Add systemd socket activation support

inbound/default.go

@@ -14,6 +14,8 @@ import (
 	E "github.com/sagernet/sing/common/exceptions"
 	M "github.com/sagernet/sing/common/metadata"
 	N "github.com/sagernet/sing/common/network"
+
+	"golang.org/x/sys/unix"
 )
 
 var _ adapter.Inbound = (*myInboundAdapter)(nil)
@@ -38,6 +40,8 @@ type myInboundAdapter struct {
 
 	// internal
 
+	tcpFd                int
+	udpFd                int
 	tcpListener          net.Listener
 	udpConn              *net.UDPConn
 	udpAddr              M.Socksaddr
@@ -111,6 +115,24 @@ func (a *myInboundAdapter) Close() error {
 	))
 }
 
+func (a *myInboundAdapter) initFds() {
+	if len(a.listenOptions.Fds) != 0 && a.tcpFd == 0 && a.udpFd == 0 {
+		for _, fd := range a.listenOptions.Fds {
+			sotype, err := unix.GetsockoptInt(fd, unix.SOL_SOCKET, unix.SO_TYPE)
+			if err != nil {
+				a.logger.Error("fd:", fd, " get type error: ", err)
+				continue
+			}
+			switch sotype {
+			case unix.SOCK_STREAM:
+				a.tcpFd = fd
+			case unix.SOCK_DGRAM:
+				a.udpFd = fd
+			}
+		}
+	}
+}
+
 func (a *myInboundAdapter) upstreamHandler(metadata adapter.InboundContext) adapter.UpstreamHandlerAdapter {
 	return adapter.NewUpstreamHandler(metadata, a.newConnection, a.streamPacketConnection, a)
 }

inbound/default_tcp.go

@@ -3,6 +3,7 @@ package inbound
 import (
 	"context"
 	"net"
+	"os"
 
 	"github.com/sagernet/sing-box/adapter"
 	"github.com/sagernet/sing-box/common/proxyproto"
@@ -15,12 +16,25 @@ import (
 
 func (a *myInboundAdapter) ListenTCP() (net.Listener, error) {
 	var err error
-	bindAddr := M.SocksaddrFrom(a.listenOptions.Listen.Build(), a.listenOptions.ListenPort)
 	var tcpListener net.Listener
-	if !a.listenOptions.TCPFastOpen {
+	a.initFds()
-		tcpListener, err = net.ListenTCP(M.NetworkFromNetAddr(N.NetworkTCP, bindAddr.Addr), bindAddr.TCPAddr())
+	if a.tcpFd != 0 {
+		if a.listenOptions.TCPFastOpen {
+			err = tfo.SetTFOListener(uintptr(a.tcpFd))
+			if err != nil {
+				a.logger.Warn("fd:", a.tcpFd, " set tfo error: ", err)
+			}
+		}
+		f := os.NewFile(uintptr(a.tcpFd), "")
+		tcpListener, err = net.FileListener(f)
+		f.Close()
 	} else {
-		tcpListener, err = tfo.ListenTCP(M.NetworkFromNetAddr(N.NetworkTCP, bindAddr.Addr), bindAddr.TCPAddr())
+		bindAddr := M.SocksaddrFrom(a.listenOptions.Listen.Build(), a.listenOptions.ListenPort)
+		if !a.listenOptions.TCPFastOpen {
+			tcpListener, err = net.ListenTCP(M.NetworkFromNetAddr(N.NetworkTCP, bindAddr.Addr), bindAddr.TCPAddr())
+		} else {
+			tcpListener, err = tfo.ListenTCP(M.NetworkFromNetAddr(N.NetworkTCP, bindAddr.Addr), bindAddr.TCPAddr())
+		}
 	}
 	if err == nil {
 		a.logger.Info("tcp server started at ", tcpListener.Addr())

inbound/default_udp.go

@@ -12,21 +12,49 @@ import (
 	E "github.com/sagernet/sing/common/exceptions"
 	M "github.com/sagernet/sing/common/metadata"
 	N "github.com/sagernet/sing/common/network"
+
+	"golang.org/x/sys/unix"
 )
 
 func (a *myInboundAdapter) ListenUDP() (net.PacketConn, error) {
-	bindAddr := M.SocksaddrFrom(a.listenOptions.Listen.Build(), a.listenOptions.ListenPort)
+	var bindAddr M.Socksaddr
-	var lc net.ListenConfig
 	var udpFragment bool
 	if a.listenOptions.UDPFragment != nil {
 		udpFragment = *a.listenOptions.UDPFragment
 	} else {
 		udpFragment = a.listenOptions.UDPFragmentDefault
 	}
-	if !udpFragment {
+	var udpConn net.PacketConn
-		lc.Control = control.Append(lc.Control, control.DisableUDPFragment())
+	var err error
+	a.initFds()
+	if a.udpFd != 0 {
+		if !udpFragment {
+			if err := unix.SetsockoptInt(a.udpFd, unix.IPPROTO_IP, unix.IP_MTU_DISCOVER, unix.IP_PMTUDISC_DO); err != nil {
+				a.logger.Warn("SETSOCKOPT IP_MTU_DISCOVER IP_PMTUDISC_DO: ", err)
+			}
+			sa, err := unix.Getsockname(a.udpFd)
+			if err == nil {
+				if _, isIpv6 := sa.(*unix.SockaddrInet6); isIpv6 {
+					if err := unix.SetsockoptInt(a.udpFd, unix.IPPROTO_IPV6, unix.IPV6_MTU_DISCOVER, unix.IP_PMTUDISC_DO); err != nil {
+						a.logger.Warn("SETSOCKOPT IPV6_MTU_DISCOVER IP_PMTUDISC_DO", err)
+					}
+				}
+			} else {
+				a.logger.Error("fd:", a.udpFd, " get addr error: ", err)
+			}
+		}
+		f := os.NewFile(uintptr(a.udpFd), "")
+		udpConn, err = net.FilePacketConn(f)
+		f.Close()
+		bindAddr = M.SocksaddrFromNet(udpConn.LocalAddr())
+	} else {
+		var lc net.ListenConfig
+		bindAddr = M.SocksaddrFrom(a.listenOptions.Listen.Build(), a.listenOptions.ListenPort)
+		if !udpFragment {
+			lc.Control = control.Append(lc.Control, control.DisableUDPFragment())
+		}
+		udpConn, err = lc.ListenPacket(a.ctx, M.NetworkFromNetAddr(N.NetworkUDP, bindAddr.Addr), bindAddr.String())
 	}
-	udpConn, err := lc.ListenPacket(a.ctx, M.NetworkFromNetAddr(N.NetworkUDP, bindAddr.Addr), bindAddr.String())
 	if err != nil {
 		return nil, err
 	}

option/inbound.go

@@ -119,6 +119,7 @@ type InboundOptions struct {
 type ListenOptions struct {
 	Listen                      *ListenAddress `json:"listen,omitempty"`
 	ListenPort                  uint16         `json:"listen_port,omitempty"`
+	Fds                         []int          `json:"fds,omitempty"`
 	TCPFastOpen                 bool           `json:"tcp_fast_open,omitempty"`
 	UDPFragment                 *bool          `json:"udp_fragment,omitempty"`
 	UDPFragmentDefault          bool           `json:"-"`