path: root/net
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authorSamuel Jero <sj323707@ohio.edu>2011-07-24 21:05:16 -0600
committerGerrit Renker <gerrit@erg.abdn.ac.uk>2011-08-01 07:52:36 -0600
commit0ce95dc792549e0cf704e74aa8acb15a401f8cca (patch)
tree77a4b71b1de4e985e5ac8b711c8bca980195235f /net
parentdccp ccid-2: prevent cwnd > Sequence Window (diff)
dccp ccid-2: increment cwnd correctly
This patch fixes an issue where CCID-2 will not increase the congestion window for numerous RTTs after an idle period, application-limited period, or a loss once the algorithm is in Congestion Avoidance. What happens is that, when CCID-2 is in Congestion Avoidance mode, it will increase hc->tx_packets_acked by one for every packet and will increment cwnd every cwnd packets. However, if there is now an idle period in the connection, cwnd will be reduced, possibly below the slow start threshold. This will cause the connection to go into Slow Start. However, in Slow Start CCID-2 performs this test to increment cwnd every second ack: ++hc->tx_packets_acked == 2 Unfortunately, this will be incorrect, if cwnd previous to the idle period was larger than 2 and if tx_packets_acked was close to cwnd. For example: cwnd=50 and tx_packets_acked=45. In this case, the current code, will increment tx_packets_acked until it equals two, which will only be once tx_packets_acked (an unsigned 32-bit integer) overflows. My fix is simply to change that test for tx_packets_acked greater than or equal to two in slow start. Signed-off-by: Samuel Jero <sj323707@ohio.edu> Acked-by: Gerrit Renker <gerrit@erg.abdn.ac.uk>
Diffstat (limited to 'net')
1 files changed, 1 insertions, 1 deletions
diff --git a/net/dccp/ccids/ccid2.c b/net/dccp/ccids/ccid2.c
index 9dbc4d88af16..d9dbd9ffe8cd 100644
--- a/net/dccp/ccids/ccid2.c
+++ b/net/dccp/ccids/ccid2.c
@@ -411,7 +411,7 @@ static void ccid2_new_ack(struct sock *sk, struct ccid2_seq *seqp,
if (hc->tx_cwnd < dp->dccps_l_seq_win &&
r_seq_used < dp->dccps_r_seq_win) {
if (hc->tx_cwnd < hc->tx_ssthresh) {
- if (*maxincr > 0 && ++hc->tx_packets_acked == 2) {
+ if (*maxincr > 0 && ++hc->tx_packets_acked >= 2) {
hc->tx_cwnd += 1;
*maxincr -= 1;
hc->tx_packets_acked = 0;