From 127862f626f39d52b758084931e0fbdc91db745c Mon Sep 17 00:00:00 2001
From: Maria Matejka <mq@ucw.cz>
Date: Wed, 26 Jan 2022 21:16:19 +0100
Subject: [PATCH] Asynchronous neighbor notifications fixes

---
 nest/iface.h          |  1 +
 nest/neighbor.c       | 41 ++++++++++++++++++++++++++++++++++++-----
 proto/bgp/bgp.c       |  2 +-
 sysdep/unix/io-loop.c |  6 ++++--
 4 files changed, 42 insertions(+), 8 deletions(-)

diff --git a/nest/iface.h b/nest/iface.h
index 5deb5432..6e8c8448 100644
--- a/nest/iface.h
+++ b/nest/iface.h
@@ -153,6 +153,7 @@ typedef struct neighbor {
 #define NEF_STICKY	1
 #define NEF_ONLINK	2
 #define NEF_IFACE	4		/* Entry for whole iface */
+#define NEF_NOTIFY_MAIN	0x100		/* Notify from main_birdloop context */
 
 
 neighbor *neigh_find(struct proto *p, ip_addr a, struct iface *ifa, uint flags);
diff --git a/nest/neighbor.c b/nest/neighbor.c
index 7466e510..e4d42b4d 100644
--- a/nest/neighbor.c
+++ b/nest/neighbor.c
@@ -60,6 +60,7 @@
 static slab *neigh_slab;
 static list neigh_hash_table[NEIGH_HASH_SIZE], sticky_neigh_list;
 static void neigh_do_notify(void *);
+static void neigh_do_notify_main(void *);
 
 static inline uint
 neigh_hash(struct proto *p, ip_addr a, struct iface *i)
@@ -270,15 +271,29 @@ neigh_find(struct proto *p, ip_addr a, struct iface *iface, uint flags)
   n->proto = p;
   n->flags = flags;
   n->scope = scope;
-  n->event = (event) { .hook = neigh_do_notify, .data = n };
+
   ASSERT_DIE(birdloop_inside(p->loop));
 
-  if (p->loop == &main_birdloop)
-    n->event.list = &global_event_list;
+  if (flags & NEF_NOTIFY_MAIN)
+    n->event = (event) {
+      .hook = neigh_do_notify_main,
+      .data = n,
+      .list = &global_event_list,
+    };
+  else if (p->loop == &main_birdloop)
+    n->event = (event) {
+      .hook = neigh_do_notify,
+      .data = n,
+      .list = &global_event_list,
+    };
   else
   {
     birdloop_link(p->loop);
-    n->event.list = birdloop_event_list(p->loop);
+    n->event = (event) {
+      .hook = neigh_do_notify,
+      .data = n,
+      .list = birdloop_event_list(p->loop),
+    };
   }
 
   IFACE_UNLOCK;
@@ -340,6 +355,14 @@ neigh_notify(neighbor *n)
   ev_send(n->event.list, &n->event);
 }
 
+static void
+neigh_do_notify_main(void *data)
+{
+  neighbor *n = data;
+  PROTO_LOCKED_FROM_MAIN(n->proto)
+    neigh_do_notify(data);
+}
+
 static void
 neigh_do_notify(void *data)
 {
@@ -382,10 +405,18 @@ neigh_down(neighbor *n)
 static inline void
 neigh_free(neighbor *n)
 {
+  ASSERT_DIE(birdloop_inside(n->proto->loop));
+
+  if (n->flags & NEF_NOTIFY_MAIN)
+    ASSERT_DIE(birdloop_inside(&main_birdloop));
+
   rem_node(&n->n);
   rem_node(&n->if_n);
+
+  if (n->event.list != &global_event_list)
+    birdloop_unlink(n->proto->loop);
+
   ev_postpone(&n->event);
-  birdloop_unlink(n->proto->loop);
   sl_free(neigh_slab, n);
 }
 
diff --git a/proto/bgp/bgp.c b/proto/bgp/bgp.c
index b825f778..7e803f64 100644
--- a/proto/bgp/bgp.c
+++ b/proto/bgp/bgp.c
@@ -1541,7 +1541,7 @@ bgp_start_locked(struct object_lock *lock)
     return;
   }
 
-  neighbor *n = neigh_find(&p->p, p->remote_ip, cf->iface, NEF_STICKY);
+  neighbor *n = neigh_find(&p->p, p->remote_ip, cf->iface, NEF_STICKY | NEF_NOTIFY_MAIN);
   if (!n)
   {
     log(L_ERR "%s: Invalid remote address %I%J", p->p.name, p->remote_ip, cf->iface);
diff --git a/sysdep/unix/io-loop.c b/sysdep/unix/io-loop.c
index ec805dce..1d3a555f 100644
--- a/sysdep/unix/io-loop.c
+++ b/sysdep/unix/io-loop.c
@@ -498,7 +498,9 @@ void
 birdloop_unlink(struct birdloop *loop)
 {
   ASSERT_DIE(birdloop_inside(loop));
-  loop->links--;
+  ASSERT_DIE(loop->links);
+  if (!--loop->links)
+    birdloop_ping(loop);
 }
 
 static void
@@ -541,7 +543,7 @@ birdloop_main(void *arg)
 
     birdloop_enter(loop);
 
-    if (loop->stopped)
+    if (loop->stopped && !loop->links)
       break;
 
     loop_begin = current_time();