linux-toradex.git/net/tipc/link.c, branch v4.0.2

tipc: fix bug in link failover handling

2015-03-09T20:20:41+00:00

In commit c637c1035534867b85b78b453c38c495b58e2c5a
("tipc: resolve race problem at unicast message reception") we
introduced a new mechanism for delivering buffers upwards from link
to socket layer.

That code contains a bug in how we handle the new link input queue
during failover. When a link is reset, some of its users may be blocked
because of congestion, and in order to resolve this, we add any pending
wakeup pseudo messages to the link's input queue, and deliver them to
the socket. This misses the case where the other, remaining link also
may have congested users. Currently, the owner node's reference to the
remaining link's input queue is unconditionally overwritten by the
reset link's input queue. This has the effect that wakeup events from
the remaining link may be unduely delayed (but not lost) for a
potentially long period.

We fix this by adding the pending events from the reset link to the
input queue that is currently referenced by the node, whichever one
it is.

This commit should be applied to both net and net-next.

Signed-off-by: Jon Maloy 
Signed-off-by: David S. Miller

tipc: nl compat add noop and remove legacy nl framework

2015-02-09T21:20:49+00:00

Add TIPC_CMD_NOOP to compat layer and remove the old framework.

All legacy nl commands are now converted to the compat layer in
netlink_compat.c.

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 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: move and rename the legacy nl api to "nl compat"

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

The new netlink API is no longer "v2" but rather the standard API and
the legacy API is now "nl compat". We split them into separate
start/stop and put them in different files in order to further
distinguish them.

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

tipc: separate link starting event from link timeout event

2015-02-05T00:09:31+00:00

When a new link instance is created, it is trigged to start by
sending it a TIPC_STARTING_EVT, whereafter a regular link
reset is applied to it.

The starting event is codewise treated as a timeout event, and prompts
a link RESET message to be sent to the peer node, carrying a link
session identifier. The later link_reset() call nudges this session
identifier, whereafter all subsequent RESET messages will be sent out
with the new identifier. The latter session number overrides the former,
causing the peer to unconditionally accept it irrespective of its
current working state.

We don't think that this causes any problem, but it is not in accordance
with the protocol spec, and may cause confusion when debugging TIPC
sessions.

To avoid this, we make the starting event distinct from the
subsequent timeout events, by not allowing the former to send
out any RESET message. This eliminates the described problem.

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

tipc: add reference count to struct tipc_link

2015-02-05T00:09:31+00:00

When a bearer is disabled, all pertaining links will be reset and
deleted. However, if there is a second active link towards a killed
link's destination, the delete has to be postponed until the failover
is finished. During this interval, we currently put the link in zombie
mode, i.e., we take it out of traffic, delete its timer, but leave it
attached to the owner node structure until all missing packets have
been received.  When this is done, we detach the link from its node
and delete it, assuming that the synchronous timer deletion that was
initiated earlier in a different thread has finished.

This is unsafe, as the failover may finish before del_timer_sync()
has returned in the other thread.

We fix this by adding an atomic reference counter of type kref in
struct tipc_link. The counter keeps track of the references kept
to the link by the owner node and the timer. We then do a conditional
delete, based on the reference counter, both after the failover has
been finished and when the timer expires, if applicable. Whoever
comes last, will actually delete the link. This approach also implies
that we can make the deletion of the timer asynchronous.

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