Adding upstream version 1.20.14.upstream/1.20.14upstream

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 249 insertions, 0 deletions

diff --git a/src/net/nss.go b/src/net/nss.go
new file mode 100644
index 0000000..092b515
--- /dev/null
+++ b/src/net/nss.go
@@ -0,0 +1,249 @@
+// Copyright 2015 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 (
+	"errors"
+	"internal/bytealg"
+	"os"
+	"sync"
+	"time"
+)
+
+const (
+	nssConfigPath = "/etc/nsswitch.conf"
+)
+
+var nssConfig nsswitchConfig
+
+type nsswitchConfig struct {
+	initOnce sync.Once // guards init of nsswitchConfig
+
+	// ch is used as a semaphore that only allows one lookup at a
+	// time to recheck nsswitch.conf
+	ch          chan struct{} // guards lastChecked and modTime
+	lastChecked time.Time     // last time nsswitch.conf was checked
+
+	mu      sync.Mutex // protects nssConf
+	nssConf *nssConf
+}
+
+func getSystemNSS() *nssConf {
+	nssConfig.tryUpdate()
+	nssConfig.mu.Lock()
+	conf := nssConfig.nssConf
+	nssConfig.mu.Unlock()
+	return conf
+}
+
+// init initializes conf and is only called via conf.initOnce.
+func (conf *nsswitchConfig) init() {
+	conf.nssConf = parseNSSConfFile("/etc/nsswitch.conf")
+	conf.lastChecked = time.Now()
+	conf.ch = make(chan struct{}, 1)
+}
+
+// tryUpdate tries to update conf.
+func (conf *nsswitchConfig) tryUpdate() {
+	conf.initOnce.Do(conf.init)
+
+	// Ensure only one update at a time checks nsswitch.conf
+	if !conf.tryAcquireSema() {
+		return
+	}
+	defer conf.releaseSema()
+
+	now := time.Now()
+	if conf.lastChecked.After(now.Add(-5 * time.Second)) {
+		return
+	}
+	conf.lastChecked = now
+
+	var mtime time.Time
+	if fi, err := os.Stat(nssConfigPath); err == nil {
+		mtime = fi.ModTime()
+	}
+	if mtime.Equal(conf.nssConf.mtime) {
+		return
+	}
+
+	nssConf := parseNSSConfFile(nssConfigPath)
+	conf.mu.Lock()
+	conf.nssConf = nssConf
+	conf.mu.Unlock()
+}
+
+func (conf *nsswitchConfig) acquireSema() {
+	conf.ch <- struct{}{}
+}
+
+func (conf *nsswitchConfig) tryAcquireSema() bool {
+	select {
+	case conf.ch <- struct{}{}:
+		return true
+	default:
+		return false
+	}
+}
+
+func (conf *nsswitchConfig) releaseSema() {
+	<-conf.ch
+}
+
+// nssConf represents the state of the machine's /etc/nsswitch.conf file.
+type nssConf struct {
+	mtime   time.Time              // time of nsswitch.conf modification
+	err     error                  // any error encountered opening or parsing the file
+	sources map[string][]nssSource // keyed by database (e.g. "hosts")
+}
+
+type nssSource struct {
+	source   string // e.g. "compat", "files", "mdns4_minimal"
+	criteria []nssCriterion
+}
+
+// standardCriteria reports all specified criteria have the default
+// status actions.
+func (s nssSource) standardCriteria() bool {
+	for i, crit := range s.criteria {
+		if !crit.standardStatusAction(i == len(s.criteria)-1) {
+			return false
+		}
+	}
+	return true
+}
+
+// nssCriterion is the parsed structure of one of the criteria in brackets
+// after an NSS source name.
+type nssCriterion struct {
+	negate bool   // if "!" was present
+	status string // e.g. "success", "unavail" (lowercase)
+	action string // e.g. "return", "continue" (lowercase)
+}
+
+// standardStatusAction reports whether c is equivalent to not
+// specifying the criterion at all. last is whether this criteria is the
+// last in the list.
+func (c nssCriterion) standardStatusAction(last bool) bool {
+	if c.negate {
+		return false
+	}
+	var def string
+	switch c.status {
+	case "success":
+		def = "return"
+	case "notfound", "unavail", "tryagain":
+		def = "continue"
+	default:
+		// Unknown status
+		return false
+	}
+	if last && c.action == "return" {
+		return true
+	}
+	return c.action == def
+}
+
+func parseNSSConfFile(file string) *nssConf {
+	f, err := open(file)
+	if err != nil {
+		return &nssConf{err: err}
+	}
+	defer f.close()
+	mtime, _, err := f.stat()
+	if err != nil {
+		return &nssConf{err: err}
+	}
+
+	conf := parseNSSConf(f)
+	conf.mtime = mtime
+	return conf
+}
+
+func parseNSSConf(f *file) *nssConf {
+	conf := new(nssConf)
+	for line, ok := f.readLine(); ok; line, ok = f.readLine() {
+		line = trimSpace(removeComment(line))
+		if len(line) == 0 {
+			continue
+		}
+		colon := bytealg.IndexByteString(line, ':')
+		if colon == -1 {
+			conf.err = errors.New("no colon on line")
+			return conf
+		}
+		db := trimSpace(line[:colon])
+		srcs := line[colon+1:]
+		for {
+			srcs = trimSpace(srcs)
+			if len(srcs) == 0 {
+				break
+			}
+			sp := bytealg.IndexByteString(srcs, ' ')
+			var src string
+			if sp == -1 {
+				src = srcs
+				srcs = "" // done
+			} else {
+				src = srcs[:sp]
+				srcs = trimSpace(srcs[sp+1:])
+			}
+			var criteria []nssCriterion
+			// See if there's a criteria block in brackets.
+			if len(srcs) > 0 && srcs[0] == '[' {
+				bclose := bytealg.IndexByteString(srcs, ']')
+				if bclose == -1 {
+					conf.err = errors.New("unclosed criterion bracket")
+					return conf
+				}
+				var err error
+				criteria, err = parseCriteria(srcs[1:bclose])
+				if err != nil {
+					conf.err = errors.New("invalid criteria: " + srcs[1:bclose])
+					return conf
+				}
+				srcs = srcs[bclose+1:]
+			}
+			if conf.sources == nil {
+				conf.sources = make(map[string][]nssSource)
+			}
+			conf.sources[db] = append(conf.sources[db], nssSource{
+				source:   src,
+				criteria: criteria,
+			})
+		}
+	}
+	return conf
+}
+
+// parses "foo=bar !foo=bar"
+func parseCriteria(x string) (c []nssCriterion, err error) {
+	err = foreachField(x, func(f string) error {
+		not := false
+		if len(f) > 0 && f[0] == '!' {
+			not = true
+			f = f[1:]
+		}
+		if len(f) < 3 {
+			return errors.New("criterion too short")
+		}
+		eq := bytealg.IndexByteString(f, '=')
+		if eq == -1 {
+			return errors.New("criterion lacks equal sign")
+		}
+		if hasUpperCase(f) {
+			lower := []byte(f)
+			lowerASCIIBytes(lower)
+			f = string(lower)
+		}
+		c = append(c, nssCriterion{
+			negate: not,
+			status: f[:eq],
+			action: f[eq+1:],
+		})
+		return nil
+	})
+	return
+}