16_x less restrictive DDP header acceptance & bugfix

[DedeHai]

this is basically the same as #5547 but with the uncertain buffer checks for e131 packets removed

Summary by CodeRabbit

Release Notes

• Bug Fixes

  • Improved packet length validation and safety checks for DDP protocol handling to prevent out-of-bounds reads.
  • Enhanced E1.31/Art-Net packet validation with stricter length checks and better error handling.
  • Added filtering to reject invalid control, status, and configuration packets.

• Improvements

  • Improved color type compatibility by accepting unsupported types and defaulting to RGB channel layout.
  • Clarified DDP sequence number handling in protocol documentation.

[coderabbitai]

Walkthrough

This PR adds packet length validation throughout the E1.31/DDP protocol handling pipeline. It propagates the incoming UDP packet length from the async parser through the callback chain and handler signature, uses it to validate DDP packet structure and filter unsupported packet types, changes color type handling to accept all data types by defaulting to RGB, and tightens DMX channel validation.

Changes

Cohort / File(s)	Summary
Packet Length Parameter Integration wled00/fcn_declare.h, wled00/src/dependencies/e131/ESPAsyncE131.h, wled00/src/dependencies/e131/ESPAsyncE131.cpp, wled00/ws.cpp	Adds size_t packetLen parameter throughout the E1.31 packet handling call chain: updates the callback function type signature, propagates packet length from the async parser to the handler, and passes remaining payload size to handleE131Packet for protocol processing.
DDP Protocol Validation & Filtering wled00/e131.cpp	Implements length-based safety checks (early return if packet too short for header, rejection if actual length cannot satisfy header/data expectations), expands DDP packet type filtering (drops control/status/config and query/reply packets, rejects storage unless PUSH flag set), changes color type handling to accept all data types with RGB default instead of rejecting unsupported types, and tightens E1.31/Art-Net entry validation including minimum-length check for Art-Net and stricter DMX channel count validation.
DDP Documentation & Sequence Handling wled00/data/common.js, wled00/udp.cpp	Clarifies that DDP byte 2's lower nibble represents sequence number (where 0 disables checking), and adds TODO comment documenting sequence number valid range (1–15) with 0 reserved as unused.

Sequence Diagram(s)

sequenceDiagram
    participant Client as UDP/WebSocket Client
    participant Parser as ESPAsyncE131 Parser
    participant Handler as handleE131Packet
    participant DDP as DDP Processor

    Client->>Parser: Send packet (payload + length)
    Parser->>Parser: Capture packet length
    Note over Parser: Validate min length for E1.31/Art-Net<br/>before ACN ID check
    Parser->>Handler: Dispatch callback(packet, IP, protocol, packetLen)
    
    Handler->>Handler: Receive packetLen parameter
    alt Protocol is DDP
        Handler->>DDP: Process with packetLen
        DDP->>DDP: Validate header length
        DDP->>DDP: Check if actual length satisfies<br/>header + data expectations
        DDP->>DDP: Filter packet types<br/>(drop control/status/config/query)
        DDP->>DDP: Resolve color type<br/>(accept unknown, default to RGB)
        DDP->>DDP: Render pixels if PUSH flag set
    else Protocol is E1.31
        Handler->>Handler: Validate DMX channel count > 0
    end

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Estimated code review effort

🎯 4 (Complex) | ⏱️ ~40 minutes

Possibly related PRs

• DDP input: reject packets with unsupported data type or non-display destination #5390 — Modifies the same DDP-related files (e131.cpp, ESPAsyncE131.h, ws.cpp, udp.cpp, common.js) to update DDP flags and filtering logic, but differs by rejecting unsupported color data types rather than accepting them.
• Adding DDP over WS, moving duplicate WS-connection to common.js #4997 — Touches the DDP-over-WebSocket flow by modifying common.js, ws.cpp, and adding DDP-specific packet length and bounds checks during handler integration.

Suggested labels

connectivity

Suggested reviewers

• willmmiles
• blazoncek

🚥 Pre-merge checks | ✅ 4 | ❌ 1

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Docstring Coverage	⚠️ Warning	Docstring coverage is 57.14% which is insufficient. The required threshold is 80.00%.	Write docstrings for the functions missing them to satisfy the coverage threshold.

✅ Passed checks (4 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Title check	✅ Passed	The title 'less restrictive DDP header acceptance & bugfix' accurately describes the main changes: DDP protocol is less restrictive and a bugfix is included, which aligns with the core modifications across e131.cpp, fcn_declare.h, ESPAsyncE131 files, and related handlers.

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[DedeHai]

@coderabbitai review

[coderabbitai]

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[softhack007]

Looks good to me 👍