linux-stable.git/net/tipc/link.h, branch linux-4.2.y

tipc: purge backlog queue counters when broadcast link is reset

2015-06-28T23:43:02+00:00

In commit 1f66d161ab3d8b518903fa6c3f9c1f48d6919e74
("tipc: introduce starvation free send algorithm")
we introduced a counter per priority level for buffers
in the link backlog queue. We also introduced a new
function tipc_link_purge_backlog(), to reset these
counters to zero when the link is reset.

Unfortunately, we missed to call this function when
the broadcast link is reset, with the result that the
values of these counters might be permanently skewed
when new nodes are attached. This may in the worst case
lead to permananent, but spurious, broadcast link
congestion, where no broadcast packets can be sent at
all.

We fix this bug with this commit.

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

tipc: simplify link supervision checkpointing

2015-05-14T16:24:46+00:00

We change the sequence number checkpointing that is performed
by the timer in order to discover if the peer is active. Currently,
we store a checkpoint of the next expected sequence number "rcv_nxt"
at each timer expiration, and compare it to the current expected
number at next timeout expiration. Instead, we now use the already
existing field "silent_intv_cnt" for this task. We step the counter
at each timeout expiration, and zero it at each valid received packet.
If no valid packet has been received from the peer after "abort_limit"
number of silent timer intervals, the link is declared faulty and reset.

We also remove the multiple instances of timer activation from inside
the FSM function "link_state_event()", and now do it at only one place;
at the end of the timer function itself.

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

tipc: rename fields in struct tipc_link

2015-05-14T16:24:46+00:00

We rename some fields in struct tipc_link, in order to give them more
descriptive names:

next_in_no -> rcv_nxt
next_out_no-> snd_nxt
fsm_msg_cnt-> silent_intv_cnt
cont_intv  -> keepalive_intv
last_retransmitted -> last_retransm

There are no functional changes in this commit.

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

tipc: simplify packet sequence number handling

2015-05-14T16:24:46+00:00

Although the sequence number in the TIPC protocol is 16 bits, we have
until now stored it internally as an unsigned 32 bits integer.
We got around this by always doing explicit modulo-65535 operations
whenever we need to access a sequence number.

We now make the incoming and outgoing sequence numbers to unsigned
16-bit integers, and remove the modulo operations where applicable.

We also move the arithmetic inline functions for 16 bit integers
to core.h, and the function buf_seqno() to msg.h, so they can easily
be accessed from anywhere in the code.

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

tipc: simplify resetting and disabling of bearers

2015-05-14T16:24:45+00:00

Since commit 4b475e3f2f8e4e241de101c8240f1d74d0470494
("tipc: eliminate delayed link deletion at link failover") the extra
boolean parameter "shutting_down" is not any longer needed for the
functions bearer_disable() and tipc_link_delete_list().

Furhermore, the function tipc_link_reset_links(), called from
bearer_reset()  is now unnecessary. We can just as well delete
all the links, as we do in bearer_disable(), and start over with
creating new links.

This commit introduces those changes.

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

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