Module dtls 

DTLS session management for EST-coaps transport security.

RFC 9148 §5 mandates DTLS to secure all EST-coaps exchanges. This module provides session tracking, caching abstractions, and a concrete OpenSSL-based DTLS implementation using memory BIOs for UDP transport.

Session Resumption

Constrained devices benefit significantly from DTLS session resumption (RFC 6347 §4.2.8, RFC 9147 §5) because the full handshake involves multiple round trips and is computationally expensive, especially with post-quantum key exchange (ML-KEM).

The DtlsSessionCache provides a bounded, TTL-expiring cache of established sessions keyed by peer address.

OpenSSL DTLS Integration

The DtlsContext wraps an openssl::ssl::SslContext configured for DTLS server operation with optional client certificate authentication. DtlsConnection handles individual peer sessions using memory BIOs for non-blocking UDP I/O.

Structs

ClientCertInfo

Client certificate information extracted from a DTLS handshake.

DtlsConnection

DtlsContext

OpenSSL DTLS server context for EST-coaps.

DtlsSession

An established DTLS session for a CoAP/EST-coaps connection.

DtlsSessionCache

A bounded, TTL-expiring cache of DTLS sessions keyed by peer address.

Enums

DtlsVersion

DTLS protocol version.