[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: 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>

1 files changed, 5 insertions, 9 deletions

diff --git a/net/dccp/ccids/ccid3.c b/net/dccp/ccids/ccid3.c
index 2745d835f037..62c304200eda 100644
--- a/net/dccp/ccids/ccid3.c
+++ b/net/dccp/ccids/ccid3.c
@@ -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;