Support openvswitch bridges

We detect whether ovs-vsctl is available.  If so, then we support
adding network interfaces to openvswitch bridges with it.

Note that with this patch, veths do not appear to be removed from the
openvswitch bridge.  This seems a bug in openvswitch, as the veths
in fact do disappear from the system.  If lxc is required to remove
the port from the bridge manually, that becomes more complicated
for unprivileged containers, as it would require a setuid-root
wrapper to be called at shutdown.

Signed-off-by: Serge Hallyn <serge.hallyn@ubuntu.com>

configure.ac

@@ -190,6 +190,16 @@ fi
 
 AM_CONDITIONAL([ENABLE_API_DOCS], [test "x$HAVE_DOXYGEN" != "x"])
 
+# Openvswitch
+AC_PATH_PROG([OVS_CTL_PATH],[ovs-vsctl])
+if test "x$OVS_CTL_PATH" != "x"; then
+	enable_ovs="yes"
+	AS_AC_EXPAND(OVS_CTL_PATH, "$OVS_CTL_PATH")
+else
+	enable_ovs="no"
+fi
+AM_CONDITIONAL([HAVE_OVS], [test "x$enable_ovs" = "xyes"])
+
 # Apparmor
 AC_ARG_ENABLE([apparmor],
 	[AC_HELP_STRING([--enable-apparmor], [enable apparmor support [default=auto]])],
@@ -755,6 +765,7 @@ Environment:
  - rpath: $enable_rpath
  - GnuTLS: $enable_gnutls
  - Bash integration: $enable_bash
+ - Openvswitch: $enable_ovs
 
 Security features:
  - Apparmor: $enable_apparmor

src/lxc/Makefile.am

@@ -128,6 +128,10 @@ if ENABLE_APPARMOR
 AM_CFLAGS += -DHAVE_APPARMOR
 endif
 
+if HAVE_OVS
+AM_CFLAGS += -DHAVE_OVS -DOVS_CTL_PATH=\"$(OVS_CTL_PATH)\"
+endif
+
 if ENABLE_CGMANAGER
 AM_CFLAGS += -DHAVE_CGMANAGER
 endif

src/lxc/network.c

@@ -48,6 +48,7 @@
 #include "nl.h"
 #include "network.h"
 #include "conf.h"
+#include "utils.h"
 
 #if HAVE_IFADDRS_H
 #include <ifaddrs.h>
@@ -1170,6 +1171,45 @@ int lxc_ipv6_dest_add(int ifindex, struct in6_addr *dest)
 	return ip_route_dest_add(AF_INET6, ifindex, dest);
 }
 
+#ifdef HAVE_OVS
+static bool is_ovs_bridge(const char *bridge)
+{
+	char brdirname[22 + IFNAMSIZ + 1] = {0};
+	struct stat sb;
+
+	snprintf(brdirname, 22 +IFNAMSIZ + 1, "/sys/class/net/%s/bridge", bridge);
+	if (stat(brdirname, &sb) == -1 && errno == ENOENT)
+		return true;
+	return false;
+}
+
+static int attach_to_ovs_bridge(const char *bridge, const char *nic)
+{
+	pid_t pid;
+	const char *progname;
+
+	pid = fork();
+	if (pid < 0)
+		return -1;
+	if (pid > 0)
+		return wait_for_pid(pid);
+
+	progname = strrchr(OVS_CTL_PATH, '/');
+	if (!progname) // not sane, should we just fail?
+		progname = OVS_CTL_PATH;
+	if (execl(OVS_CTL_PATH, progname, "add-port", bridge, nic, NULL))
+		exit(1);
+	// not reached
+	exit(1);
+}
+#else
+static inline bool is_ovs_bridge(const char *bridge) { return false; }
+static inline int attach_to_ovs_bridge(const char *bridge, const char *nic)
+{
+	retun -1;
+}
+#endif
+
 /*
  * There is a lxc_bridge_attach, but no need of a bridge detach
  * as automatically done by kernel when a netdev is deleted.
@@ -1186,6 +1226,9 @@ int lxc_bridge_attach(const char *bridge, const char *ifname)
 	if (!index)
 		return -EINVAL;
 
+	if (is_ovs_bridge(bridge))
+		return attach_to_ovs_bridge(bridge, ifname);
+
 	fd = socket(AF_INET, SOCK_STREAM, 0);
 	if (fd < 0)
 		return -errno;