[10996] - use 'ip' structured data to safely retrieve default route interface #11800

mosys0815 · 2025-10-07T09:43:34Z

Using ip route structured data allows to query safely the default route interface, no matter the output of the standard 'ip route' output.

commit dbe1f87 Merge: 35b7a74 4d46bec Author: Bjoern Anters <[email protected]> Date: Mon Jul 14 09:41:30 2025 +0200 Merge branch 'main' into 10996_get_default_nic commit 35b7a74 Author: Bjoern Anters <[email protected]> Date: Thu Jun 26 16:25:57 2025 +0200 use ip route structured data to retrieve default interface commit 234dfd3 Merge: a310b80 16c60c7 Author: Björn Anters <[email protected]> Date: Tue Jun 24 17:51:37 2025 +0200 Merge branch 'apache:main' into 10996_get_default_nic commit a310b80 Author: Bjoern Anters <[email protected]> Date: Mon Jun 23 16:40:10 2025 +0200 use ip route structured data to retrieve default interface commit 8e8549c Author: Bjoern Anters <[email protected]> Date: Mon Jun 23 15:47:13 2025 +0200 Revert "make debian build vars work" This reverts commit c1ccb16. commit 0446631 Author: Bjoern Anters <[email protected]> Date: Mon Jun 23 15:45:37 2025 +0200 Revert "use ip route structured data to retrieve default interface" This reverts commit 91578d7. commit c1ccb16 Author: Bjoern Anters <[email protected]> Date: Tue Jun 17 12:06:44 2025 +0200 make debian build vars work commit 91578d7 Author: Bjoern Anters <[email protected]> Date: Mon Jun 16 16:18:36 2025 +0200 use ip route structured data to retrieve default interface commit dbaeeda Author: Bjoern Anters <[email protected]> Date: Mon Jun 16 16:17:49 2025 +0200 use ip route structured data to retrieve default interface commit 44207cd Author: Bjoern Anters <[email protected]> Date: Mon Jun 16 16:15:33 2025 +0200 use ip route structured data to retrieve default interface commit c88a905 Author: Bjoern Anters <[email protected]> Date: Mon Jun 16 16:12:13 2025 +0200 use ip route structured data to retrieve default interface commit 6200d66 Author: Bjoern Anters <[email protected]> Date: Mon Jun 16 16:07:40 2025 +0200 use ip route structured data to retrieve default interface commit e547724 Author: Bjoern Anters <[email protected]> Date: Mon Jun 16 15:53:43 2025 +0200 use ip route structured data to retrieve default interface commit 9fb0150 Author: Bjoern Anters <[email protected]> Date: Tue Jun 10 17:23:45 2025 +0200 use ip route structured data to retrieve default interface

boring-cyborg · 2025-10-07T09:43:37Z

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codecov · 2025-10-07T13:11:24Z

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 17.54%. Comparing base (4d46bec) to head (6b9c422).
⚠️ Report is 331 commits behind head on main.

Additional details and impacted files

@@             Coverage Diff              @@
##               main   #11800      +/-   ##
============================================
+ Coverage     16.57%   17.54%   +0.96%     
- Complexity    13987    15467    +1480     
============================================
  Files          5746     5897     +151     
  Lines        510860   527397   +16537     
  Branches      62140    64407    +2267     
============================================
+ Hits          84696    92516    +7820     
- Misses       416690   424486    +7796     
- Partials       9474    10395     +921

Flag	Coverage Δ
uitests	`3.60% <ø> (-0.31%)`	⬇️
unittests	`18.60% <100.00%> (+1.12%)`	⬆️

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weizhouapache · 2025-10-07T13:18:54Z

it worked on ubuntu 24

# /bin/ip -j a | /bin/jq -r '.[] | .addr_info | map(select(.local == "'`/bin/ip -j r s default | /bin/jq -r '.[0] | .prefsrc'`'")) | .[].label'
eth0

however, on RHEL and variants, the path of ip is not /bin/ip

# which ip
/usr/sbin/ip

mosys0815 · 2025-10-07T14:51:54Z

well, until now plain ip is used, i could replace is with just ip, or the script can get the path beforehand, what would you prefer?

mosys0815 · 2025-10-08T10:24:22Z

I changed the script to use short-paths for ipand jq, as like as it was before

mosys0815 · 2025-11-17T12:41:44Z

@weizhouapache anything missing still?

daviftorres · 2025-11-17T15:00:12Z

Dear @mosys0815,

I agree with the goal of finding a more reliable way to retrieve the interface, but I want to apologize in advance for my straightforward feedback on the proposed solutions:

The approach feels overly complex, which makes it hard to understand and, in my opinion, not an effective way to achieve the goal.

When I tried to run it, it didn’t work due to unescaped characters (as @weizhouapache also mentioned).

Were you able to run the command successfully? If so, could you share your environment or context?

I would prefer updating the PR to use the following instead:

ip route show default | awk '{print $5}'

The following one also accomplish the same goal but I would prefer to use the one above because does not require jq to be installed.

ip -j r s default | jq -r '.[0] | .dev'

Regards,

daviftorres · 2025-11-17T15:01:36Z

utils/src/main/java/com/cloud/utils/net/NetUtils.java

            return defDev;
        }
-        return Script.runSimpleBashScript("ip route show default 0.0.0.0/0 | head -1 | awk '{print $5}'");
+        return Script.runSimpleBashScript("ip -j a | jq -r '.[] | .addr_info | map(select(.local == \"'`ip -j r s default | jq -r '.[0] | .prefsrc'`'\")) | .[].label'");


Suggested change

return Script.runSimpleBashScript("ip -j a | jq -r '.[] | .addr_info | map(select(.local == \"'`ip -j r s default | jq -r '.[0] | .prefsrc'`'\")) | .[].label'");

return Script.runSimpleBashScript("ip route show default | awk '{print $5}'");

My suggestion.

Suggested change

return Script.runSimpleBashScript("ip -j a | jq -r '.[] | .addr_info | map(select(.local == \"'`ip -j r s default | jq -r '.[0] | .prefsrc'`'\")) | .[].label'");

return Script.runSimpleBashScript("ip route show default | awk '{print $5}'");

My suggestion.

agree with it

Thanks for your feedback @daviftorres :)

Using json to retrieve structured data makes plain text parsing unnecessary, it does not matter how the text output is formatted and how the content differs in the future.

Tbh i am not quite sure whether jq is available in a minimal installation, but i wouldn't see it as a big deal or security relevant dependency.

For testing purposes you can not just copy the script into your console. I had to escape and quote parts additionally because of the general quoting in Script.runSimpleBashScript. The End result, which you also can see in debug output of management server log looks like:

ip -j a | jq -r '.[] | .addr_info | map(select(.local == "'`ip -j r s default | jq -r '.[0] | .prefsrc'`'")) | .[].label'

To show you the output of your suggestion on our l3 network:

~$ ip route show default default proto bird src 10.64.16.3 metric 32 nexthop via inet6 fe80::9e5a:80ff:feaf:b108 dev eth1a weight 1 nexthop via inet6 fe80::e65e:ccff:fe44:1a08 dev eth1b weight 1 default via 10.64.17.229 dev eth1b proto static src 10.64.17.230 metric 1024 onlink default via 10.64.16.229 dev eth1a proto static src 10.64.16.230 metric 1024 onlink

~$ ip route show default | awk '{print $5}' 10.64.16.3 dev dev eth1b eth1a

That is nothing different from where I come from, hence proposing my change.
Using json structured data and filtering for "label" in "prefsrc" always gives the correct default outgoing interface.

Your json variant

~$ ip -j r s default | jq -r '.[0] | .dev' null

unfortunately does not return any interface at all.

remove fullpath from ip and jq commands

6b9c422

mosys0815 changed the title ~~[10996] - use 'ip route' structured data to safely retrieve default route interface~~ [10996] - use 'ip' structured data to safely retrieve default route interface Oct 8, 2025

daviftorres reviewed Nov 17, 2025

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[10996] - use 'ip' structured data to safely retrieve default route interface #11800

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	return Script.runSimpleBashScript("ip -j a \| jq -r '.[] \| .addr_info \| map(select(.local == \"'`ip -j r s default \| jq -r '.[0] \| .prefsrc'`'\")) \| .[].label'");
	return Script.runSimpleBashScript("ip route show default \| awk '{print $5}'");

[10996] - use 'ip' structured data to safely retrieve default route interface #11800

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[10996] - use 'ip' structured data to safely retrieve default route interface #11800

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