zebra: support route replace semantics in FPM

Set `NLM_F_REPLACE` instead of adding and removing the same route for an
update.

Signed-off-by: Rafael Zalamena <rzalamena@opensourcerouting.org>

zebra/dplane_fpm_nl.c

@@ -65,6 +65,7 @@ struct fpm_nl_ctx {
 	bool disabled;
 	bool connecting;
 	bool use_nhg;
+	bool use_route_replace;
 	struct sockaddr_storage addr;
 
 	/* data plane buffers. */
@@ -282,6 +283,25 @@ DEFUN(no_fpm_use_nhg, no_fpm_use_nhg_cmd,
 	return CMD_SUCCESS;
 }
 
+DEFUN(fpm_use_route_replace, fpm_use_route_replace_cmd,
+      "fpm use-route-replace",
+      FPM_STR
+      "Use netlink route replace semantics\n")
+{
+	gfnc->use_route_replace = true;
+	return CMD_SUCCESS;
+}
+
+DEFUN(no_fpm_use_route_replace, no_fpm_use_route_replace_cmd,
+      "no fpm use-route-replace",
+      NO_STR
+      FPM_STR
+      "Use netlink route replace semantics\n")
+{
+	gfnc->use_route_replace = false;
+	return CMD_SUCCESS;
+}
+
 DEFUN(fpm_reset_counters, fpm_reset_counters_cmd,
       "clear fpm counters",
       CLEAR_STR
@@ -396,6 +416,11 @@ static int fpm_write_config(struct vty *vty)
 		written = 1;
 	}
 
+	if (!gfnc->use_route_replace) {
+		vty_out(vty, "no fpm use-route-replace\n");
+		written = 1;
+	}
+
 	return written;
 }
 
@@ -807,12 +832,20 @@ static int fpm_nl_enqueue(struct fpm_nl_ctx *fnc, struct zebra_dplane_ctx *ctx)
 
 	frr_mutex_lock_autounlock(&fnc->obuf_mutex);
 
+	/*
+	 * If route replace is enabled then directly encode the install which
+	 * is going to use `NLM_F_REPLACE` (instead of delete/add operations).
+	 */
+	if (fnc->use_route_replace && op == DPLANE_OP_ROUTE_UPDATE)
+		op = DPLANE_OP_ROUTE_INSTALL;
+
 	switch (op) {
 	case DPLANE_OP_ROUTE_UPDATE:
 	case DPLANE_OP_ROUTE_DELETE:
 		rv = netlink_route_multipath_msg_encode(RTM_DELROUTE, ctx,
 							nl_buf, sizeof(nl_buf),
-							true, fnc->use_nhg);
+							true, fnc->use_nhg,
+							false);
 		if (rv <= 0) {
 			zlog_err(
 				"%s: netlink_route_multipath_msg_encode failed",
@@ -828,9 +861,12 @@ static int fpm_nl_enqueue(struct fpm_nl_ctx *fnc, struct zebra_dplane_ctx *ctx)
 
 		/* FALL THROUGH */
 	case DPLANE_OP_ROUTE_INSTALL:
-		rv = netlink_route_multipath_msg_encode(
+		rv = netlink_route_multipath_msg_encode(RTM_NEWROUTE, ctx,
-			RTM_NEWROUTE, ctx, &nl_buf[nl_buf_len],
+							&nl_buf[nl_buf_len],
-			sizeof(nl_buf) - nl_buf_len, true, fnc->use_nhg);
+							sizeof(nl_buf) -
+								nl_buf_len,
+							true, fnc->use_nhg,
+							fnc->use_route_replace);
 		if (rv <= 0) {
 			zlog_err(
 				"%s: netlink_route_multipath_msg_encode failed",
@@ -1469,6 +1505,7 @@ static int fpm_nl_start(struct zebra_dplane_provider *prov)
 
 	/* Set default values. */
 	fnc->use_nhg = true;
+	fnc->use_route_replace = true;
 
 	return 0;
 }
@@ -1609,6 +1646,8 @@ static int fpm_nl_new(struct event_loop *tm)
 	install_element(CONFIG_NODE, &no_fpm_set_address_cmd);
 	install_element(CONFIG_NODE, &fpm_use_nhg_cmd);
 	install_element(CONFIG_NODE, &no_fpm_use_nhg_cmd);
+	install_element(CONFIG_NODE, &fpm_use_route_replace_cmd);
+	install_element(CONFIG_NODE, &no_fpm_use_route_replace_cmd);
 
 	return 0;
 }

zebra/rt_netlink.c

@@ -2060,10 +2060,10 @@ static int netlink_route_nexthop_encap(struct nlmsghdr *n, size_t nlen,
  * Returns -1 on failure, 0 when the msg doesn't fit entirely in the buffer
  * otherwise the number of bytes written to buf.
  */
-ssize_t netlink_route_multipath_msg_encode(int cmd,
+ssize_t netlink_route_multipath_msg_encode(int cmd, struct zebra_dplane_ctx *ctx,
-					   struct zebra_dplane_ctx *ctx,
 					   uint8_t *data, size_t datalen,
-					   bool fpm, bool force_nhg)
+					   bool fpm, bool force_nhg,
+					   bool force_rr)
 {
 	int bytelen;
 	struct nexthop *nexthop = NULL;
@@ -2097,8 +2097,9 @@ ssize_t netlink_route_multipath_msg_encode(int cmd,
 	req->n.nlmsg_len = NLMSG_LENGTH(sizeof(struct rtmsg));
 	req->n.nlmsg_flags = NLM_F_CREATE | NLM_F_REQUEST;
 
-	if ((cmd == RTM_NEWROUTE) &&
+	if (((cmd == RTM_NEWROUTE) &&
-	    ((p->family == AF_INET) || v6_rr_semantics))
+	     ((p->family == AF_INET) || v6_rr_semantics)) ||
+	    force_rr)
 		req->n.nlmsg_flags |= NLM_F_REPLACE;
 
 	req->n.nlmsg_type = cmd;
@@ -2953,14 +2954,14 @@ static ssize_t netlink_newroute_msg_encoder(struct zebra_dplane_ctx *ctx,
 					    void *buf, size_t buflen)
 {
 	return netlink_route_multipath_msg_encode(RTM_NEWROUTE, ctx, buf,
-						  buflen, false, false);
+						  buflen, false, false, false);
 }
 
 static ssize_t netlink_delroute_msg_encoder(struct zebra_dplane_ctx *ctx,
 					    void *buf, size_t buflen)
 {
 	return netlink_route_multipath_msg_encode(RTM_DELROUTE, ctx, buf,
-						  buflen, false, false);
+						  buflen, false, false, false);
 }
 
 enum netlink_msg_status

zebra/rt_netlink.h

@@ -56,7 +56,8 @@ extern ssize_t netlink_mpls_multipath_msg_encode(int cmd,
 extern ssize_t netlink_route_multipath_msg_encode(int cmd,
 						  struct zebra_dplane_ctx *ctx,
 						  uint8_t *data, size_t datalen,
-						  bool fpm, bool force_nhg);
+						  bool fpm, bool force_nhg,
+						  bool force_rr);
 extern ssize_t netlink_macfdb_update_ctx(struct zebra_dplane_ctx *ctx,
 					 void *data, size_t datalen);