[ovs-discuss] Implicit causes of rx packet drops

[Damiaan Twelker]

Thanks, Joe. Turns out that the model switch used (P-3290) does not support the mod_ip_dst action in hardware, and therefore forwards all packets matching the flow from asic to CPU, causing a “packet-list overflow” as logged in /tmp/log/messages.

Kind regards,

Damiaan Twelker

> On 14 Apr 2016, at 01:32, Joe Stringer <joe at ovn.org> wrote:
> 
> On 13 April 2016 at 08:33, Damiaan Twelker
> <damiaan.twelker at student.uva.nl <mailto:damiaan.twelker at student.uva.nl>> wrote:
>> Hi,
>> 
>> I have set up a bridge with 3 physical ports (vlan_mode=access). The following rules are active in order to redirect data sent from 10.0.0.1 destined for 10.0.0.2 to 10.0.0.3:
>> 
>> cookie=0x0, duration=2725.863s, table=0, n_packets=n/a, n_bytes=33572528154, ip,in_port=25,nw_dst=10.0.0.2 actions=set_field:10.0.0.3->ip_dst,set_field:96:5f:91:02:cf:3f->eth_dst,output:27
>> cookie=0x0, duration=2670.657s, table=0, n_packets=n/a, n_bytes=48832, arp,in_port=26 actions=output:25
>> cookie=0x0, duration=2680.799s, table=0, n_packets=n/a, n_bytes=4672, arp,in_port=25 actions=output:26
>> 
>> 10.0.0.1 is connected to port 25, 10.0.0.2 to port 26, 10.0.0.3 to port 27
>> 
>> I have noticed that when sending ~15 MB/s from 10.0.0.1, only about 10% actually arrives at 10.0.0.3. The `dump-flows` command shows that the bytes are dropped at port 25:
>> 
>> root at PicOS-OVS$ovs-ofctl dump-ports th1
>> OFPST_PORT reply (OF1.4) (xid=0x2): 4 ports
>>  port 25: rx pkts=24956726, bytes=33491813828, drop=22503515, errs=0, frame=0, over=0, crc=0
>>           tx pkts=73, bytes=4672, drop=0, errs=0, coll=0
>>           duration=3355.201s
>> 
>> Aside from an explicit flow that defines a drop action, what could be the cause of the bytes being dropped coming into port 25? I have verified that no other visible or hidden flows are active that could cause packet drops.
>> 
>> I am using Open vSwitch version 2.0.90 and OpenFlow 1.4 on a pica8 hardware switch. No controller is active.
> 
> You might get some more information from /tmp/log/messages.
> 
> I suggest though that you follow this up with pica8 unless you have a
> reproducible setup with an official release version of OVS.

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