Commit 76d12777 authored Dec 03, 2006 by Gerrit Renker Committed by Arnaldo Carvalho de Melo Dec 03, 2006

[DCCP]: Fix BUG in retransmission delay calculation



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: 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@mandriva.com>

parent 8a508ac2

net/dccp/ccids/ccid3.c

+1 −1

Original line number	Diff line number	Diff line
		@@ -339,7 +339,7 @@ static int ccid3_hc_tx_send_packet(struct sock sk, struct sk_buff skb)
		* else
		* // send the packet in (t_nom - t_now) milliseconds.
		*/
		if (delay >= hctx->ccid3hctx_delta)
		if (delay - (long)hctx->ccid3hctx_delta >= 0)
		return delay / 1000L;
		break;
		case TFRC_SSTATE_TERM:

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