zebra: process information about new addresses (BZ#486)

Because of a change of semantics in the Linux kernel, information
about changes made by zebra itself was not considered for updates.
This change should fix this by accounting for the new semantics.

It is based on a patch by lich posted to the bugzilla #486

Signed-off-by: Christian Franke <chris@opensourcerouting.org>
Signed-off-by: David Lamparter <equinox@opensourcerouting.org>
zebra: make if_subnet_delete a bit more strict

Enhance if_subnet_delete so it will complain about improper use.
Also, fix one occurence of improper use where it was called for
IPv6 as well.

Signed-off-by: Christian Franke <chris@opensourcerouting.org>
Signed-off-by: David Lamparter <equinox@opensourcerouting.org>
zebra: clear ZEBRA_IFC_CONFIGURED on "no ipv6 addr"

To match the semantics of IPv4, the ZEBRA_IFC_CONFIGURED flag
should be cleared when an IPv6 connected is uninstalled via
vty.

Signed-off-by: Christian Franke <chris@opensourcerouting.org>
Signed-off-by: David Lamparter <equinox@opensourcerouting.org>
zebra: consolidate connected_implicit_withdraw

connected_implicit_withdraw is used at two places and followed by exactly
the same code. Move that code into connected_implicit_withdraw and give
that function a more descriptive name.

Signed-off-by: Christian Franke <chris@opensourcerouting.org>
Signed-off-by: David Lamparter <equinox@opensourcerouting.org>
zebra: warn if advertising connected with _REAL unset

The implementation in zebra and the zclient protocol allow to communicate
addresses to clients which are not yet in the kernel.

This is usually not done and most clients seem to expect an address to be
configured in the kernel when they receive it. Therefore, it seems
reasonable to issue a warning when advertising an address to the clients
that is not yet in the kernel.

Signed-off-by: Christian Franke <chris@opensourcerouting.org>
Signed-off-by: David Lamparter <equinox@opensourcerouting.org>
zebra: add ZEBRA_IFC_QUEUED to keep track of kernel state

As there are timeframes when we don't get a notification from the kernel
about new addresses. (e.g. while Linux performs IPv6 DAD), we need to
have some information whether an address has been sent to the kernel or
not.

One case where this is relevant would be a user adding an IPv6 address,
but deleting it before DAD has been complete. With the next patch which
removes some (ill assuming) synchronous parts in address setup,
ipv6_address_uninstall would not know whether or not it has to actually
delete the prefix from the kernel. Resolving these windows where we lack
information is what the flag ZEBRA_IFC_QUEUED is intended for.

Signed-off-by: Christian Franke <chris@opensourcerouting.org>
Signed-off-by: David Lamparter <equinox@opensourcerouting.org>
zebra: don't change connected state from zebra/interface.c

Try to avoid changing connected state from zebra/interface.c as this
means making assumptions about kernel behaviour which may be or may
become wrong. This state should rather be updated by events from the
kernel.

Signed-off-by: Christian Franke <chris@opensourcerouting.org>
Signed-off-by: David Lamparter <equinox@opensourcerouting.org>
zebra: improve interface shutdown behaviour

Linux removes IPv6 addresses when the interface is set down. Those
addresses need to be readded when the interface is set up again.

Also, an interface should not be reactivated from shutdown by configuring
an ip address.

Finally, remove the three-state logic for the shutdown setting as its
sole current use may be mild confusion.

Signed-off-by: Christian Franke <chris@opensourcerouting.org>
Signed-off-by: David Lamparter <equinox@opensourcerouting.org>