netdev - Re: VRF Issue Since kernel 5

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Date:   Thu, 12 Sep 2019 06:54:59 +0000
From:   Gowen <gowen@...atocomputing.co.uk>
To:     David Ahern <dsahern@...il.com>,
        Alexis Bauvin <abauvin@...ine.net>,
        "mmanning@...tta.att-mail.com" <mmanning@...tta.att-mail.com>
CC:     "netdev@...r.kernel.org" <netdev@...r.kernel.org>
Subject: Re: VRF Issue Since kernel 5


currently:

vmAdmin@...M06:~$ uname -r
5.0.0-1018-azure

vmAdmin@...M06:~$ cat /etc/lsb-release
DISTRIB_ID=Ubuntu
DISTRIB_RELEASE=18.04
DISTRIB_CODENAME=bionic
DISTRIB_DESCRIPTION="Ubuntu 18.04.3 LTS"


I don't keep a history of kernel versions on test but I noticed it had gone to kernel 5 and stopped working - I'm about 80% sure that happened at the same time - I'll try and dig out some logs today to see what I can find for you as Linux is fairly new to me

Gareth





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

Sent: 11 September 2019 17:09

To: Gowen <gowen@...atocomputing.co.uk>; Alexis Bauvin <abauvin@...ine.net>; mmanning@...tta.att-mail.com <mmanning@...tta.att-mail.com>

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

Subject: Re: VRF Issue Since kernel 5

 


On 9/11/19 3:01 PM, Gowen wrote:

> Hi all,

> 

> It looks like ip vrf exec checks /etc/resolv.conf (found with strace -e

> trace=file sudo ip vrf exec mgmt-vrf host www.google.co.uk &>

> ~/straceFileOfVrfHost.txt) , but as I'm on an Azure machine using

> netplan, this file isn't updated with DNS servers. I have added my DNS

> server to resolv.conf and now can update the cache with "sudo ip vrf

> exec sudo apt update", if I am correct (which I'm not sure about as not

> really my area) then this might be affecting more than just me.

> 

> Also still not able to fix the updating cache from global VRF - which

> would cause bother in prod environment to others as well so think it

> would be good to get an RCA for it?

> 

> thanks for your help so far, has been really interesting.

> 

> Gareth

> 

> 

> ------------------------------------------------------------------------

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

> *Sent:* 11 September 2019 13:48

> *To:* David Ahern <dsahern@...il.com>; Alexis Bauvin

> <abauvin@...ine.net>; mmanning@...tta.att-mail.com

> <mmanning@...tta.att-mail.com>

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

> *Subject:* Re: VRF Issue Since kernel 5

>  

> yep no problem:

> 

> Admin@...M06:~$ sudo sysctl -a | grep l3mdev

> net.ipv4.raw_l3mdev_accept = 1

> net.ipv4.tcp_l3mdev_accept = 1

> net.ipv4.udp_l3mdev_accept = 1

> 

> 

> The source of the DNS issue in the vrf exec command is something to do

> with networkd managing the DNS servers, I can fix it by explicitly

> mentioning the DNS server:

> 

> systemd-resolve --status --no-page

> 

> <OUTPUT OMITTED>

> 

> Link 4 (mgmt-vrf)

>       Current Scopes: none

>        LLMNR setting: yes

> MulticastDNS setting: no

>       DNSSEC setting: no

>     DNSSEC supported: no

> 

> Link 3 (eth1)

>       Current Scopes: DNS

>        LLMNR setting: yes

> MulticastDNS setting: no

>       DNSSEC setting: no

>     DNSSEC supported: no

>          DNS Servers: 10.24.65.203

>                       10.24.65.204

>                       10.25.65.203

>                       10.25.65.204

>           DNS Domain: reddog.microsoft.com

> 

> Link 2 (eth0)

>       Current Scopes: DNS

>        LLMNR setting: yes

> MulticastDNS setting: no

>       DNSSEC setting: no

>     DNSSEC supported: no

>          DNS Servers: 10.24.65.203

>                       10.24.65.204

>                       10.25.65.203

>                       10.25.65.204

>           DNS Domain: reddog.microsoft.com

> 

> there is no DNS server when I use ip vrf exec command (tcpdump shows

> only loopback traffic when invoked without my DNS sever explicitly

> entered) - odd as mgmt-vrf isnt L3 device so thought it would pick up

> eth0 DNS servers?

> 

> I dont think this helps with my update cache traffic from global vrf

> though on port 80

> 



Let's back up a bit: your subject line says vrf issue since kernel 5.

Did you update / change the OS as well?



ie., the previous version that worked what is the OS and kernel version?

What is the OS and kernel version with the problem?