This patch deprecates the existing use of an arbitrary value TFRC_SMALLEST_P
 for low-threshold values of p. This avoids masking low-resolution errors.
 Instead, the code now checks against real boundaries (implemented by preceding
 patch) and provides warnings whenever a real value falls below the threshold.

 If such messages are observed, it is a better solution to take this as an
 indication that the lookup table needs to be re-engineered.

Changelog:
----------
 This patch
   * makes handling all TFRC resolution errors local to the TFRC library

   * removes unnecessary test whether X_calc is 'infinity' due to p==0 -- this
     condition is already caught by tfrc_calc_x()

   * removes setting ccid3hctx_p = TFRC_SMALLEST_P in ccid3_hc_tx_packet_recv
     since this is now done by the TFRC library

   * updates BUG_ON test in ccid3_hc_tx_no_feedback_timer to take into account
     that p now is either 0 (and then X_calc is irrelevant), or it is > 0; since
     the handling of TFRC_SMALLEST_P is now taken care of in the tfrc library

Justification:
--------------
 The TFRC code uses a lookup table which has a bounded resolution.
 The lowest possible value of the loss event rate `p' which can be
 resolved is currently 0.0001.  Substituting this lower threshold for
 p when p is less than 0.0001 results in a huge, exponentially-growing
 error.  The error can be computed by the following formula:

    (f(0.0001) - f(p))/f(p) * 100      for p < 0.0001

 Currently the solution is to use an (arbitrary) value
     TFRC_SMALLEST_P  =   40 * 1E-6   =   0.00004
 and to consider all values below this value as `virtually zero'.  Due to
 the exponentially growing resolution error, this is not a good idea, since
 it hides the fact that the table can not resolve practically occurring cases.
 Already at p == TFRC_SMALLEST_P, the error is as high as 58.19%!
Signed-off-by: NGerrit Renker <gerrit@erg.abdn.ac.uk>
Acked-by: NIan McDonald <ian.mcdonald@jandi.co.nz>
Signed-off-by: NArnaldo Carvalho de Melo <acme@mandriva.com>

This avoids a (harmless) warning message being printed at the DCCP server
(the receiver of a DCCP half connection).

Incoming packets are both directed to

 * ccid_hc_rx_packet_recv() for the server half
 * ccid_hc_tx_packet_recv() for the client half

The message gets printed since on a server the client half is currently not
sending data packets.
This is resolved for the moment by checking the DCCP-role first. In future
times (bidirectional DCCP connections), this test may have to be more
sophisticated.
Signed-off-by: NGerrit Renker <gerrit@erg.abdn.ac.uk>
Acked-by: NIan McDonald <ian.mcdonald@jandi.co.nz>
Signed-off-by: NArnaldo Carvalho de Melo <acme@mandriva.com>

The main object of this patch is the following bug:
 ==> In ccid3_hc_tx_packet_recv, the parameters p and X_recv were updated
     _after_ the send rate was calculated. This is clearly an error and is
     resolved by re-ordering statements.

In addition,
  * r_sample is converted from u32 to long to check whether the time difference
    was negative (it would otherwise be converted to a large u32 value)
  * protection against RTT=0 (this is possible) is provided in a further patch
  * t_elapsed is also converted to long, to match the type of r_sample
  * adds a a more debugging information regarding current send rates
  * various trivial comment/documentation updates
Signed-off-by: NGerrit Renker <gerrit@erg.abdn.ac.uk>
Acked-by: NIan McDonald <ian.mcdonald@jandi.co.nz>
Signed-off-by: NArnaldo Carvalho de Melo <acme@mandriva.com>

This bug resulted in ccid3_hc_tx_send_packet returning negative
delay values, which in turn triggered silently dequeueing packets in
dccp_write_xmit. As a result, only a few out of the submitted packets made
it at all onto the network.  Occasionally, when dccp_wait_for_ccid was
involved, this also triggered a bug warning since ccid3_hc_tx_send_packet
returned a negative value (which in reality was a negative delay value).

The cause for this bug lies in the comparison

 if (delay >= hctx->ccid3hctx_delta)
	return delay / 1000L;

The type of `delay' is `long', that of ccid3hctx_delta is `u32'. When comparing
negative long values against u32 values, the test returned `true' whenever delay
was smaller than 0 (meaning the packet was overdue to send).

The fix is by casting, subtracting, and then testing the difference with
regard to 0.

This has been tested and shown to work.
Signed-off-by: NGerrit Renker <gerrit@erg.abdn.ac.uk>
Signed-off-by: NIan McDonald <ian.mcdonald@jandi.co.nz>
Signed-off-by: NArnaldo Carvalho de Melo <acme@mandriva.com>

The TFRC nofeedback timer normally expires after the maximum of 4
RTTs and twice the current send interval (RFC 3448, 4.3). On LANs
with a small RTT this can mean a high processing load and reduced
performance, since then the nofeedback timer is triggered very
frequently.

This patch provides a configuration option to set the bound for the
nofeedback timer, using as default 100 milliseconds.

By setting the configuration option to 0, strict RFC 3448 behaviour
can be enforced for the nofeedback timer.
Signed-off-by: NGerrit Renker <gerrit@erg.abdn.ac.uk>
Signed-off-by: NArnaldo Carvalho de Melo <acme@mandriva.com>

This patch implements a suggestion by Ian McDonald and

 1) Avoids tests against negative packet lengths by using unsigned int
    for packet payload lengths in the CCID send_packet()/packet_sent() routines

 2) As a consequence, it removes an now unnecessary test with regard to `len > 0'
    in ccid3_hc_tx_packet_sent: that condition is always true, since
      * negative packet lengths are avoided
      * ccid3_hc_tx_send_packet flags an error whenever the payload length is 0.
        As a consequence, ccid3_hc_tx_packet_sent is never called as all errors
        returned by ccid_hc_tx_send_packet are caught in dccp_write_xmit

 3) Removes the third argument of ccid_hc_tx_send_packet (the `len' parameter),
    since it is currently always set to skb->len. The code is updated with regard
    to this parameter change.
Signed-off-by: NGerrit Renker <gerrit@erg.abdn.ac.uk>
Signed-off-by: NIan McDonald <ian.mcdonald@jandi.co.nz>
Signed-off-by: NArnaldo Carvalho de Melo <acme@mandriva.com>

This implements the larger-initial-windows feature for CCID 3, as described in
section 5 of RFC 4342. When the first feedback packet arrives, the sender can
send up to 2..4 packets per RTT, instead of just one.

The patch further
 * reduces the number of timestamping calls by passing the timestamp value
   (which is computed in one of the calling functions anyway) as argument

 * renames one constant with a very long name into one which is shorter and
   resembles the one in RFC 3448 (t_mbi)

 * simplifies some of the min_t/max_t cases where both `x', `y' have the same
   type

Commiter note: renamed TFRC_t_mbi to TFRC_T_MBI, to follow Linux coding style.
Signed-off-by: NGerrit Renker <gerrit@erg.abdn.ac.uk>
Acked-by: NIan McDonald <ian.mcdonald@jandi.co.nz>
Signed-off-by: NArnaldo Carvalho de Melo <acme@mandriva.com>

Problem:

This corrects the setting of the nofeedback timer with regard to RFC
3448 - previously it was not set to max(4*R, 2*s/X) as specified. Using
the maximum of 1 second as upper bound (as it was done before) can have
detrimental effects, especially if R is small.
Signed-off-by: NIan McDonald <ian.mcdonald@jandi.co.nz>
Signed-off-by: NGerrit Renker <gerrit@erg.abdn.ac.uk>
Signed-off-by: NArnaldo Carvalho de Melo <acme@mandriva.com>

This patch
 * removes setting t_RTO in ccid3_hc_tx_init (per [RFC 3448, 4.2], t_RTO is
   undefined until feedback has been received);

 * makes some trivial changes (updates of comments);

 * performs a small optimisation by exploiting that the feedback timeout
   uses the value of t_ipi. The way it is done is safe, because the timeouts
   appear after the changes to t_ipi, ensuring that up-to-date values are used;

 * in ccid3_hc_tx_packet_recv, moves the t_rto statement closer to the calculation
   of the next_tmout. This makes the code clearer to read and is also safe, since
   t_rto is not updated until the next call of ccid3_hc_tx_packet_recv, and is not
   read by the functions called via ccid_wait_for_ccid();

 * removes a `max' statement in sk_reset_timer, this is not needed since the timeout
   value is always greater than 1E6 microseconds.

 * adds `XXX'es to highlight that currently the nofeedback timer is set
   in a non-standard way
Signed-off-by: NGerrit Renker <gerrit@erg.abdn.ac.uk>
Acked-by: NIan McDonald <ian.mcdonald@jandi.co.nz>
Signed-off-by: NArnaldo Carvalho de Melo <acme@mandriva.com>

This patch:

 * consolidates updating of parameters (t_nom, t_ipi, t_delta) which
   need to be updated at the same time, since they are inter-dependent

 * removes two inline functions which are no longer needed as a result of
   the above consolidation

 * resolves a FIXME regarding the re-calculation of t_ipi within the nofeedback
   timer, in the state where no feedback has previously been received

 * ties updating these parameters to updating the sending rate X, exploiting
   that all three parameters in turn depend on X; and using a small optimisation
   which can reduce the number of required instructions: only update the three
   parameters when X really changes
Signed-off-by: NGerrit Renker <gerrit@erg.abdn.ac.uk>
Acked-by: NIan McDonald <ian.mcdonald@jandi.co.nz>
Signed-off-by: NArnaldo Carvalho de Melo <acme@mandriva.com>

This patch concerns updating the value of the nofeedback timer when no feedback
has been received so far.

Since in this case the value of R is still undefined according to [RFC 3448,
4.2], we can not perform step (3) of [RFC 3448, 4.3].  A clarification is
provided in [RFC 4342, sec. 5], which states that in these cases the nofeedback
timer (still) expires "after two seconds".

Many thanks to Ian McDonald for pointing this out and providing the
clarification.

The patch
  * implements [RFC 4342, sec. 5] with regard to the above case
  * consolidates handling timer restart by
	- adding an appropriate jump label and
	- initialising the timeout value
Acked-by: NIan McDonald <ian.mcdonald@jandi.co.nz>
Signed-off-by: NGerrit Renker <gerrit@erg.abdn.ac.uk>
Signed-off-by: NArnaldo Carvalho de Melo <acme@mandriva.com>

This considers the  case - ACK received while no packet has been sent
so far. Resolved by printing a (rate-limited) warning message.

Further removes an unnecessary BUG_ON in ccid3_hc_tx_packet_recv,
received feedback on a terminating connection is simply ignored.
Signed-off-by: NGerrit Renker <gerrit@erg.abdn.ac.uk>
Signed-off-by: NIan McDonald <ian.mcdonald@jandi.co.nz>
Signed-off-by: NArnaldo Carvalho de Melo <acme@mandriva.com>

This patch removes a switch statement which is redundant since,
 * nothing is done in states TFRC_SSTATE_NO_SENT/TFRC_SSTATE_NO_FBACK
 * it is impossible that the function is called in the state TFRC_SSTATE_TERM, since
       --the function is called, in dccp_write_xmit, after ccid3_hc_tx_send_packet
       --if ccid3_hc_tx_send_packet is called in state TFRC_SSTATE_TERM, it returns
         -EINVAL, which means that ccid3_hc_tx_packet_sent will not be called
	 (compare dccp_write_xmit)
       --> therefore, this case is logically impossible
 * the remaining state is TFRC_SSTATE_FBACK which conditionally updates t_ipi, t_nom,
   and t_delta. This is a no-op, since
       --t_ipi only changes when feedback is received
       --however, when feedback arrives via ccid3_hc_tx_packet_recv, there is an identical
         code block which performs the same set of operations
       --performing the same set of operations again in ccid3_hc_tx_packet_sent therefore
         does not change anything, since between the time of receiving the last feedback
	 (and therefore update of t_ipi, t_nom, and t_delta), the value of t_ipi has not
	 changed
       --since t_ipi has not changed, the values of t_delta and t_nom also do not change,
         they depend fully on t_ipi
Signed-off-by: NGerrit Renker <gerrit@erg.abdn.ac.uk>
Acked-by: NIan McDonald <ian.mcdonald@jandi.co.nz>
Signed-off-by: NArnaldo Carvalho de Melo <acme@mandriva.com>

This resolves an `XXX' in ccid3_hc_tx_send_packet().

The function is only called on Data and DataAck packets and returns a negative
result on zero-sized messages. This is a reasonable policy since CCID 3 is a
congestion-control module and congestion control on zero-sized Data(Ack)
packets is in a way pathological.

The patch uses a more suitable error code for this case, it returns the Posix.1
code `EBADMSG' ("Not a data message") instead of `ENOTCONN'.

As a result of ignoring zero-sized packets, a the condition for a warning
"First packet is data" in ccid3_hc_tx_packet_sent is always satisfied; this
message has been removed since it will always be printed.
Signed-off-by: NGerrit Renker <gerrit@erg.abdn.ac.uk>
Signed-off-by: NIan McDonald <ian.mcdonald@jandi.co.nz>
Signed-off-by: NArnaldo Carvalho de Melo <acme@mandriva.com>

This makes some logically equivalent simplifications, by replacing
rc - values plus goto's with direct return statements.
Signed-off-by: NGerrit Renker <gerrit@erg.abdn.ac.uk>
Signed-off-by: NIan McDonald <ian.mcdonald@jandi.co.nz>
Signed-off-by: NArnaldo Carvalho de Melo <acme@mandriva.com>

Problem:

This patch performs a simplifying (performance) optimisation:

 In each call of the inline function ccid3_calc_new_t_ipi(), the state is
 tested against TFRC_SSTATE_NO_FBACK. This is expensive when the function
 is called very often. A simpler solution, implemented by this patch, is
 to adapt the control flow.

Background:

Problem:

This removes a non-referenced variable.
Signed-off-by: NIan McDonald <ian.mcdonald@jandi.co.nz>
Signed-off-by: NArnaldo Carvalho de Melo <acme@mandriva.com>

This reaps the benefit of the earlier patch, which changed the type of
CCID 3 states to use enums, in that many conditions are now simplified
and the number of possible (unexpected) values is greatly reduced.

In a few instances, this also allowed to simplify pre-conditions; where
care has been taken to retain logical equivalence.

[DCCP]: Introduce a consistent BUG/WARN message scheme

This refines the existing set of DCCP messages so that
 * BUG(), BUG_ON(), WARN_ON() have meaningful DCCP-specific counterparts
 * DCCP_CRIT (for severe warnings) is not rate-limited
 * DCCP_WARN() is introduced as rate-limited wrapper

Using these allows a faster and cleaner transition to their original
counterparts once the code has matured into a full DCCP implementation.
Signed-off-by: NGerrit Renker <gerrit@erg.abdn.ac.uk>
Signed-off-by: NArnaldo Carvalho de Melo <acme@mandriva.com>

This adds a CCID3 debug option to the configuration menu
which is missing in Kconfig, but already used by the code.

CCID 2 already provides such an entry.

To enable debugging, set CONFIG_IP_DCCP_CCID3_DEBUG=y

NOTE: The use of ccid3_{t,r}x_state_name is safe, since
      now only enum values can appear.
Signed-off-by: NGerrit Renker <gerrit@erg.abdn.ac.uk>
Signed-off-by: NArnaldo Carvalho de Melo <acme@mandriva.com>

This patch tackles the following problem:
       * the ccid3_hc_{t,r}x_sock define ccid3hc{t,r}x_state as `u8', but
         in reality there can only be a few, pre-defined enum names
       * this necessitates addiditional checking for unexpected values
         which would otherwise be caught by the compiler
Signed-off-by: NGerrit Renker <gerrit@erg.abdn.ac.uk>
Signed-off-by: NArnaldo Carvalho de Melo <acme@mandriva.com>

Updates the references to spec documents throughout the code, taking into
account that

* the DCCP, CCID 2, and CCID 3 drafts all became RFCs in March this year

* RFC 1063 was obsoleted by RFC 1191

* draft-ietf-tcpimpl-pmtud-0x.txt was published as an Informational
  RFC, RFC 2923 on 2000-09-22.

All references verified.
Signed-off-by: NGerrit Renker <gerrit@erg.abdn.ac.uk>
Signed-off-by: NArnaldo Carvalho de Melo <acme@mandriva.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

With constants for CCID numbers this now uses them in some places.
Signed-off-by: NIan McDonald <ian.mcdonald@jandi.co.nz>
Signed-off-by: NArnaldo Carvalho de Melo <acme@mandriva.com>

As Arnaldo Carvalho de Melo points out I should be using list_entry in case
the structure changes in future. Current code functions but is reliant
on position and requires type cast.

Noticed when doing this that I have one more variable than I needed so
removing that also.

Signed off by: Ian McDonald <ian.mcdonald@jandi.co.nz>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

This fixes CCID3 to give much closer performance to RFC4342.

CCID3 is meant to alter sending rate based on RTT and loss.

The performance was verified against:
http://wand.net.nz/~perry/max_download.php

For example I tested with netem and had the following parameters:
Delayed Acks 1, MSS 256 bytes, RTT 105 ms, packet loss 5%.

This gives a theoretical speed of 71.9 Kbits/s. I measured across three
runs with this patch set and got 70.1 Kbits/s. Without this patchset the
average was 232 Kbits/s which means Linux can't be used for CCID3 research
properly.

I also tested with netem turned off so box just acting as router with 1.2
msec RTT. The performance with this is the same with or without the patch
at around 30 Mbit/s.

Signed off by: Ian McDonald <ian.mcdonald@jandi.co.nz>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

Just updating copyright and contacts

Signed off by: Ian McDonald <ian.mcdonald@jandi.co.nz>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

Signed-off-by: NJörn Engel <joern@wohnheim.fh-wedel.de>
Signed-off-by: NAdrian Bunk <bunk@stusta.de>

And not the silly LIMIT_NETDEBUG and silently return without inserting
the option requested.

Also drop some old debugging messages associated to option insertion.
Signed-off-by: NArnaldo Carvalho de Melo <acme@mandriva.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

I guess I forgot to add it, nah, now it just works:

18:04:33.274066 IP6 ::1.1476 > ::1.5001: request (service=0)
18:04:33.334482 IP6 ::1.5001 > ::1.1476: reset (code=bad_service_code)

Ditched IP_DCCP_UNLOAD_HACK, as now we would have to do it for both
IPv6 and IPv4, so I'll come up with another way for freeing the
control sockets in upcoming changesets.
Signed-off-by: NArnaldo Carvalho de Melo <acme@mandriva.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

Signed-off-by: NArnaldo Carvalho de Melo <acme@mandriva.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

This also fixes the layout of dccp_hdr short sequence numbers, problem
was not fatal now as we only support long (48 bits) sequence numbers.
Signed-off-by: NAndrea Bittau <a.bittau@cs.ucl.ac.uk>
Signed-off-by: NArnaldo Carvalho de Melo <acme@mandriva.com>
Signed-off-by: NAl Viro <viro@zeniv.linux.org.uk>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

1. No need for ->ccid_init nor ->ccid_exit, this is what module_{init,exit}
   does and anynways neither ccid2 nor ccid3 were using it.

2. Rename struct ccid to struct ccid_operations and introduce struct ccid
   with a pointer to ccid_operations and rigth after it the rx or tx
   private state.

3. Remove the pointer to the state of the half connections from struct
   dccp_sock, now its derived thru ccid_priv() from the ccid pointer.

Now we also can implement the setsockopt for changing the CCID easily as
no ccid init routines can affect struct dccp_sock in any way that prevents
other CCIDs from working if a CCID switch operation is asked by apps.
Signed-off-by: NArnaldo Carvalho de Melo <acme@mandriva.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

Signed-off-by: NArnaldo Carvalho de Melo <acme@mandriva.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

Testing if the ccid being instantiated has these methods in
ccid_init().
Signed-off-by: NArnaldo Carvalho de Melo <acme@mandriva.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

In rare circumstances 0 is returned by dccp_li_hist_calc_i_mean which
leads to a divide by zero in ccid3_hc_rx_packet_recv. Explicitly check
for zero return now. Update copyright notice at same time.

Found by Arnaldo.
Signed-off-by: NIan McDonald <imcdnzl@gmail.com>
Signed-off-by: NArnaldo Carvalho de Melo <acme@mandriva.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

Allocation for the optnames is similar to the DCCP options, with a
range for rx and tx half connection CCIDs.
Signed-off-by: NArnaldo Carvalho de Melo <acme@mandriva.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

Signed-off-by: NArnaldo Carvalho de Melo <acme@mandriva.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

Also use some BUG_ON where appropriate and use LIMIT_NETDEBUG for the unlikely
cases where we, at this stage, want to know about, that in my tests hasn't
appeared in the radar.
Signed-off-by: NArnaldo Carvalho de Melo <acme@mandriva.com>