0001-pass-extra-file-to-child-process-as-status-handler.patch

From 244453b367dd0f005e71f400c698fe29ad070f1b Mon Sep 17 00:00:00 2001
From: "Daniel, Dao Quang Minh" <[email protected]>
Date: Wed, 8 Oct 2014 10:27:55 -0400
Subject: [PATCH] pass extra file to child process as status handler

instead of using stdout/stderr as the status handler, we pass an extra file to
the child process and write `0\n` or `1\nerror message` to it and close it
after. This allow the child process to handle stdout/stderr as normal.

Docker-DCO-1.1-Signed-off-by: Daniel, Dao Quang Minh <[email protected]> (github: dqminh)
---
 daemon/networkdriver/portmapper/proxy.go | 24 ++++++++++--------------
 1 file changed, 10 insertions(+), 14 deletions(-)

diff --git a/daemon/networkdriver/portmapper/proxy.go b/daemon/networkdriver/portmapper/proxy.go
index 404d461..c66effb 100644
--- a/daemon/networkdriver/portmapper/proxy.go
+++ b/daemon/networkdriver/portmapper/proxy.go
@@ -36,17 +36,18 @@ type proxyCommand struct {

 // execProxy is the reexec function that is registered to start the userland proxies
 func execProxy() {
-       log.SetOutput(ioutil.Discard)
+       f := os.NewFile(3, "signal-parent")
        host, container := parseHostContainerAddrs()

        p, err := proxy.NewProxy(host, container)
        if err != nil {
-               os.Stdout.WriteString("1\n")
-               fmt.Fprint(os.Stderr, err)
+               fmt.Fprintf(f, "1\n%s", err)
+               f.Close()
                os.Exit(1)
        }
        go handleStopSignals(p)
-       os.Stdout.WriteString("0\n")
+       fmt.Fprint(f, "0\n")
+       f.Close()

        // Run will block until the proxy stops
        p.Run()
@@ -112,16 +113,11 @@ func NewProxyCommand(proto string, hostIP net.IP, hostPort int, containerIP net.
 }

 func (p *proxyCommand) Start() error {
-       stdout, err := p.cmd.StdoutPipe()
+       r, w, err := os.Pipe()
        if err != nil {
-               return err
-       }
-       defer stdout.Close()
-       stderr, err := p.cmd.StderrPipe()
-       if err != nil {
-               return err
+               return fmt.Errorf("proxy unable to open os.Pipe %s", err)
        }
-       defer stderr.Close()
+       p.cmd.ExtraFiles = []*os.File{w}
        if err := p.cmd.Start(); err != nil {
                return err
        }
@@ -129,10 +125,10 @@ func (p *proxyCommand) Start() error {
        errchan := make(chan error, 1)
        go func() {
                buf := make([]byte, 2)
-               stdout.Read(buf)
+               r.Read(buf)

                if string(buf) != "0\n" {
-                       errStr, _ := ioutil.ReadAll(stderr)
+                       errStr, _ := ioutil.ReadAll(r)
                        errchan <- fmt.Errorf("Error starting userland proxy: %s", errStr)
                        return
                }
--
1.8.5