[mqtt] Implements mqtt publish tooling

vendor/github.com/docker/go-connections/sockets/sockets_unix.go

@@ -0,0 +1,35 @@
+// +build !windows
+
+package sockets
+
+import (
+	"fmt"
+	"net"
+	"net/http"
+	"syscall"
+	"time"
+)
+
+const maxUnixSocketPathSize = len(syscall.RawSockaddrUnix{}.Path)
+
+func configureUnixTransport(tr *http.Transport, proto, addr string) error {
+	if len(addr) > maxUnixSocketPathSize {
+		return fmt.Errorf("Unix socket path %q is too long", addr)
+	}
+	// No need for compression in local communications.
+	tr.DisableCompression = true
+	tr.Dial = func(_, _ string) (net.Conn, error) {
+		return net.DialTimeout(proto, addr, defaultTimeout)
+	}
+	return nil
+}
+
+func configureNpipeTransport(tr *http.Transport, proto, addr string) error {
+	return ErrProtocolNotAvailable
+}
+
+// DialPipe connects to a Windows named pipe.
+// This is not supported on other OSes.
+func DialPipe(_ string, _ time.Duration) (net.Conn, error) {
+	return nil, syscall.EAFNOSUPPORT
+}