zebra: add command for setting protodown bit

Add command for use to set protodown via frr.conf in
the case our default conflicts with another application
they are using.

Signed-off-by: Stephen Worley <sworley@nvidia.com>

doc/user/zebra.rst

@@ -255,6 +255,17 @@ Link Parameters Commands
    for InterASv2 link in OSPF (RFC5392).  Note that this option is not yet
    supported for ISIS (RFC5316).
 
+Global Commands
+------------------------
+
+.. clicmd:: zebra protodown reason-bit (0-31)
+
+   This command is only supported for linux and a kernel > 5.1.
+   Change reason-bit frr uses for setting protodown. We default to 7, but
+   if another userspace app ever conflicts with this, you can change it here.
+   The descriptor for this bit should exist in :file:`/etc/iproute2/protodown_reasons.d/`
+   to display with :clicmd:`ip -d link show`.
+
 Nexthop Tracking
 ================
 

zebra/if_netlink.c

@@ -2214,4 +2214,34 @@ void interface_list(struct zebra_ns *zns)
 	interface_addr_lookup_netlink(zns);
 }
 
+void if_netlink_set_frr_protodown_r_bit(uint8_t bit)
+{
+	if (IS_ZEBRA_DEBUG_KERNEL)
+		zlog_debug("FRR protodown reason bit change %u -> %u",
+			   frr_protodown_r_bit, bit);
+
+	frr_protodown_r_bit = bit;
+}
+
+void if_netlink_unset_frr_protodown_r_bit(void)
+{
+	if (IS_ZEBRA_DEBUG_KERNEL)
+		zlog_debug("FRR protodown reason bit change %u -> %u",
+			   frr_protodown_r_bit,
+			   FRR_PROTODOWN_REASON_DEFAULT_BIT);
+
+	frr_protodown_r_bit = FRR_PROTODOWN_REASON_DEFAULT_BIT;
+}
+
+
+bool if_netlink_frr_protodown_r_bit_is_set(void)
+{
+	return (frr_protodown_r_bit != FRR_PROTODOWN_REASON_DEFAULT_BIT);
+}
+
+uint8_t if_netlink_get_frr_protodown_r_bit(void)
+{
+	return frr_protodown_r_bit;
+}
+
 #endif /* GNU_LINUX */

zebra/if_netlink.h

@@ -72,6 +72,16 @@ netlink_put_intf_update_msg(struct nl_batch *bth, struct zebra_dplane_ctx *ctx);
  */
 int netlink_protodown(struct interface *ifp, bool down, uint32_t r_bitfield);
 
+/* Protodown bit setter/getter
+ *
+ * Allow users to change the bit if it conflicts with another
+ * on their system.
+ */
+extern void if_netlink_set_frr_protodown_r_bit(uint8_t bit);
+extern void if_netlink_unset_frr_protodown_r_bit(void);
+extern bool if_netlink_frr_protodown_r_bit_is_set(void);
+extern uint8_t if_netlink_get_frr_protodown_r_bit(void);
+
 #ifdef __cplusplus
 }
 #endif

zebra/kernel_netlink.c

@@ -210,6 +210,10 @@ int netlink_config_write_helper(struct vty *vty)
 		vty_out(vty, "zebra kernel netlink batch-tx-buf %u %u\n", size,
 			threshold);
 
+	if (if_netlink_frr_protodown_r_bit_is_set())
+		vty_out(vty, "zebra protodown reason-bit %u\n",
+			if_netlink_get_frr_protodown_r_bit());
+
 	return 0;
 }
 

zebra/zebra_vty.c

@@ -60,6 +60,7 @@
 #include "northbound_cli.h"
 #include "zebra/zebra_nb.h"
 #include "zebra/kernel_netlink.h"
+#include "zebra/if_netlink.h"
 #include "zebra/table_manager.h"
 #include "zebra/zebra_script.h"
 #include "zebra/rtadv.h"
@@ -4356,6 +4357,31 @@ DEFUN_HIDDEN(no_zebra_kernel_netlink_batch_tx_buf,
 	return CMD_SUCCESS;
 }
 
+DEFPY (zebra_protodown_bit,
+       zebra_protodown_bit_cmd,
+       "zebra protodown reason-bit (0-31)$bit",
+       ZEBRA_STR
+       "Protodown Configuration\n"
+       "Reason Bit used in the kernel for application\n"
+       "Reason Bit range\n")
+{
+	if_netlink_set_frr_protodown_r_bit(bit);
+	return CMD_SUCCESS;
+}
+
+DEFPY (no_zebra_protodown_bit,
+       no_zebra_protodown_bit_cmd,
+       "no zebra protodown reason-bit [(0-31)$bit]",
+       NO_STR
+       ZEBRA_STR
+       "Protodown Configuration\n"
+       "Reason Bit used in the kernel for setting protodown\n"
+       "Reason Bit Range\n")
+{
+	if_netlink_unset_frr_protodown_r_bit();
+	return CMD_SUCCESS;
+}
+
 #endif /* HAVE_NETLINK */
 
 DEFUN(ip_table_range, ip_table_range_cmd,
@@ -4561,6 +4587,8 @@ void zebra_vty_init(void)
 #ifdef HAVE_NETLINK
 	install_element(CONFIG_NODE, &zebra_kernel_netlink_batch_tx_buf_cmd);
 	install_element(CONFIG_NODE, &no_zebra_kernel_netlink_batch_tx_buf_cmd);
+	install_element(CONFIG_NODE, &zebra_protodown_bit_cmd);
+	install_element(CONFIG_NODE, &no_zebra_protodown_bit_cmd);
 #endif /* HAVE_NETLINK */
 
 #ifdef HAVE_SCRIPTING