[Feature] use system dns as default-nameserver

[iamtrazy]

Verify steps

• [X] 我已经在 Issue Tracker 中找过我要提出的请求 I have searched on the issue tracker for a related feature request.
• [X] 我已经仔细看过 Documentation 并无法自行解决问题 I have read the documentation and was unable to solve the issue.

Description

i have my own doh server . when i set it as my nameserver in clash it needs to lookup that address using default-nameserver . i want that to be my hotspot gateway ip . on older android devices i can manually set it as 192.168.43.1 but with new mobile phones my gateway ip keeps changing , is there any way to automatically get system dns as my default-nameserver

Possible Solution

set a way to get system default dns server as default-nameserver without specifying an ip address

[Dreamacro]

use dhcp dns instead

[iamtrazy]

for some reason using gateway ip directly as nameserver works but using dhcp://wlp2s0 doesnt work , also on windows using dhcp://Wi-Fi doesnt work.

[iamtrazy]

all DNS requests failed, first error: DHCP not responding

this is constantly on the log

https://github.com/Dreamacro/clash/issues/2135

this is the exact issue im facing with using dhcp as nameserver

on linux using auto-redir works , but udp isnt working without tun mode

[ElemenTP]

This has been discussed before: #1495