[Click] Some packets emitted but not received across the wire

[Kyriakos Zarifis]

A small follow up, I'm verifying that bounced packets leave s0 but don't
come back to it:
(these are stats before/after the ping)

s0> ifconfig eth3
          RX packets:136 errors:0 dropped:0 overruns:0 frame:0
          TX packets:151 errors:0 dropped:0 overruns:0 carrier:0
s0> ifconfig eth3
          RX packets:136 errors:0 dropped:0 overruns:0 frame:0
          TX packets:152 errors:0 dropped:0 overruns:0 carrier:0

..although they get in and back out of s1 (towards s0)
s1> ifconfig eth2
          RX packets:197 errors:0 dropped:0 overruns:0 frame:0
          TX packets:160 errors:0 dropped:0 overruns:0 carrier:0
s1> ifconfig eth2
          RX packets:198 errors:0 dropped:0 overruns:0 frame:0
          TX packets:161 errors:0 dropped:0 overruns:0 carrier:0


... I am confused.


On Thu, Jan 10, 2013 at 4:33 AM, Kyriakos Zarifis <kyr.zarifis at gmail.com>wrote:

> Hi all,
>
> I just recently started using Click (and I love it!)
>
> For experimentation/practice, I am playing with a toy element that bounces
> random packets to a port other than the one they are destined to, with a
> 10% chance.
>
> I have this topology:
>
>     s1
>      |
>     s0
>   /     \
> A       B
>
> I send single pings from A to B. The expected behavior is to see most echo
> replies/requests go only through s0, but 10% of the packets should be
> bounced to s1, back to s0, and then to their destination.
>
> The problem I am seeing is that this works _sometimes_, but most of the
> times when a packet is bounced to s1, it disappears on its way back to s0.
> This happens both in user and kernel space.
> I can verify that the bounced packet seems to be leaving s1 both by
> tcpdump (in userspace) and by IPPrints(in kernelspace), but then it never
> appears on s0's interface (neither in tcpdumps nor in click Print logs).
>
> When the bounce works, the tcpdumps/logs show it was bounced just fine,
> but I get very few successful bounces (maybe 10%), while most in most cases
> the bounced packet disappears on its way back.
>
>
> I went through the list archives and saw a few people had some similar
> problem where they couldn't emit packets to ToDevice if the same interface
> had been initialized with FromDevice, and in some cases that was resolved
> by using "METHOD LINUX". I tried that in user level but got the same
> behavior. Also, in my case the packets disappear *most* of the time, but
> not *always*, so I'm not sure if this is the same issue.
>
>
> This has been troubling me all day, and most of all I'm confused by the
> fact that it works sometimes, but I haven't been able to see a pattern,
> other than maybe that the successful bounce rate seems to be a bit higher
> right after the switch has been restarted (but I don't know how this can be
> related so it's probably just my impression)
>
> Any ideas would be very welcome, thanks.
>
>
>
> A simplified version of s0.click looks something like this:
>
> q0 :: Queue(10);
> q1 :: Queue(10);
> q2 :: Queue(10);
> s :: LinearIPLookup(10.1.1.1/32 0,
> 10.1.1.2/32 1);
> b0 :: Bouncer();   //outputs to b[0] with 90%, to b[1] with 10%
> b1 :: Bouncer();
> classifier1::Classifier(12/0806 20/0001, 12/0806 20/0002, 12/0800, -);
> FromDevice(eth0, PROMISC true) -> [0]classifier1;
> FromDevice(eth1, PROMISC true) -> [0]classifier1;
> FromDevice(eth2, PROMISC true) -> [0]classifier1;
> classifier[0]->Discard;
> classifier[1]->Discard;
> classifier[2]->Strip(14)->CheckIPHeader(INTERFACES 10.0.0.0/8)-
> >IPPrint("in")->[0]s;
> classifier1[3]->Discard;
> s[0] -> Unstrip(14)->b0;
> s[1] -> Unstrip(14)->b1;
>
> b0[0]->q0;   //forward to h0 normally
> b0[1]->q2;   //bounce to s1
> b1[0]->q1;   //forward to h1
> b0[1]->q2;   //bounce to s1
>
> q0->ToDevice(eth0);
> q1->ToDevice(eth1);
> q2->IPPrint("bounced")->ToDevice(eth2);
>
>
> and s1.click looks like this:
>
> q0 :: Queue(100);
> s :: LinearIPLookup(10.1.1.1/32 0,
> 10.1.1.2/32 0);
> classifier1::Classifier(12/0806 20/0001, 12/0806 20/0002, 12/0800, -);
> FromDevice(eth0, PROMISC true) -> [0]classifier;
> classifier[0]->Discard;
> classifier[1]->Discard;
> classifier[2]->Strip(14)->CheckIPHeader(INTERFACES 10.0.0.0/8)-
> >IPPrint("in")->[0]s;
> classifier[3]->Discard;
> s[0] -> Unstrip(14)->q1;
>
> q1->IPPrint("out q1")->ToDevice(eth0);
>
>
> Thanks!
>