Extract private upstream for iOS and fix function headers for other OS

client/internal/dns/upstream.go

@@ -8,13 +8,11 @@ import (
 	"runtime"
 	"sync"
 	"sync/atomic"
-	"syscall"
 	"time"
 
 	"github.com/cenkalti/backoff/v4"
 	"github.com/miekg/dns"
 	log "github.com/sirupsen/logrus"
-	"golang.org/x/sys/unix"
 )
 
 const (
@@ -85,38 +83,6 @@ func newUpstreamResolver(parentCTX context.Context, interfaceName string, wgAddr
 	}
 }
 
-// getClientPrivate returns a new DNS client bound to the local IP address of the Netbird interface
-// This method is needed for iOS
-func (u *upstreamResolver) getClientPrivate() *dns.Client {
-	dialer := &net.Dialer{
-		LocalAddr: &net.UDPAddr{
-			IP:   u.lIP,
-			Port: 0, // Let the OS pick a free port
-		},
-		Timeout: upstreamTimeout,
-		Control: func(network, address string, c syscall.RawConn) error {
-			var operr error
-			fn := func(s uintptr) {
-				operr = unix.SetsockoptInt(int(s), unix.IPPROTO_IP, unix.IP_BOUND_IF, u.iIndex)
-			}
-
-			if err := c.Control(fn); err != nil {
-				return err
-			}
-
-			if operr != nil {
-				log.Errorf("error while setting socket option: %s", operr)
-			}
-
-			return operr
-		},
-	}
-	client := &dns.Client{
-		Dialer: dialer,
-	}
-	return client
-}
-
 func (u *upstreamResolver) stop() {
 	log.Debugf("stopping serving DNS for upstreams %s", u.upstreamServers)
 	u.cancel()