Send VPLS MAC withdrawals.

RFC 4762 says that MAC address withdrawal messages can be used to
improve convergence time in VPLS networks. This patch makes ldpd send
MAC withdrawals whenever a non-pseudowire interface pertaining to a
VPLS goes down. The processing of received MAC withdrawals will be
implemented later.

Implement RFC 6667 (Typed Wildcard FEC for PWid).

Implement support for PWid group wildcards.

This was missing from our original RFC 4447 VPLS implementation. Now
ldpd understands group wildcards as mandated by the RFC, but we still
don't send them ourselves. I can't see any case in which sending a group
wildcard would be useful, but nonetheless this patch provides a function
called lde_send_labelwithdraw_pwid_wcard() which is ready to be used in
the future anytime we feel like it might be useful.

More renaming and whitespace cleanup.

No binary change after "strip -s".

Be more compliant with RFC 4447.

When sending a label withdraw during the pseudowire Control Word
negotiation, append a "Wrong C-bit" status TLV after the FEC TLV (in
conformance to RFC 4447 section 6.2). Apparently this has no use other
than aiding in troubleshooting.

Also, extend the recv_labelmessage() function to accept Status TLVs and
ignore them instead of shutting down the session.

Remove superfluous call to l2vpn_pw_exit().

Fix memory leak found with valgrind.

Fix small LIB<->LFIB synchronization issue.

ldpd operates only with the best routes of each IP prefix. In other words,
the routes with the lowest priorities.

When a route with a better priority is detected (possibly with a different
nexthop), we should uninstall the labels from the "old" routes and try
to install a new label for the new route (if there's one available in
the LIB).

In this specific case, ldpd was failing to uninstall the labels from the
old routes because it wasn't keeping track of each route's priority in
lde. With this missing bit of information, the parent process had no way
to get the correct label to uninstall when processing a IMSG_KLABEL_DELETE
message.

Remove superfluous includes.

Make functions and variables static whenever possible.

The benefits of this include:
* clean up of the ldpd global namespace;
* improved readability;
* more hints to the compiler/linker to generate more efficient code.

Whenever possible, move global static variables to a smaller scope
(function).

All extern variables are now declared in header files to avoid unnecessary
duplication.

This patch also cleans up the indentation of all function prototypes
and global variables.

Add support for IPv6 (RFC 7552).

This includes:
* Full compliance to RFC 7552;
* Support for MD5 on LDPov6 sessions;
* Support for pseudowires over IPv6 LSPs (we're probably the world's
first implementation doing this);
* Support for the IPv6 explicit-null label;
* Knob to specify the prefered address-family for TCP transport
connections;
* Knob to use cisco non-compliant format to send and interpret the
Dual-Stack capability TLV.

Assorted fixes and small cleanup.

Nothing really interesting here.

Don't create l2vpn targeted neighbors inside the config parser.

When removing a configured pseudowire, we remove the associated tnbr
in ldpe_l2vpn_pw_exit(). So, when a new pseudowire is configured, it
makes sense to create its tnbr in ldpe_l2vpn_pw_init() to keep things
consistent.

Create network sockets on the parent process.

We drop our privileges in ldpe right after we create the network sockets.
The problem is that we might want to change the transport-address and
reload the config, in which case we need new sockets. To allow that,
always create the network sockets in the parent process and pass them
to ldpe via imsg.

Fix bugs in pseudowire parameters negotiation.

Fix mess caused by my commit script.

I screwed up everything... trying to fix now.

Rework L2VPN code.

Check for local label before trying to install pseudowire.

While here, add a comment about ECMP and pseudowires.

Do not accept incomplete pseudowires in the configuration.

There's no point on keeping in the config something that can not be used,
it just adds unnecessary complexity. Also, it's better to warn the user
that there's something wrong rather than play nice and ignore the problem.

Minor adjustments in l2vpn code.

* Define a new constant for the default pseudowire type;
* On l2vpn_new(), initialize the l2vpn lists with LIST_NEW (cosmetic
because the struct was calloc'ed);
* Add a const qualifier to the second parameter of l2vpn_find();
* Remove l2vpn_if_del() and use just free() instead.

Standardize some log messages and fix some inconsistencies.

We were using several different names for the same thing in our log
messages: neighbor, neighbor ID, nbr ID and LSR ID.

Standardize to always use "lsr-id" to refer to a neighbor.

Also:
* Use log_warnx() instead of log_warn() when appropriate;
* Use fatal(x) instead of err(x) when appropriate;
* Fix some inconsistent log messages.

More renaming.

Rename a few more things to improve readability.

* s/F_PW_CONTROLWORD_CONF/F_PW_CWORD_CONF/ (shorter)
* s/F_PW_CONTROLWORD/F_PW_CWORD/ (shorter)
* s/LDPD_FLAG_*/F_LDPD_*/ (consistency)
* s/lde_nbr_address/lde_addr/ (shorter)
* s/ldp_discovery_socket/ldp_disc_socket/ (shorter)
* s/ldp_ediscovery_socket/ldp_edisc_socket/ (shorter)
* s/ldp_sendboth/main_imsg_compose_both/ (consistency)
* s/cons/total/ (makes more sense)
* s/kaddr/ka/ (consistency with remaining code)
* Always use 'ln' for lde_nbrs (consistency)

Move some code around.

This patch doesn't introduce any logical change.

VPLS signaling support.

This patch introduces full support for pseudowire signaling in ldpd(8),
including Control Word and Status TLV negotiation.

As of now it's not possible to configure a VPWS, but the signaling is
the same. In the future, when VPWS support is available in the kernel,
ldpd(8) can be extended to support VPWS with only a few modifications.

Limitations:
* No support for FEC 129, only FEC 128 (more widely deployed);
* No support for group withdraws (not widely deployed);
* No support for MAC withdraws (not widely deployed).

Related RFCs:
* RFC 3916: Requirements for Pseudo-Wire Emulation Edge-to-Edge (PWE3)
* RFC 3985: Pseudo Wire Emulation Edge-to-Edge (PWE3) Architecture
* RFC 4385: Pseudowire Emulation Edge-to-Edge (PWE3) Control Word for
Use over an MPLS PSN
* RFC 4446: IANA Allocations for Pseudowire Edge to Edge Emulation (PWE3)
* RFC 4447: Pseudowire Setup and Maintenance Using the Label Distribution
Protocol (LDP)
* RFC 4448: Encapsulation Methods for Transport of Ethernet over MPLS
Networks
* RFC 4905: Encapsulation Methods for Transport of Layer 2 Frames over
MPLS Networks
* RFC 4906: Transport of Layer 2 Frames Over MPLS

ok claudio@