Re: [musl] MAXNS should be increased

["zhoujingqiang (A)" <zhoujingqiang1@huawei.com>]

Thanks for reply,

It is not advisable to use localhost as a DNS server in embedded devices. It requires a resident process, which consumes many memory and bandwidth.
We only provide devices, not servers. Servers are provided by carriers. We cannot write a build-in special servers on resolv.conf.
Our devices need to be sold to carriers around the world. There are many small carriers. They have their own domain names, which are non-conflicting but unique. In this case, increasing the MAXNS limit is the simplest and most efficient way.I think raising MAXNS won't hurt anything.
Or is it possible to provide an interface for MAXNS to be dynamically configurable to make it more flexible?

-----邮件原件-----
发件人: Rich Felker [mailto:dalias@libc.org] 
发送时间: 2023年1月11日 0:29
收件人: zhoujingqiang (A) <zhoujingqiang1@huawei.com>
抄送: musl@lists.openwall.com; liudongxu <liudongxu3@huawei.com>; Yulu(Brooklyn,RTOS) <yulu20@huawei.com>; Nixiaoming <nixiaoming@huawei.com>; Wangxu <wangxu72@huawei.com>; qiuguorui <qiuguorui1@huawei.com>; wangyunhe (A) <wangyunhe@huawei.com>
主题: Re: [musl] MAXNS should be increased

On Tue, Jan 10, 2023 at 12:57:34AM +0000, zhoujingqiang (A) wrote:
> Hello,
> 
> Currently, MAXNS is set to 3 which limits the number of nameserver.
> It is not enough to meet most people's requirements for private DNS 
> servers. In my scenario, my client needs to access the networks of six 
> companies. Each company provides active/standby servers to obtain 
> private domain names. Three DNS servers are far from enough.
> 
> Expect to increase MAXNS to 12
> 
> Glibc has similar open bug[1]. The concern is that changing MAXNS 
> would cause an ABI break. Musl does not have this problem since 
> __res_state is stub.
> [1]: https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=998211
> 
> I am not subscribed and want to be Cc'd on replies, thanks.

Multiple nameservers in resolv.conf are not a means to do unioning of conflicting DNS namespaces. They're expected to be purely redundant with non-conflicting (i.e. if one doesn't know about something another does, it has to ignore the query or ServFail, not NxDomain or NODATA
it) records. If you need unioning of distinct spaces using custom rules for resolving conflicts, you need a special nameserver running on localhost or somewhere else you control that performs this logic.

Rich