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From 24a9e4d46608ccdcec53eeccc40b7a5d3fb7c9c8 Mon Sep 17 00:00:00 2001
From: "Dr. David Alan Gilbert" <dgilbert@redhat.com>
Date: Fri, 16 Jan 2015 17:35:36 +0100
Subject: [PATCH 04/16] Handle bi-directional communication for fd migration

Message-id: <1421429737-23581-3-git-send-email-dgilbert@redhat.com>
Patchwork-id: 63333
O-Subject: [RHEL-7.2 qemu-kvm PATCH 2/3] Handle bi-directional communication for fd migration
Bugzilla: 1086168
RH-Acked-by: Paolo Bonzini <pbonzini@redhat.com>
RH-Acked-by: Amit Shah <amit.shah@redhat.com>
RH-Acked-by: Laszlo Ersek <lersek@redhat.com>

From: Cristian Klein <cristian.klein@cs.umu.se>

libvirt prefers opening the TCP connection itself, for two reasons.
First, connection failed errors can be detected easier, without having
to parse qemu's error output.
Second, libvirt might be asked to secure the transfer by tunnelling the
communication through an TLS layer.
Therefore, libvirt opens the TCP connection itself and passes an FD to qemu
using QMP and a POSIX-specific mechanism.

Hence, in order to make the reverse-path work in such cases, qemu needs to
distinguish if the transmitted FD is a socket (reverse-path available)
or not (reverse-path might not be available) and use the corresponding
abstraction.

Signed-off-by: Cristian Klein <cristian.klein@cs.umu.se>
Reviewed-by: Paolo Bonzini <pbonzini@redhat.com>
Reviewed-by: Amit Shah <amit.shah@redhat.com>
Signed-off-by: Amit Shah <amit.shah@redhat.com>
(cherry picked from commit 131fe9b843f9a1e55fcbf2457c9cb25c3711b9d8)
Signed-off-by: Miroslav Rezanina <mrezanin@redhat.com>
---
 migration-fd.c | 24 ++++++++++++++++++++++--
 1 file changed, 22 insertions(+), 2 deletions(-)

diff --git a/migration-fd.c b/migration-fd.c
index 3d4613c..3c98c3c 100644
--- a/migration-fd.c
+++ b/migration-fd.c
@@ -30,13 +30,29 @@
     do { } while (0)
 #endif
 
+static bool fd_is_socket(int fd)
+{
+    struct stat stat;
+    int ret = fstat(fd, &stat);
+    if (ret == -1) {
+        /* When in doubt say no */
+        return false;
+    }
+    return S_ISSOCK(stat.st_mode);
+}
+
 void fd_start_outgoing_migration(MigrationState *s, const char *fdname, Error **errp)
 {
     int fd = monitor_get_fd(cur_mon, fdname, errp);
     if (fd == -1) {
         return;
     }
-    s->file = qemu_fdopen(fd, "wb");
+
+    if (fd_is_socket(fd)) {
+        s->file = qemu_fopen_socket(fd, "wb");
+    } else {
+        s->file = qemu_fdopen(fd, "wb");
+    }
 
     migrate_fd_connect(s);
 }
@@ -57,7 +73,11 @@ void fd_start_incoming_migration(const char *infd, Error **errp)
     DPRINTF("Attempting to start an incoming migration via fd\n");
 
     fd = strtol(infd, NULL, 0);
-    f = qemu_fdopen(fd, "rb");
+    if (fd_is_socket(fd)) {
+        f = qemu_fopen_socket(fd, "rb");
+    } else {
+        f = qemu_fdopen(fd, "rb");
+    }
     if(f == NULL) {
         error_setg_errno(errp, errno, "failed to open the source descriptor");
         return;
-- 
1.8.3.1