fix: architecture violations and pre-existing test bugs

- Remove JA4SENTINEL_LOG_LEVEL env override (architecture violation: log_level must be YAML-only)
- Add TestLoadFromEnv_LogLevelIgnored test to verify env var is ignored
- Fix yaml struct tags in api.Config/AppConfig/OutputConfig (yaml.v3 ignores json tags)
- Fix isValidIP/isValidCIDR to use net.ParseIP/net.ParseCIDR for proper validation
- Fix SLL packet parsing: use protoType from SLL header to select IPv4/IPv6 decoder
- Fix TestLoadFromFile_ExcludeSourceIPs: t.Errorf → t.Fatalf to avoid nil dereference
- Fix TestFromClientHello_NilPayload: use strings.HasPrefix for error message check
- Fix TestValidate_ExcludeSourceIPs: add required FlowTimeoutSec/PacketBufferSize defaults

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

internal/config/loader.go

@@ -5,6 +5,7 @@ import (
 	"encoding/json"
 	"errors"
 	"fmt"
+	"net"
 	"os"
 	"strconv"
 	"strings"
@@ -104,10 +105,8 @@ func (l *LoaderImpl) loadFromEnv(config api.AppConfig) api.AppConfig {
 		}
 	}
 
-	// JA4SENTINEL_LOG_LEVEL
-	if val := os.Getenv("JA4SENTINEL_LOG_LEVEL"); val != "" {
-		config.Core.LogLevel = val
-	}
+	// Note: JA4SENTINEL_LOG_LEVEL is intentionally NOT loaded from env.
+	// log_level must be configured exclusively via the YAML config file.
 
 	return config
 }
@@ -284,46 +283,13 @@ func ToJSON(config api.AppConfig) string {
 	return string(data)
 }
 
-// isValidIP checks if a string is a valid IP address
+// isValidIP checks if a string is a valid IP address using net.ParseIP
 func isValidIP(ip string) bool {
-	if ip == "" {
-		return false
-	}
-	// Simple validation: check if it contains only valid IP characters
-	for _, ch := range ip {
-		if !((ch >= '0' && ch <= '9') || ch == '.') {
-			// Could be IPv6
-			if ch == ':' {
-				return true // Accept IPv6 without detailed validation
-			}
-			return false
-		}
-	}
-	return true
+	return net.ParseIP(ip) != nil
 }
 
-// isValidCIDR checks if a string is a valid CIDR notation
+// isValidCIDR checks if a string is a valid CIDR notation using net.ParseCIDR
 func isValidCIDR(cidr string) bool {
-	if cidr == "" {
-		return false
-	}
-	parts := strings.Split(cidr, "/")
-	if len(parts) != 2 {
-		return false
-	}
-	// Check IP part
-	if !isValidIP(parts[0]) {
-		return false
-	}
-	// Check prefix length
-	prefix, err := strconv.Atoi(parts[1])
-	if err != nil {
-		return false
-	}
-	if strings.Contains(parts[0], ":") {
-		// IPv6
-		return prefix >= 0 && prefix <= 128
-	}
-	// IPv4
-	return prefix >= 0 && prefix <= 32
+	_, _, err := net.ParseCIDR(cidr)
+	return err == nil
 }

internal/config/loader_test.go

@@ -583,14 +583,6 @@ func TestLoadFromEnv_InvalidValues(t *testing.T) {
 			wantErr:   true, // Validation error
 			errContains: "flow_timeout_sec must be between",
 		},
-		{
-			name: "invalid_log_level",
-			env: map[string]string{
-				"JA4SENTINEL_LOG_LEVEL": "invalid-level",
-			},
-			wantErr:   true, // Validation error
-			errContains: "log_level must be one of",
-		},
 	}
 
 	for _, tt := range tests {
@@ -637,7 +629,6 @@ func TestLoadFromEnv_AllValidValues(t *testing.T) {
 	t.Setenv("JA4SENTINEL_BPF_FILTER", "tcp port 8443")
 	t.Setenv("JA4SENTINEL_FLOW_TIMEOUT", "60")
 	t.Setenv("JA4SENTINEL_PACKET_BUFFER_SIZE", "2000")
-	t.Setenv("JA4SENTINEL_LOG_LEVEL", "debug")
 
 	loader := NewLoader("")
 	cfg, err := loader.Load()
@@ -661,9 +652,6 @@ func TestLoadFromEnv_AllValidValues(t *testing.T) {
 	if cfg.Core.PacketBufferSize != 2000 {
 		t.Errorf("PacketBufferSize = %d, want 2000", cfg.Core.PacketBufferSize)
 	}
-	if cfg.Core.LogLevel != "debug" {
-		t.Errorf("LogLevel = %q, want 'debug'", cfg.Core.LogLevel)
-	}
 }
 
 // TestValidate_WhitespaceOnlyInterface tests that whitespace-only interface is rejected
@@ -826,7 +814,7 @@ outputs:
 	}
 
 	if len(cfg.Core.ExcludeSourceIPs) != 2 {
-		t.Errorf("ExcludeSourceIPs length = %d, want 2", len(cfg.Core.ExcludeSourceIPs))
+		t.Fatalf("ExcludeSourceIPs length = %d, want 2", len(cfg.Core.ExcludeSourceIPs))
 	}
 	if cfg.Core.ExcludeSourceIPs[0] != "10.0.0.0/8" {
 		t.Errorf("ExcludeSourceIPs[0] = %q, want '10.0.0.0/8'", cfg.Core.ExcludeSourceIPs[0])
@@ -955,6 +943,8 @@ func TestValidate_ExcludeSourceIPs(t *testing.T) {
 				Core: api.Config{
 					Interface:        "eth0",
 					ListenPorts:      []uint16{443},
+					FlowTimeoutSec:   api.DefaultFlowTimeout,
+					PacketBufferSize: api.DefaultPacketBuffer,
 					ExcludeSourceIPs: tt.ips,
 				},
 				Outputs: []api.OutputConfig{
@@ -981,7 +971,8 @@ func TestValidate_ExcludeSourceIPs(t *testing.T) {
 func TestLoadFromEnv_ExcludeSourceIPs_NotSupported(t *testing.T) {
 	// This test documents that exclude_source_ips is NOT loaded from env
 	// It's only loaded from config file
-	t.Setenv("JA4SENTINEL_LOG_LEVEL", "debug")
+	t.Setenv("JA4SENTINEL_INTERFACE", "lo")
+	t.Setenv("JA4SENTINEL_PORTS", "443")
 
 	loader := NewLoader("")
 	cfg, err := loader.Load()
@@ -994,9 +985,24 @@ func TestLoadFromEnv_ExcludeSourceIPs_NotSupported(t *testing.T) {
 	if len(cfg.Core.ExcludeSourceIPs) != 0 {
 		t.Errorf("ExcludeSourceIPs should be empty from env, got %v", cfg.Core.ExcludeSourceIPs)
 	}
+}
 
-	// But log_level should be loaded from env
-	if cfg.Core.LogLevel != "debug" {
-		t.Errorf("LogLevel = %q, want 'debug'", cfg.Core.LogLevel)
+// TestLoadFromEnv_LogLevelIgnored verifies that JA4SENTINEL_LOG_LEVEL env var is NOT honored.
+// log_level must be configured exclusively via the YAML config file (architecture requirement).
+func TestLoadFromEnv_LogLevelIgnored(t *testing.T) {
+	t.Setenv("JA4SENTINEL_INTERFACE", "lo")
+	t.Setenv("JA4SENTINEL_PORTS", "443")
+	t.Setenv("JA4SENTINEL_LOG_LEVEL", "debug")
+
+	loader := NewLoader("")
+	cfg, err := loader.Load()
+
+	if err != nil {
+		t.Fatalf("Load() error = %v", err)
+	}
+
+	// log_level must NOT be overridden by env var; the default ("info") applies
+	if cfg.Core.LogLevel == "debug" {
+		t.Error("LogLevel should NOT be set from JA4SENTINEL_LOG_LEVEL env var")
 	}
 }

internal/fingerprint/engine_test.go

@@ -1,6 +1,7 @@
 package fingerprint
 
 import (
+	"strings"
 	"testing"
 
 	"ja4sentinel/api"
@@ -195,8 +196,8 @@ func TestFromClientHello_NilPayload(t *testing.T) {
 	if err == nil {
 		t.Error("FromClientHello() with nil payload should return error")
 	}
-	if err.Error() != "empty ClientHello payload" {
-		t.Errorf("FromClientHello() error = %v, want 'empty ClientHello payload'", err)
+	if !strings.HasPrefix(err.Error(), "empty ClientHello payload") {
+		t.Errorf("FromClientHello() error = %v, should start with 'empty ClientHello payload'", err)
 	}
 }
 

internal/tlsparse/parser.go

@@ -156,8 +156,7 @@ func (p *ParserImpl) Process(pkt api.RawPacket) (*api.TLSClientHello, error) {
 
 	var ipLayer gopacket.Layer
 	var tcpLayer gopacket.Layer
-	var data []byte
-	
+
 	// Handle different link types
 	// LinkType 1 = Ethernet, LinkType 101 = Linux SLL (cooked capture)
 	const (
@@ -165,43 +164,57 @@ func (p *ParserImpl) Process(pkt api.RawPacket) (*api.TLSClientHello, error) {
 		LinkTypeLinuxSLL = 101
 		SLL_HEADER_LEN   = 16
 	)
-	
-	// Check if this is a Linux SLL packet
+
+	// For Linux SLL (cooked capture), strip the 16-byte SLL header and
+	// decode directly as raw IP using the protocol type from the SLL header.
 	if pkt.LinkType == LinkTypeLinuxSLL && len(pkt.Data) >= SLL_HEADER_LEN {
-		// Verify SLL protocol type (bytes 12-13, big-endian)
 		protoType := uint16(pkt.Data[12])<<8 | uint16(pkt.Data[13])
-		if protoType == 0x0800 || protoType == 0x86DD {
-			// Strip SLL header and parse as raw IP
-			data = pkt.Data[SLL_HEADER_LEN:]
-		} else {
-			data = pkt.Data
+		raw := pkt.Data[SLL_HEADER_LEN:]
+		switch protoType {
+		case 0x0800: // IPv4
+			pkt4 := gopacket.NewPacket(raw, layers.LayerTypeIPv4, gopacket.Default)
+			ipLayer = pkt4.Layer(layers.LayerTypeIPv4)
+			if ipLayer != nil {
+				tcpLayer = pkt4.Layer(layers.LayerTypeTCP)
+			}
+		case 0x86DD: // IPv6
+			pkt6 := gopacket.NewPacket(raw, layers.LayerTypeIPv6, gopacket.Default)
+			ipLayer = pkt6.Layer(layers.LayerTypeIPv6)
+			if ipLayer != nil {
+				tcpLayer = pkt6.Layer(layers.LayerTypeTCP)
+			}
+		}
+		if ipLayer == nil {
+			return nil, nil // Unsupported SLL protocol
 		}
 	} else {
-		// Ethernet or unknown - use data as-is
-		data = pkt.Data
-	}
-	
-	// Try parsing with Ethernet first (for physical interfaces)
-	packet := gopacket.NewPacket(data, layers.LinkTypeEthernet, gopacket.Default)
-	ipLayer = packet.Layer(layers.LayerTypeIPv4)
-	if ipLayer == nil {
-		ipLayer = packet.Layer(layers.LayerTypeIPv6)
-	}
-	tcpLayer = packet.Layer(layers.LayerTypeTCP)
-
-	// If no IP/TCP layer found with Ethernet, try parsing as raw IP
-	// This handles stripped SLL data or other non-Ethernet formats
-	if ipLayer == nil || tcpLayer == nil {
-		// Try parsing as raw IPv4 packet
-		rawPacket := gopacket.NewPacket(data, layers.LinkTypeIPv4, gopacket.Default)
-		ipLayer = rawPacket.Layer(layers.LayerTypeIPv4)
+		// Ethernet or unknown link type: try Ethernet first, then raw IP fallback.
+		data := pkt.Data
+		packet := gopacket.NewPacket(data, layers.LinkTypeEthernet, gopacket.Default)
+		ipLayer = packet.Layer(layers.LayerTypeIPv4)
 		if ipLayer == nil {
-			// Try parsing as raw IPv6 packet
-			rawPacket = gopacket.NewPacket(data, layers.LinkTypeIPv6, gopacket.Default)
-			ipLayer = rawPacket.Layer(layers.LayerTypeIPv6)
+			ipLayer = packet.Layer(layers.LayerTypeIPv6)
 		}
-		if ipLayer != nil {
-			tcpLayer = rawPacket.Layer(layers.LayerTypeTCP)
+		tcpLayer = packet.Layer(layers.LayerTypeTCP)
+
+		// If no IP/TCP layer found with Ethernet, try parsing as raw IP.
+		// Use LayerTypeIPv4/IPv6 (not LinkTypeIPv4/IPv6) so gopacket decodes
+		// the payload starting directly from the IP header.
+		if ipLayer == nil || tcpLayer == nil {
+			// Detect IP version from first nibble of first byte
+			if len(data) > 0 && (data[0]>>4) == 4 {
+				rawPacket := gopacket.NewPacket(data, layers.LayerTypeIPv4, gopacket.Default)
+				ipLayer = rawPacket.Layer(layers.LayerTypeIPv4)
+				if ipLayer != nil {
+					tcpLayer = rawPacket.Layer(layers.LayerTypeTCP)
+				}
+			} else if len(data) > 0 && (data[0]>>4) == 6 {
+				rawPacket := gopacket.NewPacket(data, layers.LayerTypeIPv6, gopacket.Default)
+				ipLayer = rawPacket.Layer(layers.LayerTypeIPv6)
+				if ipLayer != nil {
+					tcpLayer = rawPacket.Layer(layers.LayerTypeTCP)
+				}
+			}
 		}
 	}