lib: introduce global -w option for VRF netns backend

Current -n option is only for zebra and mgmtd. All other daemons receive
the VRF backend configuration from zebra upon connection to it. This
leads to a potential race condition - daemons need to know the backend
before they start reading their config, but they can be not connected to
zebra yet at this point. As the VRF backend cannot change during runtime,
let's introduce a new global -w option for setting netns backend, to
make sure that all daemons know their VRF backend immediately after
start.

The reason for introducing a new option instead of making -n global is
that ospfd already uses -n for another purposes.

Signed-off-by: Igor Ryzhov <idryzhov@gmail.com>

doc/manpages/frr-zebra.rst

@@ -38,6 +38,8 @@ OPTIONS available for the |DAEMON| command:
 
    Enable namespace VRF backend. By default, the VRF backend relies on VRF-lite support from the Linux kernel. This option permits discovering Linux named network namespaces and mapping it to FRR VRF contexts.
 
+   This option is deprecated. Please use the global -w option instead.
+
 ROUTES
 ------
 

doc/user/basic.rst

@@ -754,6 +754,17 @@ These options apply to all |PACKAGE_NAME| daemons.
    be added to all files that use the statedir.  If you have "/var/run/frr"
    as the default statedir then it will become "/var/run/frr/<namespace>".
 
+.. option:: -w, --vrfwnetns
+
+   Enable namespace VRF backend. By default, the VRF backend relies on VRF-lite
+   support from the Linux kernel. This option permits discovering Linux named
+   network namespaces and mapping them to FRR VRF contexts. This option must be
+   the same for all running daemons. The easiest way to pass the same option to
+   all daemons is to use the ``frr_global_options`` variable in the
+   :ref:`Daemons Configuration File <daemons-configuration-file>`.
+
+   .. seealso:: :ref:`zebra-vrf`
+
 .. option:: -o, --vrfdefaultname <name>
 
    Set the name used for the *Default VRF* in CLI commands and YANG models.

doc/user/zebra.rst

@@ -53,6 +53,8 @@ Besides the common invocation options (:ref:`common-invocation-options`), the
    VRF defined by *Zebra*, as usual. If this option is specified when running
    *Zebra*, one must also specify the same option for *mgmtd*.
 
+   This options is deprecated. Please use the global -w option instead.
+
    .. seealso:: :ref:`zebra-vrf`
 
 .. option:: -z <path_to_socket>, --socket <path_to_socket>

lib/libfrr.c

@@ -108,6 +108,9 @@ static const struct option lo_always[] = {
 	{ "module", no_argument, NULL, 'M' },
 	{ "profile", required_argument, NULL, 'F' },
 	{ "pathspace", required_argument, NULL, 'N' },
+#ifdef HAVE_NETLINK
+	{ "vrfwnetns", no_argument, NULL, 'w' },
+#endif
 	{ "vrfdefaultname", required_argument, NULL, 'o' },
 	{ "graceful_restart", optional_argument, NULL, 'K' },
 	{ "vty_socket", required_argument, NULL, OPTION_VTYSOCK },
@@ -120,13 +123,19 @@ static const struct option lo_always[] = {
 	{ NULL }
 };
 static const struct optspec os_always = {
+#ifdef HAVE_NETLINK
+	"w"
+#endif
 	"hvdM:F:N:o:K::",
 	"  -h, --help         Display this help and exit\n"
 	"  -v, --version      Print program version\n"
 	"  -d, --daemon       Runs in daemon mode\n"
 	"  -M, --module       Load specified module\n"
 	"  -F, --profile      Use specified configuration profile\n"
 	"  -N, --pathspace    Insert prefix into config & socket paths\n"
+#ifdef HAVE_NETLINK
+	"  -w, --vrfwnetns    Use network namespaces for VRFs\n"
+#endif
 	"  -o, --vrfdefaultname     Set default VRF name.\n"
 	"  -K, --graceful_restart   FRR starting in Graceful Restart mode, with optional route-cleanup timer\n"
 	"      --vty_socket   Override vty socket path\n"
@@ -516,6 +525,11 @@ static int frr_opt(int opt)
 			snprintf(frr_zclientpath, sizeof(frr_zclientpath),
 				 ZAPI_SOCK_NAME);
 		break;
+#ifdef HAVE_NETLINK
+	case 'w':
+		vrf_configure_backend(VRF_BACKEND_NETNS);
+		break;
+#endif
 	case 'o':
 		vrf_set_default_name(optarg);
 		break;

mgmtd/mgmt_main.c

@@ -234,7 +234,7 @@ int main(int argc, char **argv)
 	frr_opt_add(
 		"s:n" DEPRECATED_OPTIONS, longopts,
 		"  -s, --socket_size  Set MGMTD peer socket send buffer size\n"
-		"  -n, --vrfwnetns    Use NetNS as VRF backend\n");
+		"  -n, --vrfwnetns    Use NetNS as VRF backend (deprecated, use -w)\n");
 
 	/* Command line argument treatment. */
 	while (1) {
@@ -257,6 +257,8 @@ int main(int argc, char **argv)
 			buffer_size = atoi(optarg);
 			break;
 		case 'n':
+			fprintf(stderr,
+				"The -n option is deprecated, please use global -w option instead.\n");
 			vrf_configure_backend(VRF_BACKEND_NETNS);
 			break;
 		default:

zebra/main.c

@@ -373,7 +373,7 @@ int main(int argc, char **argv)
 		    "      --v6-with-v4-nexthops Underlying dataplane supports v6 routes with v4 nexthops\n"
 #ifdef HAVE_NETLINK
 		    "  -s, --nl-bufsize          Set netlink receive buffer size\n"
-		    "  -n, --vrfwnetns           Use NetNS as VRF backend\n"
+		    "  -n, --vrfwnetns           Use NetNS as VRF backend (deprecated, use -w)\n"
 		    "      --v6-rr-semantics     Use v6 RR semantics\n"
 #else
 		    "  -s,                       Set kernel socket receive buffer size\n"
@@ -434,6 +434,8 @@ int main(int argc, char **argv)
 			break;
 #ifdef HAVE_NETLINK
 		case 'n':
+			fprintf(stderr,
+				"The -n option is deprecated, please use global -w option instead.\n");
 			vrf_configure_backend(VRF_BACKEND_NETNS);
 			break;
 		case OPTION_V6_RR_SEMANTICS: