Implement network resilience features for improved upload stability during network changes

- Enable network events by default in configuration
- Integrate network resilience manager into upload handling
- Add support for automatic upload pause/resume during WLAN to 5G transitions
- Enhance documentation with network resilience settings and testing procedures
- Create a test script for validating network resilience functionality

test-network-resilience.sh

@@ -0,0 +1,135 @@
+#!/bin/bash
+
+# HMAC File Server Network Resilience Test
+# Tests WLAN to 5G switching behavior
+
+echo "🧪 HMAC File Server Network Resilience Test"
+echo "============================================="
+
+# Configuration
+SERVER_URL="http://localhost:8080"
+SECRET="your-very-secret-hmac-key"
+TEST_FILE="/tmp/test-network-resilience.dat"
+
+# Generate test file (10MB)
+echo "📄 Creating test file (10MB)..."
+dd if=/dev/zero of=$TEST_FILE bs=1024 count=10240 2>/dev/null
+
+# Function to generate HMAC
+generate_hmac() {
+    local filename="$1"
+    local secret="$2"
+    local timestamp="$3"
+    
+    # Generate HMAC signature
+    echo -n "${filename}${timestamp}" | openssl dgst -sha256 -hmac "$secret" -binary | base64
+}
+
+# Test function
+test_upload_with_network_change() {
+    echo
+    echo "🔧 Testing upload with simulated network change..."
+    
+    # Get current timestamp
+    TIMESTAMP=$(date +%s)
+    FILENAME="test-network-resilience.dat"
+    
+    # Generate HMAC
+    HMAC=$(generate_hmac "$FILENAME" "$SECRET" "$TIMESTAMP")
+    
+    echo "⏳ Starting upload..."
+    echo "📡 Filename: $FILENAME"
+    echo "🔐 HMAC: $HMAC"
+    echo "⏰ Timestamp: $TIMESTAMP"
+    
+    # Start upload in background
+    curl -v \
+        -F "file=@$TEST_FILE" \
+        -F "filename=$FILENAME" \
+        -F "timestamp=$TIMESTAMP" \
+        -F "hmac=$HMAC" \
+        -H "X-Upload-Session-ID: test-network-resilience-$$" \
+        "$SERVER_URL/upload" \
+        > /tmp/upload-result.txt 2>&1 &
+    
+    UPLOAD_PID=$!
+    
+    # Simulate network change after 2 seconds
+    sleep 2
+    echo
+    echo "🌐 Simulating network interface change (WLAN → 5G)..."
+    
+    # Check if server handles network events
+    if curl -s "$SERVER_URL/health" > /dev/null; then
+        echo "✅ Server still responding during upload"
+    else
+        echo "❌ Server not responding"
+    fi
+    
+    # Wait for upload to complete
+    wait $UPLOAD_PID
+    UPLOAD_RESULT=$?
+    
+    echo
+    echo "📊 Upload Result:"
+    cat /tmp/upload-result.txt
+    
+    if [ $UPLOAD_RESULT -eq 0 ]; then
+        echo "✅ Upload completed successfully with network resilience"
+        return 0
+    else
+        echo "❌ Upload failed (exit code: $UPLOAD_RESULT)"
+        return 1
+    fi
+}
+
+# Test network resilience configuration
+test_configuration() {
+    echo
+    echo "🔍 Checking network resilience configuration..."
+    
+    # Check if server has network events enabled
+    if curl -s "$SERVER_URL/metrics" | grep -q "networkevents"; then
+        echo "✅ Network events monitoring appears to be active"
+    else
+        echo "⚠️  Network events monitoring may not be active"
+    fi
+    
+    # Check server health
+    if curl -s "$SERVER_URL/health" | grep -q "OK"; then
+        echo "✅ Server is healthy"
+    else
+        echo "❌ Server health check failed"
+        return 1
+    fi
+}
+
+# Main test execution
+main() {
+    echo "🚀 Starting tests..."
+    
+    # Check if server is running
+    if ! curl -s "$SERVER_URL/health" > /dev/null; then
+        echo "❌ Server is not running at $SERVER_URL"
+        echo "Please start the HMAC File Server first:"
+        echo "  ./hmac-file-server -config config.toml"
+        exit 1
+    fi
+    
+    # Run tests
+    test_configuration
+    test_upload_with_network_change
+    
+    # Cleanup
+    rm -f $TEST_FILE /tmp/upload-result.txt
+    
+    echo
+    echo "✅ Network resilience test completed"
+    echo
+    echo "💡 To test real network switching:"
+    echo "1. Start upload from mobile device"
+    echo "2. Turn off WiFi during upload"
+    echo "3. Upload should pause and resume on cellular"
+}
+
+main "$@"