[CCID 3]: 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: Gerrit Renker <gerrit@xxxxxxxxxxxxxx>
---
net/dccp/ccids/ccid3.c | 14 +++++---------
1 file changed, 5 insertions(+), 9 deletions(-)
--- a/net/dccp/ccids/ccid3.c
+++ b/net/dccp/ccids/ccid3.c
@@ -282,13 +282,13 @@ static int ccid3_hc_tx_send_packet(struc
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);
@@ -411,11 +411,7 @@ static void ccid3_hc_tx_packet_sent(stru
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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