DO-NOT-MERGE: mptcp: add CI support

Currently supported:

- Github Actions:
  - build-validation: check different combinations of validation
  - IRC: send notifications to the IRC channel
  - Update TopGit tree: sync with net-next and then override the export
    branch.

- Cirrus:
  - Run tests in a KVM: selftests, kunit, packetdrill, etc.

Signed-off-by: Matthieu Baerts <matthieu.baerts@tessares.net>

.cirrus.yml

@@ -0,0 +1,48 @@
+
+# Launch 2 jobs in //: with and without debug
+task:
+  name: KVM validation
+  only_if: $CIRRUS_TAG != ''  ## only tags
+  timeout_in: 90m
+
+  container:
+    image: mptcp/mptcp-upstream-virtme-docker
+    kvm: true   ## Needed for the tests
+    cpu: 4      ## Max 16 per project, even number with kvm
+    memory: 4G  ## Max 4 per CPU
+
+  env:
+    CIRRUS_CLONE_DEPTH: 1       ## no need to have a full clone
+    CIRRUS_LOG_TIMESTAMP: true  ## useful
+    INPUT_CCACHE_MAXSIZE: 1G
+    matrix:
+      MATRIX_JOB: normal
+      MATRIX_JOB: debug
+
+  ccache_cache:
+    folder: ".virtme/ccache"
+    reupload_on_changes: true
+    fingerprint_script:
+      - echo ${MATRIX_JOB}
+
+  test_script: /entrypoint.sh expect-${MATRIX_JOB}
+
+  on_failure:
+    vmlinux_artifacts:
+      path: "vmlinux.zstd"
+
+  always:
+    conclusion_artifacts:
+      path: "conclusion.txt"
+      type: text/plain
+    summary_artifacts:
+      path: "summary.txt"
+      type: text/plain
+    tap_result_artifacts:
+      path: "*.tap"
+      type: text/plain
+    # JUnit format is for the moment only useful for PR but publish them just in case for later
+    junit_artifacts:
+      path: "*.tap.xml"
+      type: text/xml
+      format: junit

.github/workflows/build-validation.yml

@@ -0,0 +1,44 @@
+name: "MPTCP Upstream Build Validation"
+on:
+  push:
+    branches-ignore:
+      - 'archived/**' # previous branches
+      - 't/**'        # TopGit tree
+      - 'net-next'    # part of the TopGit tree
+      - 'for-review'  # part of the TopGit tree
+      - 'export'      # part of the TopGit tree
+    tags:
+      - 'export/**'   # the CI create a new tag once there is a new export
+      - 'patchew/**'  # patchew is using tags
+
+jobs:
+  build:
+    name: "Build (matrix)"
+    runs-on: ubuntu-latest
+    strategy:
+      fail-fast: false
+      matrix:
+        defconfig: ['x86_64', 'i386']
+        ipv6: ['with_ipv6', 'without_ipv6']
+        mptcp: ['with_mptcp', 'without_mptcp']
+    steps:
+      - name: "Checkout"
+        uses: actions/checkout@v2
+        with:
+          fetch-depth: 100 # we should not have more commits on top of net-next/export
+      - name: "Setup cache for CCache"
+        uses: actions/cache@v2
+        with:
+          path: ${{ github.workspace }}/.ccache
+          key: ${{ runner.os }}-build-${{ matrix.defconfig }}-${{ matrix.ipv6 }}-${{ matrix.mptcp }}-${{ github.run_id }}${{ github.sha }}
+          restore-keys: |
+            ${{ runner.os }}-build-${{ matrix.defconfig }}-${{ matrix.ipv6 }}-${{ matrix.mptcp }}-
+      - name: "Build Validation"
+        uses: multipath-tcp/mptcp-upstream-validate-export-action@main
+        with:
+          # we want to validate each commits on top of net-next/export except for stable
+          each_commit: ${{ ! startswith(github.ref, 'refs/heads/stable/') }}
+          ccache_maxsize: 620M ## 5/2^3=625: 5GB = project limit ; 2^3 = matrix
+          defconfig: ${{ matrix.defconfig }}
+          ipv6: ${{ matrix.ipv6 }}
+          mptcp: ${{ matrix.mptcp }}