Rework label mapping algorithms to be more in line with the RFC.

This patch presents a thoroughly review of the label mapping
algorithms. Most of the changes are minor bug fixes in the handling of
received label messages.

Additional improvements:
* Add a few more references to the Appendix A of the RFC5036 ("LDP
  Label Distribution Procedures") into the code;
* Add full multipath support;
* Send label withdraws when appropriate;
* Add label withdraw/release wildcard support.

NOTE: As a result of implementing only the "Liberal Label Retention" and
"Downstream Unsolicited" modes, we will never send a label request
("Request  Never"). And that means that we can ignore the following
notification messages: "Label Request Aborted", "No Label Resources",
"No Route" and "Label Resources Available". The following algorithms
mentioned in the RFC can also be ignored: "Timeout of Deferred Label
Request", "Detect Local Label Resources Have Become Available" and
"Receive Label Abort Request".

Now, considering that we only support one combination of all modes of
operation, we can say that we have an almost complete implementation of
the protocol.

ok claudio@

1 files changed, 5 insertions, 4 deletions

diff --git a/usr.sbin/ldpd/ldpd.h b/usr.sbin/ldpd/ldpd.h
index 31dd4342122..ed600251b57 100644
--- a/usr.sbin/ldpd/ldpd.h
+++ b/usr.sbin/ldpd/ldpd.h
@@ -1,4 +1,4 @@
-/*	$OpenBSD: ldpd.h,v 1.47 2015/07/19 20:50:03 renato Exp $ */
+/*	$OpenBSD: ldpd.h,v 1.48 2015/07/19 20:54:17 renato Exp $ */
 
 /*
  * Copyright (c) 2009 Michele Marchetto <michele@openbsd.org>
@@ -99,6 +99,8 @@ enum imsg_type {
 	IMSG_MAPPING_ADD_END,
 	IMSG_RELEASE_ADD,
 	IMSG_RELEASE_ADD_END,
+	IMSG_WITHDRAW_ADD,
+	IMSG_WITHDRAW_ADD_END,
 	IMSG_ADDRESS_ADD,
 	IMSG_ADDRESS_DEL,
 	IMSG_NOTIFICATION_SEND,
@@ -160,15 +162,14 @@ TAILQ_HEAD(mapping_head, mapping_entry);
 
 struct map {
 	struct in_addr	prefix;
+	u_int8_t	prefixlen;
 	u_int32_t	label;
 	u_int32_t	messageid;
 	u_int32_t	requestid;
-	u_int8_t	prefixlen;
 	u_int8_t	flags;
 };
 #define F_MAP_WILDCARD	0x01	/* wildcard FEC */
-#define F_MAP_OPTLABEL	0x02	/* optional label present */
-#define F_MAP_REQ_ID	0x04	/* optional request message id present */
+#define F_MAP_REQ_ID	0x02	/* optional request message id present */
 
 struct notify_msg {
 	u_int32_t	messageid;