From: Marcelo Ricardo Leitner <marcelo.leitner@xxxxxxxxx> 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@xxxxxxxxx> Applied. -- To unsubscribe from this list: send the line "unsubscribe linux-sctp" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
