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Verify rsync protocol version match prior to proceeding - Rebased on current master. #71

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Jul 2, 2020
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Verify rsync protocol version match prior to proceeding - Rebased on current master. #71

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f745670
Verify rsync protocol version match prior to proceeding.
stephenwithav Jul 1, 2020
5538af6
Add context to sync.Version.
stephenwithav Jul 1, 2020
54cecb2
Correct syncCmd.version, sync.Version.
stephenwithav Jul 2, 2020
35ee1de
Update local, remote version checks to avoid blanks.
stephenwithav Jul 2, 2020
21976c6
Remove go from io.Copy in internal/sync/sync.go#Version
stephenwithav Jul 2, 2020
d853066
Return error directly in internal/sync/sync.go#Version
stephenwithav Jul 2, 2020
e8abef2
Update [vV]ersion comment strings; remove extraneous error check.
stephenwithav Jul 2, 2020
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46 changes: 46 additions & 0 deletions cmd/coder/sync.go
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Original file line number Diff line number Diff line change
@@ -1,7 +1,12 @@
package main

import (
"bufio"
"errors"
"fmt"
"log"
"os"
"os/exec"
"path/filepath"
"strings"

Expand Down Expand Up @@ -29,6 +34,37 @@ func (cmd *syncCmd) RegisterFlags(fl *pflag.FlagSet) {
fl.BoolVarP(&cmd.init, "init", "i", false, "do initial transfer and exit")
}

// See https://lxadm.com/Rsync_exit_codes#List_of_standard_rsync_exit_codes.
var IncompatRsync = errors.New("rsync: exit status 2")
var StreamErrRsync = errors.New("rsync: exit status 12")
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Probably leftover from a rebase, these were removed in master.


// Returns local rsync protocol version as a string.
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Apologies for missing this earlier in the review. These comments should start with the function/method name. So this would be "version returns local rsync protocol version as a string."

(And same for the other Version method)

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No problem. I appreciate you teaching me the style you prefer prior to the interview next week so if I get the job, I'm already style trained.

func (s *syncCmd) version() string {
cmd := exec.Command("rsync", "--version")
stdout, err := cmd.StdoutPipe()
if err != nil {
log.Fatal(err)
}

if err := cmd.Start(); err != nil {
log.Fatal(err)
}

r := bufio.NewReader(stdout)
if err := cmd.Wait(); err != nil {
log.Fatal(err)
}

firstLine, err := r.ReadString('\n')
if err != nil {
return ""
}

versionString := strings.Split(firstLine, "protocol version ")

return versionString[1]
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The way this is laid out, version will always return an empty string. Reading from r will always error, because the pipe will be closed before we start reading from the command.

I would suggest replacing reading the output of the command with:

out, err := cmd.CombinedOutput()
if err != nil {
    log.Fatal(err)
}

And I would replace reading the first line with:

firstLine, err := bytes.NewBuffer(out).ReadString('\n')
if err != nil {
    log.Fatal(err)
}

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Will do.

}

func (cmd *syncCmd) Run(fl *pflag.FlagSet) {
var (
local = fl.Arg(0)
Expand Down Expand Up @@ -71,6 +107,16 @@ func (cmd *syncCmd) Run(fl *pflag.FlagSet) {
LocalDir: absLocal,
Client: entClient,
}

localVersion := cmd.version()
remoteVersion, rsyncErr := s.Version()

if rsyncErr != nil {
flog.Info("Unable to determine remote rsync version. Proceeding cautiously.")
} else if localVersion != remoteVersion {
flog.Fatal(fmt.Sprintf("rsync protocol mismatch. local is %s; remote is %s.", localVersion, remoteVersion))
}

for err == nil || err == sync.ErrRestartSync {
err = s.Run()
}
Expand Down
42 changes: 42 additions & 0 deletions internal/sync/sync.go
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Original file line number Diff line number Diff line change
@@ -1,6 +1,7 @@
package sync

import (
"bufio"
"context"
"errors"
"fmt"
Expand All @@ -10,6 +11,7 @@ import (
"os/exec"
"path"
"path/filepath"
"strings"
"sync"
"sync/atomic"
"time"
Expand Down Expand Up @@ -261,6 +263,46 @@ const (
maxAcceptableDispatch = time.Millisecond * 50
)

// Returns remote protocol version as a string.
// Or, an error if one exists.
func (s Sync) Version() (string, error) {
ctx, cancel := context.WithTimeout(context.Background(), time.Second*10)
defer cancel()

conn, err := s.Client.DialWsep(ctx, s.Env)
if err != nil {
return "", err
}
defer conn.Close(websocket.CloseNormalClosure, "")

execer := wsep.RemoteExecer(conn)
process, err := execer.Start(ctx, wsep.Command{
Command: "rsync",
Args: []string{"--version"},
})
if err != nil {
return "", err
}
r := bufio.NewReader(process.Stdout())
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We have the same issue here with the reader never reading anything.

I think the best solution here would be to replace this reader with:

buf := &bytes.Buffer{}
io.Copy(buf, process.Stdout())

And buf can be used down below to read the first line.

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Will do.

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@stephenwithav stephenwithav Jul 2, 2020 •
edited
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@scsmithr Do you want the remote check to log.Fatal fail if we can't retrieve it?

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I think I prefer the behavior you had, where we just return the error and warn the user.

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The remote check still has that.


err = process.Wait()
if code, ok := err.(wsep.ExitError); ok {
return "", fmt.Errorf("Version heck exit status: %v", code)
}
if err != nil {
return "", fmt.Errorf("Server version mismatch")
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I'd prefer returning the error here instead.

}

firstLine, err := r.ReadString('\n')
if err != nil {
return "", err
}

versionString := strings.Split(firstLine, "protocol version ")

return versionString[1], nil
}

// Run starts the sync synchronously.
// Use this command to debug what wasn't sync'd correctly:
// rsync -e "coder sh" -nicr ~/Projects/cdr/coder-cli/. ammar:/home/coder/coder-cli/
Expand Down