| Message ID | 14d1eef1c9da4fcebc53d428a59ecaefab439b2c.1482510284.git.marcelo.leitner@gmail.com |
|---|---|
| State | Accepted, archived |
| Delegated to: | David Miller |
| Headers | show |
From: Marcelo Ricardo Leitner <marcelo.leitner@gmail.com> Date: Fri, 23 Dec 2016 14:29:02 -0200 > It's possible that we receive a packet that is larger than current > window. If it's the first packet in this way, it will cause it to > increase rwnd_over. Then, if we receive another data chunk (specially as > SCTP allows you to have one data chunk in flight even during 0 window), > rwnd_over will be overwritten instead of added to. > > In the long run, this could cause the window to grow bigger than its > initial size, as rwnd_over would be charged only for the last received > data chunk while the code will try open the window for all packets that > were received and had its value in rwnd_over overwritten. This, then, > can lead to the worsening of payload/buffer ratio and cause rwnd_press > to kick in more often. > > The fix is to sum it too, same as is done for rwnd_press, so that if we > receive 3 chunks after closing the window, we still have to release that > same amount before re-opening it. > > Log snippet from sctp_test exhibiting the issue: > [ 146.209232] sctp: sctp_assoc_rwnd_decrease: asoc:ffff88013928e000 > rwnd decreased by 1 to (0, 1, 114221) > [ 146.209232] sctp: sctp_assoc_rwnd_decrease: > association:ffff88013928e000 has asoc->rwnd:0, asoc->rwnd_over:1! > [ 146.209232] sctp: sctp_assoc_rwnd_decrease: asoc:ffff88013928e000 > rwnd decreased by 1 to (0, 1, 114221) > [ 146.209232] sctp: sctp_assoc_rwnd_decrease: > association:ffff88013928e000 has asoc->rwnd:0, asoc->rwnd_over:1! > [ 146.209232] sctp: sctp_assoc_rwnd_decrease: asoc:ffff88013928e000 > rwnd decreased by 1 to (0, 1, 114221) > [ 146.209232] sctp: sctp_assoc_rwnd_decrease: > association:ffff88013928e000 has asoc->rwnd:0, asoc->rwnd_over:1! > [ 146.209232] sctp: sctp_assoc_rwnd_decrease: asoc:ffff88013928e000 > rwnd decreased by 1 to (0, 1, 114221) > > Signed-off-by: Marcelo Ricardo Leitner <marcelo.leitner@gmail.com> Applied.
On Fri, Dec 23, 2016 at 02:29:02PM -0200, Marcelo Ricardo Leitner wrote: > It's possible that we receive a packet that is larger than current > window. If it's the first packet in this way, it will cause it to > increase rwnd_over. Then, if we receive another data chunk (specially as > SCTP allows you to have one data chunk in flight even during 0 window), > rwnd_over will be overwritten instead of added to. > > In the long run, this could cause the window to grow bigger than its > initial size, as rwnd_over would be charged only for the last received > data chunk while the code will try open the window for all packets that > were received and had its value in rwnd_over overwritten. This, then, > can lead to the worsening of payload/buffer ratio and cause rwnd_press > to kick in more often. > > The fix is to sum it too, same as is done for rwnd_press, so that if we > receive 3 chunks after closing the window, we still have to release that > same amount before re-opening it. > > Log snippet from sctp_test exhibiting the issue: > [ 146.209232] sctp: sctp_assoc_rwnd_decrease: asoc:ffff88013928e000 > rwnd decreased by 1 to (0, 1, 114221) > [ 146.209232] sctp: sctp_assoc_rwnd_decrease: > association:ffff88013928e000 has asoc->rwnd:0, asoc->rwnd_over:1! > [ 146.209232] sctp: sctp_assoc_rwnd_decrease: asoc:ffff88013928e000 > rwnd decreased by 1 to (0, 1, 114221) > [ 146.209232] sctp: sctp_assoc_rwnd_decrease: > association:ffff88013928e000 has asoc->rwnd:0, asoc->rwnd_over:1! > [ 146.209232] sctp: sctp_assoc_rwnd_decrease: asoc:ffff88013928e000 > rwnd decreased by 1 to (0, 1, 114221) > [ 146.209232] sctp: sctp_assoc_rwnd_decrease: > association:ffff88013928e000 has asoc->rwnd:0, asoc->rwnd_over:1! > [ 146.209232] sctp: sctp_assoc_rwnd_decrease: asoc:ffff88013928e000 > rwnd decreased by 1 to (0, 1, 114221) > > Signed-off-by: Marcelo Ricardo Leitner <marcelo.leitner@gmail.com> > --- > net/sctp/associola.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/net/sctp/associola.c b/net/sctp/associola.c > index 68428e1f71810fbe65b7f86c750c3ad61f0266ec..56ddcfaeb4f64235b54b0daa915fabf0cc0170a9 100644 > --- a/net/sctp/associola.c > +++ b/net/sctp/associola.c > @@ -1539,7 +1539,7 @@ void sctp_assoc_rwnd_decrease(struct sctp_association *asoc, unsigned int len) > asoc->rwnd = 0; > } > } else { > - asoc->rwnd_over = len - asoc->rwnd; > + asoc->rwnd_over += len - asoc->rwnd; > asoc->rwnd = 0; > } > > -- > 2.9.3 > > Acked-by: Neil Horman <nhorman@tuxdriver.com>
diff --git a/net/sctp/associola.c b/net/sctp/associola.c index 68428e1f71810fbe65b7f86c750c3ad61f0266ec..56ddcfaeb4f64235b54b0daa915fabf0cc0170a9 100644 --- a/net/sctp/associola.c +++ b/net/sctp/associola.c @@ -1539,7 +1539,7 @@ void sctp_assoc_rwnd_decrease(struct sctp_association *asoc, unsigned int len) asoc->rwnd = 0; } } else { - asoc->rwnd_over = len - asoc->rwnd; + asoc->rwnd_over += len - asoc->rwnd; asoc->rwnd = 0; }
It's possible that we receive a packet that is larger than current window. If it's the first packet in this way, it will cause it to increase rwnd_over. Then, if we receive another data chunk (specially as SCTP allows you to have one data chunk in flight even during 0 window), rwnd_over will be overwritten instead of added to. In the long run, this could cause the window to grow bigger than its initial size, as rwnd_over would be charged only for the last received data chunk while the code will try open the window for all packets that were received and had its value in rwnd_over overwritten. This, then, can lead to the worsening of payload/buffer ratio and cause rwnd_press to kick in more often. The fix is to sum it too, same as is done for rwnd_press, so that if we receive 3 chunks after closing the window, we still have to release that same amount before re-opening it. Log snippet from sctp_test exhibiting the issue: [ 146.209232] sctp: sctp_assoc_rwnd_decrease: asoc:ffff88013928e000 rwnd decreased by 1 to (0, 1, 114221) [ 146.209232] sctp: sctp_assoc_rwnd_decrease: association:ffff88013928e000 has asoc->rwnd:0, asoc->rwnd_over:1! [ 146.209232] sctp: sctp_assoc_rwnd_decrease: asoc:ffff88013928e000 rwnd decreased by 1 to (0, 1, 114221) [ 146.209232] sctp: sctp_assoc_rwnd_decrease: association:ffff88013928e000 has asoc->rwnd:0, asoc->rwnd_over:1! [ 146.209232] sctp: sctp_assoc_rwnd_decrease: asoc:ffff88013928e000 rwnd decreased by 1 to (0, 1, 114221) [ 146.209232] sctp: sctp_assoc_rwnd_decrease: association:ffff88013928e000 has asoc->rwnd:0, asoc->rwnd_over:1! [ 146.209232] sctp: sctp_assoc_rwnd_decrease: asoc:ffff88013928e000 rwnd decreased by 1 to (0, 1, 114221) Signed-off-by: Marcelo Ricardo Leitner <marcelo.leitner@gmail.com> --- net/sctp/associola.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)