Remove Linux XDP support

[Copilot]

Description

Linux XDP has become a costly maintenance burden with no active community commitment. This removes all Linux XDP code, build infrastructure, CI, and documentation while leaving Windows XDP support fully intact.

Deleted:

• src/platform/datapath_raw_xdp_linux.c — Linux XDP datapath implementation
• src/platform/datapath_raw_xdp_linux_kern.c — BPF kernel program
• Associated CLOG-generated files in src/generated/linux/

Build system:

• Removed QUIC_LINUX_XDP_ENABLED CMake option and CXPLAT_LINUX_XDP_ENABLED preprocessor define
• Simplified Linux platform CMakeLists.txt — always uses datapath_raw_dummy.c, no XDP library detection or BPF compilation step
• Removed -UseXdp from build.ps1 (Linux path only); -UseXdp in prepare-machine.ps1/test.ps1/spin.ps1 retained for Windows XDP

CI/CD:

• Removed Linux XDP matrix entries from build.yml, test.yml, stress.yml, dotnet-test.yml, package-linux.yml, package-reuse-linux.yml, build-reuse-unix.yml, and Azure DevOps templates
• Removed XDP build-stage from both Ubuntu Dockerfiles
• Removed XDP build dependencies from codeql-analysis.yml
• Fixed invalid YAML in test.yml — restored accidentally deleted - name: Install ETW Manifest step separator that caused duplicate shell and run keys

Packaging:

• Removed libxdp/libbpf/libnl dependency injection from RPM/DEB packages
• Removed BPF kernel object (datapath_raw_xdp_kern.o) from package artifacts

Source simplifications:

• Removed !defined(CXPLAT_LINUX_XDP_ENABLED) guards in api.c, listener.c, ApiTest.cpp — hard partitioning is now gated solely on !defined(CXPLAT_USE_IO_URING) on Linux

Testing

No new tests. Existing Linux tests continue to run (without XDP variants). Windows XDP test matrix is unchanged.

Documentation

Removed Linux XDP installation, build, test, and Q&A sections from docs/BUILD.md. Removed Linux XDP logging section from docs/TroubleshootingGuide.md. Windows XDP docs (QTIP.md, Settings.md, Architecture.md) are unaffected.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 84.86%. Comparing base (f9c01c7) to head (3efe805).
⚠️ Report is 1 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #5921      +/-   ##
==========================================
- Coverage   86.18%   84.86%   -1.32%     
==========================================
  Files          60       60              
  Lines       18731    18731              
==========================================
- Hits        16143    15896     -247     
- Misses       2588     2835     +247     

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[ProjectsByJackHe]

@copilot the test.yml syntax is not valid.

[mtfriesen]

@copilot resolve this CI error:

GitHub Actions
/ .github/workflows/test.yml
Invalid workflow file

(Line: 188, Col: 7): 'shell' is already defined, (Line: 189, Col: 7): 'run' is already defined

[Copilot]

@copilot resolve this CI error:

...

Fixed in commit 3efe805. The - name: Install ETW Manifest step separator was accidentally deleted when removing the Linux XDP step, causing its if:, shell:, and run: fields to be orphaned into the preceding "Prepare Machine" step — resulting in the duplicate shell and run keys. Restored the missing - name: line to properly separate the two steps.