Add RFC 9653 and fuzz tests

[philipch07]

Description

• Adds support for RFC 9653.
• Adds fuzz tests to validate the RFC 9653 core properties.

Requires #407 to be merged first. Merged!

Reference issue

A part of #124. Closes #405.

[codecov]

Codecov Report

❌ Patch coverage is 94.23077% with 3 lines in your changes missing coverage. Please review.
✅ Project coverage is 83.76%. Comparing base (a69c6a2) to head (9d097a8).

Files with missing lines	Patch %	Lines
chunk_init.go	93.93%	1 Missing and 1 partial ⚠️
param_zero_checksum.go	66.66%	0 Missing and 1 partial ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #406      +/-   ##
==========================================
- Coverage   83.84%   83.76%   -0.09%     
==========================================
  Files          51       51              
  Lines        3448     3486      +38     
==========================================
+ Hits         2891     2920      +29     
- Misses        417      424       +7     
- Partials      140      142       +2     

Flag	Coverage Δ
go	83.76% <94.23%> (-0.09%)	⬇️

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[Sean-Der]

Amazing! I think we can get this merged tonight.

can you break this into singular PRs? Just so I can learn/understand since you are fixing my mistakes :)

it will make it easier for others to maintain/learn

[philipch07]

Amazing! I think we can get this merged tonight.

can you break this into singular PRs? Just so I can learn/understand since you are fixing my mistakes :)

it will make it easier for others to maintain/learn

Yes, I can try! It may be a little difficult though since a lot of things got mixed together as I was working on it.

[philipch07]

I created #407 from this PR; that one is purely focused on making packet.go conform to RFC 9260, along with some fuzz tests. This PR will have to be rebased after that one is merged, at which point the diffs will be cleaner. The resulting diffs should only be the RFC 9653 implementation along with some fuzz tests for it. Let me know if you think anything else can be broken down!

[philipch07]

#407 has been merged so this PR is ready for review!

[Copilot]

Pull Request Overview

This PR implements RFC 9653 Zero Checksum Acceptable (ZCA) extension for SCTP, allowing zero checksums when alternate error detection methods (like DTLS) are in use. The key changes ensure proper negotiation of ZCA parameters and enforce sender/receiver rules that restrict zero checksums for critical chunks like INIT and COOKIE-ECHO.

• Adds ZCA parameter parsing/marshaling for INIT and INIT-ACK chunks with EDMID validation
• Implements RFC 9653 sender rules: forces CRC32c for INIT/COOKIE-ECHO, allows zero checksum otherwise when negotiated
• Updates packet marshal/unmarshal to handle ZCA-enabled paths with proper validation logic

Reviewed Changes

Copilot reviewed 11 out of 11 changed files in this pull request and generated 4 comments.

Show a summary per file

File	Description
param_zero_checksum.go	Adds strict length validation (must be 8) for ZCA parameters per RFC 9653 section 4
param_zero_checksum_test.go	Adds test cases for arbitrary EDMID round-trip and invalid length validation
packet_test.go	Adds comprehensive tests and fuzz testing for RFC 9653 sender/receiver rules
chunk_init.go	Implements ZCA parameter scanning, parsing, and marshaling for INIT chunks
chunk_init_ack.go	Implements ZCA parameter handling for INIT-ACK chunks
chunk_init_test.go	Adds tests to verify ZCA parameters don't get duplicated on re-marshal
chunk_init_common.go	Adds constant for INIT fixed value length used in parameter parsing
chunk_cookie_echo.go	Adds comment clarifying reserved flags behavior per RFC 9260
chunk_cookie_echo_test.go	Adds test verifying COOKIE-ECHO forces CRC32c even with ZCA enabled
association.go	Refactors checksum logic to delegate enforcement to packet.marshal()
association_test.go	Updates existing tests to use strict mode (false) instead of ZCA mode

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[Copilot]

Pull Request Overview

Copilot reviewed 11 out of 11 changed files in this pull request and generated 5 comments.

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