musl - Re: DNS resolver patch

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Message-ID: <1956158595.3040187.1544124961290.JavaMail.zimbra@totalphase.com>
Date: Thu, 6 Dec 2018 11:36:01 -0800 (PST)
From: Tarun Johar  <tjohar@...alphase.com>
To: Natanael Copa <ncopa@...inelinux.org>, Florian Weimer <fweimer@...hat.com>
Cc: musl@...ts.openwall.com
Subject: Re: DNS resolver patch

I managed to add the proposed fixes to https://www.virtualbox.org/ticket/18171 as comment. Hopefully, this helps our cause. 

Thanks, 
Tarun 

----- Original Message -----

From: "Tarun Johar" <tjohar@...alphase.com> 
To: "Natanael Copa" <ncopa@...inelinux.org>, "Florian Weimer" <fweimer@...hat.com> 
Cc: musl@...ts.openwall.com 
Sent: Friday, December 7, 2018 12:20:24 AM 
Subject: Re: [musl] DNS resolver patch 

Hi Natanael/Florian, 

A couple of solutions for this are stated below. 

The code is in src/VBox/Devices/Network/slirp/hostres.c :517 

if ( qtype != Type_A 
&& qtype != Type_CNAME 
&& qtype != Type_PTR 
&& qtype != Type_ANY) 
{ 
LogErr(("NAT: hostres: unsupported qtype %d\n", qtype)); 
return refuse(res, RCode_NotImp); 
} 

There are two possible fixes: 

- Add a conditional above this code for Type_AAAA where the resolver returns RCode_NXDomain instead of RCode_NotImp: 

if (qtype == Type_AAAA) { 
LogErr(("NAT: hostres: cannot resolve qtype %d\n", qtype)); 
return refuse(res, RCode_NXDomain); 
} 

- Implement IPv6 resolution for AAAA records. The resolve() function at line 574 would need to be updated. 

I just came across ticket filed by Natanael with Virtual box at https://www.virtualbox.org/ticket/18171 . Since one of us is already talking with them, could you propose the above solutions to them (and add me to the loop at well). 

Thanks, 
Tarun 

----- Original Message -----

From: "Natanael Copa" <ncopa@...inelinux.org> 
To: "Florian Weimer" <fweimer@...hat.com> 
Cc: musl@...ts.openwall.com, "Tarun Johar" <tjohar@...alphase.com> 
Sent: Thursday, December 6, 2018 9:18:20 PM 
Subject: Re: [musl] DNS resolver patch 

On Thu, 06 Dec 2018 15:53:43 +0100 
Florian Weimer <fweimer@...hat.com> wrote: 



* Tarun Johar: 

> The VirtualBox --natdnsresolver does not support IPv6 AAAA address 
> queries. It returns "NotImp" (code 4) for such queries. 

I think that's not the only bug, and glibc fails to work around all of 
them. We occasionally get bug reports about DNS resolution issues under 
VirtualBox, too. Oracle really needs to fix this properly. 

Thanks, 
Florian 

Problem is here: 



https://www.virtualbox.org/browser/vbox/trunk/src/VBox/Devices/Network/slirp/hostres.c?rev=59202#L408 

402 if ( qtype != Type_A 
403 && qtype != Type_CNAME 
404 && qtype != Type_PTR 
405 && qtype != Type_ANY) 
406 { 
407 LogErr(("NAT: hostres: unsupported qtype %d\n", qtype)); 
408 return refuse(pData, m, RCode_NotImp); 
409 } 


They should return RCode_NXDomain instead of RCode_NotImp. Seems like 
they also have more of those invalid use of NotImp. 

-nc 


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