From aa70e14c9e4cfeb70d2dc9cee497c40057dc105e Mon Sep 17 00:00:00 2001
From: Ondrej Zajicek <santiago@crfreenet.org>
Date: Tue, 29 Aug 2023 18:23:29 +0200
Subject: [PATCH] BFD: Improve handling of AdminDown

According to RFC 5882, system should not interpret the local or remote
session state transition to AdminDown as failure. We followed that for
the local session state but not for the remote session state (which
just triggered a transition of the local state to Down). The patch
fixes that.

We do not properly generate AdminDown on our side, so the patch is
relevant just for interoperability with other systems.

Thanks to Sunnat Samadov for the bugreport.
---
 proto/bfd/bfd.c | 20 +++++++++++---------
 1 file changed, 11 insertions(+), 9 deletions(-)

diff --git a/proto/bfd/bfd.c b/proto/bfd/bfd.c
index 873e2ed5..97eb2d9b 100644
--- a/proto/bfd/bfd.c
+++ b/proto/bfd/bfd.c
@@ -638,7 +638,7 @@ bfd_reconfigure_iface(struct bfd_proto *p, struct bfd_iface *ifa, struct bfd_con
  */
 
 static void
-bfd_request_notify(struct bfd_request *req, u8 state, u8 diag)
+bfd_request_notify(struct bfd_request *req, u8 state, u8 remote, u8 diag)
 {
   u8 old_state = req->state;
 
@@ -648,7 +648,7 @@ bfd_request_notify(struct bfd_request *req, u8 state, u8 diag)
   req->state = state;
   req->diag = diag;
   req->old_state = old_state;
-  req->down = (old_state == BFD_STATE_UP) && (state == BFD_STATE_DOWN);
+  req->down = (old_state == BFD_STATE_UP) && (state == BFD_STATE_DOWN) && (remote != BFD_STATE_ADMIN_DOWN);
 
   if (req->hook)
     req->hook(req);
@@ -670,7 +670,7 @@ bfd_add_request(struct bfd_proto *p, struct bfd_request *req)
 
   uint ifindex = req->iface ? req->iface->index : 0;
   struct bfd_session *s = bfd_find_session_by_addr(p, req->addr, ifindex);
-  u8 state, diag;
+  u8 loc_state, rem_state, diag;
 
   if (!s)
     s = bfd_add_session(p, req->addr, req->local, req->iface, &req->opts);
@@ -680,11 +680,12 @@ bfd_add_request(struct bfd_proto *p, struct bfd_request *req)
   req->session = s;
 
   bfd_lock_sessions(p);
-  state = s->loc_state;
+  loc_state = s->loc_state;
+  rem_state = s->rem_state;
   diag = s->loc_diag;
   bfd_unlock_sessions(p);
 
-  bfd_request_notify(req, state, diag);
+  bfd_request_notify(req, loc_state, rem_state, diag);
 
   return 1;
 }
@@ -701,7 +702,7 @@ bfd_submit_request(struct bfd_request *req)
   rem_node(&req->n);
   add_tail(&bfd_wait_list, &req->n);
   req->session = NULL;
-  bfd_request_notify(req, BFD_STATE_ADMIN_DOWN, 0);
+  bfd_request_notify(req, BFD_STATE_ADMIN_DOWN, BFD_STATE_ADMIN_DOWN, 0);
 }
 
 static void
@@ -926,7 +927,7 @@ bfd_notify_hook(sock *sk, uint len UNUSED)
   struct bfd_proto *p = sk->data;
   struct bfd_session *s;
   list tmp_list;
-  u8 state, diag;
+  u8 loc_state, rem_state, diag;
   node *n, *nn;
 
   pipe_drain(sk->fd);
@@ -941,13 +942,14 @@ bfd_notify_hook(sock *sk, uint len UNUSED)
   {
     bfd_lock_sessions(p);
     rem_node(&s->n);
-    state = s->loc_state;
+    loc_state = s->loc_state;
+    rem_state = s->rem_state;
     diag = s->loc_diag;
     bfd_unlock_sessions(p);
 
     s->notify_running = 1;
     WALK_LIST_DELSAFE(n, nn, s->request_list)
-      bfd_request_notify(SKIP_BACK(struct bfd_request, n, n), state, diag);
+      bfd_request_notify(SKIP_BACK(struct bfd_request, n, n), loc_state, rem_state, diag);
     s->notify_running = 0;
 
     /* Remove the session if all requests were removed in notify hooks */