fix TCP flags not being extracted from capture correctly

2026-08-21 15:09:05 +00:00 · 2025-06-03 00:45:11 -03:00
parent 55bc765d92
commit 2d71907241
4 changed files with 290 additions and 71 deletions
@@ -0,0 +1,98 @@
+package pcap
+
+import (
+	"math"
+	"math/rand"
+	"testing"
+
+	"github.com/soypat/lneto"
+	"github.com/soypat/lneto/ethernet"
+	"github.com/soypat/lneto/http/httpraw"
+	"github.com/soypat/lneto/internal/ltesto"
+	"github.com/soypat/lneto/ipv4"
+	"github.com/soypat/lneto/tcp"
+)
+
+func TestCap(t *testing.T) {
+	const mtu = 1500
+	var buf [mtu]byte
+	var gen ltesto.PacketGen
+	rng := rand.New(rand.NewSource(1))
+	gen.RandomizeAddrs(rng)
+	pkt := gen.AppendRandomIPv4TCPPacket(buf[:0], rng, tcp.Segment{
+		SEQ:     100,
+		ACK:     200,
+		DATALEN: 256,
+		WND:     1024,
+		Flags:   tcp.FlagFIN, //tcp.FlagSYN | tcp.FlagACK | tcp.FlagPSH,
+	})
+	var hdr httpraw.Header
+	hdr.SetStatus("200", "OK")
+	hdr.Set("Cookie", "ABC=123")
+	var pbreak PacketBreakdown
+	frames, err := pbreak.CaptureEthernet(nil, pkt, 0)
+	if err != nil {
+		t.Fatal(err)
+	}
+	// Ethernet+IPv4+TCP+HTTP = 4 frames
+	if len(frames) != 4 {
+		t.Errorf("want 4 frames, got %d", len(frames))
+	}
+	getClass := func(frame Frame, class FieldClass) uint64 {
+		idx, err := frame.FieldByClass(class)
+		if err != nil {
+			return 0xffff_ffff_ffff_ffff
+		}
+		v, _ := frame.FieldAsUint(idx, pkt)
+		return v
+	}
+	getName := func(frame Frame, name string) uint64 {
+		for i := range frame.Fields {
+			if frame.Fields[i].Name == name {
+				v, _ := frame.FieldAsUint(i, pkt)
+				return v
+			}
+		}
+		return math.MaxUint64
+	}
+	efrm, _ := ethernet.NewFrame(pkt)
+	pefrm := frames[0]
+	pifrm := frames[1]
+	ptfrm := frames[2]
+	// phfrm := frames[3]
+	gotEproto := ethernet.Type(getClass(pefrm, FieldClassProto))
+	if gotEproto != efrm.EtherTypeOrSize() {
+		t.Errorf("want %s ethernet type, got %s", efrm.EtherTypeOrSize().String(), gotEproto.String())
+	}
+
+	ifrm, _ := ipv4.NewFrame(efrm.Payload())
+	gotIproto := lneto.IPProto(getClass(pifrm, FieldClassProto))
+	if gotIproto != ifrm.Protocol() {
+		t.Errorf("want %s IP proto, got %s", ifrm.Protocol().String(), gotIproto.String())
+	}
+	gotToS := ipv4.ToS(getName(pifrm, "Type of Service"))
+	wantToS := ifrm.ToS()
+	if gotToS != wantToS {
+		t.Errorf("want %x IP ToS, got %x", wantToS, gotToS)
+	}
+	gotIflags := ipv4.Flags(getClass(pifrm, FieldClassFlags))
+	if gotIflags != ifrm.Flags() {
+		t.Errorf("want %x IP flags, got %x", ifrm.Flags(), gotIflags)
+	}
+	gotVersion := getClass(pifrm, FieldClassVersion)
+	wantVersion, _ := ifrm.VersionAndIHL()
+	if gotVersion != uint64(wantVersion) {
+		t.Errorf("want %d IP version, got %d", wantVersion, gotVersion)
+	}
+
+	tfrm, _ := tcp.NewFrame(ifrm.Payload())
+	gotTCPFlags := tcp.Flags(getClass(ptfrm, FieldClassFlags))
+	wantHeaderLen, wantTCPflags := tfrm.OffsetAndFlags()
+	if gotTCPFlags != wantTCPflags {
+		t.Errorf("want %s TCP flags, got %s", wantTCPflags.String(), gotTCPFlags.String())
+	}
+	gotHeaderLen := getClass(ptfrm, FieldClassSize)
+	if gotHeaderLen != uint64(wantHeaderLen) {
+		t.Errorf("want %d TCP header length, got %d", wantHeaderLen, gotHeaderLen)
+	}
+}