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[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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Squashed commit of the following:
Oct 7, 2025
6b9c422
remove fullpath from ip and jq commands
Oct 8, 2025
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2 changes: 1 addition & 1 deletion utils/src/main/java/com/cloud/utils/net/NetUtils.java
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Original file line number Diff line number Diff line change
Expand Up @@ -306,7 +306,7 @@ public static String getDefaultEthDevice() {
final String defDev = Script.runSimpleBashScript("/sbin/route -n get default 2> /dev/null | grep interface | awk '{print $2}'");
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'");
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@daviftorres daviftorres Nov 17, 2025

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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.

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@weizhouapache weizhouapache Nov 17, 2025

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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

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@weizhouapache weizhouapache Nov 17, 2025

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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

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@mosys0815 mosys0815 Nov 18, 2025

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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.

}

public static String getLocalIPString() {
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