From 2ee2003d564e9c39f62b436690a98721ab640ef0 Mon Sep 17 00:00:00 2001
From: "Richard W.M. Jones" <rjones@redhat.com>
Date: Sat, 7 Nov 2015 12:20:23 +0000
Subject: [PATCH] daemon: Allow --channel fd:N

In this case, the daemon has been passed an open file descriptor which
it uses directly for the channel.
---
 daemon/guestfsd.c   | 40 +++++++++++++++++++++++-----------------
 daemon/guestfsd.pod |  5 +++++
 2 files changed, 28 insertions(+), 17 deletions(-)

diff --git a/daemon/guestfsd.c b/daemon/guestfsd.c
index 994023db1..0a29aa6b3 100644
--- a/daemon/guestfsd.c
+++ b/daemon/guestfsd.c
@@ -284,23 +284,29 @@ main (int argc, char *argv[])
 
   int sock;
   if (!listen_mode) {
-    sock = open (channel, O_RDWR|O_CLOEXEC);
-    if (sock == -1) {
-      fprintf (stderr,
-               "\n"
-               "Failed to connect to virtio-serial channel.\n"
-               "\n"
-               "This is a fatal error and the appliance will now exit.\n"
-               "\n"
-               "Usually this error is caused by either QEMU or the appliance\n"
-               "kernel not supporting the vmchannel method that the\n"
-               "libguestfs library chose to use.  Please run\n"
-               "'libguestfs-test-tool' and provide the complete, unedited\n"
-               "output to the libguestfs developers, either in a bug report\n"
-               "or on the libguestfs redhat com mailing list.\n"
-               "\n");
-      perror (channel);
-      exit (EXIT_FAILURE);
+    if (STRPREFIX (channel, "fd:")) {
+      if (sscanf (channel+3, "%d", &sock) != 1)
+        error (EXIT_FAILURE, 0, "cannot parse --channel %s", channel);
+    }
+    else {
+      sock = open (channel, O_RDWR|O_CLOEXEC);
+      if (sock == -1) {
+        fprintf (stderr,
+                 "\n"
+                 "Failed to connect to virtio-serial channel.\n"
+                 "\n"
+                 "This is a fatal error and the appliance will now exit.\n"
+                 "\n"
+                 "Usually this error is caused by either QEMU or the appliance\n"
+                 "kernel not supporting the vmchannel method that the\n"
+                 "libguestfs library chose to use.  Please run\n"
+                 "'libguestfs-test-tool' and provide the complete, unedited\n"
+                 "output to the libguestfs developers, either in a bug report\n"
+                 "or on the libguestfs redhat com mailing list.\n"
+                 "\n");
+        perror (channel);
+        exit (EXIT_FAILURE);
+      }
     }
   }
   else {
diff --git a/daemon/guestfsd.pod b/daemon/guestfsd.pod
index f1672ae0b..d2c3cc745 100644
--- a/daemon/guestfsd.pod
+++ b/daemon/guestfsd.pod
@@ -54,10 +54,15 @@ Display brief help.
 
 =item B<--channel> CHANNEL
 
+=item B<--channel> fd:N
+
 Pass the name of the virtio-serial channel, serial port, etc.  over
 which guestfsd will communicate with the library.  If this parameter
 is not given, then an internal default port is used.
 
+The C<fd:N> form causes guestfsd to use the file descriptor C<N>
+directly.
+
 =item B<-l>
 
 =item B<--listen>