[libvirt] [PATCH v2 8/8] rpc: pass listen FD to the daemon being started

[Martin Kletzander]

This eliminates the need for active waiting.

Resolves: https://bugzilla.redhat.com/show_bug.cgi?id=927369

Signed-off-by: Martin Kletzander <mkletzan at redhat.com>
---
 src/rpc/virnetsocket.c | 58 +++++++++++++++++++++++++++++++++-----------------
 1 file changed, 39 insertions(+), 19 deletions(-)

diff --git a/src/rpc/virnetsocket.c b/src/rpc/virnetsocket.c
index a94b2bc..c00209c 100644
--- a/src/rpc/virnetsocket.c
+++ b/src/rpc/virnetsocket.c
@@ -1,7 +1,7 @@
 /*
  * virnetsocket.c: generic network socket handling
  *
- * Copyright (C) 2006-2013 Red Hat, Inc.
+ * Copyright (C) 2006-2014 Red Hat, Inc.
  * Copyright (C) 2006 Daniel P. Berrange
  *
  * This library is free software; you can redistribute it and/or
@@ -121,7 +121,7 @@ VIR_ONCE_GLOBAL_INIT(virNetSocket)


 #ifndef WIN32
-static int virNetSocketForkDaemon(const char *binary)
+static int virNetSocketForkDaemon(const char *binary, int passfd)
 {
     int ret;
     virCommandPtr cmd = virCommandNewArgList(binary,
@@ -134,6 +134,10 @@ static int virNetSocketForkDaemon(const char *binary)
     virCommandAddEnvPassBlockSUID(cmd, "XDG_RUNTIME_DIR", NULL);
     virCommandClearCaps(cmd);
     virCommandDaemonize(cmd);
+    if (passfd) {
+        virCommandPassFD(cmd, passfd, VIR_COMMAND_PASS_FD_CLOSE_PARENT);
+        virCommandPassListenFDs(cmd);
+    }
     ret = virCommandRun(cmd, NULL);
     virCommandFree(cmd);
     return ret;
@@ -542,8 +546,7 @@ int virNetSocketNewConnectUNIX(const char *path,
 {
     virSocketAddr localAddr;
     virSocketAddr remoteAddr;
-    int fd;
-    int retries = 0;
+    int fd, passfd;

     memset(&localAddr, 0, sizeof(localAddr));
     memset(&remoteAddr, 0, sizeof(remoteAddr));
@@ -569,28 +572,45 @@ int virNetSocketNewConnectUNIX(const char *path,
     if (remoteAddr.data.un.sun_path[0] == '@')
         remoteAddr.data.un.sun_path[0] = '\0';

- retry:
-    if (connect(fd, &remoteAddr.data.sa, remoteAddr.len) < 0) {
-        if ((errno == ECONNREFUSED ||
-             errno == ENOENT) &&
-            spawnDaemon && retries < 20) {
-            VIR_DEBUG("Connection refused for %s, trying to spawn %s",
-                      path, binary);
-            if (retries == 0 &&
-                virNetSocketForkDaemon(binary) < 0)
-                goto error;
+    if (spawnDaemon) {
+        if ((passfd = socket(PF_UNIX, SOCK_STREAM, 0)) < 0) {
+            virReportSystemError(errno, "%s", _("Failed to create socket"));
+            goto error;
+        }

-            retries++;
-            usleep(1000 * 100 * retries);
-            goto retry;
+        /*
+         * We cannot do the umask() trick here because that's not
+         * thread-safe.  fchmod(), however, is not guaranteed to work on
+         * some BSD favours, but *should* work on Linux before the socket
+         * is bound.  POSIX says the behaviour of fchmod() called on
+         * socket is unspecified, though.
+         */
+        if (fchmod(passfd, 0700) < 0) {
+            virReportSystemError(errno, "%s",
+                                 _("Failed to change permissions on socket"));
+            goto error;
         }

-        virReportSystemError(errno,
-                             _("Failed to connect socket to '%s'"),
+        if (bind(passfd, &remoteAddr.data.sa, remoteAddr.len) < 0) {
+            virReportSystemError(errno, _("Failed to bind socket to %s"), path);
+            goto error;
+        }
+
+        if (listen(passfd, 0) < 0) {
+            virReportSystemError(errno, "%s", _("Failed to listen on socket to"));
+            goto error;
+        }
+    }
+
+    if (connect(fd, &remoteAddr.data.sa, remoteAddr.len) < 0) {
+        virReportSystemError(errno, _("Failed to connect socket to '%s'"),
                              path);
         goto error;
     }

+    if (spawnDaemon && virNetSocketForkDaemon(binary, passfd) < 0)
+        goto error;
+
     localAddr.len = sizeof(localAddr.data);
     if (getsockname(fd, &localAddr.data.sa, &localAddr.len) < 0) {
         virReportSystemError(errno, "%s", _("Unable to get local socket name"));
-- 
2.0.0