add hosts file support
This commit is contained in:
parent
b1ff41c523
commit
e89a7141e5
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@ -184,6 +184,7 @@ func (c *cluster) members() (<-chan []node, <-chan error) {
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continue
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}
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nodes = append(nodes, node{
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Name: n.Name,
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Addr: n.Addr,
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nodeMeta: meta,
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})
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@ -200,6 +201,7 @@ func (c *cluster) members() (<-chan []node, <-chan error) {
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}
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type node struct {
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Name string
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Addr net.IP
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nodeMeta
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}
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@ -17,6 +17,7 @@ type config struct {
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WireguardPort int `id:"wireguard-port" desc:"port used for wireguard traffic (UDP); must be the same across cluster" default:"51820"`
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OverlayNet *network `id:"overlay-net" desc:"the network in which to allocate addresses for the overlay mesh network (CIDR format); smaller networks increase the chance of IP collision" default:"10.0.0.0/8"`
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Interface string `desc:"name of the wireguard interface to create and manage" default:"wgoverlay"`
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NoEtcHosts bool `id:"no-etc-hosts" desc:"disable writing of entries to /etc/hosts"`
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LogLevel string `id:"log-level" desc:"set the verbosity (debug/info/warn/error)" default:"warn"`
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// for easier local testing
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@ -0,0 +1,164 @@
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package etchosts
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import (
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"bufio"
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"fmt"
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"io"
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"io/ioutil"
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"os"
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"path"
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"strings"
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log "github.com/sirupsen/logrus"
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)
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// DefaultBanner is the default magic comment used to identify entries managed by etchosts
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const DefaultBanner = "# ! MANAGED AUTOMATICALLY !"
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// DefaultPath is the default path used to write hosts entries
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const DefaultPath = "/etc/hosts"
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// EtcHosts contains the options used to write hosts entries.
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// The zero value can be used to write to DefaultPath using DefaultBanner as a marker.
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type EtcHosts struct {
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// Banner is the magic comment used to identify entries managed by etchosts; if not set, will use DefaultBanner.
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// It must start with "#" to mark it as a comment.
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Banner string
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// Path is the path to the /etc/hosts file; if not set, will use DefaultPath.
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Path string
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// Logger is an optional logrus.StdLogger interface, used for debugging.
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Logger log.StdLogger
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}
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// WriteEntries is used to write the hosts entries to EtcHosts.Path
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// Each IP address with their (potentially multiple) hostnames are written to a line marked with EtcHosts.Banner, to
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// avoid overwriting preexisting entries.
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func (eh *EtcHosts) WriteEntries(ipsToNames map[string][]string) error {
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hostsPath := eh.Path
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if hostsPath == "" {
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hostsPath = DefaultPath
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}
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// We do not want to create the hosts file; if it's not there, we probably have the wrong path.
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etcHosts, err := os.OpenFile(hostsPath, os.O_RDWR, 0644)
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if err != nil {
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return fmt.Errorf("could not open %s for reading: %s", hostsPath, err)
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}
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defer etcHosts.Close()
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// create tmpfile in same folder as
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tmp, err := ioutil.TempFile(path.Dir(hostsPath), "etchosts")
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if err != nil {
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return fmt.Errorf("could not create tempfile")
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}
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// remove tempfile; this might fail if we managed to move it, which is ok
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defer func(file *os.File) {
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file.Close()
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if err := os.Remove(file.Name()); err != nil && !os.IsNotExist(err) {
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if eh.Logger != nil {
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eh.Logger.Printf("unexpected error trying to remove temp file %s: %s", file.Name(), err)
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}
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}
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}(tmp)
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if err := eh.writeEntries(etcHosts, tmp, ipsToNames); err != nil {
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return err
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}
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if err = eh.movePreservePerms(tmp, etcHosts); err != nil {
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return err
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}
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return nil
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}
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func (eh *EtcHosts) writeEntries(orig io.Reader, dest io.Writer, ipsToNames map[string][]string) error {
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banner := eh.Banner
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if banner == "" {
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banner = DefaultBanner
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}
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// go through file and update existing entries/prune nonexistent entries
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scanner := bufio.NewScanner(orig)
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for scanner.Scan() {
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line := scanner.Text()
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if strings.HasSuffix(strings.TrimSpace(line), strings.TrimSpace(banner)) {
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tokens := strings.Fields(line)
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if len(tokens) < 1 {
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continue // remove empty managed line
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}
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ip := tokens[0]
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if names, ok := ipsToNames[ip]; ok {
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err := eh.writeEntryWithBanner(dest, banner, ip, names)
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if err != nil {
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return err
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}
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delete(ipsToNames, ip) // otherwise we'll append it again below
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}
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} else {
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// keep original unmanaged line
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fmt.Fprintf(dest, "%s\n", line)
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}
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}
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if err := scanner.Err(); err != nil {
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return fmt.Errorf("error reading hosts file: %s", err)
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}
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// append remaining entries to file
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for ip, names := range ipsToNames {
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if err := eh.writeEntryWithBanner(dest, banner, ip, names); err != nil {
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return err
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}
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}
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return nil
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}
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func (eh *EtcHosts) writeEntryWithBanner(tmp io.Writer, banner, ip string, names []string) error {
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if ip != "" && len(names) > 0 {
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if eh.Logger != nil {
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eh.Logger.Printf("writing entry for %s (%s)", ip, names)
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}
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if _, err := fmt.Fprintf(tmp, "%s\t%s\t%s\n", ip, strings.Join(names, " "), banner); err != nil {
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return fmt.Errorf("error writing entry for %s: %s", ip, err)
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}
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}
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return nil
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}
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func (eh *EtcHosts) movePreservePerms(src, dst *os.File) error {
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if err := src.Sync(); err != nil {
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return fmt.Errorf("could not sync changes to %s: %s", src.Name(), err)
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}
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etcHostsInfo, err := dst.Stat()
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if err != nil {
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return fmt.Errorf("could not stat %s: %s", dst.Name(), err)
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}
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if err = os.Rename(src.Name(), dst.Name()); err != nil {
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log.Infof("could not rename to %s; falling back to copy (%s)", dst.Name(), err)
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if _, err := src.Seek(0, io.SeekStart); err != nil {
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return err
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}
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if _, err := dst.Seek(0, io.SeekStart); err != nil {
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return err
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}
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if err := dst.Truncate(0); err != nil {
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return err
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}
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_, err = io.Copy(dst, src)
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return err
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}
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// ensure we're not running with some umask that might break things
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if err := src.Chmod(etcHostsInfo.Mode()); err != nil {
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return fmt.Errorf("could not chmod %s: %s", src.Name(), err)
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}
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// TODO: also keep user?
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return nil
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}
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@ -0,0 +1,120 @@
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package etchosts
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import (
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"bytes"
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"fmt"
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"io"
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"strings"
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"testing"
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log "github.com/sirupsen/logrus"
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)
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func TestEtcHosts_writeEntryWithBanner(t *testing.T) {
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type args struct {
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banner string
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ip string
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names []string
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}
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eh := &EtcHosts{}
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tests := []struct {
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name string
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args args
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wantTmp string
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wantErr bool
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}{
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{"do not write empty ip", args{DefaultBanner, "", []string{"somename", "someothername"}}, "", false},
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{"do not write empty names", args{DefaultBanner, "1.2.3.4", []string{}}, "", false},
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{"complete entry", args{DefaultBanner, "1.2.3.4", []string{"somename", "someothername"}}, fmt.Sprintf("1.2.3.4\tsomename someothername\t%s\n", DefaultBanner), false},
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{"custom banner", args{"# somebanner", "1.2.3.4", []string{"somename", "someothername"}}, fmt.Sprintf("1.2.3.4\tsomename someothername\t%s\n", "# somebanner"), false},
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}
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for _, tt := range tests {
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t.Run(tt.name, func(t *testing.T) {
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tmp := &bytes.Buffer{}
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if err := eh.writeEntryWithBanner(tmp, tt.args.banner, tt.args.ip, tt.args.names); (err != nil) != tt.wantErr {
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t.Errorf("writeEntryWithBanner() error = %v, wantErr %v", err, tt.wantErr)
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return
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}
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if gotTmp := tmp.String(); gotTmp != tt.wantTmp {
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t.Errorf("writeEntryWithBanner() got:\n%#v, want\n%#v", gotTmp, tt.wantTmp)
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}
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})
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}
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}
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func TestEtcHosts_writeEntries(t *testing.T) {
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type fields struct {
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Banner string
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Path string
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Logger log.StdLogger
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}
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type args struct {
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orig io.Reader
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ipsToNames map[string][]string
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}
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tests := []struct {
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name string
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fields fields
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args args
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wantDest string
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wantErr bool
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}{
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{
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"simple empty write",
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fields{},
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args{strings.NewReader(""), map[string][]string{"1.2.3.4": []string{"foo", "bar"}}},
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"1.2.3.4\tfoo bar\t# ! MANAGED AUTOMATICALLY !\n",
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false,
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},
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{
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"do not touch comments",
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fields{},
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args{strings.NewReader("# some comment\n"), map[string][]string{"1.2.3.4": []string{"foo", "bar"}}},
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"# some comment\n1.2.3.4\tfoo bar\t# ! MANAGED AUTOMATICALLY !\n",
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false,
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},
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{
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"do not touch existing entries",
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fields{},
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args{strings.NewReader("4.3.2.1 hostname1 hostname2\n"), map[string][]string{"1.2.3.4": []string{"foo", "bar"}}},
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"4.3.2.1 hostname1 hostname2\n1.2.3.4\tfoo bar\t# ! MANAGED AUTOMATICALLY !\n",
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false,
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},
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{
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"remove managed entry not in map",
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fields{},
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args{strings.NewReader("4.3.2.1 fooz baarz # ! MANAGED AUTOMATICALLY !\n"), map[string][]string{"1.2.3.4": []string{"foo", "bar"}}},
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"1.2.3.4\tfoo bar\t# ! MANAGED AUTOMATICALLY !\n",
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false,
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},
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{
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"custom banner",
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fields{Banner: "# somebanner"},
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args{strings.NewReader(""), map[string][]string{"1.2.3.4": []string{"foo", "bar"}}},
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"1.2.3.4\tfoo bar\t# somebanner\n",
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false,
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},
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}
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for _, tt := range tests {
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t.Run(tt.name, func(t *testing.T) {
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eh := &EtcHosts{
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Banner: tt.fields.Banner,
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Path: tt.fields.Path,
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Logger: tt.fields.Logger,
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}
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dest := &bytes.Buffer{}
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if err := eh.writeEntries(tt.args.orig, dest, tt.args.ipsToNames); (err != nil) != tt.wantErr {
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t.Errorf("EtcHosts.writeEntries() error = %v, wantErr %v", err, tt.wantErr)
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return
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}
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if gotDest := dest.String(); gotDest != tt.wantDest {
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t.Errorf("EtcHosts.writeEntries() = '%#v', want '%#v'", gotDest, tt.wantDest)
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}
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})
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}
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}
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// 1.2.3.4 foo bar # ! MANAGED AUTOMATICALLY !
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// 1.2.3.4 foo bar # ! MANAGED AUTOMATICALLY !
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21
main.go
21
main.go
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@ -6,6 +6,8 @@ import (
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"syscall"
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"github.com/sirupsen/logrus"
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"github.com/costela/wesher/etchosts"
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)
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func main() {
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@ -52,12 +54,31 @@ func main() {
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if err := wg.upInterface(); err != nil {
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logrus.Errorf("could not up interface: %s", err)
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}
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if !config.NoEtcHosts {
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if err := writeToEtcHosts(nodes); err != nil {
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logrus.Errorf("could not write hosts entries: %s", err)
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}
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}
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case errs := <-errc:
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logrus.Errorf("could not receive node info: %s", errs)
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case <-incomingSigs:
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logrus.Info("terminating...")
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cluster.leave()
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if err := writeToEtcHosts(nil); err != nil {
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logrus.Errorf("could not remove stale hosts entries: %s", err)
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}
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os.Exit(0)
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}
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}
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}
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func writeToEtcHosts(nodes []node) error {
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hosts := make(map[string][]string, len(nodes))
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for _, n := range nodes {
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hosts[n.OverlayAddr.String()] = []string{n.Name}
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}
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hostsFile := &etchosts.EtcHosts{
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Logger: logrus.StandardLogger(),
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}
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return hostsFile.WriteEntries(hosts)
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}
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