1 files changed, 58 insertions, 0 deletions
diff --git a/src/net/dnsconfig_windows.go b/src/net/dnsconfig_windows.go
new file mode 100644
index 0000000..5d640da
--- /dev/null
+++ b/src/net/dnsconfig_windows.go
@@ -0,0 +1,58 @@
+// Copyright 2022 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package net
+
+import (
+	"syscall"
+	"time"
+)
+
+func dnsReadConfig(ignoredFilename string) (conf *dnsConfig) {
+	conf = &dnsConfig{
+		ndots:    1,
+		timeout:  5 * time.Second,
+		attempts: 2,
+	}
+	defer func() {
+		if len(conf.servers) == 0 {
+			conf.servers = defaultNS
+		}
+	}()
+	aas, err := adapterAddresses()
+	if err != nil {
+		return
+	}
+	// TODO(bradfitz): this just collects all the DNS servers on all
+	// the interfaces in some random order. It should order it by
+	// default route, or only use the default route(s) instead.
+	// In practice, however, it mostly works.
+	for _, aa := range aas {
+		for dns := aa.FirstDnsServerAddress; dns != nil; dns = dns.Next {
+			sa, err := dns.Address.Sockaddr.Sockaddr()
+			if err != nil {
+				continue
+			}
+			var ip IP
+			switch sa := sa.(type) {
+			case *syscall.SockaddrInet4:
+				ip = IPv4(sa.Addr[0], sa.Addr[1], sa.Addr[2], sa.Addr[3])
+			case *syscall.SockaddrInet6:
+				ip = make(IP, IPv6len)
+				copy(ip, sa.Addr[:])
+				if ip[0] == 0xfe && ip[1] == 0xc0 {
+					// Ignore these fec0/10 ones. Windows seems to
+					// populate them as defaults on its misc rando
+					// interfaces.
+					continue
+				}
+			default:
+				// Unexpected type.
+				continue
+			}
+			conf.servers = append(conf.servers, JoinHostPort(ip.String(), "53"))
+		}
+	}
+	return conf
+}