Use dialer in relay checks (fixes #2732)

lib/osutil/osutil.go

@@ -11,12 +11,10 @@ import (
 	"errors"
 	"fmt"
 	"io"
-	"net"
 	"os"
 	"path/filepath"
 	"runtime"
 	"strings"
-	"time"
 
 	"github.com/calmh/du"
 	"github.com/syncthing/syncthing/lib/sync"
@@ -223,21 +221,3 @@ func DiskFreePercentage(path string) (freePct float64, err error) {
 	u, err := du.Get(path)
 	return (float64(u.FreeBytes) / float64(u.TotalBytes)) * 100, err
 }
-
-// SetTCPOptions sets syncthings default TCP options on a TCP connection
-func SetTCPOptions(conn *net.TCPConn) error {
-	var err error
-	if err = conn.SetLinger(0); err != nil {
-		return err
-	}
-	if err = conn.SetNoDelay(false); err != nil {
-		return err
-	}
-	if err = conn.SetKeepAlivePeriod(60 * time.Second); err != nil {
-		return err
-	}
-	if err = conn.SetKeepAlive(true); err != nil {
-		return err
-	}
-	return nil
-}

lib/osutil/ping.go

@@ -7,20 +7,18 @@
 package osutil
 
 import (
-	"net"
 	"net/url"
 	"time"
+
+	"github.com/syncthing/syncthing/lib/dialer"
 )
 
 // TCPPing returns the duration required to establish a TCP connection
 // to the given host. ICMP packets require root priviledges, hence why we use
 // tcp.
 func TCPPing(address string) (time.Duration, error) {
-	dialer := net.Dialer{
-		Deadline: time.Now().Add(time.Second),
-	}
 	start := time.Now()
-	conn, err := dialer.Dial("tcp", address)
+	conn, err := dialer.DialTimeout("tcp", address, time.Second)
 	if conn != nil {
 		conn.Close()
 	}