From 574d7eb241a60622b0573ab1460cb23d968ba1cc Mon Sep 17 00:00:00 2001
From: Alexander Zubkov <green@qrator.net>
Date: Wed, 7 Feb 2024 19:11:10 +0100
Subject: [PATCH] BGP: Allow multiple EBGP neighbors with the same peer.

We can distinguish BGP sessions if at least one side uses a different IP
address. Extend olock mechanism to handle local IP as a part of key, with
optional wildcard, so BGP sessions could local IP in the olock and not
block themselves.
---
 lib/ip.h        | 4 ++++
 nest/locks.c    | 5 +++--
 nest/locks.h    | 3 ++-
 proto/bgp/bgp.c | 1 +
 4 files changed, 10 insertions(+), 3 deletions(-)

diff --git a/lib/ip.h b/lib/ip.h
index f2650d3f..8dd925ed 100644
--- a/lib/ip.h
+++ b/lib/ip.h
@@ -176,6 +176,10 @@ static inline ip6_addr ip6_not(ip6_addr a)
 #define ipa_xor(x,y) ip6_xor(x,y)
 #define ipa_not(x) ip6_not(x)
 
+/* Compare addresses when zero address works like a wildcard */
+static inline int ipa_equal_wildcard(ip_addr x, ip_addr y)
+{ return ipa_zero(x) || ipa_zero(y) || ipa_equal(x, y); }
+
 
 /*
  * A zero address is either a token for invalid/unused, or the prefix of default
diff --git a/nest/locks.c b/nest/locks.c
index 812a6534..637f2c15 100644
--- a/nest/locks.c
+++ b/nest/locks.c
@@ -48,7 +48,8 @@ olock_same(struct object_lock *x, struct object_lock *y)
     x->vrf == y->vrf &&
     x->port == y->port &&
     x->inst == y->inst &&
-    ipa_equal(x->addr, y->addr);
+    ipa_equal(x->addr, y->addr) &&
+    ipa_equal_wildcard(x->addr_local, y->addr_local);
 }
 
 static void
@@ -91,7 +92,7 @@ olock_dump(resource *r)
   struct object_lock *l = (struct object_lock *) r;
   static char *olock_states[] = { "free", "locked", "waiting", "event" };
 
-  debug("(%d:%s:%I:%d:%d) [%s]\n", l->type, (l->iface ? l->iface->name : "?"), l->addr, l->port, l->inst, olock_states[l->state]);
+  debug("(%d:%s:%I:%I:%d:%d) [%s]\n", l->type, (l->iface ? l->iface->name : "?"), l->addr, l->addr_local, l->port, l->inst, olock_states[l->state]);
   if (!EMPTY_LIST(l->waiters))
     debug(" [wanted]\n");
 }
diff --git a/nest/locks.h b/nest/locks.h
index 37026c68..1686e6ec 100644
--- a/nest/locks.h
+++ b/nest/locks.h
@@ -25,7 +25,8 @@
 
 struct object_lock {
   resource r;
-  ip_addr addr;		/* Identification of a object: IP address */
+  ip_addr addr;		/* Identification of a object: IP address (strict compare) */
+  ip_addr addr_local;	/* ... another IP address (allow zero IP wildcard) */
   uint type;		/* ... object type (OBJLOCK_xxx) */
   uint port;		/* ... port number */
   uint inst;		/* ... instance ID */
diff --git a/proto/bgp/bgp.c b/proto/bgp/bgp.c
index cd57c32b..e97b45e6 100644
--- a/proto/bgp/bgp.c
+++ b/proto/bgp/bgp.c
@@ -1616,6 +1616,7 @@ bgp_start(struct proto *P)
   struct object_lock *lock;
   lock = p->lock = olock_new(P->pool);
   lock->addr = p->remote_ip;
+  lock->addr_local = p->cf->local_ip;
   lock->port = p->cf->remote_port;
   lock->iface = p->cf->iface;
   lock->vrf = p->cf->iface ? NULL : p->p.vrf;