Allow Host / Domain Names starting with an Underscore [master]

[shundhammer]

Target Branch

This is the merge PR for master of PR #1301 / PR #1302.

Bugzilla

https://bugzilla.suse.com/show_bug.cgi?id=1219920

Problem

Modern DNS setups require using a leading underscore for hostnames in some situations, e.g. _mydomain.example.com. But that is not possible to enter in the YaST DNS Server module: Underscores are generally rejected.

Fix

Allow a leading underscore for host and domain names. Not just anywhere, just as the leading character.

Since the check is in Hostname.rb which belongs to the yast2 package (repo yast-yast2), this is not in the yast2-dns-server package where it might be expected.

Known Limitation

This allows a leading underscore for all components of a FQDN in all circumstances. Users need to have some expertise to know when that is suitable.

The Error Message

The error message quoted in the bug remains the same; we are not changing it, so not all translations will be broken, resulting in purely English error messages for all international users. The message does not contain anything about the leading underscore. But the message should not appear when this is used correctly.

Screenshot

Notice that leading underscores are now allowed, while underscores in other places are not.

Testing

Manual testing with sudo yast2 dns-server after a manual sudo rake install.

Reference

• https://learn.microsoft.com/en-us/microsoft-365/security/office-365-security/email-authentication-dkim-configure?view=o365-worldwide#syntax-for-dkim-cname-records

Related PRs

• Original PR for SLE-15-SP5: Allow Host / Domain Names starting with an Underscore [SLE-15-SP5] #1301
• Merge PR for SLE-15-SP6: Allow Host / Domain Names starting with an Underscore [SLE-15-SP6] #1302

[coveralls]

coverage: 41.887% (+0.008%) from 41.879%
when pulling 6e29230 on huha-hostname-master
into e734000 on master.

[teclator]

LGTM

[yast-bot]

✔️ Internal Jenkins job #228 successfully finished
✔️ Created OBS submit request #1147374