chore(pmtud): remove calls to syscall in favor of unix and windows

- syscall is deprecated and is not kept up-to-date
- each OS is inherently different hence the syscall being deprecated

internal/pmtud/ip/ipheader.go

@@ -3,7 +3,6 @@ package ip
 import (
 	"encoding/binary"
 	"net/netip"
-	"syscall"
 
 	"github.com/qdm12/gluetun/internal/pmtud/constants"
 )
@@ -19,7 +18,7 @@ func HeaderV4(srcIP, dstIP netip.Addr, payloadLength uint32) []byte {
 	const flagsAndOffset uint16 = 0x4000                                      // DF bit set
 	putUint16(ipHeader[6:], flagsAndOffset)
 	ipHeader[8] = 64 // ttl
-	ipHeader[9] = syscall.IPPROTO_TCP
+	ipHeader[9] = constants.IPPROTO_TCP
 	srcIPBytes := srcIP.As4()
 	copy(ipHeader[12:16], srcIPBytes[:])
 	dstIPBytes := dstIP.As4()
@@ -51,7 +50,7 @@ func ipChecksum(header []byte) uint16 {
 
 // HeaderV6 makes an IPv6 header.
 // payloadLen is the length of the payload following the header.
-// nextHeader can be byte([syscall.IPPROTO_TCP]) for example.
+// nextHeader can be byte([constants.IPPROTO_TCP]) for example.
 func HeaderV6(srcIP, dstIP netip.Addr,
 	payloadLen uint16, nextHeader byte,
 ) []byte {

internal/pmtud/ip/ipv4_unix.go

@@ -2,8 +2,8 @@
 
 package ip
 
-import "syscall"
+import "golang.org/x/sys/unix"
 
 func SetIPv4HeaderIncluded(fd int) error {
-	return syscall.SetsockoptInt(fd, syscall.IPPROTO_IP, syscall.IP_HDRINCL, 1)
+	return unix.SetsockoptInt(fd, unix.IPPROTO_IP, unix.IP_HDRINCL, 1)
 }

internal/pmtud/ip/ipv4_windows.go

@@ -1,12 +1,10 @@
 package ip
 
 import (
-	"syscall"
-
 	"golang.org/x/sys/windows"
 )
 
-func SetIPv4HeaderIncluded(handle syscall.Handle) error {
+func SetIPv4HeaderIncluded(handle windows.Handle) error {
 	const ipHdrIncluded = windows.IP_HDRINCL
-	return syscall.SetsockoptInt(handle, syscall.IPPROTO_IP, ipHdrIncluded, 1)
+	return windows.SetsockoptInt(handle, windows.IPPROTO_IP, ipHdrIncluded, 1)
 }

internal/pmtud/ip/ipv6_linux.go

@@ -1,8 +1,7 @@
 package ip
 
-import "syscall"
+import "golang.org/x/sys/unix"
 
 func SetIPv6HeaderIncluded(fd int) error {
-	const ipv6HdrIncluded = 36 // IPV6_HDRINCL
-	return syscall.SetsockoptInt(fd, syscall.IPPROTO_IPV6, ipv6HdrIncluded, 1)
+	return unix.SetsockoptInt(fd, unix.IPPROTO_IPV6, unix.IPV6_HDRINCL, 1)
 }

internal/pmtud/ip/ipv6_windows.go

@@ -1,7 +1,7 @@
 package ip
 
-import "syscall"
+import "golang.org/x/sys/windows"
 
-func SetIPv6HeaderIncluded(fd syscall.Handle) error {
+func SetIPv6HeaderIncluded(fd windows.Handle) error {
 	panic("windows does not allow an application to build IPv6 headers")
 }

internal/pmtud/ip/source.go

@@ -3,9 +3,9 @@ package ip
 import (
 	"fmt"
 	"net/netip"
-	"syscall"
 
 	"github.com/jsimonetti/rtnetlink"
+	"github.com/qdm12/gluetun/internal/pmtud/constants"
 )
 
 // SrcAddr determines the appropriate source IP address to use when sending a packet to the
@@ -35,9 +35,9 @@ func srcIP(dst netip.Addr) (netip.Addr, error) {
 	}
 	defer conn.Close()
 
-	family := uint8(syscall.AF_INET)
+	family := uint8(constants.AF_INET)
 	if dst.Is6() {
-		family = syscall.AF_INET6
+		family = constants.AF_INET6
 	}
 
 	// Request route to destination
@@ -71,53 +71,34 @@ func srcIP(dst netip.Addr) (netip.Addr, error) {
 // It doesn't actually listen on the port.
 // The cleanup function returned should be called to release the port when done.
 func srcPort(srcAddr netip.Addr, proto int) (srcPort uint16, cleanup func(), err error) {
-	family := syscall.AF_INET
+	family := constants.AF_INET
 	if srcAddr.Is6() {
-		family = syscall.AF_INET6
+		family = constants.AF_INET6
 	}
 
-	fd, err := syscall.Socket(family, syscall.SOCK_STREAM, proto)
+	fd, err := socket(family, constants.SOCK_STREAM, proto)
 	if err != nil {
 		return 0, nil, fmt.Errorf("creating reservation socket: %w", err)
 	}
 	cleanup = func() {
-		_ = syscall.Close(fd)
+		_ = closeSocket(fd)
 	}
 
 	// Bind to port 0 to get an ephemeral port
 	const port = 0
-	var bindAddr syscall.Sockaddr
-	if srcAddr.Is4() {
-		bindAddr = &syscall.SockaddrInet4{
-			Port: port,
-			Addr: srcAddr.As4(),
-		}
-	} else {
-		bindAddr = &syscall.SockaddrInet6{
-			Port: port,
-			Addr: srcAddr.As16(),
-		}
-	}
+	bindAddr := makeSockAddr(srcAddr, port)
 
-	err = syscall.Bind(fd, bindAddr)
+	err = bind(fd, bindAddr)
 	if err != nil {
 		cleanup()
 		return 0, nil, fmt.Errorf("binding reservation socket: %w", err)
 	}
 
-	sockAddr, err := syscall.Getsockname(fd)
+	srcPort, err = extractPortFromFD(fd)
 	if err != nil {
 		cleanup()
-		return 0, nil, fmt.Errorf("getting bound socket name: %w", err)
+		return 0, nil, fmt.Errorf("extracting port from socket fd: %w", err)
 	}
 
-	switch typedSockAddr := sockAddr.(type) {
-	case *syscall.SockaddrInet4:
-		srcPort = uint16(typedSockAddr.Port) //nolint:gosec
-	case *syscall.SockaddrInet6:
-		srcPort = uint16(typedSockAddr.Port) //nolint:gosec
-	default:
-		panic(fmt.Sprintf("unexpected sockaddr type: %T", typedSockAddr))
-	}
 	return srcPort, cleanup, nil
 }

internal/pmtud/ip/source_unix.go

@@ -0,0 +1,51 @@
+//go:build linux || darwin
+
+package ip
+
+import (
+	"fmt"
+	"net/netip"
+
+	"golang.org/x/sys/unix"
+)
+
+func socket(domain int, typ int, proto int) (fd int, err error) {
+	return unix.Socket(domain, typ, proto)
+}
+
+func closeSocket(fd int) error {
+	return unix.Close(fd)
+}
+
+func bind(fd int, addr unix.Sockaddr) error {
+	return unix.Bind(fd, addr)
+}
+
+func makeSockAddr(ip netip.Addr, port uint16) unix.Sockaddr {
+	if ip.Is4() {
+		return &unix.SockaddrInet4{
+			Port: int(port),
+			Addr: ip.As4(),
+		}
+	}
+	return &unix.SockaddrInet6{
+		Port: int(port),
+		Addr: ip.As16(),
+	}
+}
+
+func extractPortFromFD(fd int) (uint16, error) {
+	sockAddr, err := unix.Getsockname(fd)
+	if err != nil {
+		return 0, fmt.Errorf("getting sockname: %w", err)
+	}
+
+	switch typedSockAddr := sockAddr.(type) {
+	case *unix.SockaddrInet4:
+		return uint16(typedSockAddr.Port), nil //nolint:gosec
+	case *unix.SockaddrInet6:
+		return uint16(typedSockAddr.Port), nil //nolint:gosec
+	default:
+		panic(fmt.Sprintf("unexpected sockaddr type: %T", typedSockAddr))
+	}
+}

internal/pmtud/ip/source_windows.go

@@ -0,0 +1,49 @@
+package ip
+
+import (
+	"fmt"
+	"net/netip"
+
+	"golang.org/x/sys/windows"
+)
+
+func socket(domain int, typ int, proto int) (fd windows.Handle, err error) {
+	return windows.Socket(domain, typ, proto)
+}
+
+func closeSocket(fd windows.Handle) error {
+	return windows.Close(fd)
+}
+
+func bind(fd windows.Handle, addr windows.Sockaddr) error {
+	return windows.Bind(fd, addr)
+}
+
+func makeSockAddr(ip netip.Addr, port uint16) windows.Sockaddr {
+	if ip.Is4() {
+		return &windows.SockaddrInet4{
+			Port: int(port),
+			Addr: ip.As4(),
+		}
+	}
+	return &windows.SockaddrInet6{
+		Port: int(port),
+		Addr: ip.As16(),
+	}
+}
+
+func extractPortFromFD(fd windows.Handle) (uint16, error) {
+	sockAddr, err := windows.Getsockname(fd)
+	if err != nil {
+		return 0, fmt.Errorf("getting sockname: %w", err)
+	}
+
+	switch typedSockAddr := sockAddr.(type) {
+	case *windows.SockaddrInet4:
+		return uint16(typedSockAddr.Port), nil //nolint:gosec
+	case *windows.SockaddrInet6:
+		return uint16(typedSockAddr.Port), nil //nolint:gosec
+	default:
+		panic(fmt.Sprintf("unexpected sockaddr type: %T", typedSockAddr))
+	}
+}