bgpd: vpn-vrf leaking: use dynamic label pool for "auto" labels

Add support for CLI "auto" keyword in vrf->vpn export label:

    router bgp NNN vrf FOO
	address-family ipv4 unicast
	    label vpn export auto
	exit-address-family

Signed-off-by: G. Paul Ziemba <paulz@labn.net>

bgpd/bgp_mplsvpn.c

@@ -310,6 +310,65 @@ void vpn_leak_zebra_vrf_label_withdraw(struct bgp *bgp, afi_t afi)
 	bgp->vpn_policy[afi].tovpn_zebra_vrf_label_last_sent = label;
 }
 
+int vpn_leak_label_callback(
+	mpls_label_t label,
+	void *labelid,
+	bool allocated)
+{
+	struct vpn_policy *vp = (struct vpn_policy *)labelid;
+	int debug = BGP_DEBUG(vpn, VPN_LEAK_LABEL);
+
+	if (debug)
+		zlog_debug("%s: label=%u, allocated=%d",
+			__func__, label, allocated);
+
+	if (!allocated) {
+		/*
+		 * previously-allocated label is now invalid
+		 */
+		if (CHECK_FLAG(vp->flags, BGP_VPN_POLICY_TOVPN_LABEL_AUTO) &&
+			(vp->tovpn_label != MPLS_LABEL_NONE)) {
+
+			vpn_leak_prechange(BGP_VPN_POLICY_DIR_TOVPN,
+				vp->afi, bgp_get_default(), vp->bgp);
+			vp->tovpn_label = MPLS_LABEL_NONE;
+			vpn_leak_postchange(BGP_VPN_POLICY_DIR_TOVPN,
+				vp->afi, bgp_get_default(), vp->bgp);
+		}
+		return 0;
+	}
+
+	/*
+	 * New label allocation
+	 */
+	if (!CHECK_FLAG(vp->flags, BGP_VPN_POLICY_TOVPN_LABEL_AUTO)) {
+
+		/*
+		 * not currently configured for auto label, reject allocation
+		 */
+		return -1;
+	}
+
+	if (vp->tovpn_label != MPLS_LABEL_NONE) {
+		if (label == vp->tovpn_label) {
+			/* already have same label, accept but do nothing */
+			return 0;
+		}
+		/* Shouldn't happen: different label allocation */
+		zlog_err("%s: %s had label %u but got new assignment %u",
+			__func__, vp->bgp->name_pretty, vp->tovpn_label, label);
+		/* use new one */
+	}
+
+	vpn_leak_prechange(BGP_VPN_POLICY_DIR_TOVPN,
+		vp->afi, bgp_get_default(), vp->bgp);
+	vp->tovpn_label = label;
+	vpn_leak_postchange(BGP_VPN_POLICY_DIR_TOVPN,
+		vp->afi, bgp_get_default(), vp->bgp);
+
+	return 0;
+}
+
 static int ecom_intersect(struct ecommunity *e1, struct ecommunity *e2)
 {
 	int i;

bgpd/bgp_mplsvpn.h

@@ -77,6 +77,7 @@ extern void vpn_leak_to_vrf_withdraw(struct bgp *bgp_vpn,
 
 extern void vpn_leak_zebra_vrf_label_update(struct bgp *bgp, afi_t afi);
 extern void vpn_leak_zebra_vrf_label_withdraw(struct bgp *bgp, afi_t afi);
+extern int vpn_leak_label_callback(mpls_label_t label, void *lblid, bool alloc);
 
 static inline int vpn_leak_to_vpn_active(struct bgp *bgp_vrf, afi_t afi,
 					 const char **pmsg)
@@ -111,6 +112,17 @@ static inline int vpn_leak_to_vpn_active(struct bgp *bgp_vrf, afi_t afi,
 			*pmsg = "rd not defined";
 		return 0;
 	}
+
+	/* Is there an "auto" export label that isn't allocated yet? */
+	if (CHECK_FLAG(bgp_vrf->vpn_policy[afi].flags,
+		BGP_VPN_POLICY_TOVPN_LABEL_AUTO) &&
+		(bgp_vrf->vpn_policy[afi].tovpn_label == MPLS_LABEL_NONE)) {
+
+		if (pmsg)
+			*pmsg = "auto label not allocated";
+		return 0;
+	}
+
 	return 1;
 }
 

bgpd/bgp_vty.c

@@ -6245,12 +6245,13 @@ ALIAS (af_rd_vpn_export,
 
 DEFPY (af_label_vpn_export,
        af_label_vpn_export_cmd,
-       "[no] label vpn export (0-1048575)$label_val",
+       "[no] label vpn export <(0-1048575)$label_val|auto$label_auto>",
        NO_STR
        "label value for VRF\n"
        "Between current address-family and vpn\n"
        "For routes leaked from current address-family to vpn\n"
-       "Label Value <0-1048575>\n")
+       "Label Value <0-1048575>\n"
+       "Automatically assign a label\n")
 {
 	VTY_DECLVAR_CONTEXT(bgp, bgp);
 	mpls_label_t label = MPLS_LABEL_NONE;
@@ -6263,8 +6264,10 @@ DEFPY (af_label_vpn_export,
 	if (argv_find(argv, argc, "no", &idx))
 		yes = 0;
 
-	if (yes)
+	if (yes) {
-		label = label_val; /* rely on parser to force unsigned */
+		if (!label_auto)
+			label = label_val; /* parser should force unsigned */
+	}
 
 	ret = vpn_policy_getafi(vty, doafi);
 	if (ret != CMD_SUCCESS)
@@ -6274,13 +6277,48 @@ DEFPY (af_label_vpn_export,
 		if (!doafi[afi])
 			continue;
 
+		if (label_auto && CHECK_FLAG(bgp->vpn_policy[afi].flags,
+			BGP_VPN_POLICY_TOVPN_LABEL_AUTO))
+
+			continue; /* no change */
+
 		/*
 		 * pre-change: un-export vpn routes (vpn->vrf routes unaffected)
 		 */
 		vpn_leak_prechange(BGP_VPN_POLICY_DIR_TOVPN, afi,
 				   bgp_get_default(), bgp);
 
+		if (!label_auto && CHECK_FLAG(bgp->vpn_policy[afi].flags,
+			BGP_VPN_POLICY_TOVPN_LABEL_AUTO)) {
+
+			if (bgp->vpn_policy[afi].tovpn_label !=
+				MPLS_LABEL_NONE) {
+
+				/*
+				 * label has previously been automatically
+				 * assigned by labelpool: release it
+				 *
+				 * NB if tovpn_label == MPLS_LABEL_NONE it
+				 * means the automatic assignment is in flight
+				 * and therefore the labelpool callback must
+				 * detect that the auto label is not needed.
+				 */
+
+				bgp_lp_release(LP_TYPE_VRF,
+					&bgp->vpn_policy[afi],
+					bgp->vpn_policy[afi].tovpn_label);
+			}
+			UNSET_FLAG(bgp->vpn_policy[afi].flags,
+				BGP_VPN_POLICY_TOVPN_LABEL_AUTO);
+		}
+
 		bgp->vpn_policy[afi].tovpn_label = label;
+		if (label_auto) {
+			SET_FLAG(bgp->vpn_policy[afi].flags,
+				BGP_VPN_POLICY_TOVPN_LABEL_AUTO);
+			bgp_lp_get(LP_TYPE_VRF, &bgp->vpn_policy[afi],
+				vpn_leak_label_callback);
+		}
 
 		/* post-change: re-export vpn routes */
 		vpn_leak_postchange(BGP_VPN_POLICY_DIR_TOVPN, afi,
@@ -11706,9 +11744,16 @@ void bgp_vpn_policy_config_write_afi(struct vty *vty, struct bgp *bgp,
 {
 	int indent = 2;
 
-	if (bgp->vpn_policy[afi].tovpn_label != MPLS_LABEL_NONE) {
+	if (CHECK_FLAG(bgp->vpn_policy[afi].flags,
-		vty_out(vty, "%*slabel vpn export %u\n", indent, "",
+		BGP_VPN_POLICY_TOVPN_LABEL_AUTO)) {
-			bgp->vpn_policy[afi].tovpn_label);
+
+		vty_out(vty, "%*slabel vpn export %s\n", indent, "", "auto");
+
+	} else {
+		if (bgp->vpn_policy[afi].tovpn_label != MPLS_LABEL_NONE) {
+			vty_out(vty, "%*slabel vpn export %u\n", indent, "",
+				bgp->vpn_policy[afi].tovpn_label);
+		}
 	}
 	if (CHECK_FLAG(bgp->vpn_policy[afi].flags,
 		       BGP_VPN_POLICY_TOVPN_RD_SET)) {

bgpd/bgp_zebra.c

@@ -1878,7 +1878,7 @@ static void bgp_zebra_connected(struct zclient *zclient)
 	bfd_client_sendmsg(zclient, ZEBRA_BFD_CLIENT_REGISTER);
 
 	/* tell label pool that zebra is connected */
-	lp_event_zebra_up();
+	bgp_lp_event_zebra_up();
 
 	/* TODO - What if we have peers and networks configured, do we have to
 	 * kick-start them?
@@ -2075,7 +2075,7 @@ static void bgp_zebra_process_label_chunk(
 			first, last, response_keep);
 	}
 
-	lp_event_chunk(response_keep, first, last);
+	bgp_lp_event_chunk(response_keep, first, last);
 
 stream_failure:		/* for STREAM_GETX */
 	return;

bgpd/bgpd.c

@@ -2951,6 +2951,8 @@ static struct bgp *bgp_create(as_t *as, const char *name,
 #endif /* ENABLE_BGP_VNC */
 
 	for (afi = AFI_IP; afi < AFI_MAX; afi++) {
+		bgp->vpn_policy[afi].bgp = bgp;
+		bgp->vpn_policy[afi].afi = afi;
 		bgp->vpn_policy[afi].tovpn_label = MPLS_LABEL_NONE;
 		bgp->vpn_policy[afi].tovpn_zebra_vrf_label_last_sent =
 			MPLS_LABEL_NONE;
@@ -7537,7 +7539,7 @@ void bgp_master_init(struct thread_master *master)
 	bgp_option_set(BGP_OPT_MULTIPLE_INSTANCE);
 
 	/* mpls label dynamic allocation pool */
-	lp_init(bm->master, &bm->labelpool);
+	bgp_lp_init(bm->master, &bm->labelpool);
 
 	QOBJ_REG(bm, bgp_master);
 }
@@ -7718,5 +7720,5 @@ void bgp_terminate(void)
 	if (bm->t_rmap_update)
 		BGP_TIMER_OFF(bm->t_rmap_update);
 
-	lp_finish();
+	bgp_lp_finish();
 }

bgpd/bgpd.h

@@ -171,6 +171,25 @@ typedef enum {
 	BGP_VPN_POLICY_DIR_MAX = 2
 } vpn_policy_direction_t;
 
+struct vpn_policy {
+	struct bgp *bgp; /* parent */
+	afi_t afi;
+	struct ecommunity *rtlist[BGP_VPN_POLICY_DIR_MAX];
+	struct ecommunity *import_redirect_rtlist;
+	char *rmap_name[BGP_VPN_POLICY_DIR_MAX];
+	struct route_map *rmap[BGP_VPN_POLICY_DIR_MAX];
+
+	/* should be mpls_label_t? */
+	uint32_t tovpn_label; /* may be MPLS_LABEL_NONE */
+	uint32_t tovpn_zebra_vrf_label_last_sent;
+	struct prefix_rd tovpn_rd;
+	struct prefix tovpn_nexthop; /* unset => set to 0 */
+	uint32_t flags;
+#define BGP_VPN_POLICY_TOVPN_LABEL_AUTO        (1 << 0)
+#define BGP_VPN_POLICY_TOVPN_RD_SET            (1 << 1)
+#define BGP_VPN_POLICY_TOVPN_NEXTHOP_SET       (1 << 2)
+};
+
 /*
  * Type of 'struct bgp'.
  * - Default: The default instance
@@ -469,22 +488,7 @@ struct bgp {
 	/* route map for advertise ipv4/ipv6 unicast (type-5 routes) */
 	struct bgp_rmap adv_cmd_rmap[AFI_MAX][SAFI_MAX];
 
-	/* vpn-policy */
+	struct vpn_policy vpn_policy[AFI_MAX];
-	struct {
-		struct ecommunity *rtlist[BGP_VPN_POLICY_DIR_MAX];
-		struct ecommunity *import_redirect_rtlist;
-		char *rmap_name[BGP_VPN_POLICY_DIR_MAX];
-		struct route_map *rmap[BGP_VPN_POLICY_DIR_MAX];
-
-		/* should be mpls_label_t? */
-		uint32_t tovpn_label; /* may be MPLS_LABEL_NONE */
-		uint32_t tovpn_zebra_vrf_label_last_sent;
-		struct prefix_rd tovpn_rd;
-		struct prefix tovpn_nexthop; /* unset => set to 0 */
-		uint32_t flags;
-#define BGP_VPN_POLICY_TOVPN_RD_SET            0x00000004
-#define BGP_VPN_POLICY_TOVPN_NEXTHOP_SET       0x00000008
-	} vpn_policy[AFI_MAX];
 
 	QOBJ_FIELDS
 };

doc/user/bgp.rst

@@ -1606,14 +1606,17 @@ address-family:
 
    Deletes any previously-configured import or export route-target list.
 
-.. index:: label vpn export (0..1048575)
+.. index:: label vpn export (0..1048575)|auto
-.. clicmd:: label vpn export (0..1048575)
+.. clicmd:: label vpn export (0..1048575)|auto
 
    Specifies an optional MPLS label to be attached to a route exported from the
-   current unicast VRF to VPN.
+   current unicast VRF to VPN. If label is specified as ``auto``, the label
+   value is automatically assigned from a pool maintained by the zebra
+   daemon. If zebra is not running, automatic label assignment will not
+   complete, which will block corresponding route export.
 
-.. index:: no label vpn export [(0..1048575)]
+.. index:: no label vpn export [(0..1048575)|auto]
-.. clicmd:: no label vpn export [(0..1048575)]
+.. clicmd:: no label vpn export [(0..1048575)|auto]
 
    Deletes any previously-configured export label.