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moby--moby/libnetwork/etchosts/etchosts.go

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package etchosts
import (
"bytes"
"fmt"
"io"
"io/ioutil"
"os"
"regexp"
)
// Record Structure for a single host record
type Record struct {
Hosts string
IP string
}
// WriteTo writes record to file and returns bytes written or error
func (r Record) WriteTo(w io.Writer) (int64, error) {
n, err := fmt.Fprintf(w, "%s\t%s\n", r.IP, r.Hosts)
return int64(n), err
}
// Default hosts config records slice
var defaultContent = []Record{
{Hosts: "localhost", IP: "127.0.0.1"},
{Hosts: "localhost ip6-localhost ip6-loopback", IP: "::1"},
{Hosts: "ip6-localnet", IP: "fe00::0"},
{Hosts: "ip6-mcastprefix", IP: "ff00::0"},
{Hosts: "ip6-allnodes", IP: "ff02::1"},
{Hosts: "ip6-allrouters", IP: "ff02::2"},
}
// Build function
// path is path to host file string required
// IP, hostname, and domainname set main record leave empty for no master record
// extraContent is an array of extra host records.
func Build(path, IP, hostname, domainname string, extraContent []Record) error {
content := bytes.NewBuffer(nil)
if IP != "" {
//set main record
var mainRec Record
mainRec.IP = IP
if domainname != "" {
mainRec.Hosts = fmt.Sprintf("%s.%s %s", hostname, domainname, hostname)
} else {
mainRec.Hosts = hostname
}
if _, err := mainRec.WriteTo(content); err != nil {
return err
}
}
// Write defaultContent slice to buffer
for _, r := range defaultContent {
if _, err := r.WriteTo(content); err != nil {
return err
}
}
// Write extra content from function arguments
for _, r := range extraContent {
if _, err := r.WriteTo(content); err != nil {
return err
}
}
return ioutil.WriteFile(path, content.Bytes(), 0644)
}
// Add adds an arbitrary number of Records to an already existing /etc/hosts file
func Add(path string, recs []Record) error {
if len(recs) == 0 {
return nil
}
f, err := os.Open(path)
if err != nil {
return err
}
content := bytes.NewBuffer(nil)
_, err = content.ReadFrom(f)
if err != nil {
return err
}
for _, r := range recs {
if _, err := r.WriteTo(content); err != nil {
return err
}
}
return ioutil.WriteFile(path, content.Bytes(), 0644)
}
// Delete deletes an arbitrary number of Records already existing in /etc/hosts file
func Delete(path string, recs []Record) error {
if len(recs) == 0 {
return nil
}
old, err := ioutil.ReadFile(path)
if err != nil {
return err
}
regexpStr := fmt.Sprintf("\\S*\\t%s\\n", regexp.QuoteMeta(recs[0].Hosts))
for _, r := range recs[1:] {
regexpStr = regexpStr + "|" + fmt.Sprintf("\\S*\\t%s\\n", regexp.QuoteMeta(r.Hosts))
}
var re = regexp.MustCompile(regexpStr)
return ioutil.WriteFile(path, re.ReplaceAll(old, []byte("")), 0644)
}
// Update all IP addresses where hostname matches.
// path is path to host file
// IP is new IP address
// hostname is hostname to search for to replace IP
func Update(path, IP, hostname string) error {
old, err := ioutil.ReadFile(path)
if err != nil {
return err
}
var re = regexp.MustCompile(fmt.Sprintf("(\\S*)(\\t%s)", regexp.QuoteMeta(hostname)))
return ioutil.WriteFile(path, re.ReplaceAll(old, []byte(IP+"$2")), 0644)
}