Fix #11589 by adding README and comments to exported functions

Signed-off-by: Arthur Barr <arthur.barr@uk.ibm.com>

pkg/resolvconf/README.md

@@ -0,0 +1 @@
+Package resolvconf provides utility code to query and update DNS configuration in /etc/resolv.conf

pkg/resolvconf/resolvconf.go

@@ -1,3 +1,4 @@
+// Package resolvconf provides utility code to query and update DNS configuration in /etc/resolv.conf
 package resolvconf
 
 import (
@@ -38,6 +39,7 @@ var lastModified struct {
 	contents []byte
 }
 
+// Get returns the contents of /etc/resolv.conf
 func Get() ([]byte, error) {
 	resolv, err := ioutil.ReadFile("/etc/resolv.conf")
 	if err != nil {
@@ -46,7 +48,7 @@ func Get() ([]byte, error) {
 	return resolv, nil
 }
 
-// Retrieves the host /etc/resolv.conf file, checks against the last hash
+// GetIfChanged retrieves the host /etc/resolv.conf file, checks against the last hash
 // and, if modified since last check, returns the bytes and new hash.
 // This feature is used by the resolv.conf updater for containers
 func GetIfChanged() ([]byte, string, error) {
@@ -70,7 +72,7 @@ func GetIfChanged() ([]byte, string, error) {
 	return nil, "", nil
 }
 
-// retrieve the last used contents and hash of the host resolv.conf
+// GetLastModified retrieves the last used contents and hash of the host resolv.conf.
 // Used by containers updating on restart
 func GetLastModified() ([]byte, string) {
 	lastModified.Lock()
@@ -79,14 +81,14 @@ func GetLastModified() ([]byte, string) {
 	return lastModified.contents, lastModified.sha256
 }
 
-// FilterResolvDns has two main jobs:
+// FilterResolvDns cleans up the config in resolvConf.  It has two main jobs:
 // 1. It looks for localhost (127.*|::1) entries in the provided
 //    resolv.conf, removing local nameserver entries, and, if the resulting
 //    cleaned config has no defined nameservers left, adds default DNS entries
 // 2. Given the caller provides the enable/disable state of IPv6, the filter
 //    code will remove all IPv6 nameservers if it is not enabled for containers
 //
-// It also returns a boolean to notify the caller if changes were made at all
+// It returns a boolean to notify the caller if changes were made at all
 func FilterResolvDns(resolvConf []byte, ipv6Enabled bool) ([]byte, bool) {
 	changed := false
 	cleanedResolvConf := localhostNSRegexp.ReplaceAll(resolvConf, []byte{})
@@ -126,7 +128,7 @@ func getLines(input []byte, commentMarker []byte) [][]byte {
 	return output
 }
 
-// returns true if the IP string matches the localhost IP regular expression.
+// IsLocalhost returns true if ip matches the localhost IP regular expression.
 // Used for determining if nameserver settings are being passed which are
 // localhost addresses
 func IsLocalhost(ip string) bool {
@@ -171,6 +173,9 @@ func GetSearchDomains(resolvConf []byte) []string {
 	return domains
 }
 
+// Build writes a configuration file to path containing a "nameserver" entry
+// for every element in dns, and a "search" entry for every element in
+// dnsSearch.
 func Build(path string, dns, dnsSearch []string) error {
 	content := bytes.NewBuffer(nil)
 	for _, dns := range dns {