IPv6 DNS bug

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eddiewu
Posts: 2
Joined: Wed Nov 25, 2020 9:10 am

IPv6 DNS bug

Post by eddiewu » Wed Nov 25, 2020 9:20 am

Hello,

I have found a bug in the latest version of Softether (4.34 Build 9745 RTM) regarding DNS resolver.
My setup is a pretty simple one using SecureNAT without any local bridge.
By design, the server should forward client's DNS request to the real dns listed in /etc/resolv.conf in Linux.

However, if the resolv.conf has IPv6 servers before IPv4 ones, itwill fail if the client connects via IPv4.
For example, in resolv.conf this is fine:
nameserver 8.8.8.8
nameserver 2001:4860:4860::8888

But this will fail any dns lookup:
nameserver 2001:4860:4860::8888
nameserver 8.8.8.8

The server itself can use the IPv6 dns without any problem, by the way.

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