Codex may run many per-thread proxy instances, so hardcoded proxy ports
are brittle and conflict-prone. The previous "ephemeral" approach still
had a race: `build()` read `local_addr()` from temporary listeners and
dropped them before `run()` rebound the ports. That left a
[TOCTOU](https://en.wikipedia.org/wiki/Time-of-check_to_time-of-use)
window where the OS (or another process) could reuse the same port,
causing intermittent `EADDRINUSE` and partial proxy startup.
Change the managed proxy path to reserve real listener sockets up front
and keep them alive until startup:
- add `ReservedListeners` on `NetworkProxy` to hold HTTP/SOCKS/admin std
listeners allocated during `build()`
- in managed mode, bind `127.0.0.1:0` for each listener and carry those
bound sockets into `run()` instead of rebinding by address later
- add `run_*_with_std_listener` entry points for HTTP, SOCKS5, and admin
servers so `run()` can start services from already-reserved sockets
- keep static/configured ports only when `managed_by_codex(false)`,
including explicit `socks_addr` override support
- remove fallback synthetic port allocation and add tests for managed
ephemeral loopback binding and unmanaged configured-port behavior
This makes managed startup deterministic, avoids port collisions, and
preserves the intended distinction between Codex-managed ephemeral ports
and externally managed fixed ports.
## Summary
Add explicit, model-visible network policy decision metadata to blocked
proxy responses/errors.
Introduces a standardized prefix line: `CODEX_NETWORK_POLICY_DECISION
{json}`
and wires it through blocked paths for:
- HTTP requests
- HTTPS CONNECT
- SOCKS5 TCP/UDP denials
## Why
The model should see *why* a request was blocked
(reason/source/protocol/host/port) so it can choose the correct next
action.
## Notes
- This PR is intentionally independent of config-layering/network-rule
runtime integration.
- Focus is blocked decision surface only.
Constructors with long param lists can be hard to reason about when a
number of the args are `None`, in practice. Introducing a struct to use
as the args type helps make things more self-documenting.
### Summary
- Adds an optional SOCKS5 listener via `rama-socks5`
- SOCKS5 is disabled by default and gated by config
- Reuses existing policy enforcement and blocked-request recording
- Blocks SOCKS5 in limited mode to prevent method-policy bypass
- Applies bind clamping to the SOCKS5 listener
### Config
New/used fields under `network_proxy`:
- `enable_socks5`
- `socks_url`
- `enable_socks5_udp`
### Scope
- Changes limited to `codex-rs/network-proxy` (+ `codex-rs/Cargo.lock`)
### Testing
```bash
cd codex-rs
just fmt
cargo test -p codex-network-proxy --offline
