clustermesh: fix pattern to match IPv4 address

[mhofstetter]

Executing cilium clustermesh vm install install-external-workload.sh fails if the randomly generated IP (v4) contains a zero (0) in its first byte.

Error: Malformed CLUSTER_ADDR: 104.198.85.126:2379

Therefore, this commit changes the pattern that is used to detect an IPv4 address (with port).

Until now i don't understand why it's working with the prefix [^[] for all other cases but not if the first byte is containing a zero 🤷‍♂️ I just think that this part isn't necessary - and shouldn't break anything 🙏

Detected on a cilium/cilium CI run: https://github.com/cilium/cilium/actions/runs/7067930793/job/19241908576

[marseel]

I wanted to understand that before approving as it was not obvious to me as well. I simplified the case to:

shopt -s extglob

pattern='[^[]@(25[0-5]|2[0-4][0-9]|[1][0-9][0-9]|[1-9][0-9]|[0-9])'
pattern2='@(25[0-5]|2[0-4][0-9]|[1][0-9][0-9]|[1-9][0-9]|[0-9])'
data='255'
data2='205'

if [[ $data == $pattern ]]; then echo yes; else echo no; fi
if [[ $data == $pattern2 ]]; then echo yes; else echo no; fi
if [[ $data2 == $pattern ]]; then echo yes; else echo no; fi
if [[ $data2 == $pattern2 ]]; then echo yes; else echo no; fi

output:

yes
yes
no
yes

So what happens is that [^[] means match any character except for ']': explanation
so the rest of pattern thinks that IP starts with 0.

Looks like we also accept the 12345.123.123.123 IP in both cases 🤷

[mhofstetter]

Thanks @marseel

I think you meant any character except for [ ?

Now that this is clear, the reason for this might have been to prevent matching any ipv6 address (without [..]) with this match 🤔 (which i don't think is necessary because these should be separated with colon anyway)

[marseel]

I think you meant any character except for [ ?

yea, sorry for that.

(which i don't think is necessary because these should be separated with colon anyway)

I don't think it's necessary either.

[michi-covalent]

a very innocent regex