In build_aspath() be more careful in the len == 0 case. For len == 0

aspath->data should not be touched so just exit early.
While there also initalize source_as correctly in the rev case. This
does not matter here but is more correct.
Problem noticed by anton@
OK tb@

diff --git a/regress/usr.sbin/bgpd/unittests/rde_aspa_test.c b/regress/usr.sbin/bgpd/unittests/rde_aspa_test.c
index e1e067d..ca75c57 100644 (file)
--- a/regress/usr.sbin/bgpd/unittests/rde_aspa_test.c
+++ b/regress/usr.sbin/bgpd/unittests/rde_aspa_test.c
@@ -1,4 +1,4 @@
-/*     $OpenBSD: rde_aspa_test.c,v 1.1 2023/01/11 13:55:08 claudio Exp $ */
+/*     $OpenBSD: rde_aspa_test.c,v 1.2 2023/01/12 08:47:07 claudio Exp $ */
 
 /*
  * Copyright (c) 2022 Claudio Jeker <claudio@openbsd.org>
@@ -615,8 +615,15 @@ build_aspath(const uint32_t *asns, uint32_t asncnt, int rev)
        aspath->len = len;
        aspath->ascnt = asncnt; /* lie but nothing cares */
        aspath->source_as = 0;
-       if (len != 0)
+
+       if (len == 0)
+               return aspath;
+
+       if (rev)
+               aspath->source_as = asns[asncnt - 1];
+       else
                aspath->source_as = asns[0];
+
        aspath->data[0] = AS_SEQUENCE;
        aspath->data[1] = asncnt;
        for (i = 0; i < asncnt; i++) {