Skip to content

L
linux
Switch branch/tag
  1. 08 Nov, 2013 36 commits
  3. 07 Nov, 2013 4 commits
    • David S. Miller's avatar
      Merge branch 'tipc_fragmentation' · 95ed4019
      David S. Miller authored 
      Erik Hugne says:

====================
tipc: message reassembly using fragment chain

We introduce a new reassembly algorithm that improves performance
and eliminates the risk of causing out-of-memory situations.

v3: -Use skb_try_coalesce, and revert to fraglist if this does not succeed.
    -Make sure reassembly list head is uncloned.

v2: -Rebased on Ying's indentation fix.
    -Node unlock call in msg_fragmenter case moved from patch #2 to #1.
     ('continue' with this lock held would cause spinlock recursion if only
      patch #1 is used)
====================
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
      95ed4019
    • Erik Hugne's avatar
      tipc: reassembly failures should cause link reset · a715b49e
      Erik Hugne authored 
      If appending a received fragment to the pending fragment chain
in a unicast link fails, the current code tries to force a retransmission
of the fragment by decrementing the 'next received sequence number'
field in the link. This is done under the assumption that the failure
is caused by an out-of-memory situation, an assumption that does
not hold true after the previous patch in this series.

A failure to append a fragment can now only be caused by a protocol
violation by the sending peer, and it must hence be assumed that it
is either malicious or buggy.  Either way, the correct behavior is now
to reset the link instead of trying to revert its sequence number.
So, this is what we do in this commit.
Signed-off-by: default avatarErik Hugne <erik.hugne@ericsson.com>
Reviewed-by: default avatarPaul Gortmaker <paul.gortmaker@windriver.com>
Signed-off-by: default avatarJon Maloy <jon.maloy@ericsson.com>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
      a715b49e
    • Erik Hugne's avatar
      tipc: message reassembly using fragment chain · 40ba3cdf
      Erik Hugne authored 
      When the first fragment of a long data data message is received on a link, a
reassembly buffer large enough to hold the data from this and all subsequent
fragments of the message is allocated. The payload of each new fragment is
copied into this buffer upon arrival. When the last fragment is received, the
reassembled message is delivered upwards to the port/socket layer.

Not only is this an inefficient approach, but it may also cause bursts of
reassembly failures in low memory situations. since we may fail to allocate
the necessary large buffer in the first place. Furthermore, after 100 subsequent
such failures the link will be reset, something that in reality aggravates the
situation.

To remedy this problem, this patch introduces a different approach. Instead of
allocating a big reassembly buffer, we now append the arriving fragments
to a reassembly chain on the link, and deliver the whole chain up to the
socket layer once the last fragment has been received. This is safe because
the retransmission layer of a TIPC link always delivers packets in strict
uninterrupted order, to the reassembly layer as to all other upper layers.
Hence there can never be more than one fragment chain pending reassembly at
any given time in a link, and we can trust (but still verify) that the
fragments will be chained up in the correct order.
Signed-off-by: default avatarErik Hugne <erik.hugne@ericsson.com>
Reviewed-by: default avatarPaul Gortmaker <paul.gortmaker@windriver.com>
Signed-off-by: default avatarJon Maloy <jon.maloy@ericsson.com>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
      40ba3cdf
    • Erik Hugne's avatar
      tipc: don't reroute message fragments · 528f6f4b
      Erik Hugne authored 
      When a message fragment is received in a broadcast or unicast link,
the reception code will append the fragment payload to a big reassembly
buffer through a call to the function tipc_recv_fragm(). However, after
the return of that call, the logics goes on and passes the fragment
buffer to the function tipc_net_route_msg(), which will simply drop it.
This behavior is a remnant from the now obsolete multi-cluster
functionality, and has no relevance in the current code base.

Although currently harmless, this unnecessary call would be fatal
after applying the next patch in this series, which introduces
a completely new reassembly algorithm. So we change the code to
eliminate the redundant call.
Signed-off-by: default avatarErik Hugne <erik.hugne@ericsson.com>
Reviewed-by: default avatarPaul Gortmaker <paul.gortmaker@windriver.com>
Signed-off-by: default avatarJon Maloy <jon.maloy@ericsson.com>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
      528f6f4b
GitLab Nexedi Edition | About GitLab | About Nexedi | 沪ICP备2021021310号-2 | 沪ICP备2021021310号-7