Support client default routes for Linux (#1667)

All routes are now installed in a custom netbird routing table.
Management and wireguard traffic is now marked with a custom fwmark.
When the mark is present the traffic is routed via the main routing table, bypassing the VPN.
When the mark is absent the traffic is routed via the netbird routing table, if:
- there's no match in the main routing table
- it would match the default route in the routing table

IPv6 traffic is blocked when a default route IPv4 route is configured to avoid leakage.

.github/workflows/golang-test-linux.yml

@@ -14,8 +14,8 @@ jobs:
   test:
     strategy:
       matrix:
-        arch: ['386','amd64']
-        store: ['jsonfile', 'sqlite']
+        arch: [ '386','amd64' ]
+        store: [ 'jsonfile', 'sqlite' ]
     runs-on: ubuntu-latest
     steps:
       - name: Install Go
@@ -36,7 +36,11 @@ jobs:
         uses: actions/checkout@v3
 
       - name: Install dependencies
-        run: sudo apt update && sudo apt install -y -q libgtk-3-dev libayatana-appindicator3-dev libgl1-mesa-dev xorg-dev gcc-multilib
+        run: sudo apt update && sudo apt install -y -q libgtk-3-dev libayatana-appindicator3-dev libgl1-mesa-dev xorg-dev gcc-multilib libpcap-dev
+
+      - name: Install 32-bit libpcap
+        if: matrix.arch == '386'
+        run: sudo dpkg --add-architecture i386 && sudo apt update && sudo apt-get install -y libpcap0.8-dev:i386
 
       - name: Install modules
         run: go mod tidy
@@ -67,7 +71,7 @@ jobs:
         uses: actions/checkout@v3
 
       - name: Install dependencies
-        run: sudo apt update && sudo apt install -y -q libgtk-3-dev libayatana-appindicator3-dev libgl1-mesa-dev xorg-dev gcc-multilib
+        run: sudo apt update && sudo apt install -y -q libgtk-3-dev libayatana-appindicator3-dev libgl1-mesa-dev xorg-dev gcc-multilib libpcap-dev
 
       - name: Install modules
         run: go mod tidy
@@ -82,7 +86,7 @@ jobs:
         run: CGO_ENABLED=0 go test -c -o sharedsock-testing.bin ./sharedsock
 
       - name: Generate RouteManager Test bin
-        run: CGO_ENABLED=0 go test -c -o routemanager-testing.bin ./client/internal/routemanager/...
+        run: CGO_ENABLED=1 go test -c -o routemanager-testing.bin -tags netgo -ldflags '-w -extldflags "-static -ldbus-1 -lpcap"' ./client/internal/routemanager/...
 
       - name: Generate nftables Manager Test bin
         run: CGO_ENABLED=0 go test -c -o nftablesmanager-testing.bin ./client/firewall/nftables/...
@@ -109,7 +113,7 @@ jobs:
 
       - name: Run Engine tests in docker with file store
         run: docker run -t --cap-add=NET_ADMIN --privileged --rm -v $PWD:/ci -w /ci/client/internal -e NETBIRD_STORE_ENGINE="jsonfile" --entrypoint /busybox/sh gcr.io/distroless/base:debug -c /ci/engine-testing.bin  -test.timeout 5m -test.parallel 1
-      
+
       - name: Run Engine tests in docker with sqlite store
         run: docker run -t --cap-add=NET_ADMIN --privileged --rm -v $PWD:/ci -w /ci/client/internal -e NETBIRD_STORE_ENGINE="sqlite" --entrypoint /busybox/sh gcr.io/distroless/base:debug -c /ci/engine-testing.bin  -test.timeout 5m -test.parallel 1