- Add `UseProxy` field to `p2p.Config` and corresponding `--use-proxy` CLI flag.
- Implement proxy-aware `tcpDialer` (uses `golang.org/x/net/proxy` and attempts context-aware DialContext when supported).
- Wire `UseProxy` through `Server` to the dialer so peer dials can go via SOCKS5 proxy defined by `ALL_PROXY`/`all_proxy`.
- Minor debug `start.sh` for running geth with `--use-proxy`.
Signed-off-by: cloorc <wittcnezh@foxmail.com>
This is an alternative for #27407 with a solution based on gencodec.
With the PR, one can now configure like this:
```
# config.toml
[Node.P2P]
NAT = "extip:33.33.33.33"
```
```shell
$ geth --config config.toml
...
INFO [01-17|16:37:31.436] Started P2P networking self=enode://2290...ab@33.33.33.33:30303
```
