tasklwIP - A Lightweight TCP/IP stack - Tasks: task #14129, DNS: implement domain search list...


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task #14129: DNS: implement domain search list (e.g. filled via DHCP)

Submitter:  Simon Goldschmidt <goldsimon>
Submitted:  Tue 23 Aug 2016 07:49:58 AM UTC
Category:  None Should Start On:  Tue 23 Aug 2016 12:00:00 AM UTC
Should be Finished on:  Tue 23 Aug 2016 12:00:00 AM UTC Priority:  5 - Normal
Status:  None Privacy:  Public
Assigned to:  None Percent Complete:  0%
Open/Closed:  Open Planned Release:  None
Effort:  0.00

Wed 14 Nov 2018 07:47:32 PM UTC, comment #4: 

Re comment #2:
I know. Comment #1 was meant as a reminder that we need to filter out '.local' from the DNS search list, even if someone sets it (e.g. via DHCP).

Re comment #3:
Yes, do you want to provide a patch?

Simon Goldschmidt <goldsimon>
Group administrator
Wed 14 Nov 2018 01:41:58 AM UTC, comment #3: 

A single domain can be obtained from DHCP option 15.

A domain search list could also be obtained from DHCP option 119. However, from what I've read, Windows doesn't request option 119, and Windows DHCP servers don't provide it. Linux and MacOS do request it though. See: Which DHCP Client OS Support DHCP Option 119 Domain Suffix Search? - Server Fault.

Note that getting the domain from DHCP option 15 may be useful for other things besides DNS domain. For example, RFC 3958 defines DDDS which does DNS look-ups of services (using NAPTR, SRV) for the local domain which can be discovered with DHCP option 15. E.g. RFC 6011 SIP User Agent Configuration can use this. So, adding DHCP option 15 support can be useful even before DNS adds support for a domain search list.

Craig McQueen <cmcqueen1975>
Wed 14 Nov 2018 12:25:40 AM UTC, comment #2: 

I have not seen PC systems (Windows or Linux) in which ".local" is a DNS search domain. So ".local" must be explicitly in the hostname in order to do an mDNS lookup.

See here for a usage example for Mac: Adding “local” to the DNS Search Domains has no effect

Craig McQueen <cmcqueen1975>
Wed 07 Dec 2016 11:19:42 AM UTC, comment #1: 

Important when used with mDNS: ".local" shall not be added to domains (not ending with ".") with 2 or more parts to prevent "stealing" identity when the normal DNS server does not reply.

Simon Goldschmidt <goldsimon>
Group administrator
Tue 23 Aug 2016 07:49:58 AM UTC, original submission:  

Simon Goldschmidt <goldsimon>
Group administrator


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