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dccp tfrc: Return type of update_i_mean is void

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This changes the return type of tfrc_lh_update_i_mean() to void, since that 
function returns always `false'. This is due to 

 	len = dccp_delta_seqno(cur->li_seqno, DCCP_SKB_CB(skb)->dccpd_seq) + 1;
 
 	if (len - (s64)cur->li_length <= 0)	/* duplicate or reordered */
		return 0;

which means that update_i_mean can only increase the length of the open loss
interval I_0, and hence the value of I_tot0 (RFC 3448, 5.4). Consequently the
test `i_mean < old_i_mean' at the end of the function always evaluates to false.

There is no known way by which a loss interval can suddenly become shorter,
therefore the return type of the function is changed to void. (That is, under
the given circumstances step (3) in RFC 3448, 6.1 will not occur.)

Further changes:
----------------
 * the function is now called from tfrc_rx_handle_loss, which is equivalent
   to the previous way of calling from rx_packet_recv (it was called whenever
   there was no new or pending loss, now  it is also updated when there is
   a pending loss - this increases the accuracy a bit);
 * added a FIXME to possibly consider NDP counting as per RFC 4342 (this is
   not implemented yet).

Signed-off-by: Gerrit Renker <gerrit@erg.abdn.ac.uk>
This commit is contained in:
Gerrit Renker
2008-09-04 07:30:19 +02:00
parent d20ed95f8b
commit 3ca7aea041
4 changed files with 17 additions and 18 deletions
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8
net/dccp/ccids/ccid3.c
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@@ -767,15 +767,7 @@ static void ccid3_hc_rx_packet_recv(struct sock *sk, struct sk_buff *skb)
*/
if (sample != 0)
hcrx->rtt = tfrc_ewma(hcrx->rtt, sample, 9);
} else if (tfrc_lh_update_i_mean(&hcrx->li_hist, skb)) {
/*
* Step (3) of [RFC 3448, 6.1]: Recompute I_mean and, if I_mean
* has decreased (resp. p has increased), send feedback now.
*/
do_feedback = CCID3_FBACK_PARAM_CHANGE;
}
/*
* Check if the periodic once-per-RTT feedback is due; RFC 4342, 10.3
*/