1 files changed, 45 insertions, 0 deletions
diff --git a/src/net/dnsconfig.go b/src/net/dnsconfig.go
new file mode 100644
index 0000000..c86a70b
--- /dev/null
+++ b/src/net/dnsconfig.go
@@ -0,0 +1,45 @@
+// 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 (
+	"os"
+	"sync/atomic"
+	"time"
+)
+
+var (
+	defaultNS   = []string{"127.0.0.1:53", "[::1]:53"}
+	getHostname = os.Hostname // variable for testing
+)
+
+type dnsConfig struct {
+	servers       []string      // server addresses (in host:port form) to use
+	search        []string      // rooted suffixes to append to local name
+	ndots         int           // number of dots in name to trigger absolute lookup
+	timeout       time.Duration // wait before giving up on a query, including retries
+	attempts      int           // lost packets before giving up on server
+	rotate        bool          // round robin among servers
+	unknownOpt    bool          // anything unknown was encountered
+	lookup        []string      // OpenBSD top-level database "lookup" order
+	err           error         // any error that occurs during open of resolv.conf
+	mtime         time.Time     // time of resolv.conf modification
+	soffset       uint32        // used by serverOffset
+	singleRequest bool          // use sequential A and AAAA queries instead of parallel queries
+	useTCP        bool          // force usage of TCP for DNS resolutions
+	trustAD       bool          // add AD flag to queries
+	noReload      bool          // do not check for config file updates
+}
+
+// serverOffset returns an offset that can be used to determine
+// indices of servers in c.servers when making queries.
+// When the rotate option is enabled, this offset increases.
+// Otherwise it is always 0.
+func (c *dnsConfig) serverOffset() uint32 {
+	if c.rotate {
+		return atomic.AddUint32(&c.soffset, 1) - 1 // return 0 to start
+	}
+	return 0
+}