net: Failed net.LookupAddr in ipv6 wrt leading zeroes

[gopherbot]

by viriketo:

IPv6 addresses may have leading zeros or not. They are optional. The address comparisons
for net.LookupAddr work by string comparison, so they may fail in case of the /etc/hosts
entry not matching exactly the LookupAddr parameter.

For example, these are equivalent addresses:
fce6:d1ad:ca44:9625:e589:3806:0248:8591
fce6:d1ad:ca44:9625:e589:3806:248:8591

The related code: http://golang.org/src/pkg/net/hosts.go

[gopherbot]

Comment 1 by viriketo:

The same can be said of ipv4 addresses in fact. They can have leading zeroes.

[ianlancetaylor]

Comment 2:

Labels changed: added repo-main, release-go1.5.

[odeke-em]

If anyone has a way to, would you mind providing some test cases in direct relation to this issue? This is because I've been looking at this and so far I have built an independent package for ip comparison. Thank you.

[nightlyone]

An alternative aproach would be to look for ":0" or ".0" in the provided address and call net.ParseIP() followed by String() on it to normalize such rare cases and do the lookup with that result instead.

[odeke-em]

Nice, thank you for that @nightlyone. For some reason, I assumed that since this hadn't been implemented in the standard library, that there were problems with the parsing itself. Turns out your approach is way simpler and cleaner.

[gopherbot]

CL https://golang.org/cl/10306 mentions this issue.