tunnel: support setting dns domain suffix

Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>

2 files changed, 36 insertions, 0 deletions

diff --git a/tunnel/addressconfig.go b/tunnel/addressconfig.go
index 777c96cd..462e1052 100644
--- a/tunnel/addressconfig.go
+++ b/tunnel/addressconfig.go
@@ -159,6 +159,15 @@ func configureInterface(family winipcfg.AddressFamily, conf *conf.Config, tun *t
 		return err
 	}
 
+	if len(conf.Interface.DNSSearch) > 0 {
+		err = luid.SetDNSDomain(conf.Interface.DNSSearch[0])
+		if err != nil {
+			return nil
+		}
+		if len(conf.Interface.DNSSearch) > 1 {
+			log.Printf("Warning: %d DNS search domains were specified, but only one is supported, so the first one (%s) was used.", len(conf.Interface.DNSSearch), conf.Interface.DNSSearch[0])
+		}
+	}
 	err = luid.SetDNSForFamily(family, conf.Interface.DNS)
 	if err != nil {
 		return err
diff --git a/tunnel/winipcfg/luid.go b/tunnel/winipcfg/luid.go
index 396fbbb2..e1aafb61 100644
--- a/tunnel/winipcfg/luid.go
+++ b/tunnel/winipcfg/luid.go
@@ -6,10 +6,12 @@
 package winipcfg
 
 import (
+	"errors"
 	"fmt"
 	"net"
 
 	"golang.org/x/sys/windows"
+	"golang.org/x/sys/windows/registry"
 )
 
 // LUID represents a network interface.
@@ -426,3 +428,28 @@ func (luid LUID) SetDNSForFamily(family AddressFamily, dnses []net.IP) error {
 	}
 	return runNetsh(cmds)
 }
+
+// SetDNSDomain method sets the interface-specific DNS domain.
+func (luid LUID) SetDNSDomain(domain string) error {
+	guid, err := luid.GUID()
+
+	key, err := registry.OpenKey(registry.LOCAL_MACHINE, fmt.Sprintf("SYSTEM\\CurrentControlSet\\Services\\Tcpip\\Parameters\\Adapters\\%v", guid), registry.QUERY_VALUE)
+	if err != nil {
+		return fmt.Errorf("Error opening adapter-specific TCP/IP network registry key: %v", err)
+	}
+	paths, _, err := key.GetStringsValue("IpConfig")
+	key.Close()
+	if err != nil {
+		return fmt.Errorf("Error reading IpConfig registry key: %v", err)
+	}
+	if len(paths) == 0 {
+		return errors.New("No TCP/IP interfaces found on adapter")
+	}
+	key, err = registry.OpenKey(registry.LOCAL_MACHINE, fmt.Sprintf("SYSTEM\\CurrentControlSet\\Services\\%s", paths[0]), registry.SET_VALUE)
+	if err != nil {
+		return fmt.Errorf("Unable to open TCP/IP network registry key: %v", err)
+	}
+	err = key.SetStringValue("Domain", domain)
+	key.Close()
+	return err
+}