Try gateway IP from routing table for DIND connection

- Get default gateway IP from routing table
- Test connection to DIND on gateway
- Provide instructions if connection fails
- Network isolation might need runner configuration fix

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <noreply@anthropic.com>

.forgejo/workflows/docker-build.yml

@@ -12,26 +12,30 @@ jobs:
       image: docker:latest
 
     steps:
-      - name: Find DIND daemon
+      - name: Debug network configuration
         run: |
-          echo "=== Checking /etc/hosts ==="
-          cat /etc/hosts
+          echo "=== Network interfaces and routes ==="
+          ip route show 2>/dev/null || route -n
 
           echo ""
-          echo "=== Testing DIND connection options ==="
+          echo "=== Testing gateway IP directly ==="
+          GATEWAY_IP=$(ip route show | grep default | awk '{print $3}')
+          echo "Gateway IP: $GATEWAY_IP"
 
-          # Try different hostnames/IPs
-          for host in docker-runner.docker.internal host.docker.internal 172.17.0.1 gateway.docker.internal; do
-            echo "Testing: $host"
-            if timeout 2 sh -c "cat < /dev/null > /dev/tcp/$host/2375" 2>/dev/null; then
-              echo "✅ SUCCESS: Can reach DIND at $host:2375"
-              echo "DOCKER_HOST=tcp://$host:2375" >> $GITHUB_ENV
-              export DOCKER_HOST=tcp://$host:2375
-              docker version && break
-            else
-              echo "❌ FAILED: Cannot reach $host:2375"
-            fi
-          done
+          if timeout 2 sh -c "cat < /dev/null > /dev/tcp/$GATEWAY_IP/2375" 2>/dev/null; then
+            echo "✅ Can reach DIND at $GATEWAY_IP:2375"
+            echo "DOCKER_HOST=tcp://$GATEWAY_IP:2375" >> $GITHUB_ENV
+            export DOCKER_HOST=tcp://$GATEWAY_IP:2375
+          else
+            echo "❌ Cannot reach gateway at $GATEWAY_IP:2375"
+            echo "The DIND container might not be accessible from job containers"
+            echo "You may need to configure the runner to use --network=host or expose DIND port on host"
+            exit 1
+          fi
+
+      - name: Verify Docker connection
+        run: |
+          docker version
 
       - name: Checkout repository
         run: |