1 files changed, 139 insertions, 0 deletions
diff --git a/src/net/hosts.go b/src/net/hosts.go
new file mode 100644
index 0000000..5c560f3
--- /dev/null
+++ b/src/net/hosts.go
@@ -0,0 +1,139 @@
+// 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.
+
+package net
+
+import (
+	"internal/bytealg"
+	"sync"
+	"time"
+)
+
+const cacheMaxAge = 5 * time.Second
+
+func parseLiteralIP(addr string) string {
+	var ip IP
+	var zone string
+	ip = parseIPv4(addr)
+	if ip == nil {
+		ip, zone = parseIPv6Zone(addr)
+	}
+	if ip == nil {
+		return ""
+	}
+	if zone == "" {
+		return ip.String()
+	}
+	return ip.String() + "%" + zone
+}
+
+// hosts contains known host entries.
+var hosts struct {
+	sync.Mutex
+
+	// Key for the list of literal IP addresses must be a host
+	// name. It would be part of DNS labels, a FQDN or an absolute
+	// FQDN.
+	// For now the key is converted to lower case for convenience.
+	byName map[string][]string
+
+	// Key for the list of host names must be a literal IP address
+	// including IPv6 address with zone identifier.
+	// We don't support old-classful IP address notation.
+	byAddr map[string][]string
+
+	expire time.Time
+	path   string
+	mtime  time.Time
+	size   int64
+}
+
+func readHosts() {
+	now := time.Now()
+	hp := testHookHostsPath
+
+	if now.Before(hosts.expire) && hosts.path == hp && len(hosts.byName) > 0 {
+		return
+	}
+	mtime, size, err := stat(hp)
+	if err == nil && hosts.path == hp && hosts.mtime.Equal(mtime) && hosts.size == size {
+		hosts.expire = now.Add(cacheMaxAge)
+		return
+	}
+
+	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 := bytealg.IndexByteString(line, '#'); i >= 0 {
+			// Discard comments.
+			line = line[0:i]
+		}
+		f := getFields(line)
+		if len(f) < 2 {
+			continue
+		}
+		addr := parseLiteralIP(f[0])
+		if addr == "" {
+			continue
+		}
+		for i := 1; i < len(f); i++ {
+			name := absDomainName([]byte(f[i]))
+			h := []byte(f[i])
+			lowerASCIIBytes(h)
+			key := absDomainName(h)
+			hs[key] = append(hs[key], addr)
+			is[addr] = append(is[addr], name)
+		}
+	}
+	// Update the data cache.
+	hosts.expire = now.Add(cacheMaxAge)
+	hosts.path = hp
+	hosts.byName = hs
+	hosts.byAddr = is
+	hosts.mtime = mtime
+	hosts.size = size
+	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 {
+		// TODO(jbd,bradfitz): avoid this alloc if host is already all lowercase?
+		// or linear scan the byName map if it's small enough?
+		lowerHost := []byte(host)
+		lowerASCIIBytes(lowerHost)
+		if ips, ok := hosts.byName[absDomainName(lowerHost)]; ok {
+			ipsCp := make([]string, len(ips))
+			copy(ipsCp, ips)
+			return ipsCp
+		}
+	}
+	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()
+	addr = parseLiteralIP(addr)
+	if addr == "" {
+		return nil
+	}
+	if len(hosts.byAddr) != 0 {
+		if hosts, ok := hosts.byAddr[addr]; ok {
+			hostsCp := make([]string, len(hosts))
+			copy(hostsCp, hosts)
+			return hostsCp
+		}
+	}
+	return nil
+}