locked and erroring out
> because it finds it can't unlock it.
>
> The error message ovs-appctl displays is the same for both cases though:
> _cannot read pidfile "/usr/var/run/openvswitch/ovs-vswitchd.pid"_.
>
> I just now out of curiousity tried adding the --pidfile to the ovs-dpdk init
> script (where it invokes vswitchd daemon, and found that now ovs-appctl
> works!
>
> I'll follow that faq again now armed with a working ovs-appctl. I wonder if a
> bug should be opened against this to add the --pidfile to the ovs-dpdk-init
> script.
>
> Thanks for taking your time to help me out! I'll post back with anything
> else I
> find that might be an defect.
> Gabe
>
>
>
> > -----Original Message-----
> > From: Ben Pfaff [mailto:b...@nicira.com]
> > Sent: Friday, August 28, 2015 9:08 AM
> > To: Gabe Black
> > Cc: Mooney, Sean K; b...@openvswitch.org
> > Subject: Re: [ovs-discuss] millions of packets going to a flow?
> >
> > On Fri, Aug 28, 2015 at 03:01:52PM +0000, Gabe Black wrote:
> > > However, all the commands I show in this inquiry are ovs-xyz commands.
> > > My questions are around how to debug/troubleshoot where the packets
> > > are going. I am new to all of this, but to me this did seem like
> > > the most relevant list to post that question.
> >
> > Maybe you want this FAQ.
> >
> > ### Q: I have a sophisticated network setup involving Open vSwitch, VMs
> or
> > multiple hosts, and other components. The behavior isn't what I
> > expect. Help!
> >
> > A: To debug network behavior problems, trace the path of a packet,
> > hop-by-hop, from its origin in one host to a remote host. If
> > that's correct, then trace the path of the response packet back to
> > the origin.
> >
> > Usually a simple ICMP echo request and reply ("ping") packet is
> > good enough. Start by initiating an ongoing "ping" from the origin
> > host to a remote host. If you are tracking down a connectivity
> > problem, the "ping" will not display any successful output, but
> > packets are still being sent. (In this case the packets being sent
> > are likely ARP rather than ICMP.)
> >
> > Tools available for tracing include the following:
> >
> > - "tcpdump" and "wireshark" for observing hops across network
> > devices, such as Open vSwitch internal devices and physical
> > wires.
> >
> > - "ovs-appctl dpif/dump-flows <br>" in Open vSwitch 1.10 and
> > later or "ovs-dpctl dump-flows <br>" in earlier versions.
> > These tools allow one to observe the actions being taken on
> > packets in ongoing flows.
> >
> > See ovs-vswitchd(8) for "ovs-appctl dpif/dump-flows"
> > documentation, ovs-dpctl(8) for "ovs-dpctl dump-flows"
> > documentation, and "Why are there so many different ways to
> > dump flows?" above for some background.
> >
> > - "ovs-appctl ofproto/trace" to observe the logic behind how
> > ovs-vswitchd treats packets. See ovs-vswitchd(8) for
> > documentation. You can out more details about a given flow
> > that "ovs-dpctl dump-flows" displays, by cutting and pasting
> > a flow from the output into an "ovs-appctl ofproto/trace"
> > command.
> >
> > - SPAN, RSPAN, and ERSPAN features of physical switches, to
> > observe what goes on at these physical hops.
> >
> > Starting at the origin of a given packet, observe the packet at
> > each hop in turn. For example, in one plausible scenario, you
> > might:
> >
> > 1. "tcpdump" the "eth" interface through which an ARP egresses
> > a VM, from inside the VM.
> >
> > 2. "tcpdump" the "vif" or "tap" interface through which the ARP
> > ingresses the host machine.
> >
> > 3. Use "ovs-dpctl dump-flows" to spot the ARP flow and observe
> > the host interface through which the ARP egresses the
> > physical machine. You may need to use "ovs-dpctl show" to
> > interpret the port numbers. If the output seems surprising,
> > you can use "ovs-appctl ofproto/trace" to observe details of
> > how ovs-vswitchd determined the actions in the "ovs-dpctl
> > dump-flows" output.
> >
> > 4. "tcpdump" the "eth" interface through which the ARP egresses
> > the physical machine.
> >
> > 5. "tcpdump" the "eth" interface through which the ARP
> > ingresses the physical machine, at the remote host that
> > receives the ARP.
> >
> > 6. Use "ovs-dpctl dump-flows" to spot the ARP flow on the
> > remote host that receives the ARP and observe the VM "vif"
> > or "tap" interface to which the flow is directed. Again,
> > "ovs-dpctl show" and "ovs-appctl ofproto/trace" might help.
> >
> > 7. "tcpdump" the "vif" or "tap" interface to which the ARP is
> > directed.
> >
> > 8. "tcpdump" the "eth" interface through which the ARP
> > ingresses a VM, from inside the VM.
> >
> > It is likely that during one of these steps you will figure out the
> > problem. If not, then follow the ARP reply back to the origin, in
> > reverse.
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