Fix dns resolution skipping over nameservers with valid responses

[dwelch-r7]

Continuation of #18660

Recommend turning whitespace changes off for this one https://github.com/rapid7/metasploit-framework/pull/18662/files?diff=unified&w=1

There have been a few issues reported with DNS resolution recently this PR aims to resolve (😁) those

Noticed a couple of issues:

1. Only a single nameserver was ever being pulled out of /etc/resolv.conf with the last nameserver overwriting the previous one(s)
2. Looping over the nameservers until we get a valid response was not correctly returning the answer from DNS instead moving on to the next nameserver until it ran out and saying the dns resolution was failing

[adfoster-r7]

Does the windows codepath get handled correctly? Probably worth a check after the unix-y path works 👀

[dwelch-r7]

according to this random issue report (I couldn't find a better example of what gets returned) it should be correct for windows
https://bugs.ruby-lang.org/issues/12604

but I'll be sure to verify this on windows myself too

[adfoster-r7]

I have a windows dev env set up too, let me know if you've got replication steps you want me to follow 👍

[adfoster-r7]

Can we verify with the docs/schema that there isn't more edegcases to consider in the /etc/resolv.conf config format? 🤞

Edit: Looks like there's some options that we could potentially support, but not needed in this PR

[dwelch-r7]

Can we verify with the docs/schema that there isn't more edegcases to consider in the /etc/resolv.conf config format? 🤞

Edit: Looks like there's some options that we could potentially support, but not needed in this PR

Forgot to reply to this earlier apologies
yea was looking through these docs, only thing that stands out like you said are the options
https://www.ibm.com/docs/en/aix/7.3?topic=formats-resolvconf-file-format-tcpip

[adfoster-r7]

Not a blocker: This would be easier to test if there was a top level resolve command, similar to the one in Meterpreter 😄

[adfoster-r7]

Worked against my custom /etc/resolv.conf file 👍

search foo.bar.com localdomain
nameserver x.x.x.x
nameserver x.x.x.x

[adfoster-r7]

Release Notes

Fixes an edgecase where features set dns_feature true did not correctly parse a user's /etc/resolv.conf file if there were multiple nameservers present

[adfoster-r7]

Not a blocker: This would be easier to test if there was a top level resolve command, similar to the one in Meterpreter 😄

I think @zeroSteiner has got us covered here now with the work he's doing in the same area🤞