Problem communicating with IPv6 only servers

[Maxwellads]

Please read contributing guidelines. Thanks. I am so glad that this project is still maintained. Describe the bug So I have an IPv6 only server, which I deployed shadowsocks-rust and tested it on my computer, works fine. But this isn't happening to shadowsocks-android - at least not in VPN mode. When I connect to the server, the client (android) complains that "connection was closed", while server says:

2024-10-24T17:39:58.252053437+00:00 ERROR tcp tunnel [::1]:44570 -> [An_IPv4]:443 connect failed, error: Network is unreachable (os error 101)

But something funny is that, while the connection doesn't go well with VPN mode, the socks5 proxy port delivers connection in the correct way.

Looks like the shadowsocks-rust code worked well, but something went wrong on the VPN codes.

To Reproduce Steps to reproduce the behavior:

1. Deploy an IPv6 only server (Optional: use kcptun to ensure connectivity)
2. Connect to the server by shadowsocks-android

Expected behavior As the logging mentioned above, the server will be trying to feedback information to the client's IPv4 address, instead of IPv6, which prevents IPv6 server to communicate with the client.

Screenshots If applicable, add screenshots to help explain your problem.

Smartphone (please complete the following information):

• Android/Chrome OS version: Android 11
• Device: LG-G710
• Version: 5.3.4
• Last version that did not exhibit the issue: [not applicable]

Configuration Put an x inside the [ ] that applies.

• [ ] IPv4 server address
• [x] IPv6 server address
• [x] Client IPv4 availability
• [x] Client IPv6 availability
• Encrypt method: aes-256-gcm
• Route
  • [x] All
  • [ ] Bypass LAN
  • [ ] Bypass China
  • [ x] Bypass LAN & China
  • [ ] GFW List
  • [ ] China List
  • [ ] Custom rules
• [ ] IPv6 route
• [x] Apps VPN mode
  • [ ] Bypass mode
• Remote DNS: 8.8.8.8
• [ ] DNS over UDP
• Plugin configuration (if applicable):
• [ ] Auto Connect
• [ ] TCP Fast Open
• If you're not using VPN mode, please supply more details here:

Additional context Add any other context about the problem here.

[Maxwellads]

I can exclude the possible cause that the remote end does not have an IPv4 address, as the default "test for connection" target is cp.cloudflare.com, which indeed has one; Also, in VPN mode, I tried to connnect to google.com via Chrome, which has both IPv4 and v6 and also didn't work. However, I can easily access Telegram servers by using pointing its socks5 proxy to client's socks5 port.

[madeye]

Try enable the "IPv6 route" option.

[Maxwellads]

Try enable the "IPv6 route" option.

I have already tried it before submitting this issue, which had no luck. I wish I could provide logs on the client end to help.