tipc: implement configuration of UDP media MTU

In previous commit, we changed the default emulated MTU for UDP bearers
to 14k.

This commit adds the functionality to set/change the default value
by configuring new MTU for UDP media. UDP bearer(s) have to be disabled
and enabled back for the new MTU to take effect.

Acked-by: Ying Xue <ying.xue@windriver.com>
Acked-by: Jon Maloy <jon.maloy@ericsson.com>
Signed-off-by: GhantaKrishnamurthy MohanKrishna <mohan.krishna.ghanta.krishnamurthy@ericsson.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

tipc: add UDP remoteip dump to netlink API

When using replicast a UDP bearer can have an arbitrary amount of
remote ip addresses associated with it. This means we cannot simply
add all remote ip addresses to an existing bearer data message as it
might fill the message, leaving us with a truncated message that we
can't safely resume. To handle this we introduce the new netlink
command TIPC_NL_UDP_GET_REMOTEIP. This command is intended to be
called when the bearer data message has the
TIPC_NLA_UDP_MULTI_REMOTEIP flag set, indicating there are more than
one remote ip (replicast).

Signed-off-by: Richard Alpe <richard.alpe@ericsson.com>
Reviewed-by: Jon Maloy <jon.maloy@ericsson.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

tipc: add the ability to get UDP options via netlink

Add UDP bearer options to netlink bearer get message. This is used by
the tipc user space tool to display UDP options.

The UDP bearer information is passed using either a sockaddr_in or
sockaddr_in6 structs. This means the user space receiver should
intermediately store the retrieved data in a large enough struct
(sockaddr_strage) before casting to the proper IP version type.

Signed-off-by: Richard Alpe <richard.alpe@ericsson.com>
Reviewed-by: Jon Maloy <jon.maloy@ericsson.com>
Acked-by: Ying Xue <ying.xue@windriver.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

tipc: introduce UDP replicast

This patch introduces UDP replicast. A concept where we emulate
multicast by sending multiple unicast messages to configured peers.

The purpose of replicast is mainly to be able to use TIPC in cloud
environments where IP multicast is disabled. Using replicas to unicast
multicast messages is costly as we have to copy each skb and send the
copies individually.

Signed-off-by: Richard Alpe <richard.alpe@ericsson.com>
Reviewed-by: Jon Maloy <jon.maloy@ericsson.com>
Signed-off-by: David S. Miller <davem@davemloft.net>