Interfaces listing is not stable

[iTrooz]

Description

If you run ip a a lot of times inside a container, you will notice interfaces moves around. For example, here is one such output:

3: eth1: <UP,LOWER_UP> mtu 1500 
    link/ether 3e:15:7b:cc:27:c7 brd ff:ff:ff:ff:ff:ff
    inet 172.19.0.3/24 scope global dynamic 
1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65522 
    link/loopback 00:00:00:00:00:00 brd ff:ff:ff:ff:ff:ff
    inet 127.0.0.1/8 scope global dynamic 
2: eth0: <UP,LOWER_UP> mtu 1500 
    link/ether 0e:23:9d:55:49:92 brd ff:ff:ff:ff:ff:ff
    inet 172.23.0.4/16 scope global dynamic 

(Notice that lo is in the middle).
Doing ip a again may yield another order

Steps to reproduce

See above

runsc version

runsc version release-20260323.0
spec: 1.1.0-rc.1

docker version (if using docker)

Reproducible with `runsc do ip a`

uname

Linux somehost 6.19.10-arch1-1 #1 SMP PREEMPT_DYNAMIC Thu, 26 Mar 2026 19:20:28 +0000 x86_64 GNU/Linux

kubectl (if using Kubernetes)

repo state (if built from source)

No response

runsc debug logs (if available)

[iTrooz]

I'd be happy to submit a PR for this, if the bug is confirmed :)

[ayushr2]

cc @nybidari

Happy to review PRs.

[nybidari]

Yes, in gVisor it is displayed from a map and the order can change. Linux typically displays interfaces in the interface index order. The fix should be to display based on the interface index.

@iTrooz please go ahead and submit the PR, thanks!