commit 532116e7e33d80a79e176f043defffbfc2b8d06e
Author: Ondrej Zajicek (work) <santiago@crfreenet.org>
Date:   Wed Dec 12 17:36:54 2018 +0100

    BGP: Do not prepend ASN in export from non-RS EBGP to RS EBGP
    
    When route is exported to regular EBGP, local ASN should be prepended to
    AS_PATH. When route is propagated by route server (between RS-marked
    EBGP peers), it should not change AS_PATH. Question is what to do in
    other cases (from non-RS EBGP, IBGP, or locally originated to RS EBGP).
    
    In 1.6.x, we did not prepend ASN in non-RS EBGP or IBGP to RS EBGP, but
    we prepended in local to RS EBGP.
    
    In 2.0.x, we changed that so only RS-EBGP to RS-EBGP is not prepended.
    We received some negative responses (thanks to heisenbug and Alexander
    Zubkov), we decided to change it back. One reason is that it is simple
    to modify the AS_PATH by filters, but not possible to un-modify
    changes done by BGP itself. Also, as 1.6.x behavior was not really
    consistent, the final behavior is that ASN is never prepended when
    exported to RS EBGP, like to IBGP.
    
    Note that i do not express an opinion about whether such configurations
    are even reasonable.

diff --git a/proto/bgp/attrs.c b/proto/bgp/attrs.c
index 572adff8..868caca5 100644
--- a/proto/bgp/attrs.c
+++ b/proto/bgp/attrs.c
@@ -1454,8 +1454,7 @@ bgp_update_attrs(struct bgp_proto *p, struct bgp_channel *c, rte *e, ea_list *at
     ad = as_path_strip_confed(pool, ad);
 
   /* AS_PATH attribute - keep or prepend ASN */
-  if (p->is_internal ||
-      (p->rs_client && src && src->rs_client))
+  if (p->is_internal || p->rs_client)
   {
     /* IBGP or route server -> just ensure there is one */
     if (!a)