backport v1.11: Recompute the transport checksum on self-forwarded packets (#1880)

* Recompute the transport checksum on self-forwarded packets (#1862)

(cherry picked from commit ec3304e3a9)

* try to backport

* fix miss backport

* backport anyFragment logic

* restore test

---------

Co-authored-by: Caleb Jasik <calebjasik@jasik.xyz>

.github/workflows/smoke.yml

@@ -61,3 +61,24 @@ jobs:
       run: NAME="smoke-p256" ./smoke.sh
 
     timeout-minutes: 10
+
+  smoke-self:
+    name: Run self traffic smoke test on macOS
+    runs-on: macos-latest
+    steps:
+
+    - uses: actions/checkout@v7
+
+    - uses: actions/setup-go@v7
+      with:
+        go-version: '1.26'
+        check-latest: true
+
+    - name: build
+      run: make bin
+
+    - name: run smoke-self
+      working-directory: ./.github/workflows/smoke
+      run: ./smoke-self.sh
+
+    timeout-minutes: 10