netdev - Re: [BUG] Iproute2 batch-mode fails to bring up veth

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Date:   Tue, 16 Mar 2021 10:39:27 +0200
From:   Ido Schimmel <idosch@...sch.org>
To:     Tim Rice <trice@...teo.net>, petrm@...dia.com
Cc:     netdev@...r.kernel.org
Subject: Re: [BUG] Iproute2 batch-mode fails to bring up veth

+ Petr

On Tue, Mar 16, 2021 at 06:22:08AM +1100, Tim Rice wrote:
> Hey all,
> 
> Sorry if this isn't the right place to report Iproute2 bugs. It was implied by README.devel as well as a couple of entries I saw in bugzilla.
> 
> I use iproute2 batch mode to construct network namespaces. Example script:
> 
>   $ cat ~/bin/netns-test.sh
>   #! /bin/bash
> 
>   gw=192.168.5.1
>   ip=192.168.5.2
>   ns=netns-test
>   veth0=${ns}-0
>   veth1=${ns}-1
> 
>   /usr/local/sbin/ip -b - << EOF
>   link add $veth0 type veth peer name $veth1
>   addr add $gw peer $ip dev $veth0
>   link set dev $veth0 up
>   netns add $ns
>   link set $veth1 netns $ns
>   netns exec $ns ip link set dev lo up
>   netns exec $ns ip link set dev $veth1 up
>   netns exec $ns ip addr add $ip/24 dev $veth1
>   netns exec $ns ip addr add $ip peer $gw dev $veth1
>   netns exec $ns ip route add default via $gw dev $veth1
>   netns exec $ns ip route add 192.168.0.0/24 via $gw dev $veth1
>   EOF
> 
> 
> I noticed when version 5.11.0 dropped that this stops working. Batch mode fails to bring up the inner veth.
> 
> Expected usage (as produced by v5.10.0):
> 
>   $ sudo ./bin/netns-test.sh
>   $ sudo ip netns exec netns-test ip route
>   default via 192.168.5.1 dev netns-test-1
>   192.168.0.0/24 via 192.168.5.1 dev netns-test-1
>   192.168.5.0/24 dev netns-test-1 proto kernel scope link src 192.168.5.2
>   192.168.5.1 dev netns-test-1 proto kernel scope link src 192.168.5.2
> 
> Actual behaviour:
> 
>   $ sudo ./bin/netns-test.sh
>   $ sudo ip netns exec netns-test ip route  # Notice the empty output
>   $ sudo ip netns exec netns-test ip link
>   1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 qdisc noqueue state UNKNOWN mode DEFAULT group default qlen 1000
>       link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00
>   39: netns-test-1@...0: <BROADCAST,MULTICAST> mtu 1500 qdisc noop state DOWN mode DEFAULT group default qlen 1000
>       link/ether 1a:96:4e:4f:84:31 brd ff:ff:ff:ff:ff:ff link-netnsid 0
> 
> System info:
> 
> * Distro: Void Linux
> * Kernel version: 5.10.23
> * CPU: AMD Ryzen 7 1800X and Ryzen 5 2600. (Reproduced on both.)
> 
> Git bisect pinpoints this commit: https://github.com/shemminger/iproute2/commit/1d9a81b8c9f30f9f4abeb875998262f61bf10577
> 
> That commit was focused on refactoring batch mode. This is consistent with my experience that only batch mode is affected. Everything works as expected when running the commands manually.
> 
> ~ Tim