lib, bgp: add initial support for asdot format

AS number can be defined as an unsigned long number, or
two uint16 values separated by a period (.). The possible
valus are:
- usual 32 bit values : [1;2^32 -1]
- <1.65535>.<0.65535> for dot notation
- <0.65535>.<0.65535> for dot+ notation.

The 0.0 value is forbidden when configuring BGP instances
or peer configurations.

A new ASN type is added for parsing in the vty.
The following commands use that new identifier:
- router bgp ..
- bgp confederation ..
- neighbor <> remote-as <>
- neighbor <> local-as <>
- clear ip bgp <>
- route-map / set as-path <>

An asn library is available in lib/ and provides some
services:
- convert an as string into an as number.
- parse an as path list string and extract a number.
- convert an as number into a string.

Also, the bgp tests forge an as_zero_path, and to do that,
an API to relax the possibility to have a 0 as value is
specifically called from the tests.

Signed-off-by: Philippe Guibert <philippe.guibert@6wind.com>

1 files changed, 48 insertions, 0 deletions

diff --git a/lib/asn.h b/lib/asn.h
new file mode 100644
index 0000000000..baaaf4d807
--- /dev/null
+++ b/lib/asn.h
@@ -0,0 +1,48 @@
+/*
+ * AS number structure
+ * Copyright 2022 6WIND
+ *
+ * This file is part of GNU Zebra.
+ *
+ * GNU Zebra is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published
+ * by the Free Software Foundation; either version 2, or (at your
+ * option) any later version.
+ *
+ * GNU Zebra is distributed in the hope that it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License along
+ * with this program; see the file COPYING; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
+ */
+
+#ifndef _FRR_ASN_H
+#define _FRR_ASN_H
+
+#include "zebra.h"
+#include "command_match.h"
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+#define ASN_STRING_MAX_SIZE	12
+
+typedef uint32_t as_t;
+
+extern bool asn_str2asn(const char *asstring, as_t *asn);
+extern const char *asn_asn2asplain(as_t asn);
+extern const char *asn_str2asn_parse(const char *asstring, as_t *asn,
+				     bool *found_ptr);
+extern enum match_type asn_str2asn_match(const char *str);
+/* for test */
+extern void asn_relax_as_zero(bool relax);
+
+#ifdef __cplusplus
+}
+#endif
+
+#endif /* _FRR_ASN_H */