1 files changed, 86 insertions, 0 deletions
diff --git a/src/net/hosts.go b/src/net/hosts.go
new file mode 100644
index 000000000..9400503e4
--- /dev/null
+++ b/src/net/hosts.go
@@ -0,0 +1,86 @@
+// Copyright 2009 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.
+
+// Read static host/IP entries from /etc/hosts.
+
+package net
+
+import (
+	"sync"
+	"time"
+)
+
+const cacheMaxAge = 5 * time.Minute
+
+// hostsPath points to the file with static IP/address entries.
+var hostsPath = "/etc/hosts"
+
+// Simple cache.
+var hosts struct {
+	sync.Mutex
+	byName map[string][]string
+	byAddr map[string][]string
+	expire time.Time
+	path   string
+}
+
+func readHosts() {
+	now := time.Now()
+	hp := hostsPath
+	if len(hosts.byName) == 0 || now.After(hosts.expire) || hosts.path != hp {
+		hs := make(map[string][]string)
+		is := make(map[string][]string)
+		var file *file
+		if file, _ = open(hp); file == nil {
+			return
+		}
+		for line, ok := file.readLine(); ok; line, ok = file.readLine() {
+			if i := byteIndex(line, '#'); i >= 0 {
+				// Discard comments.
+				line = line[0:i]
+			}
+			f := getFields(line)
+			if len(f) < 2 || ParseIP(f[0]) == nil {
+				continue
+			}
+			for i := 1; i < len(f); i++ {
+				h := f[i]
+				hs[h] = append(hs[h], f[0])
+				is[f[0]] = append(is[f[0]], h)
+			}
+		}
+		// Update the data cache.
+		hosts.expire = now.Add(cacheMaxAge)
+		hosts.path = hp
+		hosts.byName = hs
+		hosts.byAddr = is
+		file.close()
+	}
+}
+
+// lookupStaticHost looks up the addresses for the given host from /etc/hosts.
+func lookupStaticHost(host string) []string {
+	hosts.Lock()
+	defer hosts.Unlock()
+	readHosts()
+	if len(hosts.byName) != 0 {
+		if ips, ok := hosts.byName[host]; ok {
+			return ips
+		}
+	}
+	return nil
+}
+
+// lookupStaticAddr looks up the hosts for the given address from /etc/hosts.
+func lookupStaticAddr(addr string) []string {
+	hosts.Lock()
+	defer hosts.Unlock()
+	readHosts()
+	if len(hosts.byAddr) != 0 {
+		if hosts, ok := hosts.byAddr[addr]; ok {
+			return hosts
+		}
+	}
+	return nil
+}