refactor(sniffing): split sniffer monolith into focused files, extract testable helpers

Split ~850-line sniffer.go into 6 focused files (http, h2, tls, ws,
rewrite, test), extract pure helpers (clampBodySize, normalizeHost,
effectiveReadTimeout), fix "DeafultSampleRate" typo, add doc comments
on all exported symbols, and add 22 unit tests.

internal/util/sniffing/sniffer_ws.go

@@ -0,0 +1,130 @@
+package sniffing
+
+import (
+	"bytes"
+	"context"
+	"io"
+	"math"
+	"time"
+
+	"github.com/go-gost/core/logger"
+	ws_util "github.com/go-gost/x/internal/util/ws"
+	xrecorder "github.com/go-gost/x/recorder"
+	"golang.org/x/time/rate"
+)
+
+// sniffingWebsocketFrame copies WebSocket frames between rw and cc while
+// recording frame metadata. It runs two goroutines for bidirectional copy
+// and waits for the first error.
+func (h *Sniffer) sniffingWebsocketFrame(ctx context.Context, rw, cc io.ReadWriter, ro *xrecorder.HandlerRecorderObject, log logger.Logger) error {
+	errc := make(chan error, 1)
+
+	sampleRate := h.WebsocketSampleRate
+	if sampleRate == 0 {
+		sampleRate = DefaultSampleRate
+	}
+	if sampleRate < 0 {
+		sampleRate = math.MaxFloat64
+	}
+
+	go func() {
+		ro2 := &xrecorder.HandlerRecorderObject{}
+		*ro2 = *ro
+		ro := ro2
+
+		limiter := rate.NewLimiter(rate.Limit(sampleRate), int(sampleRate))
+
+		buf := &bytes.Buffer{}
+		for {
+			start := time.Now()
+
+			if err := h.copyWebsocketFrame(cc, rw, buf, "client", ro); err != nil {
+				errc <- err
+				return
+			}
+
+			if limiter.Allow() {
+				ro.Duration = time.Since(start)
+				ro.Time = time.Now()
+				if err := ro.Record(ctx, h.Recorder); err != nil {
+					log.Errorf("record: %v", err)
+				}
+			}
+		}
+	}()
+
+	go func() {
+		ro2 := &xrecorder.HandlerRecorderObject{}
+		*ro2 = *ro
+		ro := ro2
+
+		limiter := rate.NewLimiter(rate.Limit(sampleRate), int(sampleRate))
+
+		buf := &bytes.Buffer{}
+		for {
+			start := time.Now()
+
+			if err := h.copyWebsocketFrame(rw, cc, buf, "server", ro); err != nil {
+				errc <- err
+				return
+			}
+
+			if limiter.Allow() {
+				ro.Duration = time.Since(start)
+				ro.Time = time.Now()
+				if err := ro.Record(ctx, h.Recorder); err != nil {
+					log.Errorf("record: %v", err)
+				}
+			}
+		}
+	}()
+
+	<-errc
+	return nil
+}
+
+// copyWebsocketFrame reads one WebSocket frame from r, records its metadata,
+// and writes it to w.
+func (h *Sniffer) copyWebsocketFrame(w io.Writer, r io.Reader, buf *bytes.Buffer, from string, ro *xrecorder.HandlerRecorderObject) (err error) {
+	fr := ws_util.Frame{}
+	if _, err = fr.ReadFrom(r); err != nil {
+		return err
+	}
+
+	ws := &xrecorder.WebsocketRecorderObject{
+		From:    from,
+		Fin:     fr.Header.Fin,
+		Rsv1:    fr.Header.Rsv1,
+		Rsv2:    fr.Header.Rsv2,
+		Rsv3:    fr.Header.Rsv3,
+		OpCode:  int(fr.Header.OpCode),
+		Masked:  fr.Header.Masked,
+		MaskKey: fr.Header.MaskKey,
+		Length:  fr.Header.PayloadLength,
+	}
+
+	if bodySize := clampBodySize(h.RecorderOptions); bodySize > 0 {
+		buf.Reset()
+		if _, err := io.Copy(buf, io.LimitReader(fr.Data, int64(bodySize))); err != nil {
+			return err
+		}
+		ws.Payload = buf.Bytes()
+	}
+
+	ro.Websocket = ws
+	length := uint64(fr.Header.Length()) + uint64(fr.Header.PayloadLength)
+	if from == "client" {
+		ro.InputBytes = length
+		ro.OutputBytes = 0
+	} else {
+		ro.InputBytes = 0
+		ro.OutputBytes = length
+	}
+
+	fr.Data = io.MultiReader(bytes.NewReader(buf.Bytes()), fr.Data)
+	if _, err := fr.WriteTo(w); err != nil {
+		return err
+	}
+
+	return nil
+}