improve: rootless trace on macOS

trace/icmp_ipv4.go

@@ -12,6 +12,7 @@ import (
 	"sync"
 	"time"
 
+	"github.com/xgadget-lab/nexttrace/trace/internal"
 	"golang.org/x/net/context"
 	"golang.org/x/net/icmp"
 	"golang.org/x/net/ipv4"
@@ -64,7 +65,7 @@ func (t *ICMPTracer) Execute() (*Result, error) {
 
 	var err error
 
-	t.icmpListen, err = net.ListenPacket("ip4:1", t.SrcAddr)
+	t.icmpListen, err = internal.ListenICMP("ip4:1", t.SrcAddr)
 	if err != nil {
 		return &t.res, err
 	}

trace/icmp_ipv6.go

@@ -10,6 +10,7 @@ import (
 	"sync"
 	"time"
 
+	"github.com/xgadget-lab/nexttrace/trace/internal"
 	"golang.org/x/net/context"
 	"golang.org/x/net/icmp"
 	"golang.org/x/net/ipv6"
@@ -65,7 +66,7 @@ func (t *ICMPTracerv6) Execute() (*Result, error) {
 
 	var err error
 
-	t.icmpListen, err = net.ListenPacket("ip6:58", t.SrcAddr)
+	t.icmpListen, err = internal.ListenICMP("ip6:58", t.SrcAddr)
 	if err != nil {
 		return &t.res, err
 	}

trace/internal/icmp_darwin.go

@@ -0,0 +1,49 @@
+//go:build darwin
+
+package internal
+
+import (
+	"context"
+	"errors"
+	"net"
+	"os"
+	"syscall"
+	"unsafe"
+)
+
+//go:linkname internetSocket net.internetSocket
+func internetSocket(ctx context.Context, net string, laddr, raddr interface{}, sotype, proto int, mode string, ctrlCtxFn func(context.Context, string, string, syscall.RawConn) error) (fd unsafe.Pointer, err error)
+
+//go:linkname newIPConn net.newIPConn
+func newIPConn(fd unsafe.Pointer) *net.IPConn
+
+var (
+	errUnknownNetwork = errors.New("unknown network type")
+
+	networkMap = map[string]string{
+		"ip4:icmp": "udp4",
+		"ip4:1":    "udp4",
+		"ip6:icmp": "udp6",
+		"ip6:58":   "udp6",
+	}
+)
+
+func ListenICMP(network string, laddr string) (net.PacketConn, error) {
+	if os.Getuid() == 0 { // root
+		return net.ListenPacket(network, laddr)
+	} else {
+		if nw, ok := networkMap[network]; ok {
+			proto := syscall.IPPROTO_ICMP
+			if nw == "udp6" {
+				proto = syscall.IPPROTO_ICMPV6
+			}
+			isock, err := internetSocket(context.Background(), nw, nil, nil, syscall.SOCK_DGRAM, proto, "listen", nil)
+			if err != nil {
+				panic(err)
+			}
+			return newIPConn(isock), nil
+		} else {
+			return nil, errUnknownNetwork
+		}
+	}
+}

trace/internal/icmp_general.go

@@ -0,0 +1,9 @@
+//go:build !darwin
+
+package internal
+
+import "net"
+
+func ListenICMP(network string, laddr string) (net.PacketConn, error) {
+	return net.ListenPacket(network, laddr)
+}

trace/trace.go

@@ -2,12 +2,12 @@ package trace
 
 import (
 	"errors"
-	"github.com/xgadget-lab/nexttrace/util"
 	"net"
 	"sync"
 	"time"
 
 	"github.com/xgadget-lab/nexttrace/ipgeo"
+	"github.com/xgadget-lab/nexttrace/util"
 )
 
 var (