fix: improve error logging with source/destination details

Logging improvements:
- Add src_ip, src_port, dst_ip, dst_port to tlsparse error logs
- Add connection details to fingerprint error logs (conn_id, payload_len)
- Include 'unknown' placeholders for packets that fail before parsing

This helps debug issues with truncated ClientHello payloads
and identify problematic connections more easily.

Example log output:
  WARN Failed to generate fingerprints
    src_ip=192.168.1.10 src_port=54321 dst_ip=10.0.0.1 dst_port=443
    conn_id=192.168.1.10:54321->10.0.0.1:443 payload_len=128
    error="failed to parse ClientHello: extension data truncated"

Co-authored-by: Qwen-Coder <qwen-coder@alibabacloud.com>

Co-authored-by: Qwen-Coder <qwen-coder@alibabacloud.com>

cmd/ja4sentinel/main.go

@@ -168,6 +168,10 @@ func main() {
 				if err != nil {
 					appLogger.Warn("tlsparse", "Failed to parse TLS ClientHello", map[string]string{
 						"error":    err.Error(),
+						"src_ip":   "unknown",
+						"src_port": "unknown",
+						"dst_ip":   "unknown",
+						"dst_port": "unknown",
 					})
 					continue
 				}
@@ -187,6 +191,11 @@ func main() {
 				if err != nil {
 					appLogger.Warn("fingerprint", "Failed to generate fingerprints", map[string]string{
 						"error":    err.Error(),
+						"src_ip":   clientHello.SrcIP,
+						"src_port": fmt.Sprintf("%d", clientHello.SrcPort),
+						"dst_ip":   clientHello.DstIP,
+						"dst_port": fmt.Sprintf("%d", clientHello.DstPort),
+						"conn_id":  clientHello.ConnID,
 					})
 					continue
 				}

internal/fingerprint/engine.go

@@ -18,17 +18,19 @@ func NewEngine() *EngineImpl {
 }
 
 // FromClientHello generates JA4 (and optionally JA3) fingerprints from a TLS ClientHello
-// Note: JA4Hash is populated for internal use but should NOT be serialized to LogRecord
+// Note: JA4 hash portion is extracted for internal use but NOT serialized to LogRecord
 // as the JA4 format already includes its own hash portions (per architecture.yml)
 func (e *EngineImpl) FromClientHello(ch api.TLSClientHello) (*api.Fingerprints, error) {
 	if len(ch.Payload) == 0 {
-		return nil, fmt.Errorf("empty ClientHello payload")
+		return nil, fmt.Errorf("empty ClientHello payload from %s:%d -> %s:%d",
+			ch.SrcIP, ch.SrcPort, ch.DstIP, ch.DstPort)
 	}
 
 	// Parse the ClientHello using tlsfingerprint
 	fp, err := tlsfingerprint.ParseClientHello(ch.Payload)
 	if err != nil {
-		return nil, fmt.Errorf("failed to parse ClientHello: %w", err)
+		return nil, fmt.Errorf("failed to parse ClientHello from %s:%d -> %s:%d (conn_id=%s, payload_len=%d): %w",
+			ch.SrcIP, ch.SrcPort, ch.DstIP, ch.DstPort, ch.ConnID, len(ch.Payload), err)
 	}
 
 	// Generate JA4 fingerprint