I finally figured it out. FAUCET sets ofp_switch_config.miss_send_len = 0 when the switch connects. We do this because we don't want any packets coming to the controller, if there is no matching flow in a table. We program a priority 0, actions=drop flow in all tables as well, to really hammer the point home (I guess :-).
Experimentally, I tried explicitly adding a priority 0 flow in one table (instead of the explicit drop) that looks like this: cookie=0x5adc15c0, duration=21.851s, table=3, n_packets=65, n_bytes=4794, priority=0 actions=CONTROLLER:96,goto_table:7 The counters increment, but OVS (2.9.0) doesn't send a PacketIn - I'm guessing because the the code that checks miss_send_len doesn't know the difference between the implicit packet in (where you don't program any priority=0 flow) and the explicit one. Now. Is it a bug? Perhaps not. The OF standard 1.3.5/sec 5.4 does explain as you did, that priority=0 is a special case, and further more a priority 0 flow just might not have the same capabilities as a regular flow, and that you should probably avoid using it for backward compatibility reasons. So, we won't use explicit actions at priority 0. :) That's fine. Perhaps it's a documentation/check thing? miss_send_len = 0 applying to these explicit output to controller was a surprise, but maybe I just shouldn't be surprised. :-) Thanks, On Fri, May 18, 2018 at 5:14 AM Ben Pfaff <b...@ovn.org> wrote: > If you can try to narrow it down further, that's helpful. If you don't > have any luck with that, let me know and I'll see if I can figure > anything out. > > On Thu, May 17, 2018 at 05:26:54PM +1200, Josh Bailey wrote: > > I apologize, I dropped the ball. I'll go take another look at this. I > had a > > go at reproducing it (with just a single table) and failed - the packet > in > > is sent. > > > > It's only not sent, when FAUCET has put other flows in other tables and > the > > problem priority 0 rule is in table 2. I have some work to do clearly to > > try and narrow that down. > > > > I also tried setting miss length to various values and that made no > > difference. > > > > > > > > On Sat, Apr 7, 2018 at 4:42 AM Ben Pfaff <b...@ovn.org> wrote: > > > > > On Tue, Mar 06, 2018 at 11:20:40AM -0800, Ben Pfaff wrote: > > > > On Tue, Mar 06, 2018 at 06:54:30AM +0000, Josh Bailey via discuss > wrote: > > > > > Hoping I'm missing something obvious! > > > > > > > > > > I have a flow like this: > > > > > > > > > > $ grep CONTROLLER sab-dump-flows.log > > > > > cookie=0x5adc15c0, duration=63.446s, table=3, n_packets=60, > > > n_bytes=3436, > > > > > priority=0 actions=CONTROLLER:96 > > > > > > > > > > I can cause packets to match it, but no packets are output ot the > > > > > controller. > > > > > > > > > > faucet@faucet > > > > :/var/tmp/faucet-tests-1KL3eg/FaucetUntaggedTestZeroPriorityFlowsTest-test_untagged$ > > > > > tshark -l -n -Q -d tcp.port==40649,openflow -O openflow_v4 -Y > > > > > "openflow_v4.packet_in.total_len>0" -r fa*cap|wc -l > > > > > 0 > > > > > > > > > > If I specify any priority other than 0, it works (packets are > output to > > > > > controller via packet in messages). > > > > > > > > > > Is there something special about priority=0 flows and the > CONTROLLER > > > action? > > > > > > > > Yes, in fact OpenFlow specifies special cases for priority=0 flows > that > > > > match no fields. It calls these "table-miss" flows, see e.g. section > > > > 5.4 in OpenFlow 1.5.1. Open vSwitch has some explicit special-case > code > > > > for dealing with them. > > > > > > > > I can't think of a particular reason why this special case would > make a > > > > difference for you. Maybe there is a bug. Do you have a way for us > to > > > > reproduce it? > > > > > > > > Did you try "ofproto/trace"? Maybe it will show a reason why the > packet > > > > is not sent to the controller. > > > > > > > > (I'm at a conference this week, so my schedule is weird.) > > > > > > I wonder whether you figured out anything here and whether you have any > > > more of a bug report for us. Happy to help, if so. > > > >
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