feat(p2p/discover): implement v5.1 wire protocol #21647

[gzliudan]

Proposed changes

This change implements the Discovery v5.1 wire protocol and also adds an interactive test suite for this protocol.

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• build: Changes that affect the build system or external dependencies
• ci: Changes to CI configuration files and scripts
• chore: Changes that don't change source code or tests
• docs: Documentation only changes
• feat: A new feature
• fix: A bug fix
• perf: A code change that improves performance
• refactor: A code change that neither fixes a bug nor adds a feature
• revert: Revert something
• style: Changes that do not affect the meaning of the code
• test: Adding missing tests or correcting existing tests

Impacted Components

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• Consensus
• Account
• Network
• Geth
• Smart Contract
• External components
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Checklist

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• This PR has sufficient test coverage (unit/integration test) OR I have provided reason in the PR description for not having test coverage
• Tested on a private network from the genesis block and monitored the chain operating correctly for multiple epochs.
• Provide an end-to-end test plan in the PR description on how to manually test it on the devnet/testnet.
• Tested the backwards compatibility.
• Tested with XDC nodes running this version co-exist with those running the previous version.
• Relevant documentation has been updated as part of this PR
• N/A

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[Copilot]

Pull request overview

This PR upgrades the Discovery v5 implementation to the v5.1 wire format by introducing a new p2p/discover/v5wire codec package, wiring UDPv5 to use it, and adding an interactive protocol test suite to devp2p.

Changes:

• Add p2p/discover/v5wire (codec, crypto, session cache, message types) plus v5.1 test vectors and unit tests.
• Refactor p2p/discover/UDPv5 and its tests to use v5wire.Packet and the new handshake/nonce mapping.
• Add devp2p discv5 test plus an embedded test runner (internal/utesting) and the discv5 interactive test suite.

Reviewed changes

Copilot reviewed 24 out of 24 changed files in this pull request and generated 3 comments.

Show a summary per file

File	Description
p2p/netutil/error.go	Add timeout detection helper for network ops.
p2p/discover/v5wire/testdata/v5.1-whoareyou.txt	Add v5.1 WHOAREYOU test vector.
p2p/discover/v5wire/testdata/v5.1-ping-message.txt	Add v5.1 encrypted PING test vector.
p2p/discover/v5wire/testdata/v5.1-ping-handshake.txt	Add v5.1 handshake PING test vector (no ENR).
p2p/discover/v5wire/testdata/v5.1-ping-handshake-enr.txt	Add v5.1 handshake PING test vector (with ENR).
p2p/discover/v5wire/session.go	Introduce v5.1 session cache + nonce generation hooks for tests.
p2p/discover/v5wire/msg.go	Define v5.1 packet/message types and decoding.
p2p/discover/v5wire/encoding.go	Implement v5.1 packet encoding/decoding + handshake logic.
p2p/discover/v5wire/encoding_test.go	Add codec handshake tests, vectors, and benchmarks.
p2p/discover/v5wire/crypto.go	Add v5.1 crypto helpers (ECDH/HKDF/GCM, signatures).
p2p/discover/v5wire/crypto_test.go	Add crypto test vectors and key derivation tests.
p2p/discover/v5_udp.go	Refactor UDPv5 transport to use v5wire.Codec and v5.1 message set; add TALKREQ support.
p2p/discover/v5_udp_test.go	Update UDPv5 tests for v5.1 message set; add talk tests and stronger E2E lookup assertions.
p2p/discover/v5_encoding.go	Remove legacy v5 wire codec (replaced by v5wire).
p2p/discover/v5_encoding_test.go	Remove legacy v5 codec tests (replaced by v5wire tests).
p2p/discover/v4_lookup_test.go	Adjust pubkey decode call site to new decodePubkey([]byte) signature.
p2p/discover/table_util_test.go	Update shared test helpers used by discovery tests.
p2p/discover/node.go	Change decodePubkey to accept []byte and validate length.
internal/utesting/utesting.go	Add embeddable testing harness for standalone tools.
cmd/devp2p/README.md	Document new discv5 test suite usage.
cmd/devp2p/internal/v5test/framework.go	Add discv5 test framework for interactive protocol checks.
cmd/devp2p/internal/v5test/discv5tests.go	Add discv5 interactive test suite cases (ping/talk/findnode).
cmd/devp2p/discv5cmd.go	Add devp2p discv5 test command + flags and test execution.
cmd/devp2p/discv4cmd.go	Improve fallback IP selection based on actual listen address.