feat(p2p/nat): limit UPNP request concurrency #21390

[gzliudan]

Proposed changes

This adds a lock around requests because some routers can't handle concurrent requests. Requests are also rate-limited.

The Map function request a new mapping exactly when the map timeout occurs instead of 5 minutes earlier. This should prevent duplicate mappings.

Ref: ethereum#21390

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[Copilot]

Pull request overview

This PR updates the UPnP NAT implementation to better handle routers that misbehave under concurrent SOAP requests by serializing and rate-limiting requests, and adjusts port-mapping refresh timing to avoid overlapping/duplicate mappings.

Changes:

• Add per-UPnP-instance request serialization and a 200ms minimum delay between SOAP requests (withRateLimit), and route UPnP client calls through it.
• Change UPnP discovery to check NAT enablement via a rate-limited helper (natEnabled) and refactor the matcher callback signature.
• Adjust nat.Map refresh scheduling to renew mappings exactly at the mapping timeout (but also changes the timeout value).

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 4 comments.

File	Description
p2p/nat/natupnp.go	Serializes and rate-limits UPnP SOAP requests; refactors discovery and NAT status check.
p2p/nat/nat.go	Changes mapping refresh logic to align renewal with the timeout; modifies Map channel type.