From c6bf7f4723158eb53383ed721150a1b4d0bf2e48 Mon Sep 17 00:00:00 2001
From: Donatas Abraitis <donatas@opensourcerouting.org>
Date: Fri, 6 Oct 2023 17:41:18 +0300
Subject: [PATCH] bgpd: Add `clear bgp capabilities` command to resend some
 dynamic capabilities

For instance, it's not possible to resend FQDN capability without resetting
the session, so let's create some more elegant way to do that.

Signed-off-by: Donatas Abraitis <donatas@opensourcerouting.org>
---
 bgpd/bgp_vty.c |  9 ++++++---
 bgpd/bgpd.c    | 13 +++++++++++++
 bgpd/bgpd.h    |  3 ++-
 3 files changed, 21 insertions(+), 4 deletions(-)

diff --git a/bgpd/bgp_vty.c b/bgpd/bgp_vty.c
index 9b4d8936828a..9b53eba411b1 100644
--- a/bgpd/bgp_vty.c
+++ b/bgpd/bgp_vty.c
@@ -10601,7 +10601,7 @@ static int bgp_clear_prefix(struct vty *vty, const char *view_name,
 /* one clear bgp command to rule them all */
 DEFUN (clear_ip_bgp_all,
        clear_ip_bgp_all_cmd,
-       "clear [ip] bgp [<view|vrf> VIEWVRFNAME] [<ipv4|ipv6|l2vpn> [<unicast|multicast|vpn|labeled-unicast|flowspec|evpn>]] <*|A.B.C.D$neighbor|X:X::X:X$neighbor|WORD$neighbor|ASNUM|external|peer-group PGNAME> [<soft [<in|out>]|in [prefix-filter]|out|message-stats>]",
+       "clear [ip] bgp [<view|vrf> VIEWVRFNAME] [<ipv4|ipv6|l2vpn> [<unicast|multicast|vpn|labeled-unicast|flowspec|evpn>]] <*|A.B.C.D$neighbor|X:X::X:X$neighbor|WORD$neighbor|ASNUM|external|peer-group PGNAME> [<soft [<in|out>]|in [prefix-filter]|out|message-stats|capabilities>]",
        CLEAR_STR
        IP_STR
        BGP_STR
@@ -10624,7 +10624,8 @@ DEFUN (clear_ip_bgp_all,
        BGP_SOFT_IN_STR
        "Push out prefix-list ORF and do inbound soft reconfig\n"
        BGP_SOFT_OUT_STR
-       "Reset message statistics\n")
+       "Reset message statistics\n"
+       "Resend capabilities\n")
 {
 	char *vrf = NULL;
 
@@ -10681,7 +10682,7 @@ DEFUN (clear_ip_bgp_all,
 		clr_sort = clear_external;
 	}
 
-	/* [<soft [<in|out>]|in [prefix-filter]|out|message-stats>] */
+	/* [<soft [<in|out>]|in [prefix-filter]|out|message-stats|capabilities>] */
 	if (argv_find(argv, argc, "soft", &idx)) {
 		if (argv_find(argv, argc, "in", &idx)
 		    || argv_find(argv, argc, "out", &idx))
@@ -10698,6 +10699,8 @@ DEFUN (clear_ip_bgp_all,
 		clr_type = BGP_CLEAR_SOFT_OUT;
 	} else if (argv_find(argv, argc, "message-stats", &idx)) {
 		clr_type = BGP_CLEAR_MESSAGE_STATS;
+	} else if (argv_find(argv, argc, "capabilities", &idx)) {
+		clr_type = BGP_CLEAR_CAPABILITIES;
 	} else
 		clr_type = BGP_CLEAR_SOFT_NONE;
 
diff --git a/bgpd/bgpd.c b/bgpd/bgpd.c
index e760d4158768..b13ce5ad0b15 100644
--- a/bgpd/bgpd.c
+++ b/bgpd/bgpd.c
@@ -8034,6 +8034,16 @@ static void peer_reset_message_stats(struct peer *peer)
 	}
 }
 
+/* Helper function to resend some BGP capabilities that are uncontrolled.
+ * For instance, FQDN capability, that can't be turned off, but let's say
+ * we changed the hostname, we need to resend it.
+ */
+static void peer_clear_capabilities(struct peer *peer, afi_t afi, safi_t safi)
+{
+	bgp_capability_send(peer, afi, safi, CAPABILITY_CODE_FQDN,
+			    CAPABILITY_ACTION_SET);
+}
+
 /*
  * If peer clear is invoked in a loop for all peers on the BGP instance,
  * it may end up freeing the doppelganger, and if this was the next node
@@ -8142,6 +8152,9 @@ int peer_clear_soft(struct peer *peer, afi_t afi, safi_t safi,
 	if (stype == BGP_CLEAR_MESSAGE_STATS)
 		peer_reset_message_stats(peer);
 
+	if (stype == BGP_CLEAR_CAPABILITIES)
+		peer_clear_capabilities(peer, afi, safi);
+
 	return 0;
 }
 
diff --git a/bgpd/bgpd.h b/bgpd/bgpd.h
index 8f78e33f6517..665a38e76bcc 100644
--- a/bgpd/bgpd.h
+++ b/bgpd/bgpd.h
@@ -2067,7 +2067,8 @@ enum bgp_clear_type {
 	BGP_CLEAR_SOFT_IN,
 	BGP_CLEAR_SOFT_BOTH,
 	BGP_CLEAR_SOFT_IN_ORF_PREFIX,
-	BGP_CLEAR_MESSAGE_STATS
+	BGP_CLEAR_MESSAGE_STATS,
+	BGP_CLEAR_CAPABILITIES,
 };
 
 /* Macros. */