Make the AS_SET handling for source-as even simpler. It is enough to only

extract the rightmost AS of a segment if the segment is not an AS_SET.
Then if we hit the final segment as will contain the last aggregator AS.
This fixes a possible issue with a path like 1 2 3 { 4 5 } { 6 7 } which
should match for source-as 3.
OK benno@

diff --git a/usr.sbin/bgpd/util.c b/usr.sbin/bgpd/util.c
index c62e7e1..dabf6eb 100644 (file)
--- a/usr.sbin/bgpd/util.c
+++ b/usr.sbin/bgpd/util.c
@@ -1,4 +1,4 @@
-/*     $OpenBSD: util.c,v 1.29 2018/08/09 21:12:33 claudio Exp $ */
+/*     $OpenBSD: util.c,v 1.30 2018/08/10 11:13:01 claudio Exp $ */
 
 /*
  * Copyright (c) 2006 Claudio Jeker <claudio@openbsd.org>
@@ -334,7 +334,7 @@ aspath_match(void *data, u_int16_t len, struct filter_as *f, u_int32_t match)
        int              final;
        u_int16_t        seg_size;
        u_int8_t         i, seg_len;
-       u_int32_t        as = 0, preas;
+       u_int32_t        as = 0;
 
        if (f->type == AS_EMPTY) {
                if (len == 0)
@@ -360,18 +360,18 @@ aspath_match(void *data, u_int16_t len, struct filter_as *f, u_int32_t match)
 
                final = (len == seg_size);
 
-               /* just check the rightmost AS */
                if (f->type == AS_SOURCE) {
-                       /* keep previous AS in case an AS_SET is rightmost */
-                       preas = as;
-                       as = aspath_extract(seg, seg_len - 1);
+                       /*
+                        * Just extract the rightmost AS
+                        * but if that segment is an AS_SET then the rightmost
+                        * AS of a previous non AS_SET segment should be used.
+                        * Because of that simply skip AS_SET segments.
+                        */
+                       if (seg[0] != AS_SET)
+                               as = aspath_extract(seg, seg_len - 1);
                        /* not yet in the final segment */
                        if (!final)
                                continue;
-                       if (seg[0] == AS_SET)
-                               /* use aggregator AS per rfc6472 */
-                               if (preas)
-                                       as = preas;
                        if (as_compare(f, as, match))
                                return (1);
                        else