linux-stable.git/net/dccp/options.c, branch linux-3.2.y

dccp: handle invalid feature options length

2011-05-06T20:05:50+00:00

A length of zero (after subtracting two for the type and len fields) for
the DCCPO_{CHANGE,CONFIRM}_{L,R} options will cause an underflow due to
the subtraction.  The subsequent code may read past the end of the
options value buffer when parsing.  I'm unsure of what the consequences
of this might be, but it's probably not good.

Signed-off-by: Dan Rosenberg 
Cc: stable@kernel.org
Acked-by: Gerrit Renker 
Signed-off-by: David S. Miller

dccp ccid-2: Separate option parsing from CCID processing

2010-11-15T06:12:01+00:00

This patch replaces an almost identical replication of code: large parts
of dccp_parse_options() re-appeared as ccid2_ackvector() in ccid2.c.

Apart from the duplication, this caused two more problems:
 1. CCIDs should not need to be concerned with parsing header options;
 2. one can not assume that Ack Vectors appear as a contiguous area within an
    skb, it is legal to insert other options and/or padding in between. The
    current code would throw an error and stop reading in such a case.

Since Ack Vectors provide CCID-specific information, they are now processed
by the CCID directly, separating this functionality from the main DCCP code.

Signed-off-by: Gerrit Renker

dccp ccid-2: Schedule Sync as out-of-band mechanism

2010-11-15T06:12:00+00:00

The problem with Ack Vectors is that
  i) their length is variable and can in principle grow quite large,
 ii) it is hard to predict exactly how large they will be.

Due to the second point it seems not a good idea to reduce the MPS; in
particular when on average there is enough room for the Ack Vector and an
increase in length is momentarily due to some burst loss, after which the
Ack Vector returns to its normal/average length.

The solution taken by this patch is to subtract a minimum-expected Ack Vector
length from the MPS, and to defer any larger Ack Vectors onto a separate
Sync - but only if indeed there is no space left on the skb.

This patch provides the infrastructure to schedule Sync-packets for transporting
(urgent) out-of-band data. Its signalling is quicker than scheduling an Ack, since
it does not need to wait for new application data.

Signed-off-by: Gerrit Renker

dccp ccid-2: Algorithm to update buffer state

2010-11-15T06:11:59+00:00

This provides a routine to consistently update the buffer state when the
peer acknowledges receipt of Ack Vectors; updating state in the list of Ack
Vectors as well as in the circular buffer.

While based on RFC 4340, several additional (and necessary) precautions were
added to protect the consistency of the buffer state. These additions are
essential, since analysis and experience showed that the basic algorithm was
insufficient for this task (which lead to problems that were hard to debug).

The algorithm now
 * deals with HC-sender acknowledging to HC-receiver and vice versa,
 * keeps track of the last unacknowledged but received seqno in tail_ackno,
 * has special cases to reset the overflow condition when appropriate,
 * is protected against receiving older information (would mess up buffer state).

Signed-off-by: Gerrit Renker

dccp ccid-2: Implementation of circular Ack Vector buffer with overflow handling

2010-11-10T20:21:35+00:00

This completes the implementation of a circular buffer for Ack Vectors, by
extending the current (linear array-based) implementation.  The changes are:

 (a) An `overflow' flag to deal with the case of overflow. As before, dynamic
     growth of the buffer will not be supported; but code will be added to deal
     robustly with overflowing Ack Vector buffers.

 (b) A `tail_seqno' field. When naively implementing the algorithm of Appendix A
     in RFC 4340, problems arise whenever subsequent Ack Vector records overlap,
     which can bring the entire run length calculation completely out of synch.
     (This is documented on http://www.erg.abdn.ac.uk/users/gerrit/dccp/notes/\
                                             ack_vectors/tracking_tail_ackno/ .)
 (c) The buffer length is now computed dynamically (i.e. current fill level),
     as the span between head to tail.

As a result, dccp_ackvec_pending() is now simpler - the #ifdef is no longer
necessary since buf_empty is always true when IP_DCCP_ACKVEC is not configured.

Signed-off-by: Gerrit Renker

dccp ccid-2: Separate internals of Ack Vectors from option-parsing code

2010-11-10T20:21:02+00:00

This patch
 * separates Ack Vector housekeeping code from option-insertion code;
 * shifts option-specific code from ackvec.c into options.c;
 * introduces a dedicated routine to take care of the Ack Vector records;
 * simplifies the dccp_ackvec_insert_avr() routine: the BUG_ON was redundant,
   since the list is automatically arranged in descending order of ack_seqno.

Signed-off-by: Gerrit Renker

dccp ccid-2: Ack Vector interface clean-up

2010-11-10T20:20:07+00:00

This patch brings the Ack Vector interface up to date. Its main purpose is
to lay the basis for the subsequent patches of this set, which will use the
new data structure fields and routines.

There are no real algorithmic changes, rather an adaptation:

 (1) Replaced the static Ack Vector size (2) with a #define so that it can
     be adapted (with low loss / Ack Ratio, a value of 1 works, so 2 seems
     to be sufficient for the moment) and added a solution so that computing
     the ECN nonce will continue to work - even with larger Ack Vectors.

 (2) Replaced the #defines for Ack Vector states with a complete enum.

 (3) Replaced #defines to compute Ack Vector length and state with general
     purpose routines (inlines), and updated code to use these.

 (4) Added a `tail' field (conversion to circular buffer in subsequent patch).

 (5) Updated the (outdated) documentation for Ack Vector struct.

 (6) All sequence number containers now trimmed to 48 bits.

 (7) Removal of unused bits:
     * removed dccpav_ack_nonce from struct dccp_ackvec, since this is already
       redundantly stored in the `dccpavr_ack_nonce' (of Ack Vector record);
     * removed Elapsed Time for Ack Vectors (it was nowhere used);
     * replaced semantics of dccpavr_sent_len with dccpavr_ack_runlen, since
       the code needs to be able to remember the old run length;
     * reduced the de-/allocation routines (redundant / duplicate tests).

Signed-off-by: Gerrit Renker

dccp: schedule an Ack when receiving timestamps

2010-10-12T04:57:43+00:00

This schedules an Ack when receiving a timestamp, exploiting the
existing inet_csk_schedule_ack() function, saving one case in the
`dccp_ack_pending()' function.

Signed-off-by: Gerrit Renker

dccp: Kill dead code and add static markers.

2010-10-07T06:12:07+00:00

Remove dead code and make some functions static.
Compile tested only.

Signed-off-by: Stephen Hemminger 
Signed-off-by: David S. Miller

dccp: Replace magic CCID-specific numbers by symbolic constants

2010-09-21T10:14:25+00:00

The constants DCCPO_{MIN,MAX}_CCID_SPECIFIC are nowhere used in the code, but
instead for the CCID-specific options numbers are used.

This patch unifies the use of CCID-specific option numbers, by adding symbolic
names reflecting the definitions in RFC 4340, 10.3.

Signed-off-by: Gerrit Renker