netdev - Re: VRF Issue Since kernel 5

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Message-ID: <CWLP265MB1554604C9DB9B28D245E47A2FDB10@CWLP265MB1554.GBRP265.PROD.OUTLOOK.COM>
Date:   Wed, 11 Sep 2019 11:49:51 +0000
From:   Gowen <gowen@...atocomputing.co.uk>
To:     David Ahern <dsahern@...il.com>, Alexis Bauvin <abauvin@...ine.net>
CC:     "netdev@...r.kernel.org" <netdev@...r.kernel.org>
Subject: Re: VRF Issue Since kernel 5


previously mentioned attchements




From: Gowen <gowen@...atocomputing.co.uk>

Sent: 11 September 2019 12:19

To: David Ahern <dsahern@...il.com>; Alexis Bauvin <abauvin@...ine.net>

Cc: netdev@...r.kernel.org <netdev@...r.kernel.org>

Subject: Re: VRF Issue Since kernel 5

 


Hi there,



Your perf command:



  isc-worker0000 20261 [000]  2215.013849: fib:fib_table_lookup: table 10 oif 0 iif 0 proto 0 0.0.0.0/0 -> 127.0.0.1/0 tos 0 scope 0 flags 0 ==> dev eth0 gw 10.24.12.1 src 10.24.12.10 err 0

  isc-worker0000 20261 [000]  2215.013915: fib:fib_table_lookup: table 10 oif 4 iif 1 proto 17 0.0.0.0/52138 -> 127.0.0.53/53 tos 0 scope 0 flags 4 ==> dev eth0 gw 10.24.12.1 src 10.24.12.10 err 0

  isc-worker0000 20261 [000]  2220.014006: fib:fib_table_lookup: table 10 oif 4 iif 1 proto 17 0.0.0.0/52138 -> 127.0.0.53/53 tos 0 scope 0 flags 4 ==> dev eth0 gw 10.24.12.1 src 10.24.12.10 err 0



Also I set all iptables to policy ACCEPT and flushed the rules, enabled forwarding, checked the sysctl settings are all '1'. I've looked at tracing DNS through the iptables and I see that DNS uses a loopback interface as source and destination - this would
 be odd on a Cisco box but having looked around this appears to be normal?



I also gathered an strace of updating the package cache as well as a perf of the same command - will send if interested (is more verbose and not sure if the spam filter will block it)



Gareth













From: Gowen



Sent: 11 September 2019 06:09



To: David Ahern <dsahern@...il.com>; Alexis Bauvin <abauvin@...ine.net>



Cc: netdev@...r.kernel.org <netdev@...r.kernel.org>



Subject: RE: VRF Issue Since kernel 5



 





Thanks for the link - that's really useful. I did re-order ip rules Friday (I think) - no change







-----Original Message-----



From: David Ahern <dsahern@...il.com> 



Sent: 10 September 2019 17:36



To: Alexis Bauvin <abauvin@...ine.net>; Gowen <gowen@...atocomputing.co.uk>



Cc: netdev@...r.kernel.org



Subject: Re: VRF Issue Since kernel 5







On 9/9/19 1:01 PM, Alexis Bauvin wrote:



> Could you try swapping the local and l3mdev rules?



> 



> `ip rule del pref 0; ip rule add from all lookup local pref 1001`







yes, the rules should be re-ordered so that local rule is after l3mdev rule (VRF is implemented as policy routing). In general, I would reverse the order of those commands to ensure no breakage.







Also, 5.0 I think it was (too many kernel versions) added a new l3mdev sysctl (raw_l3mdev_accept). Check all 3 of them and nmake sure they are set properly for your use case.







These slides do not cover 5.0 changes but are still the best collection of notes on VRF:



http://schd.ws/hosted_files/ossna2017/fe/vrf-tutorial-oss.pdf




View attachment "perfAptUpdate.txt" of type "text/plain" (26235 bytes)

View attachment "straceAptUpdate.txt" of type "text/plain" (39294 bytes)