Add ping proxy implementation

icmp_privileged.go

@@ -0,0 +1,112 @@
+package tun
+
+import (
+	"context"
+	"net"
+	"net/netip"
+	"os"
+
+	"github.com/sagernet/sing-tun/internal/gtcpip/checksum"
+	"github.com/sagernet/sing-tun/internal/gtcpip/header"
+	"github.com/sagernet/sing/common/atomic"
+	"github.com/sagernet/sing/common/buf"
+	E "github.com/sagernet/sing/common/exceptions"
+	"github.com/sagernet/sing/common/logger"
+	M "github.com/sagernet/sing/common/metadata"
+	N "github.com/sagernet/sing/common/network"
+)
+
+type PrivilegedICMPDestination struct {
+	ctx          context.Context
+	cancel       context.CancelCauseFunc
+	logger       logger.Logger
+	routeContext DirectRouteContext
+	isIPv6       bool
+	localAddr    atomic.TypedValue[netip.Addr]
+	rawConn      net.Conn
+}
+
+func NewPrivilegedICMPDestination(ctx context.Context, logger logger.Logger, dialer net.Dialer, network string, address netip.Addr, routeContext DirectRouteContext) (DirectRouteDestination, error) {
+	var dialNetwork string
+	switch network {
+	case N.NetworkICMPv4:
+		dialNetwork = "ip4:icmp"
+	case N.NetworkICMPv6:
+		dialNetwork = "ip6:icmp"
+	default:
+		return nil, E.New("unsupported network: ", network)
+	}
+	ctx, cancel := context.WithCancelCause(ctx)
+	rawConn, err := dialer.DialContext(ctx, dialNetwork, address.String())
+	if err != nil {
+		cancel(err)
+		return nil, err
+	}
+	d := &PrivilegedICMPDestination{
+		ctx:          ctx,
+		cancel:       cancel,
+		logger:       logger,
+		routeContext: routeContext,
+		isIPv6:       network == N.NetworkICMPv6,
+		rawConn:      rawConn,
+	}
+	go d.loopRead()
+	return d, nil
+}
+
+func (d *PrivilegedICMPDestination) loopRead() {
+	for {
+		buffer := buf.NewPacket()
+		_, err := buffer.ReadOnceFrom(d.rawConn)
+		if err != nil {
+			return
+		}
+		if !d.isIPv6 {
+			ipHdr := header.IPv4(buffer.Bytes())
+			ipHdr.SetDestinationAddr(d.localAddr.Load())
+			ipHdr.SetChecksum(0)
+			ipHdr.SetChecksum(^ipHdr.CalculateChecksum())
+			icmpHdr := header.ICMPv4(ipHdr.Payload())
+			icmpHdr.SetChecksum(header.ICMPv4Checksum(icmpHdr[:header.ICMPv4MinimumSize], checksum.Checksum(icmpHdr.Payload(), 0)))
+		} else {
+			ipHdr := header.IPv6(buffer.Bytes())
+			ipHdr.SetDestinationAddr(d.localAddr.Load())
+			icmpHdr := header.ICMPv6(ipHdr.Payload())
+			icmpHdr.SetChecksum(header.ICMPv6Checksum(header.ICMPv6ChecksumParams{
+				Header: icmpHdr,
+				Src:    ipHdr.SourceAddress(),
+				Dst:    ipHdr.DestinationAddress(),
+			}))
+		}
+		err = d.routeContext.WritePacket(buffer.Bytes())
+		if err != nil {
+			d.logger.Error(err)
+		}
+	}
+}
+
+func (d *PrivilegedICMPDestination) WritePacket(packet *buf.Buffer) error {
+	if !d.isIPv6 {
+		ipHdr := header.IPv4(packet.Bytes())
+		d.localAddr.Store(M.AddrFromIP(ipHdr.SourceAddressSlice()))
+		icmpHdr := header.ICMPv6(ipHdr.Payload())
+		_, err := d.rawConn.Write(icmpHdr)
+		if err != nil {
+			return err
+		}
+	} else {
+		ipHdr := header.IPv6(packet.Bytes())
+		d.localAddr.Store(M.AddrFromIP(ipHdr.SourceAddressSlice()))
+		icmpHdr := header.ICMPv6(ipHdr.Payload())
+		_, err := d.rawConn.Write(icmpHdr)
+		if err != nil {
+			return err
+		}
+	}
+	return nil
+}
+
+func (d *PrivilegedICMPDestination) Close() error {
+	d.cancel(os.ErrClosed)
+	return d.rawConn.Close()
+}