1 files changed, 158 insertions, 0 deletions
diff --git a/src/net/nss.go b/src/net/nss.go
new file mode 100644
index 0000000..c4c608f
--- /dev/null
+++ b/src/net/nss.go
@@ -0,0 +1,158 @@
+// 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"
+	"io"
+	"os"
+)
+
+// nssConf represents the state of the machine's /etc/nsswitch.conf file.
+type nssConf struct {
+	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 := os.Open(file)
+	if err != nil {
+		return &nssConf{err: err}
+	}
+	defer f.Close()
+	return parseNSSConf(f)
+}
+
+func parseNSSConf(r io.Reader) *nssConf {
+	slurp, err := readFull(r)
+	if err != nil {
+		return &nssConf{err: err}
+	}
+	conf := new(nssConf)
+	conf.err = foreachLine(slurp, func(line []byte) error {
+		line = trimSpace(removeComment(line))
+		if len(line) == 0 {
+			return nil
+		}
+		colon := bytealg.IndexByte(line, ':')
+		if colon == -1 {
+			return errors.New("no colon on line")
+		}
+		db := string(trimSpace(line[:colon]))
+		srcs := line[colon+1:]
+		for {
+			srcs = trimSpace(srcs)
+			if len(srcs) == 0 {
+				break
+			}
+			sp := bytealg.IndexByte(srcs, ' ')
+			var src string
+			if sp == -1 {
+				src = string(srcs)
+				srcs = nil // done
+			} else {
+				src = string(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.IndexByte(srcs, ']')
+				if bclose == -1 {
+					return errors.New("unclosed criterion bracket")
+				}
+				var err error
+				criteria, err = parseCriteria(srcs[1:bclose])
+				if err != nil {
+					return errors.New("invalid criteria: " + string(srcs[1:bclose]))
+				}
+				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 nil
+	})
+	return conf
+}
+
+// parses "foo=bar !foo=bar"
+func parseCriteria(x []byte) (c []nssCriterion, err error) {
+	err = foreachField(x, func(f []byte) 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.IndexByte(f, '=')
+		if eq == -1 {
+			return errors.New("criterion lacks equal sign")
+		}
+		lowerASCIIBytes(f)
+		c = append(c, nssCriterion{
+			negate: not,
+			status: string(f[:eq]),
+			action: string(f[eq+1:]),
+		})
+		return nil
+	})
+	return
+}