From: Marcelo Ricardo Leitner Date: Fri, 23 Dec 2016 16:29:02 +0000 (-0200) Subject: sctp: do not loose window information if in rwnd_over X-Git-Url: https://git.karo-electronics.de/?a=commitdiff_plain;h=58b94d88deb9ac913740e7778f2005f3ce6d0443;p=linux-beck.git sctp: do not loose window information if in rwnd_over 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 Signed-off-by: David S. Miller --- diff --git a/net/sctp/associola.c b/net/sctp/associola.c index 68428e1f7181..56ddcfaeb4f6 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; }