From bc2ce4aaa8d1e4d56776ee35352c5e2caa09a0e5 Mon Sep 17 00:00:00 2001
From: Maria Matejka <mq@ucw.cz>
Date: Tue, 12 Jul 2022 12:40:18 +0200
Subject: 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.
---
 proto/bgp/attrs.c | 62 +++++++++++++++++++++++++++++++++++++++++--------------
 1 file changed, 47 insertions(+), 15 deletions(-)

(limited to 'proto/bgp/attrs.c')

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);
+  }
 }
 
 
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