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/tcp/tcp_unix.go

@@ -3,26 +3,49 @@
 package tcp
 
 import (
-	"syscall"
+	"net/netip"
 	"time"
+
+	"golang.org/x/sys/unix"
 )
 
 // fileDescriptor is a platform-independent type for socket file descriptors.
 type fileDescriptor int
 
-func sendTo(fd fileDescriptor, p []byte, flags int, to syscall.Sockaddr) (err error) {
-	return syscall.Sendto(int(fd), p, flags, to)
+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 sendTo(fd fileDescriptor, p []byte, flags int, to unix.Sockaddr) (err error) {
+	return unix.Sendto(int(fd), p, flags, to)
 }
 
 func setSocketTimeout(fd fileDescriptor, timeout time.Duration) (err error) {
-	timeval := syscall.NsecToTimeval(timeout.Nanoseconds())
-	return syscall.SetsockoptTimeval(int(fd), syscall.SOL_SOCKET, syscall.SO_RCVTIMEO, &timeval)
+	timeval := unix.NsecToTimeval(timeout.Nanoseconds())
+	return unix.SetsockoptTimeval(int(fd), unix.SOL_SOCKET, unix.SO_RCVTIMEO, &timeval)
 }
 
-func recvFrom(fd fileDescriptor, p []byte, flags int) (n int, from syscall.Sockaddr, err error) {
-	return syscall.Recvfrom(int(fd), p, flags)
+func recvFrom(fd fileDescriptor, p []byte, flags int) (n int, from unix.Sockaddr, err error) {
+	return unix.Recvfrom(int(fd), p, flags)
 }
 
 func setNonBlock(fd int) error {
-	return syscall.SetNonblock(fd, true)
+	return unix.SetNonblock(fd, true)
+}
+
+func makeSockAddr(addr netip.AddrPort) unix.Sockaddr {
+	if addr.Addr().Is4() {
+		return &unix.SockaddrInet4{
+			Port: int(addr.Port()),
+			Addr: addr.Addr().As4(),
+		}
+	}
+	return &unix.SockaddrInet6{
+		Port: int(addr.Port()),
+		Addr: addr.Addr().As16(),
+	}
 }