From ec7d6a506ecae89e5019ce7fcb380a713be28bce Mon Sep 17 00:00:00 2001
From: Michal 'vorner' Vaner <michal.vaner@nic.cz>
Date: Thu, 17 Aug 2017 11:34:25 +0200
Subject: [PATCH] RAdv: Configure how long a dead prefix is advertised

---
 doc/bird.sgml       | 6 ++++++
 proto/radv/config.Y | 4 +++-
 proto/radv/radv.c   | 4 ++--
 proto/radv/radv.h   | 6 +++++-
 4 files changed, 16 insertions(+), 4 deletions(-)

diff --git a/doc/bird.sgml b/doc/bird.sgml
index ffd28964..d8dad431 100644
--- a/doc/bird.sgml
+++ b/doc/bird.sgml
@@ -3436,6 +3436,12 @@ dsc-iface
 	as a default router. For <cf/sensitive/ option, see <ref id="radv-trigger" name="trigger">.
 	Default: 3 * <cf/max ra	interval/, <cf/sensitive/ yes.
 
+	<tag><label id="radv-iface-linger-time">linger time <m/expr/</tag>
+	When a prefix disappears, it is advertised for some time with 0 lifetime,
+	to inform clients the prefix is no longer usable. This sets the time for
+	how long it is advertised (in seconds). Maximum is 3600, 0 means
+	disable. Default 300.
+
 	<tag><label id="radv-iface-default-preference-low">default preference low|medium|high</tag>
 	This option specifies the Default Router Preference value to advertise
 	to hosts. Default: medium.
diff --git a/proto/radv/config.Y b/proto/radv/config.Y
index da300667..0ff84aeb 100644
--- a/proto/radv/config.Y
+++ b/proto/radv/config.Y
@@ -27,7 +27,7 @@ static u8 radv_mult_val;	/* Used by radv_mult for second return value */
 CF_DECLS
 
 CF_KEYWORDS(RADV, PREFIX, INTERFACE, MIN, MAX, RA, DELAY, INTERVAL,
-	MANAGED, OTHER, CONFIG, LINK, MTU, REACHABLE, TIME, RETRANS,
+	MANAGED, OTHER, CONFIG, LINGER, LINK, MTU, REACHABLE, TIME, RETRANS,
 	TIMER, CURRENT, HOP, LIMIT, DEFAULT, VALID, PREFERRED, MULT,
 	LIFETIME, SKIP, ONLINK, AUTONOMOUS, RDNSS, DNSSL, NS, DOMAIN,
 	LOCAL, TRIGGER, SENSITIVE, PREFERENCE, LOW, MEDIUM, HIGH)
@@ -82,6 +82,7 @@ radv_iface_start:
   RADV_IFACE->max_ra_int = DEFAULT_MAX_RA_INT;
   RADV_IFACE->min_delay = DEFAULT_MIN_DELAY;
   RADV_IFACE->current_hop_limit = DEFAULT_CURRENT_HOP_LIMIT;
+  RADV_IFACE->linger_time = DEFAULT_LINGER_TIME;
   RADV_IFACE->default_lifetime = -1;
   RADV_IFACE->default_lifetime_sensitive = 1;
   RADV_IFACE->default_preference = RA_PREF_MEDIUM;
@@ -96,6 +97,7 @@ radv_iface_item:
  | LINK MTU expr { RADV_IFACE->link_mtu = $3; if ($3 < 0) cf_error("Link MTU must be 0 or positive"); }
  | REACHABLE TIME expr { RADV_IFACE->reachable_time = $3; if (($3 < 0) || ($3 > 3600000)) cf_error("Reachable time must be in range 0-3600000"); }
  | RETRANS TIMER expr { RADV_IFACE->retrans_timer = $3; if ($3 < 0) cf_error("Retrans timer must be 0 or positive"); }
+ | LINGER TIME expr { RADV_IFACE->linger_time = $3; if (($3 < 0) || ($3 > 3600)) cf_error("Linger time must be in range 0-3600"); }
  | CURRENT HOP LIMIT expr { RADV_IFACE->current_hop_limit = $4; if (($4 < 0) || ($4 > 255))  cf_error("Current hop limit must be in range 0-255"); }
  | DEFAULT LIFETIME expr radv_sensitive {
      RADV_IFACE->default_lifetime = $3;
diff --git a/proto/radv/radv.c b/proto/radv/radv.c
index 303cf251..44040a4b 100644
--- a/proto/radv/radv.c
+++ b/proto/radv/radv.c
@@ -115,6 +115,7 @@ static void
 prefixes_prepare(struct radv_iface *ifa)
 {
   struct radv_proto *p = ifa->ra;
+  struct radv_iface_config *cf = ifa->cf;
   /* First mark all the prefixes as unused */
   struct radv_prefix *pfx;
 
@@ -164,8 +165,7 @@ prefixes_prepare(struct radv_iface *ifa)
    * dropped just yet). If something is dead and rots there for long enough,
    * clean it up.
    */
-  // XXX: Make these 5 minutes it configurable
-  bird_clock_t rotten = now + 300;
+  bird_clock_t rotten = now + cf->linger_time;
   struct radv_prefix *next;
   bird_clock_t expires_soonest = 0;
   WALK_LIST_DELSAFE(pfx, next, ifa->prefixes) {
diff --git a/proto/radv/radv.h b/proto/radv/radv.h
index 54d7c6f0..777c6e16 100644
--- a/proto/radv/radv.h
+++ b/proto/radv/radv.h
@@ -35,6 +35,7 @@
 #define DEFAULT_MAX_RA_INT 600
 #define DEFAULT_MIN_DELAY 3
 #define DEFAULT_CURRENT_HOP_LIMIT 64
+#define DEFAULT_LINGER_TIME 300
 
 #define DEFAULT_VALID_LIFETIME 86400
 #define DEFAULT_PREFERRED_LIFETIME 14400
@@ -66,6 +67,9 @@ struct radv_iface_config
   u32 max_ra_int;
   u32 min_delay;
 
+  u32 linger_time;		/* How long a dead prefix should still be advertised with 0
+				   lifetime */
+
   u8 rdnss_local;		/* Global list is not used for RDNSS */
   u8 dnssl_local;		/* Global list is not used for DNSSL */
 
@@ -77,7 +81,7 @@ struct radv_iface_config
   u32 current_hop_limit;
   u32 default_lifetime;
   u8 default_lifetime_sensitive; /* Whether default_lifetime depends on trigger */
-  u8 default_preference;	/* Default Router Preference (RFC 4191) */
+  u8 default_preference;	 /* Default Router Preference (RFC 4191) */
 };
 
 struct radv_prefix_config