From 86f567e13c2202fc3c3a1ce49f9a35220a50f117 Mon Sep 17 00:00:00 2001
From: Ondrej Zajicek <santiago@crfreenet.org>
Date: Sat, 16 May 2015 20:17:59 +0200
Subject: [PATCH] Fix minor issue in pipe route propagation

In some circumstances during reconfiguration, routes propagated by pipes
to other tables may hang there even after the primary routes are removed.

There is already a workaround for this issue in the code which removes
these stale routes by flush process when source protocols are shut down.

This patch is a cleaner fix and allows to simplify the flush process
---
 nest/rt-table.c | 27 +++++++++++++++++++++++----
 1 file changed, 23 insertions(+), 4 deletions(-)

diff --git a/nest/rt-table.c b/nest/rt-table.c
index dbe0c50d..a8fe137c 100644
--- a/nest/rt-table.c
+++ b/nest/rt-table.c
@@ -347,11 +347,13 @@ do_rt_notify(struct announce_hook *ah, net *net, rte *new, rte *old, ea_list *tm
 }
 
 static void
-rt_notify_basic(struct announce_hook *ah, net *net, rte *new, rte *old, ea_list *tmpa, int refeed)
+rt_notify_basic(struct announce_hook *ah, net *net, rte *new0, rte *old0, ea_list *tmpa, int refeed)
 {
-  // struct proto *p = ah->proto;
+  struct proto *p = ah->proto;
   struct proto_stats *stats = ah->stats;
 
+  rte *new = new0;
+  rte *old = old0;
   rte *new_free = NULL;
   rte *old_free = NULL;
 
@@ -369,7 +371,7 @@ rt_notify_basic(struct announce_hook *ah, net *net, rte *new, rte *old, ea_list
    * FIXME - this is broken because 'configure soft' may change
    * filters but keep routes. Refeed is expected to be called after
    * change of the filters and with old == new, therefore we do not
-   * even try to run the filter on an old route, This may lead to 
+   * even try to run the filter on an old route, This may lead to
    * 'spurious withdraws' but ensure that there are no 'missing
    * withdraws'.
    *
@@ -386,9 +388,26 @@ rt_notify_basic(struct announce_hook *ah, net *net, rte *new, rte *old, ea_list
   if (old && !refeed)
     old = export_filter(ah, old, &old_free, NULL, 1);
 
-  /* FIXME - This is broken because of incorrect 'old' value (see above) */
   if (!new && !old)
+  {
+    /*
+     * As mentioned above, 'old' value may be incorrect in some race conditions.
+     * We generally ignore it with the exception of withdraw to pipe protocol.
+     * In that case we rather propagate unfiltered withdraws regardless of
+     * export filters to ensure that when a protocol is flushed, its routes are
+     * removed from all tables. Possible spurious unfiltered withdraws are not
+     * problem here as they are ignored if there is no corresponding route at
+     * the other end of the pipe. We directly call rt_notify() hook instead of
+     * do_rt_notify() to avoid logging and stat counters.
+     */
+
+#ifdef CONFIG_PIPE
+    if ((p->proto == &proto_pipe) && !new0 && (p != old0->sender->proto))
+      p->rt_notify(p, ah->table, net, NULL, old0, NULL);
+#endif
+
     return;
+  }
 
   do_rt_notify(ah, net, new, old, tmpa, refeed);