1 files changed, 88 insertions, 0 deletions
diff --git a/conf/dnsresolver_windows.go b/conf/dnsresolver_windows.go
new file mode 100644
index 00000000..9c1e817c
--- /dev/null
+++ b/conf/dnsresolver_windows.go
@@ -0,0 +1,88 @@
+/* SPDX-License-Identifier: MIT
+ *
+ * Copyright (C) 2019 WireGuard LLC. All Rights Reserved.
+ */
+
+package conf
+
+import (
+	"fmt"
+	"golang.org/x/sys/windows"
+	"log"
+	"net"
+	"syscall"
+	"time"
+	"unsafe"
+)
+
+//sys internetGetConnectedState(flags *uint32, reserved uint32) (connected bool) = wininet.InternetGetConnectedState
+
+func resolveHostname(name string) (resolvedIpString string, err error) {
+	const maxTries = 10
+
+	for i := 0; i < maxTries; i++ {
+		resolvedIpString, err = resolveHostnameOnce(name)
+		if err == nil {
+			return
+		}
+		if err == windows.WSATRY_AGAIN {
+			log.Printf("Temporary DNS error when resolving %s, sleeping for 4 seconds", name)
+			time.Sleep(time.Second * 4)
+			continue
+		}
+		var state uint32
+		if err == windows.WSAHOST_NOT_FOUND && !internetGetConnectedState(&state, 0) {
+			log.Printf("Host not found when resolving %s, but no Internet connection available, sleeping for 4 seconds", name)
+			time.Sleep(time.Second * 4)
+			continue
+		}
+		return
+	}
+	return
+}
+
+func resolveHostnameOnce(name string) (resolvedIpString string, err error) {
+	hints := windows.AddrinfoW{
+		Family:   windows.AF_UNSPEC,
+		Socktype: windows.SOCK_DGRAM,
+		Protocol: windows.IPPROTO_IP,
+	}
+	var result *windows.AddrinfoW
+	name16, err := windows.UTF16PtrFromString(name)
+	if err != nil {
+		return
+	}
+	err = windows.GetAddrInfoW(name16, nil, &hints, &result)
+	if err != nil {
+		return
+	}
+	if result == nil {
+		err = windows.WSAHOST_NOT_FOUND
+		return
+	}
+	defer windows.FreeAddrInfoW(result)
+	ipv6 := ""
+	for ; result != nil; result = result.Next {
+		addr := unsafe.Pointer(result.Addr)
+		switch result.Family {
+		case windows.AF_INET:
+			a := (*syscall.RawSockaddrInet4)(addr).Addr
+			return net.IP{a[0], a[1], a[2], a[3]}.String(), nil
+		case windows.AF_INET6:
+			if len(ipv6) != 0 {
+				continue
+			}
+			a := (*syscall.RawSockaddrInet6)(addr).Addr
+			ipv6 = net.IP{a[0], a[1], a[2], a[3], a[4], a[5], a[6], a[7], a[8], a[9], a[10], a[11], a[12], a[13], a[14], a[15]}.String()
+			scope := uint32((*syscall.RawSockaddrInet6)(addr).Scope_id)
+			if scope != 0 {
+				ipv6 += fmt.Sprintf("%%%d", scope)
+			}
+		}
+	}
+	if len(ipv6) != 0 {
+		return ipv6, nil
+	}
+	err = windows.WSAHOST_NOT_FOUND
+	return
+}