[jira] [Commented] (TS-2595) DNS lookup failed with multiple search domains

["Thach Tran (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/TS-2595?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13917143#comment-13917143 ] 

Thach Tran commented on TS-2595:
--------------------------------

I agree that we could simplify by not caring about trailing dot when appending search domain.
However, if I'm not mistaken by my quick internet reading so far then apparently we shouldn't even attempt any search domain expansion if the name ends in dot. If this is true then I think we need some more code change to cater for this.
I'll read around some more and check the behaviour of other dns clients regarding trailing dot to confirm.

> DNS lookup failed with multiple search domains
> ----------------------------------------------
>
>                 Key: TS-2595
>                 URL: https://issues.apache.org/jira/browse/TS-2595
>             Project: Traffic Server
>          Issue Type: Bug
>          Components: DNS
>            Reporter: Thach Tran
>            Assignee: Leif Hedstrom
>             Fix For: 5.0.0
>
>         Attachments: ats_bad_dns.log
>
>
> I find the DNS search domain expanding logic of ATS a bit strange. On a system with multiple search domains in /etc/resolv.conf such as
> {noformat}
> search cisco.com google.com
> {noformat}
> and proxy.config.dns.search_default_domains set to 1, if ATS tries to lookup a hostname say 'developers', it will expand it to 'developers.cisco.com' first and then 'developers.cisco.com.google.com'. In other words, the next search domain will just get appended to the already expanded name. In this instance, it will end up failing as both 'developers.cisco.com' and 'developers.cisco.com.google.com' are not resolvable.
> I would expect ATS to lookup 'developers.cisco.com' first and then try 'developers.google.com' which will success.
> I have a quick look at the code and it seems like it has been that way since Oct 2009 at least. Could someone comment on whether this is intentional or it's actually a bug. I find most other dns clients (e.g., nslookup) append search domain in turn to the original name rather than work this way.



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