CapturePrinter expose Ethernet and IP printers

examples/min-working-example/main-mwe.go

@@ -148,7 +148,7 @@ func stackLoop(ctx context.Context, stack *xnet.StackAsync) {
 			fmt.Println("encaps err:", err)
 		} else if nwrite > 0 {
 			network.SendEth(buf[:nwrite])
-			cap.PrintPacket("OUT", buf[:nwrite])
+			cap.PrintEthernet("OUT", buf[:nwrite])
 		}
 		nread, err := network.RecvEth(buf[:])
 		if err != nil {
@@ -158,7 +158,7 @@ func stackLoop(ctx context.Context, stack *xnet.StackAsync) {
 			if err != nil && err != lneto.ErrPacketDrop {
 				fmt.Println("demux err:", err)
 			} else {
-				cap.PrintPacket("IN ", buf[:nread])
+				cap.PrintEthernet("IN ", buf[:nread])
 			}
 		}
 		if nwrite == 0 && nread == 0 {

x/xnet/pcap-printer.go

@@ -5,6 +5,7 @@ import (
 	"strconv"
 	"time"
 
+	"github.com/soypat/lneto"
 	"github.com/soypat/lneto/internet/pcap"
 )
 
@@ -50,7 +51,20 @@ func (stack *CapturePrinter) Formatter() *pcap.Formatter {
 	return &stack.pfmt
 }
 
-func (stack *CapturePrinter) PrintPacket(prefix string, pkt []byte) {
+// PrintIP formats and writes a breakdown of the IPv4 or IPv6 packet, prefixed by prefix.
+func (stack *CapturePrinter) PrintIP(prefix string, ipPkt []byte) {
+	stack.printPacket(prefix, true, ipPkt)
+}
+
+// PrintEthernet formats and writes a breakdown of the Ethernet frame, prefixed by prefix.
+func (stack *CapturePrinter) PrintEthernet(prefix string, ethPkt []byte) {
+	stack.printPacket(prefix, false, ethPkt)
+}
+
+func (stack *CapturePrinter) printPacket(prefix string, ip bool, pkt []byte) {
+	if len(pkt) == 0 {
+		return
+	}
 	fmtbuf := stack.fmtPcapBuf[:0]
 	useTimestamps := stack.printTimestamps()
 	var captime time.Time
@@ -58,7 +72,18 @@ func (stack *CapturePrinter) PrintPacket(prefix string, pkt []byte) {
 		captime = stack.now()
 	}
 	var err error
-	stack.frms, err = stack.cap.CaptureEthernet(stack.frms[:0], pkt, 0)
+	if ip {
+		switch pkt[0] >> 4 {
+		case 4:
+			stack.frms, err = stack.cap.CaptureIPv4(stack.frms[:0], pkt, 0)
+		case 6:
+			stack.frms, err = stack.cap.CaptureIPv6(stack.frms[:0], pkt, 0)
+		default:
+			err = lneto.ErrUnsupported
+		}
+	} else {
+		stack.frms, err = stack.cap.CaptureEthernet(stack.frms[:0], pkt, 0)
+	}
 	if err == nil {
 		if useTimestamps {
 			diff := captime.Sub(stack.origin)

x/xnet/xnet_debug_pcap.go

@@ -13,5 +13,5 @@ func init() {
 }
 
 func debugPacket(msg string, b []byte) {
-	_pcap.PrintPacket(msg, b)
+	_pcap.PrintEthernet(msg, b)
 }

x/xnet/xnet_fuzz_test.go

@@ -503,7 +503,7 @@ func testStackSeeded(t *testing.T, seed1, seed2 int64) {
 					betsAreOff = true
 				}
 				if verbose {
-					fzppr.PrintPacket(first.Hostname(), buf[:n])
+					fzppr.PrintEthernet(first.Hostname(), buf[:n])
 				}
 				err = second.IngressEthernet(buf[:n])
 				if err != nil && !betsAreOff && err != lneto.ErrPacketDrop && err != lneto.ErrExhausted {
@@ -524,7 +524,7 @@ func testStackSeeded(t *testing.T, seed1, seed2 int64) {
 					betsAreOff = true
 				}
 				if verbose {
-					fzppr.PrintPacket(second.Hostname(), buf[:n])
+					fzppr.PrintEthernet(second.Hostname(), buf[:n])
 				}
 				err = first.IngressEthernet(buf[:n])
 				if err != nil && !betsAreOff && err != lneto.ErrPacketDrop && err != lneto.ErrExhausted {
@@ -542,21 +542,21 @@ func testStackSeeded(t *testing.T, seed1, seed2 int64) {
 			limit := d == drainLimit-1
 			n, err := first.EgressEthernet(buf[:])
 			if (err != nil || n > 0) && limit {
-				fzppr.PrintPacket(first.Hostname(), buf[:n])
+				fzppr.PrintEthernet(first.Hostname(), buf[:n])
 				t.Fatal(i, "stuck in data/error loop:", err)
 			} else if n > 0 {
 				if verbose {
-					fzppr.PrintPacket(first.Hostname(), buf[:n])
+					fzppr.PrintEthernet(first.Hostname(), buf[:n])
 				}
 				second.IngressEthernet(buf[:n])
 			}
 			n, err = second.EgressEthernet(buf[:])
 			if (err != nil || n > 0) && limit {
-				fzppr.PrintPacket("(2) ", buf[:n])
+				fzppr.PrintEthernet("(2) ", buf[:n])
 				t.Fatal(i, "stuck in data/error loop:", err)
 			} else if n > 0 {
 				if verbose {
-					fzppr.PrintPacket(second.Hostname(), buf[:n])
+					fzppr.PrintEthernet(second.Hostname(), buf[:n])
 				}
 				first.IngressEthernet(buf[:n])
 			}