refactor: refactor the code for qol.go

internal/qol/capture/pcap.go

@@ -0,0 +1,101 @@
+package capture
+
+import (
+	"context"
+	"fmt"
+	"os"
+	"sync"
+	"time"
+
+	"github.com/google/gopacket"
+	"github.com/google/gopacket/pcap"
+	"github.com/google/gopacket/pcapgo"
+)
+
+type PacketCapture struct {
+	handle *pcap.Handle
+	writer *pcapgo.Writer
+	file   *os.File
+	mu     sync.Mutex
+	err    error
+}
+
+func NewPacketCapture(iface, outputPath string) (*PacketCapture, error) {
+	handle, err := pcap.OpenLive(iface, 65535, true, pcap.BlockForever)
+	if err != nil {
+		return nil, fmt.Errorf("pcap open (try running as root): %w", err)
+	}
+
+	file, err := os.Create(outputPath)
+	if err != nil {
+		handle.Close()
+		return nil, fmt.Errorf("create pcap file: %w", err)
+	}
+
+	writer := pcapgo.NewWriter(file)
+	if err := writer.WriteFileHeader(65535, handle.LinkType()); err != nil {
+		handle.Close()
+		file.Close()
+		return nil, fmt.Errorf("pcap header: %w", err)
+	}
+
+	return &PacketCapture{
+		handle: handle,
+		writer: writer,
+		file:   file,
+	}, nil
+}
+
+func (pc *PacketCapture) Start(ctx context.Context) error {
+	psrc := gopacket.NewPacketSource(pc.handle, pc.handle.LinkType())
+	pktCh := psrc.Packets()
+
+	go func() {
+		for {
+			select {
+			case pkt, ok := <-pktCh:
+				if !ok {
+					return
+				}
+				ci := pkt.Metadata().CaptureInfo
+				if err := pc.writer.WritePacket(ci, pkt.Data()); err != nil {
+					pc.mu.Lock()
+					if pc.err == nil {
+						pc.err = fmt.Errorf("pcap write error: %w", err)
+					}
+					pc.mu.Unlock()
+				}
+			case <-ctx.Done():
+				return
+			}
+		}
+	}()
+
+	return nil
+}
+
+func (pc *PacketCapture) GetError() error {
+	pc.mu.Lock()
+	defer pc.mu.Unlock()
+	return pc.err
+}
+
+func (pc *PacketCapture) Close() error {
+	var errs []error
+	
+	if pc.handle != nil {
+		pc.handle.Close()
+	}
+	
+	if pc.file != nil {
+		if err := pc.file.Close(); err != nil {
+			errs = append(errs, err)
+		}
+	}
+	
+	if len(errs) > 0 {
+		return errs[0]
+	}
+	
+	return nil
+}