linux-toradex.git/net/tipc/link.h, branch v4.1.10

tipc: simplify link mtu negotiation

2015-04-02T20:27:12+00:00

When a link is being established, the two endpoints advertise their
respective interface MTU in the transmitted RESET and ACTIVATE messages.
If there is any difference, the lower of the two MTUs will be selected
for use by both endpoints.

However, as a remnant of earlier attempts to introduce TIPC level
routing. there also exists an MTU discovery mechanism. If an intermediate
node has a lower MTU than the two endpoints, they will discover this
through a bisectional approach, and finally adopt this MTU for common use.

Since there is no TIPC level routing, and probably never will be,
this mechanism doesn't make any sense, and only serves to make the
link level protocol unecessarily complex.

In this commit, we eliminate the MTU discovery algorithm,and fall back
to the simple MTU advertising approach. This change is fully backwards
compatible.

Reviewed-by: Ying Xue 
Signed-off-by: Jon Maloy 
Signed-off-by: David S. Miller

tipc: eliminate delayed link deletion at link failover

2015-04-02T20:27:12+00:00

When a bearer is disabled manually, all its links have to be reset
and deleted. However, if there is a remaining, parallel link ready
to take over a deleted link's traffic, we currently delay the delete
of the removed link until the failover procedure is finished. This
is because the remaining link needs to access state from the reset
link, such as the last received packet number, and any partially
reassembled buffer, in order to perform a successful failover.

In this commit, we do instead move the state data over to the new
link, so that it can fulfill the procedure autonomously, without
accessing any data on the old link. This means that we can now
proceed and delete all pertaining links immediately when a bearer
is disabled. This saves us from some unnecessary complexity in such
situations.

We also choose to change the confusing definitions CHANGEOVER_PROTOCOL,
ORIGINAL_MSG and DUPLICATE_MSG to the more descriptive TUNNEL_PROTOCOL,
FAILOVER_MSG and SYNCH_MSG respectively.

Reviewed-by: Ying Xue 
Signed-off-by: Jon Maloy 
Signed-off-by: David S. Miller

tipc: eliminate race condition at dual link establishment

2015-03-25T18:05:56+00:00

Despite recent improvements, the establishment of dual parallel
links still has a small glitch where messages can bypass each
other. When the second link in a dual-link configuration is
established, part of the first link's traffic will be steered over
to the new link. Although we do have a mechanism to ensure that
packets sent before and after the establishment of the new link
arrive in sequence to the destination node, this is not enough.
The arriving messages will still be delivered upwards in different
threads, something entailing a risk of message disordering during
the transition phase.

To fix this, we introduce a synchronization mechanism between the
two parallel links, so that traffic arriving on the new link cannot
be added to its input queue until we are guaranteed that all
pre-establishment messages have been delivered on the old, parallel
link.

This problem seems to always have been around, but its occurrence is
so rare that it has not been noticed until recent intensive testing.

Reviewed-by: Ying Xue 
Reviewed-by: Erik Hugne 
Signed-off-by: Jon Maloy 
Signed-off-by: David S. Miller

tipc: introduce starvation free send algorithm

2015-03-25T18:05:56+00:00

Currently, we only use a single counter; the length of the backlog
queue, to determine whether a message should be accepted to the queue
or not. Each time a message is being sent, the queue length is compared
to a threshold value for the message's importance priority. If the queue
length is beyond this threshold, the message is rejected. This algorithm
implies a risk of starvation of low importance senders during very high
load, because it may take a long time before the backlog queue has
decreased enough to accept a lower level message.

We now eliminate this risk by introducing a counter for each importance
priority. When a message is sent, we check only the queue level for that
particular message's priority. If that is ok, the message can be added
to the backlog, irrespective of the queue level for other priorities.
This way, each level is guaranteed a certain portion of the total
bandwidth, and any risk of starvation is eliminated.

Reviewed-by: Ying Xue 
Reviewed-by: Erik Hugne 
Signed-off-by: Jon Maloy 
Signed-off-by: David S. Miller

tipc: split link outqueue

2015-03-14T18:38:32+00:00

struct tipc_link contains one single queue for outgoing packets,
where both transmitted and waiting packets are queued.

This infrastructure is hard to maintain, because we need
to keep a number of fields to keep track of which packets are
sent or unsent, and the number of packets in each category.

A lot of code becomes simpler if we split this queue into a transmission
queue, where sent/unacknowledged packets are kept, and a backlog queue,
where we keep the not yet sent packets.

In this commit we do this separation.

Reviewed-by: Erik Hugne 
Reviewed-by: Ying Xue 
Signed-off-by: Jon Maloy 
Signed-off-by: David S. Miller

tipc: convert legacy nl link stat reset to nl compat

2015-02-09T21:20:48+00:00

Convert TIPC_CMD_RESET_LINK_STATS to compat doit.

Signed-off-by: Richard Alpe 
Reviewed-by: Erik Hugne 
Reviewed-by: Ying Xue 
Reviewed-by: Jon Maloy 
Signed-off-by: David S. Miller

tipc: convert legacy nl link prop set to nl compat

2015-02-09T21:20:48+00:00

Convert setting of link proprieties to compat doit calls.

Commands converted in this patch:
TIPC_CMD_SET_LINK_TOL
TIPC_CMD_SET_LINK_PRI
TIPC_CMD_SET_LINK_WINDOW

Signed-off-by: Richard Alpe 
Reviewed-by: Erik Hugne 
Reviewed-by: Ying Xue 
Reviewed-by: Jon Maloy 
Signed-off-by: David S. Miller

tipc: convert legacy nl link stat to nl compat

2015-02-09T21:20:47+00:00

Add functionality for safely appending string data to a TLV without
keeping write count in the caller.

Convert TIPC_CMD_SHOW_LINK_STATS to compat dumpit.

Signed-off-by: Richard Alpe 
Reviewed-by: Erik Hugne 
Reviewed-by: Ying Xue 
Reviewed-by: Jon Maloy 
Signed-off-by: David S. Miller

tipc: resolve race problem at unicast message reception

2015-02-06T00:00:02+00:00

TIPC handles message cardinality and sequencing at the link layer,
before passing messages upwards to the destination sockets. During the
upcall from link to socket no locks are held. It is therefore possible,
and we see it happen occasionally, that messages arriving in different
threads and delivered in sequence still bypass each other before they
reach the destination socket. This must not happen, since it violates
the sequentiality guarantee.

We solve this by adding a new input buffer queue to the link structure.
Arriving messages are added safely to the tail of that queue by the
link, while the head of the queue is consumed, also safely, by the
receiving socket. Sequentiality is secured per socket by only allowing
buffers to be dequeued inside the socket lock. Since there may be multiple
simultaneous readers of the queue, we use a 'filter' parameter to reduce
the risk that they peek the same buffer from the queue, hence also
reducing the risk of contention on the receiving socket locks.

This solves the sequentiality problem, and seems to cause no measurable
performance degradation.

A nice side effect of this change is that lock handling in the functions
tipc_rcv() and tipc_bcast_rcv() now becomes uniform, something that
will enable future simplifications of those functions.

Reviewed-by: Ying Xue 
Signed-off-by: Jon Maloy 
Signed-off-by: David S. Miller

tipc: reduce usage of context info in socket and link

2015-02-06T00:00:01+00:00

The most common usage of namespace information is when we fetch the
own node addess from the net structure. This leads to a lot of
passing around of a parameter of type 'struct net *' between
functions just to make them able to obtain this address.

However, in many cases this is unnecessary. The own node address
is readily available as a member of both struct tipc_sock and
tipc_link, and can be fetched from there instead.
The fact that the vast majority of functions in socket.c and link.c
anyway are maintaining a pointer to their respective base structures
makes this option even more compelling.

In this commit, we introduce the inline functions tsk_own_node()
and link_own_node() to make it easy for functions to fetch the node
address from those structs instead of having to pass along and
dereference the namespace struct.

In particular, we make calls to the msg_xx() functions in msg.{h,c}
context independent by directly passing them the own node address
as parameter when needed. Those functions should be regarded as
leaves in the code dependency tree, and it is hence desirable to
keep them namspace unaware.

Apart from a potential positive effect on cache behavior, these
changes make it easier to introduce the changes that will follow
later in this series.

Reviewed-by: Ying Xue 
Signed-off-by: Jon Maloy 
Signed-off-by: David S. Miller