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236 commits

Author SHA1 Message Date
Gerrit Renker
2eeea7ba6b dccp ccid-3: Length of loss intervals
This corrects an error in the computation of the open loss interval I_0:
  * the interval length is (highest_seqno - start_seqno) + 1
  * and not (highest_seqno - start_seqno).

This condition was not fully clear in RFC 3448, but reflects the current
revision state of rfc3448bis and is also consistent with RFC 4340, 6.1.1.

Further changes:
----------------
 * variable renamed due to line length constraints;
 * explicit typecast to `s64' to avoid implicit signed/unsigned casting.

Signed-off-by: Gerrit Renker <gerrit@erg.abdn.ac.uk>
2008-07-13 11:51:40 +01:00
Gerrit Renker
b552c6231f dccp ccid-3: Fix a loss detection bug
This fixes a bug in the logic of the TFRC loss detection:
 * new_loss_indicated() should not be called while a loss is pending;
 * but the code allows this;
 * thus, for two subsequent gaps in the sequence space, when loss_count
   has not yet reached NDUPACK=3, the loss_count is falsely reduced to 1.

To avoid further and similar problems, all loss handling and loss detection is
now done inside tfrc_rx_hist_handle_loss(), using an appropriate routine to
track new losses.

Further changes:
----------------
 * added a reminder that no RX history operations should be performed when
   rx_handle_loss() has identified a (new) loss, since the function takes
   care of packet reordering during loss detection;
 * made tfrc_rx_hist_loss_pending() bool (thanks to an earlier suggestion
   by Arnaldo);		 
 * removed unused functions.

Signed-off-by: Gerrit Renker <gerrit@erg.abdn.ac.uk>
2008-07-13 11:51:40 +01:00
Gerrit Renker
5b5d0e7048 dccp: Upgrade NDP count from 3 to 6 bytes
RFC 4340, 7.7 specifies up to 6 bytes for the NDP Count option, whereas the code
is currently limited to up to 3 bytes. This seems to be a relict of an earlier 
draft version and is brought up to date by the patch.

Signed-off-by: Gerrit Renker <gerrit@erg.abdn.ac.uk>
2008-07-13 11:51:40 +01:00
Gerrit Renker
2013c7e35a dccp ccid-3: Fix error in loss detection
The TFRC loss detection code used the wrong loss condition (RFC 4340, 7.7.1):
 * the difference between sequence numbers s1 and s2 instead of 
 * the number of packets missing between s1 and s2 (one less than the distance).

Since this condition appears in many places of the code, it has been put into a
separate function, dccp_loss_free().

Further changes:
----------------
 * tidied up incorrect typing (it was using `int' for u64/s64 types);
 * optimised conditional statements for common case of non-reordered packets;
 * rewrote comments/documentation to match the changes.

Signed-off-by: Gerrit Renker <gerrit@erg.abdn.ac.uk>
2008-07-13 11:51:40 +01:00
Gerrit Renker
7deb0f8510 dccp ccid-3: X truncated due to type conversion
This fixes a bug in computing the inter-packet-interval t_ipi = s/X: 

 scaled_div32(a, b) uses u32 for b, but in "scaled_div32(s, X)" the type of the
 sending rate `X' is u64. Since X is scaled by 2^6, this truncates rates greater
 than 2^26 Bps (~537 Mbps).

Using full 64-bit division now.

Signed-off-by: Gerrit Renker <gerrit@erg.abdn.ac.uk>
2008-06-11 11:19:10 +01:00
Gerrit Renker
1e8a287c79 dccp ccid-3: TFRC reverse-lookup Bug-Fix
This fixes a bug in the reverse lookup of p: given a value f(p), instead of p,
the function returned the smallest tabulated value f(p).

The smallest tabulated value of
	 
   10^6 * f(p) =  sqrt(2*p/3) + 12 * sqrt(3*p/8) * (32 * p^3 + p) 

for p=0.0001 is 8172. 

Since this value is scaled by 10^6, the outcome of this bug is that a loss
of 8172/10^6 = 0.8172% was reported whenever the input was below the table
resolution of 0.01%.

This means that the value was over 80 times too high, resulting in large spikes
of the initial loss interval, thus unnecessarily reducing the throughput.

Also corrected the printk format (%u for u32).

Signed-off-by: Gerrit Renker <gerrit@erg.abdn.ac.uk>
2008-06-11 11:19:10 +01:00
Gerrit Renker
1e2f0e5e83 dccp: Fix sparse warnings
This patch fixes the following sparse warnings:
 * nested min(max()) expression:
   net/dccp/ccids/ccid3.c:91:21: warning: symbol '__x' shadows an earlier one
   net/dccp/ccids/ccid3.c:91:21: warning: symbol '__y' shadows an earlier one
   
 * Declaration of function prototypes in .c instead of .h file, resulting in
   "should it be static?" warnings. 

 * Declared "struct dccpw" static (local to dccp_probe).
 
 * Disabled dccp_delayed_ack() - not fully removed due to RFC 4340, 11.3
   ("Receivers SHOULD implement delayed acknowledgement timers ...").

 * Used a different local variable name to avoid
   net/dccp/ackvec.c:293:13: warning: symbol 'state' shadows an earlier one
   net/dccp/ackvec.c:238:33: originally declared here

 * Removed unused functions `dccp_ackvector_print' and `dccp_ackvec_print'.

Signed-off-by: Gerrit Renker <gerrit@erg.abdn.ac.uk>
2008-06-11 11:19:09 +01:00
Gerrit Renker
3294f202dc dccp ccid-3: Bug-Fix - Zero RTT is possible
In commit $(825de27d9e) (from 27th May, commit
message `dccp ccid-3: Fix "t_ipi explosion" bug'), the CCID-3 window counter
computation was fixed to cope with RTTs < 4 microseconds.

Such RTTs can be found e.g. when running CCID-3 over loopback. The fix removed
a check against RTT < 4, but introduced a divide-by-zero bug.

All steady-state RTTs in DCCP are filtered using dccp_sample_rtt(), which
ensures non-zero samples. However, a zero RTT is possible on initialisation,
when there is no RTT sample from the Request/Response exchange.

The fix is to use the fallback-RTT from RFC 4340, 3.4.

This is also better than just fixing update_win_count() since it allows other
parts of the code to always assume that the RTT is non-zero during the time
that the CCID is used.

Signed-off-by: Gerrit Renker <gerrit@erg.abdn.ac.uk>
2008-06-11 11:19:09 +01:00
Gerrit Renker
825de27d9e dccp ccid-3: Fix "t_ipi explosion" bug
The identification of this bug is thanks to Cheng Wei and Tomasz
Grobelny.

To avoid divide-by-zero, the implementation previously ignored RTTs
smaller than 4 microseconds when performing integer division RTT/4.

When the RTT reached a value less than 4 microseconds (as observed on
loopback), this prevented the Window Counter CCVal value from
advancing. As a result, the receiver stopped sending feedback. This in
turn caused non-ending expiries of the nofeedback timer at the sender,
so that the sending rate was progressively reduced until reaching the
minimum of one packet per 64 seconds.

The patch fixes this bug by handling integer division more
intelligently. Due to consistent use of dccp_sample_rtt(),
divide-by-zero-RTT is avoided.

Signed-off-by: Gerrit Renker <gerrit@erg.abdn.ac.uk>
Signed-off-by: David S. Miller <davem@davemloft.net>
2008-05-27 06:33:54 -07:00
Harvey Harrison
84994e16f2 dccp: ccid2.c, ccid3.c use clamp(), clamp_t()
Makes the intention of the nested min/max clear.

Signed-off-by: Harvey Harrison <harvey.harrison@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
2008-05-02 16:44:07 -07:00
Ilpo Järvinen
c4e18dade1 [CCID3]: Kill some bloat
Without a number of CONFIG.*DEBUG:

net/dccp/ccids/ccid3.c:
  ccid3_hc_tx_update_x          | -170
  ccid3_hc_tx_packet_sent       | -175
  ccid3_hc_tx_packet_recv       | -169
  ccid3_hc_tx_no_feedback_timer | -192
  ccid3_hc_tx_send_packet       | -144
 5 functions changed, 850 bytes removed, diff: -850

net/dccp/ccids/ccid3.c:
  ccid3_update_send_interval | +191
 1 function changed, 191 bytes added, diff: +191

net/dccp/ccids/ccid3.o:
 6 functions changed, 191 bytes added, 850 bytes removed, diff: -659

Signed-off-by: Ilpo Järvinen <ilpo.jarvinen@helsinki.fi>
Signed-off-by: David S. Miller <davem@davemloft.net>
2008-01-28 15:00:44 -08:00
Gerrit Renker
52515e77a7 [CCID3]: Nofeedback timer according to rfc3448bis
This implements the changes to the nofeedback timer handling suggested
in draft rfc3448bis00, section 4.4. In particular, these changes mean:

 * better handling of the lossless case (p == 0)
 * the timestamp for computing t_ld becomes obsolete
 * much more recent document (RFC 3448 is almost 5 years old)
 * concepts in rfc3448bis arose from a real, working implementation
   (cf. sec. 12)

Signed-off-by: Gerrit Renker <gerrit@erg.abdn.ac.uk>
Signed-off-by: Ian McDonald <ian.mcdonald@jandi.co.nz>
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
2008-01-28 14:58:23 -08:00
Gerrit Renker
d8d1252f74 [CCID3]: Implement rfc3448bis changes to feedback reception
This implements the algorithm to update the allowed sending rate X upon
receiving feedback packets, as described in draft rfc3448bis, 4.2/4.3.

Signed-off-by: Gerrit Renker <gerrit@erg.abdn.ac.uk>
Signed-off-by: Ian McDonald <ian.mcdonald@jandi.co.nz>
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
2008-01-28 14:58:22 -08:00
Gerrit Renker
5bd370a63d [CCID3]: Remove two irrelevant states in TX feedback handling
* the NO_SENT state is only triggered in bidirectional mode,
   costing unnecessary processing.
 * the TERM (terminating) state is irrelevant.

Signed-off-by: Gerrit Renker <gerrit@erg.abdn.ac.uk>
Signed-off-by: Ian McDonald <ian.mcdonald@jandi.co.nz>
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
2008-01-28 14:58:22 -08:00
Gerrit Renker
8e138e7949 [CCID3]: Use a function to update p_inv, and p is never used
This patch
 1) concentrates previously scattered computation of p_inv into one function;
 2) removes the `p' element of the CCID3 RX sock (it is redundant);
 3) makes the tfrc_rx_info structure standalone, only used on demand.

Signed-off-by: Gerrit Renker <gerrit@erg.abdn.ac.uk>
Signed-off-by: Ian McDonald <ian.mcdonald@jandi.co.nz>
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
2008-01-28 14:58:21 -08:00
Gerrit Renker
84a97b0af8 [CCID]: More informative registration
The patch makes the registration messages of CCID 2/3 a bit more
informative: instead of repeating the CCID number as currently done,

        "CCID: Registered CCID 2 (ccid2)"  or
        "CCID: Registered CCID 3 (ccid3)",

the descriptive names of the CCID's (from RFCs) are now used:

	"CCID: Registered CCID 2 (TCP-like)" and
	"CCID: Registered CCID 3 (TCP-Friendly Rate Control)".

To allow spaces in the name, the slab name string has been changed to
refer to the numeric CCID identifier, using the same format as before.

Signed-off-by: Gerrit Renker <gerrit@erg.abdn.ac.uk>
Signed-off-by: Ian McDonald <ian.mcdonald@jandi.co.nz>
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
2008-01-28 14:57:58 -08:00
Gerrit Renker
3f71c81ac3 [TFRC]: Remove previous loss intervals implementation
Signed-off-by: Gerrit Renker <gerrit@erg.abdn.ac.uk>
Signed-off-by: Ian McDonald <ian.mcdonald@jandi.co.nz>
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
2008-01-28 14:57:20 -08:00
Gerrit Renker
954c2db868 [CCID3]: Interface CCID3 code with newer Loss Intervals Database
This hooks up the TFRC Loss Interval database with CCID 3 packet reception.
In addition, it makes the CCID-specific computation of the first loss
interval (which requires access to all the guts of CCID3) local to ccid3.c.

The patch also fixes an omission in the DCCP code, that of a default /
fallback RTT value (defined in section 3.4 of RFC 4340 as 0.2 sec); while
at it, the  upper bound of 4 seconds for an RTT sample has  been reduced to
match the initial TCP RTO value of 3 seconds from[RFC 1122, 4.2.3.1].

Signed-off-by: Gerrit Renker <gerrit@erg.abdn.ac.uk>
Signed-off-by: Ian McDonald <ian.mcdonald@jandi.co.nz>
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
2008-01-28 14:57:20 -08:00
Gerrit Renker
de0d411cb8 [TFRC]: CCID3 (and CCID4) needs to access these inlines
This moves two inlines back to packet_history.h: these are not private
to packet_history.c, but are needed by CCID3/4 to detect whether a new
loss is indicated, or whether a loss is already pending.

Signed-off-by: Gerrit Renker <gerrit@erg.abdn.ac.uk>
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
2008-01-28 14:57:19 -08:00
Gerrit Renker
db64196038 [CCID3]: Redundant debugging output / documentation
Each time feedback is sent two lines are printed:

	ccid3_hc_rx_send_feedback: client ... - entry
	ccid3_hc_rx_send_feedback: Interval ...usec, X_recv=..., 1/p=...

The first line is redundant and thus removed.

Further, documentation of ccid3_hc_rx_sock (capitalisation) is made consistent.

Signed-off-by: Gerrit Renker <gerrit@erg.abdn.ac.uk>
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
2008-01-28 14:57:18 -08:00
Gerrit Renker
8a9c7e92e0 [TFRC]: Ringbuffer to track loss interval history
A ringbuffer-based implementation of loss interval history is easier to
maintain, allocate, and update.

The `swap' routine to keep the RX history sorted is due to and was written
by Arnaldo Carvalho de Melo, simplifying an earlier macro-based variant.

Details:
 * access to the Loss Interval Records via macro wrappers (with safety checks);
 * simplified, on-demand allocation of entries (no extra memory consumption on
   lossless links); cache allocation is local to the module / exported as service;
 * provision of RFC-compliant algorithm to re-compute average loss interval;
 * provision of comprehensive, new loss detection algorithm
 	- support for all cases of loss, including re-ordered/duplicate packets;
 	- waiting for NDUPACK=3 packets to fill the hole;
	- updating loss records when a late-arriving packet fills a hole.

Signed-off-by: Gerrit Renker <gerrit@erg.abdn.ac.uk>
Signed-off-by: Ian McDonald <ian.mcdonald@jandi.co.nz>
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
2008-01-28 14:57:18 -08:00
Gerrit Renker
8995a238ef [TFRC]: Loss interval code needs the macros/inlines that were moved
This moves the inlines (which were previously declared as macros) back into
packet_history.h since the loss detection code needs to be able to read entries
from the RX history in order to create the relevant loss entries: it needs at
least tfrc_rx_hist_loss_prev() and tfrc_rx_hist_last_rcv(), which in turn
require the definition of the other inlines (macros).

Signed-off-by: Gerrit Renker <gerrit@erg.abdn.ac.uk>
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
2008-01-28 14:57:16 -08:00
Gerrit Renker
df8f83fdd6 [TFRC]: Put RX/TX initialisation into tfrc.c
This separates RX/TX initialisation and puts all packet history / loss intervals
initialisation into tfrc.c.
The organisation is uniform: slab declaration -> {rx,tx}_init() -> {rx,tx}_exit()

Signed-off-by: Gerrit Renker <gerrit@erg.abdn.ac.uk>
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
2008-01-28 14:57:15 -08:00
Gerrit Renker
385ac2e3f2 [CCID3]: HC-receiver should not insert timestamps as HC-sender doesn't uses it
Signed-off-by: Gerrit Renker <gerrit@erg.abdn.ac.uk>
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
2008-01-28 14:57:04 -08:00
Gerrit Renker
797eba424d [TFRC]: The function tfrc_rx_hist_entry_delete() is not used anymore
Signed-off-by: Gerrit Renker <gerrit@erg.abdn.ac.uk>
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
2008-01-28 14:57:03 -08:00
Gerrit Renker
78282d2af5 [TFRC]: Move comment.
Moved up the comment "Receiver routines" above the first occurrence of
RX history routines.

Signed-off-by: Gerrit Renker <gerrit@erg.abdn.ac.uk>
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
2008-01-28 14:57:03 -08:00
Arnaldo Carvalho de Melo
b84a2189c4 [TFRC]: New rx history code
Credit here goes to Gerrit Renker, that provided the initial implementation for
this new codebase.

I modified it just to try to make it closer to the existing API, renaming some
functions, add namespacing and fix one bug where the tfrc_rx_hist_alloc was not
freeing the allocated ring entries on the error path.

Original changeset comment from Gerrit:
      -----------
This provides a new, self-contained and generic RX history service for TFRC
based protocols.

Details:
 * new data structure, initialisation and cleanup routines;
 * allocation of dccp_rx_hist entries local to packet_history.c,
   as a service exported by the dccp_tfrc_lib module.
 * interface to automatically track highest-received seqno;
 * receiver-based RTT estimation (needed for instance by RFC 3448, 6.3.1);
 * a generic function to test for `data packets' as per  RFC 4340, sec. 7.7.

Signed-off-by: Gerrit Renker <gerrit@erg.abdn.ac.uk>
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
2008-01-28 14:56:43 -08:00
Gerrit Renker
30a0eacd47 [CCID3]: The receiver of a half-connection does not set window counter values
Only the sender sets window counters [RFC 4342, sections 5 and 8.1].

Signed-off-by: Gerrit Renker <gerrit@erg.abdn.ac.uk>
Signed-off-by: Ian McDonald <ian.mcdonald@jandi.co.nz>
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
2008-01-28 14:56:43 -08:00
Arnaldo Carvalho de Melo
d58d1af03a [TFRC]: Rename dccp_rx_ to tfrc_rx_
This is in preparation for merging the new rx history code written by Gerrit Renker.

Signed-off-by: Gerrit Renker <gerrit@erg.abdn.ac.uk>
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
2008-01-28 14:56:42 -08:00
Arnaldo Carvalho de Melo
34a9e7ea91 [TFRC]: Make the rx history slab be global
This is in preparation for merging the new rx history code written by Gerrit Renker.

Signed-off-by: Gerrit Renker <gerrit@erg.abdn.ac.uk>
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
2008-01-28 14:56:41 -08:00
Arnaldo Carvalho de Melo
e9c8b24a6a [TFRC]: Rename tfrc_tx_hist to tfrc_tx_hist_slab, for consistency
Signed-off-by: Gerrit Renker <gerrit@erg.abdn.ac.uk>
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
2008-01-28 14:56:40 -08:00
Gerrit Renker
c40616c597 [TFRC]: Provide central source file and debug facility
This patch changes the tfrc_lib module in the following manner:

 (1) a dedicated tfrc source file to call the packet history &
     loss interval init/exit functions.
 (2) a dedicated tfrc_pr_debug macro with toggle switch `tfrc_debug'.

Commiter note: renamed tfrc_module.c to tfrc.c, and made CONFIG_IP_DCCP_CCID3
select IP_DCCP_TFRC_LIB.

Signed-off-by: Gerrit Renker <gerrit@erg.abdn.ac.uk>
Signed-off-by: Ian McDonald <ian.mcdonald@jandi.co.nz>
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
2008-01-28 14:56:39 -08:00
Arnaldo Carvalho de Melo
9108d5f4b2 [TFRC]: Hide tx history details from the CCIDs
Based on a previous patch by Gerrit Renker.

Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
2008-01-28 14:55:19 -08:00
Arnaldo Carvalho de Melo
276f2edc52 [TFRC]: Migrate TX history to singly-linked lis
This patch was based on another made by Gerrit Renker, his changelog was:

    ------------------------------------------------------
The patch set migrates TFRC TX history to a singly-linked list.

The details are:
 * use of a consistent naming scheme (all TFRC functions now begin with `tfrc_');
 * allocation and cleanup are taken care of internally;
 * provision of a lookup function, which is used by the CCID TX infrastructure
   to determine the time a packet was sent (in turn used for RTT sampling);
 * integration of the new interface with the present use in CCID3.
    ------------------------------------------------------

Simplifications I did:

. removing the tfrc_tx_hist_head that had a pointer to the list head and
  another for the slabcache.
. No need for creating a slabcache for each CCID that wants to use the TFRC
  tx history routines, create a single slabcache when the dccp_tfrc_lib module
  init routine is called.

Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
2008-01-28 14:55:11 -08:00
Gerrit Renker
dcfbc7e97a [CCID2]: Remove misleading comment
This removes a comment which identifies an `issue' with dccp_write_xmit() where there is none.
The comment assumes it is possible that a packet is sent between the calls to

	ccid_hc_tx_send_packet(),
	dccp_transmit_skb(),
	ccid_hc_tx_packet_sent()

(in the above order) in dccp_write_xmit().

I think that this is impossible, since dccp_write_xmit() is always called under lock:

 * when called as dccp_write_xmit(sk, 1) from dccp_send_close(), the socket is locked
   (see code comment above dccp_send_close());
 * when called as dccp_write_xmit(sk, 0) from dccp_send_msg(), it is after lock_sock() has been called;
 * when called as dccp_write_xmit(sk, 0) from dccp_write_xmit_timer(), bh_lock_sock() has been called
   and the if/else statement has made sure that sk_lock.owner is not set;
 * there are no other places where dccp_write_xmit() is called.

Furthermore, the debug statement for printing the sequence number of the packet just sent has been
removed, since the entire list is being printed anyway and so the entry of that number appears last.

Signed-off-by: Gerrit Renker <gerrit@erg.abdn.ac.uk>
Acked-by: Ian McDonald <ian.mcdonald@jandi.co.nz>
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
2008-01-28 14:55:01 -08:00
Gerrit Renker
a302002516 [CCID2]: Remove redundant ack-counting variable
The code used two different variables to count Acks, one of them redundant.
This patch reduces the number of Ack counters to one.

The type of the Ack counter has also been changed to u32 (twice the range of int);
and the variable has been renamed into `packets_acked' - for consistency with
RFC 3465 (and similarly named variables are used by TCP and SCTP).

Lastly, a slightly less aggressive `maxincr' increment is used (for even Ack Ratios,
maxincr was Ack Ratio/2 + 1 instead of Ack Ratio/2).

Signed-off-by: Gerrit Renker <gerrit@erg.abdn.ac.uk>
Acked-by: Ian McDonald <ian.mcdonald@jandi.co.nz>
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
2008-01-28 14:55:00 -08:00
Gerrit Renker
83399361c3 [CCID2]: Remove redundant synchronisation variable
This removes the synchronisation variable `ccid2hctx_sendwait', which is set to 1
when the CCID2 sender may send a new packet, and which is set to 0 otherwise

The variable is redundant, since it is only used in combination with the hc_tx_send_packet/
hc_tx_packet_sent function pair. Both functions are called under socket lock, so the
following happens when the CCID2 may send a new packet:

 * it sets sendwait = 1 in tx_send_packet and returns 0;
 * the subsequent call to tx_packet_sent clears the sendwait flag;
 * since tx_send_packet returns 0 if and only if sendwait == 1, the BUG_ON condition
   in tx_packet_sent is never satisfied, since that function is never called when
   tx_send_packet returns a value different from 0 (cf. dccp_write_xmit);
 * the call to tx_packet_sent clears the flag so that the condition "!sendwait" is
   true the next time tx_packet_sent is called.

In other words, it is sufficient to just return 0 / not-0 to synchronise tx_send_packet
and tx_packet_sent -- which is what the patch does.

Signed-off-by: Gerrit Renker <gerrit@erg.abdn.ac.uk>
Acked-by: Ian McDonald <ian.mcdonald@jandi.co.nz>
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
2008-01-28 14:54:59 -08:00
Gerrit Renker
da98e0b5d4 [CCID2]: Redundant debugging output
This reduces the amount of redundant debugging messages:

 * pipe/cwnd are printed in both tx_send_packet() and tx_packet_sent().
   Both functions are called immediately after one another, so one occurrence is sufficient.

 * Since tx_packet_sent() prints pipe/cwnd already, the second printk for pipe is redundant.

 * In tx_packet_sent() the check_sanity function is called twice (at the begin and at the end).

Signed-off-by: Gerrit Renker <gerrit@erg.abdn.ac.uk>
Acked-by: Ian McDonald <ian.mcdonald@jandi.co.nz>
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
2008-01-28 14:54:59 -08:00
Gerrit Renker
95b21d7e9d [CCID2]: Replace pipe assignment-function with assignment
The function ccid2_change_pipe only does an assignment. This patch simplifies the code by
replacing the function with the assignment it performs.

Furthermore, the type of pipe is promoted from `signed' to unsigned (increasing the range).
As a result, a BUG_ON test for negative values now becomes obsolete (for safety not removed,
but replaced with a less annoying `DCCP_BUG').

Signed-off-by: Gerrit Renker <gerrit@erg.abdn.ac.uk>
Signed-off-by: Ian McDonald <ian.mcdonald@jandi.co.nz>
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
2008-01-28 14:54:58 -08:00
Gerrit Renker
3deeadd74b [CCID2]: Replace cwnd assignment-function with assignment
The current function ccid2_change_cwnd in effect makes only an assignment, as
the test whether cwnd has reached 0 is only required when cwnd is halved.

This patch simplifies the code by replacing the function with the assignment
it performs.

Furthermore, since ssthresh derives from cwnd and appears in many assignments and
comparisons, the type of ssthresh has also been changed to match that of cwnd.

Signed-off-by: Gerrit Renker <gerrit@erg.abdn.ac.uk>
Signed-off-by: Ian McDonald <ian.mcdonald@jandi.co.nz>
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
2008-01-28 14:54:57 -08:00
Gerrit Renker
63df18ad7f [CCID2]: Replace read-only variable with constant
This replaces the field member `numdupack', which was used as a read-only
constant in the code, with a #define.

Signed-off-by: Gerrit Renker <gerrit@erg.abdn.ac.uk>
Signed-off-by: Ian McDonald <ian.mcdonald@jandi.co.nz>
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
2008-01-28 14:54:57 -08:00
Gerrit Renker
7792cd8885 [CCID2]: Remove unused variable
This removes a variable `ccid2hctx_sent' which is incremented but
never referenced/read (i.e., dead code).

Signed-off-by: Gerrit Renker <gerrit@erg.abdn.ac.uk>
Signed-off-by: Ian McDonald <ian.mcdonald@jandi.co.nz>
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
2008-01-28 14:54:56 -08:00
Gerrit Renker
900bfed471 [CCID2]: Disable broken Ack Ratio adaptation algorithm
This comments out a problematic section comprising a half-finished algorithm:

 - The variable `ccid2hctx_ackloss' is never initialised to a value different from 0 and
   hence in fact is a read-only constant.
 - The `arsent' variable counts packets other than Acks (it is incremented for every packet),
   and there is no test for Ack Loss.
 - The concept of counting Acks as such leads to a complex calculation, and the calculation
   at the moment is inconsistent with this concept.
   The problem is that the number of Acks - rather than the number of windows - is counted,
   which leads to a complex (cubic/quadratic) expression - this is not even implemented.

In its current state, the commented-out algorithm interfers with normal processing by
changing Ack Ratio incorrectly, and at the wrong times.

A new algorithm is necessary, which will not necessarily use the same variables as used by
the unfinished one; hence the old variables have been removed.

Signed-off-by: Gerrit Renker <gerrit@erg.abdn.ac.uk>
Acked-by: Ian McDonald <ian.mcdonald@jandi.co.nz>
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
2008-01-28 14:54:55 -08:00
Gerrit Renker
b00d2bbc45 [CCID2]: Larger initial windows also for CCID2
RFC 4341, sec. 5 states that "The cwnd parameter is initialized to at most
four packets for new connections, following the rules from [RFC3390]", which
is implemented by this patch.

Signed-off-by: Gerrit Renker <gerrit@erg.abdn.ac.uk>
Acked-by: Ian McDonald <ian.mcdonald@jandi.co.nz>
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
2008-01-28 14:54:55 -08:00
Gerrit Renker
d50ad163e6 [CCID2]: Deadlock and spurious timeouts when Ack Ratio > cwnd
This patch removes a bug in the current code. I agree with Andrea's comment
that there is a problem here but the way it is treated does not fix it.

The problem is that whenever Ack Ratio > cwnd, starvation/deadlock occurs:
 * the receiver will not send an Ack until (Ack Ratio - cwnd) data packets
   have arrived;
 * the sender will not send any data packet before the receipt of an Ack
   advances the send window.
The only way that the connection then progresses was via RTO timeout. In one
extreme case (bulk transfer), it was observed that this happened for every single
packet; i.e. hundreds of packets, each a RTO timeout of 1..3 seconds apart:
a transfer which normally would take a fraction of a second thus grew to
several minutes.

The solution taken by this approach is to observe the relation

                   "Ack Ratio <= cwnd"

by using the constraint (1) from RFC 4341, 6.1.2; i.e. set

                 Ack Ratio = ceil(cwnd / 2)

and update it whenever either Ack Ratio or cwnd change. This ensures that
the deadlock problem can not arise.

Signed-off-by: Gerrit Renker <gerrit@erg.abdn.ac.uk>
Acked-by: Ian McDonald <ian.mcdonald@jandi.co.nz>
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
2008-01-28 14:54:53 -08:00
Gerrit Renker
df054e1d00 [CCID2]: Don't assign negative values to Ack Ratio
Since it makes not sense to assign negative values to Ack Ratio, this
patch disallows this possibility.

As a consequence, a Bug test for negative Ack Ratio values becomes obsolete.

Furthermore, a check against overflow (as Ack Ratio may not exceed 2 bytes,
due to RFC 4340, 11.3) has been added.

Signed-off-by: Gerrit Renker <gerrit@erg.abdn.ac.uk>
Acked-by: Ian McDonald <ian.mcdonald@jandi.co.nz>
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
2008-01-28 14:54:53 -08:00
Gerrit Renker
cfbbeabc88 [CCID2]: Fix sequence number arithmetic/comparisons
This replaces use of normal subtraction with modulo-48 subtraction.

Signed-off-by: Gerrit Renker <gerrit@erg.abdn.ac.uk>
Acked-by: Ian McDonald <ian.mcdonald@jandi.co.nz>
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
2008-01-28 14:54:52 -08:00
Gerrit Renker
3de5489f47 [CCID2]: Bug in reading Ack Vectors
In CCID2 the receiver-history is sorted in ascending order of sequence number,
but the processing of received Ack Vectors requires the list traversal in the
opposite direction.

The current code has a bug in this regard: the list traversal is upwards. As a
consequence, only Ack Vectors with a run length of 1 will pass, in all other
Ack Vectors the remaining (acked) sequence numbers are missed, and may later
falsely be identified as lost.

Note: This bug is only visible when Ack Ratio > 1, since otherwise the run
      lengths of Ack Vectors are 0.

Signed-off-by: Gerrit Renker <gerrit@erg.abdn.ac.uk>
Signed-off-by: Ian McDonald <ian.mcdonald@jandi.co.nz>
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
2008-01-28 14:54:51 -08:00
Gerrit Renker
6d57b43bf8 [DCCP]: Remove redundant dependency on IP_DCCP
This cleans up the consequences of an earlier patch which
introduced the `if IP_DCCP' clause into net/dccp/Kconfig.

The CCID Kconfig menu is sourced within this clause; as a
consequence, all tests of type `depends on IP_DCCP' are now
redundant.

Signed-off-by: Gerrit Renker <gerrit@erg.abdn.ac.uk>
Signed-off-by: Ian McDonald <ian.mcdonald@jandi.co.nz>
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
2008-01-28 14:54:46 -08:00
Gerrit Renker
e333b3edc4 [DCCP]: Promote CCID2 as default CCID
This patch addresses the following problems:

 1. DCCP relies for its proper functioning on having at least one CCID module
    enabled (as in TCP plugable congestion control). Currently it is possible to
    disable both CCIDs and thus leave the DCCP module in a compiled, but entirely
    non-functional state: no sockets can be created when no CCID is available.
    Furthermore, the protocol is (again like TCP) not intended to be used without
    CCIDs. Last, a non-empty CCID list is needed for doing CCID feature negotiation.

 2. Internally the default CCID that is advertised by the Linux host is set to CCID2
    (DCCPF_INITIAL_CCID in include/linux/dccp.h). Disabling CCID2 in the Kconfig
    menu without changing the defaults leads to a failure `module not found' when
    trying to load the dccp module (which internally tries to load the default CCID).

 3. The specification (RFC 4340, sec. 10) treats CCID2 somewhat like a
    `minimum common denominator'; the specification says that:

    * "New connections start with CCID 2 for both endpoints"

    * "A DCCP implementation intended for general use, such as an implementation in a
       general-purpose operating system kernel, SHOULD implement at least CCID 2.
       The intent is to make CCID 2 broadly available for interoperability [...]"

    Providing CCID2 as minimum-required CCID (like Reno/Cubic in TCP) thus seems reasonable.

Hence this patch automatically selects CCID2 when DCCP is enabled. Documentation also added.

Discussions with Ian McDonald on this subject are gratefully acknowledged.

Signed-off-by: Gerrit Renker <gerrit@erg.abdn.ac.uk>
Signed-off-by: Ian McDonald <ian.mcdonald@jandi.co.nz>
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
2008-01-28 14:54:46 -08:00