linux.git/net/tipc, branch v5.4-rc2

tipc: fix unlimited bundling of small messages

2019-10-02T15:02:05+00:00

We have identified a problem with the "oversubscription" policy in the
link transmission code.

When small messages are transmitted, and the sending link has reached
the transmit window limit, those messages will be bundled and put into
the link backlog queue. However, bundles of data messages are counted
at the 'CRITICAL' level, so that the counter for that level, instead of
the counter for the real, bundled message's level is the one being
increased.
Subsequent, to-be-bundled data messages at non-CRITICAL levels continue
to be tested against the unchanged counter for their own level, while
contributing to an unrestrained increase at the CRITICAL backlog level.

This leaves a gap in congestion control algorithm for small messages
that can result in starvation for other users or a "real" CRITICAL
user. Even that eventually can lead to buffer exhaustion & link reset.

We fix this by keeping a 'target_bskb' buffer pointer at each levels,
then when bundling, we only bundle messages at the same importance
level only. This way, we know exactly how many slots a certain level
have occupied in the queue, so can manage level congestion accurately.

By bundling messages at the same level, we even have more benefits. Let
consider this:
- One socket sends 64-byte messages at the 'CRITICAL' level;
- Another sends 4096-byte messages at the 'LOW' level;

When a 64-byte message comes and is bundled the first time, we put the
overhead of message bundle to it (+ 40-byte header, data copy, etc.)
for later use, but the next message can be a 4096-byte one that cannot
be bundled to the previous one. This means the last bundle carries only
one payload message which is totally inefficient, as for the receiver
also! Later on, another 64-byte message comes, now we make a new bundle
and the same story repeats...

With the new bundling algorithm, this will not happen, the 64-byte
messages will be bundled together even when the 4096-byte message(s)
comes in between. However, if the 4096-byte messages are sent at the
same level i.e. 'CRITICAL', the bundling algorithm will again cause the
same overhead.

Also, the same will happen even with only one socket sending small
messages at a rate close to the link transmit's one, so that, when one
message is bundled, it's transmitted shortly. Then, another message
comes, a new bundle is created and so on...

We will solve this issue radically by another patch.

Fixes: 365ad353c256 ("tipc: reduce risk of user starvation during link congestion")
Reported-by: Hoang Le 
Acked-by: Jon Maloy 
Signed-off-by: Tuong Lien 
Signed-off-by: David S. Miller

Merge git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net

2019-09-15T12:17:27+00:00

Minor overlapping changes in the btusb and ixgbe drivers.

Signed-off-by: David S. Miller

tipc: add NULL pointer check before calling kfree_rcu

2019-09-05T07:58:49+00:00

Unlike kfree(p), kfree_rcu(p, rcu) won't do NULL pointer check. When
tipc_nametbl_remove_publ returns NULL, the panic below happens:

   BUG: unable to handle kernel NULL pointer dereference at 0000000000000068
   RIP: 0010:__call_rcu+0x1d/0x290
   Call Trace:
    
    tipc_publ_notify+0xa9/0x170 [tipc]
    tipc_node_write_unlock+0x8d/0x100 [tipc]
    tipc_node_link_down+0xae/0x1d0 [tipc]
    tipc_node_check_dest+0x3ea/0x8f0 [tipc]
    ? tipc_disc_rcv+0x2c7/0x430 [tipc]
    tipc_disc_rcv+0x2c7/0x430 [tipc]
    ? tipc_rcv+0x6bb/0xf20 [tipc]
    tipc_rcv+0x6bb/0xf20 [tipc]
    ? ip_route_input_slow+0x9cf/0xb10
    tipc_udp_recv+0x195/0x1e0 [tipc]
    ? tipc_udp_is_known_peer+0x80/0x80 [tipc]
    udp_queue_rcv_skb+0x180/0x460
    udp_unicast_rcv_skb.isra.56+0x75/0x90
    __udp4_lib_rcv+0x4ce/0xb90
    ip_local_deliver_finish+0x11c/0x210
    ip_local_deliver+0x6b/0xe0
    ? ip_rcv_finish+0xa9/0x410
    ip_rcv+0x273/0x362

Fixes: 97ede29e80ee ("tipc: convert name table read-write lock to RCU")
Reported-by: Li Shuang 
Signed-off-by: Xin Long 
Signed-off-by: David S. Miller

Merge git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net

2019-08-19T18:54:03+00:00

Merge conflict of mlx5 resolved using instructions in merge
commit 9566e650bf7fdf58384bb06df634f7531ca3a97e.

Signed-off-by: David S. Miller

tipc: clean up skb list lock handling on send path

2019-08-18T21:01:07+00:00

The policy for handling the skb list locks on the send and receive paths
is simple.

- On the send path we never need to grab the lock on the 'xmitq' list
  when the destination is an exernal node.

- On the receive path we always need to grab the lock on the 'inputq'
  list, irrespective of source node.

However, when transmitting node local messages those will eventually
end up on the receive path of a local socket, meaning that the argument
'xmitq' in tipc_node_xmit() will become the 'ínputq' argument in  the
function tipc_sk_rcv(). This has been handled by always initializing
the spinlock of the 'xmitq' list at message creation, just in case it
may end up on the receive path later, and despite knowing that the lock
in most cases never will be used.

This approach is inaccurate and confusing, and has also concealed the
fact that the stated 'no lock grabbing' policy for the send path is
violated in some cases.

We now clean up this by never initializing the lock at message creation,
instead doing this at the moment we find that the message actually will
enter the receive path. At the same time we fix the four locations
where we incorrectly access the spinlock on the send/error path.

This patch also reverts commit d12cffe9329f ("tipc: ensure head->lock
is initialised") which has now become redundant.

CC: Eric Dumazet 
Reported-by: Chris Packham 
Acked-by: Ying Xue 
Signed-off-by: Jon Maloy 
Reviewed-by: Xin Long 
Signed-off-by: David S. Miller

tipc: fix false detection of retransmit failures

2019-08-16T23:27:13+00:00

This commit eliminates the use of the link 'stale_limit' & 'prev_from'
(besides the already removed - 'stale_cnt') variables in the detection
of repeated retransmit failures as there is no proper way to initialize
them to avoid a false detection, i.e. it is not really a retransmission
failure but due to a garbage values in the variables.

Instead, a jiffies variable will be added to individual skbs (like the
way we restrict the skb retransmissions) in order to mark the first skb
retransmit time. Later on, at the next retransmissions, the timestamp
will be checked to see if the skb in the link transmq is "too stale",
that is, the link tolerance time has passed, so that a link reset will
be ordered. Note, just checking on the first skb in the queue is fine
enough since it must be the oldest one.
A counter is also added to keep track the actual skb retransmissions'
number for later checking when the failure happens.

The downside of this approach is that the skb->cb[] buffer is about to
be exhausted, however it is always able to allocate another memory area
and keep a reference to it when needed.

Fixes: 77cf8edbc0e7 ("tipc: simplify stale link failure criteria")
Reported-by: Hoang Le 
Acked-by: Ying Xue 
Acked-by: Jon Maloy 
Signed-off-by: Tuong Lien 
Signed-off-by: David S. Miller

tipc: initialise addr_trail_end when setting node addresses

2019-08-12T04:40:04+00:00

We set the field 'addr_trial_end' to 'jiffies', instead of the current
value 0, at the moment the node address is initialized. This guarantees
we don't inadvertently enter an address trial period when the node
address is explicitly set by the user.

Signed-off-by: Chris Packham 
Acked-by: Jon Maloy 
Signed-off-by: David S. Miller

tipc: add loopback device tracking

2019-08-09T05:11:39+00:00

Since node internal messages are passed directly to the socket, it is not
possible to observe those messages via tcpdump or wireshark.

We now remedy this by making it possible to clone such messages and send
the clones to the loopback interface.  The clones are dropped at reception
and have no functional role except making the traffic visible.

The feature is enabled if network taps are active for the loopback device.
pcap filtering restrictions require the messages to be presented to the
receiving side of the loopback device.

v3 - Function dev_nit_active used to check for network taps.
   - Procedure netif_rx_ni used to send cloned messages to loopback device.

Signed-off-by: John Rutherford 
Acked-by: Jon Maloy 
Acked-by: Ying Xue 
Signed-off-by: David S. Miller

Merge git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net

2019-08-07T01:44:57+00:00

Just minor overlapping changes in the conflicts here.

Signed-off-by: David S. Miller

tipc: reduce risk of wakeup queue starvation

2019-08-01T22:19:28+00:00

In commit 365ad353c256 ("tipc: reduce risk of user starvation during
link congestion") we allowed senders to add exactly one list of extra
buffers to the link backlog queues during link congestion (aka
"oversubscription"). However, the criteria for when to stop adding
wakeup messages to the input queue when the overload abates is
inaccurate, and may cause starvation problems during very high load.

Currently, we stop adding wakeup messages after 10 total failed attempts
where we find that there is no space left in the backlog queue for a
certain importance level. The counter for this is accumulated across all
levels, which may lead the algorithm to leave the loop prematurely,
although there may still be plenty of space available at some levels.
The result is sometimes that messages near the wakeup queue tail are not
added to the input queue as they should be.

We now introduce a more exact algorithm, where we keep adding wakeup
messages to a level as long as the backlog queue has free slots for
the corresponding level, and stop at the moment there are no more such
slots or when there are no more wakeup messages to dequeue.

Fixes: 365ad35 ("tipc: reduce risk of user starvation during link congestion")
Reported-by: Tung Nguyen 
Acked-by: Ying Xue 
Signed-off-by: Jon Maloy 
Signed-off-by: David S. Miller