[DCCP] ccid3: Avoid congestion control on zero-sized data packets (da335baf) · Commits · 戴 / test

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:

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>

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;

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