Removing the rte_modify API

For BGP LLGR purposes, there was an API allowing a protocol to directly
modify their stale routes in table before flushing them. This API was
called by the table prune routine which violates the future locking
requirements.

Instead of this, BGP now requests a special route export and reimports
these routes into the table, allowing for asynchronous execution without
locking the table on export.

3 files changed, 100 insertions, 19 deletions

diff --git a/proto/bgp/attrs.c b/proto/bgp/attrs.c
index 084c9b63..28eb6fee 100644
--- a/proto/bgp/attrs.c
+++ b/proto/bgp/attrs.c
@@ -2546,27 +2546,59 @@ bgp_rte_recalculate(rtable *table, net *net, rte *new, rte *old, rte *old_best)
     return !old_suppressed;
 }
 
-rte *
-bgp_rte_modify_stale(struct rte *r, struct linpool *pool)
+void
+bgp_rte_modify_stale(struct rt_export_request *req, const net_addr *n, struct rt_pending_export *rpe UNUSED, rte **feed, uint count)
 {
-  eattr *ea = ea_find(r->attrs, BGP_EA_ID(BA_COMMUNITY));
-  const struct adata *ad = ea ? ea->u.ptr : NULL;
-  uint flags = ea ? ea->flags : BAF_PARTIAL;
+  struct bgp_channel *c = SKIP_BACK(struct bgp_channel, stale_feed, req);
+  struct rt_import_hook *irh = c->c.in_req.hook;
 
-  if (ad && int_set_contains(ad, BGP_COMM_NO_LLGR))
-    return NULL;
+  /* Find our routes among others */
+  for (uint i=0; i<count; i++)
+  {
+    rte *r = feed[i];
 
-  if (ad && int_set_contains(ad, BGP_COMM_LLGR_STALE))
-    return r;
+    /* Not our route */
+    if (r->sender != irh)
+      continue;
 
-  _Thread_local static rte e0;
-  e0 = *r;
+    /* A new route, do not mark as stale */
+    if (r->stale_cycle == irh->stale_set)
+      continue;
 
-  bgp_set_attr_ptr(&e0.attrs, BA_COMMUNITY, flags,
-		   int_set_add(pool, ad, BGP_COMM_LLGR_STALE));
-  e0.pflags |= BGP_REF_STALE;
+    eattr *ea = ea_find(r->attrs, BGP_EA_ID(BA_COMMUNITY));
+    const struct adata *ad = ea ? ea->u.ptr : NULL;
+    uint flags = ea ? ea->flags : BAF_PARTIAL;
+
+    /* LLGR not allowed, withdraw the route */
+    if (ad && int_set_contains(ad, BGP_COMM_NO_LLGR))
+    {
+      rte_import(&c->c.in_req, n, NULL, r->src);
+      continue;
+    }
 
-  return &e0;
+    /* Route already marked as LLGR, do nothing */
+    if (ad && int_set_contains(ad, BGP_COMM_LLGR_STALE))
+      continue;
+
+    /* Store the tmp_linpool state to aggresively save memory */
+    struct lp_state tmpp;
+    lp_save(tmp_linpool, &tmpp);
+
+    /* Mark the route as LLGR */
+    rte e0 = *r;
+    bgp_set_attr_ptr(&e0.attrs, BA_COMMUNITY, flags, int_set_add(tmp_linpool, ad, BGP_COMM_LLGR_STALE));
+    e0.pflags &= ~BGP_REF_NOT_STALE;
+    e0.pflags |= BGP_REF_STALE;
+
+    /* We need to update the route but keep it stale. */
+    ASSERT_DIE(irh->stale_set == irh->stale_valid + 1);
+    irh->stale_set--;
+    rte_import(&c->c.in_req, n, &e0, r->src);
+    irh->stale_set++;
+
+    /* Restore the memory state */
+    lp_restore(tmp_linpool, &tmpp);
+  }
 }
 
 
diff --git a/proto/bgp/bgp.c b/proto/bgp/bgp.c
index d9008b9a..fb8fa529 100644
--- a/proto/bgp/bgp.c
+++ b/proto/bgp/bgp.c
@@ -139,6 +139,9 @@ static void bgp_update_bfd(struct bgp_proto *p, const struct bfd_options *bfd);
 static int bgp_incoming_connection(sock *sk, uint dummy UNUSED);
 static void bgp_listen_sock_err(sock *sk UNUSED, int err);
 
+static void bgp_graceful_restart_feed(struct bgp_channel *c);
+
+
 /**
  * bgp_open - open a BGP instance
  * @p: BGP instance
@@ -770,7 +773,7 @@ bgp_handle_graceful_restart(struct bgp_proto *p)
 
       case BGP_GRS_LLGR:
 	rt_refresh_begin(&c->c.in_req);
-	rt_modify_stale(c->c.table, &c->c.in_req);
+	bgp_graceful_restart_feed(c);
 	break;
       }
     }
@@ -796,6 +799,52 @@ bgp_handle_graceful_restart(struct bgp_proto *p)
   tm_start(p->gr_timer, p->conn->remote_caps->gr_time S);
 }
 
+static void
+bgp_graceful_restart_feed_done(struct rt_export_request *req)
+{
+  req->hook = NULL;
+}
+
+static void
+bgp_graceful_restart_feed_dump_req(struct rt_export_request *req)
+{
+  struct bgp_channel *c = SKIP_BACK(struct bgp_channel, stale_feed, req);
+  debug("  BGP-GR %s.%s export request %p\n", c->c.proto->name, c->c.name, req);
+}
+
+static void
+bgp_graceful_restart_feed_log_state_change(struct rt_export_request *req, u8 state)
+{
+  struct bgp_channel *c = SKIP_BACK(struct bgp_channel, stale_feed, req);
+  struct bgp_proto *p = (void *) c->c.proto;
+  BGP_TRACE(D_EVENTS, "Long-lived graceful restart export state changed to %s", rt_export_state_name(state));
+
+  if (state == TES_READY)
+    rt_stop_export(req, bgp_graceful_restart_feed_done);
+}
+
+static void
+bgp_graceful_restart_drop_export(struct rt_export_request *req UNUSED, const net_addr *n UNUSED, struct rt_pending_export *rpe UNUSED)
+{ /* Nothing to do */ }
+
+static void
+bgp_graceful_restart_feed(struct bgp_channel *c)
+{
+  c->stale_feed = (struct rt_export_request) {
+    .name = "BGP-GR",
+    .trace_routes = c->c.debug | c->c.proto->debug,
+    .dump_req = bgp_graceful_restart_feed_dump_req,
+    .log_state_change = bgp_graceful_restart_feed_log_state_change,
+    .export_bulk = bgp_rte_modify_stale,
+    .export_one = bgp_graceful_restart_drop_export,
+  };
+
+  rt_request_export(&c->c.table->exporter, &c->stale_feed);
+}
+
+
+
+
 /**
  * bgp_graceful_restart_done - finish active BGP graceful restart
  * @c: BGP channel
@@ -861,7 +910,7 @@ bgp_graceful_restart_timeout(timer *t)
       /* Channel is in GR, and supports LLGR -> start LLGR */
       c->gr_active = BGP_GRS_LLGR;
       tm_start(c->stale_timer, c->stale_time S);
-      rt_modify_stale(c->c.table, &c->c.in_req);
+      bgp_graceful_restart_feed(c);
     }
   }
   else
@@ -1672,7 +1721,6 @@ bgp_init(struct proto_config *CF)
   P->rte_better = bgp_rte_better;
   P->rte_mergable = bgp_rte_mergable;
   P->rte_recalculate = cf->deterministic_med ? bgp_rte_recalculate : NULL;
-  P->rte_modify = bgp_rte_modify_stale;
   P->rte_igp_metric = bgp_rte_igp_metric;
 
   p->cf = cf;
diff --git a/proto/bgp/bgp.h b/proto/bgp/bgp.h
index 003893e0..2e7615ea 100644
--- a/proto/bgp/bgp.h
+++ b/proto/bgp/bgp.h
@@ -371,6 +371,7 @@ struct bgp_channel {
 
   timer *stale_timer;			/* Long-lived stale timer for LLGR */
   u32 stale_time;			/* Stored LLGR stale time from last session */
+  struct rt_export_request stale_feed;	/* Feeder request for stale route modification */
 
   u8 add_path_rx;			/* Session expects receive of ADD-PATH extended NLRI */
   u8 add_path_tx;			/* Session expects transmit of ADD-PATH extended NLRI */
@@ -576,7 +577,7 @@ void bgp_done_prefix(struct bgp_channel *c, struct bgp_prefix *px, struct bgp_bu
 int bgp_rte_better(struct rte *, struct rte *);
 int bgp_rte_mergable(rte *pri, rte *sec);
 int bgp_rte_recalculate(rtable *table, net *net, rte *new, rte *old, rte *old_best);
-struct rte *bgp_rte_modify_stale(struct rte *r, struct linpool *pool);
+void bgp_rte_modify_stale(struct rt_export_request *req, const net_addr *n, struct rt_pending_export *rpe UNUSED, rte **feed, uint count);
 u32 bgp_rte_igp_metric(const rte *);
 void bgp_rt_notify(struct proto *P, struct channel *C, const net_addr *n, rte *new, const rte *old);
 int bgp_preexport(struct channel *, struct rte *);