Module protocol_version 

Protocol versioning and compatibility negotiation for P2P connections.

This module provides:

• Semantic version representation for protocols (ProtocolVersion)
• Compatibility classification between local and remote protocol versions
• Protocol descriptor with feature advertisement
• Multi-protocol version negotiation (ProtocolVersionManager)
• Statistics tracking for negotiation outcomes

Design Rationale

Compatibility is evaluated against a per-protocol min_compatible floor. A remote peer speaking version R is:

• FullyCompatible — R == local
• BackwardCompatible — R < local but R >= min_compatible (we speak down to them)
• ForwardCompatible — R > local (they are newer; we use our feature set)
• Incompatible — R < min_compatible (wire format too old to speak safely)

Feature negotiation produces the intersection of advertised feature sets. Features present locally but absent from the intersection are recorded in NegotiationResult::dropped_features.

Structs

NegotiationResult

The outcome of a successful protocol version negotiation between two peers.

ProtocolDescriptor

Full description of a protocol as advertised by one side of a connection.

ProtocolVersion

A semantic version triple for a protocol (major.minor.patch).

ProtocolVersionManager

Central registry and negotiation engine for protocol versions.

VersionStats

Running statistics for all negotiation attempts handled by a ProtocolVersionManager.

Enums

CompatibilityLevel

Classification of the compatibility relationship between two protocol version endpoints.