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Commit da335baf authored by Gerrit Renker's avatar Gerrit Renker Committed by David S. Miller
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[DCCP] ccid3: Avoid congestion control on zero-sized data packets 



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: default avatarGerrit Renker <gerrit@erg.abdn.ac.uk>
Signed-off-by: default avatarIan McDonald <ian.mcdonald@jandi.co.nz>
Signed-off-by: default avatarArnaldo Carvalho de Melo <acme@mandriva.com>
parent 7da7f456

net/dccp/ccids/ccid3.c

+5 −9
Original line number Diff line number Diff line
@@ -264,13 +264,13 @@ static int ccid3_hc_tx_send_packet(struct sock *sk, 


	BUG_ON(hctx == NULL);



	/* Check if pure ACK or Terminating*/

	/*

	 * XXX: We only call this function for DATA and DATAACK, on, these

	 * packets can have zero length, but why the comment about "pure ACK"?

	 * This function is called only for Data and DataAck packets. Sending

	 * zero-sized Data(Ack)s is theoretically possible, but for congestion

	 * control this case is pathological - ignore it.

	 */

	if (unlikely(len == 0))

		return -ENOTCONN;

		return -EBADMSG;



	/* See if last packet allocated was not sent */

	new_packet = dccp_tx_hist_head(&hctx->ccid3hctx_hist);
@@ -387,11 +387,7 @@ static void ccid3_hc_tx_packet_sent(struct sock *sk, int more, int len) 


	switch (hctx->ccid3hctx_state) {

	case TFRC_SSTATE_NO_SENT:

		/* if first wasn't pure ack */

		if (len != 0)

			DCCP_CRIT("%s, First packet sent is noted "

				  "as a data packet",  dccp_role(sk));

		return;

		/* fall through */

	case TFRC_SSTATE_NO_FBACK:

		/* t_nom, t_ipi, delta do not change until feedback arrives */

		return;