From 4d3c46e6833208428d366630aa708f6876e61fc1 Mon Sep 17 00:00:00 2001 From: Vlad Yasevich Date: Fri, 4 Sep 2009 18:20:59 -0400 Subject: sctp: drop a_rwnd to 0 when receive buffer overflows. SCTP has a problem that when small chunks are used, it is possible to exhaust the receiver buffer without fully closing receive window. This happens due to all overhead that we have account for with small messages. To fix this, when receive buffer is exceeded, we'll drop the window to 0 and save the 'drop' portion. When application starts reading data and freeing up recevie buffer space, we'll wait until we've reached the 'drop' window and then add back this 'drop' one mtu at a time. This worked well in testing and under stress produced rather even recovery. Signed-off-by: Vlad Yasevich --- net/sctp/associola.c | 37 +++++++++++++++++++++++++++++++++++-- 1 file changed, 35 insertions(+), 2 deletions(-) (limited to 'net') diff --git a/net/sctp/associola.c b/net/sctp/associola.c index 215b56951d76..39c3821b7d3d 100644 --- a/net/sctp/associola.c +++ b/net/sctp/associola.c @@ -202,6 +202,7 @@ static struct sctp_association *sctp_association_init(struct sctp_association *a asoc->a_rwnd = asoc->rwnd; asoc->rwnd_over = 0; + asoc->rwnd_press = 0; /* Use my own max window until I learn something better. */ asoc->peer.rwnd = SCTP_DEFAULT_MAXWINDOW; @@ -1374,6 +1375,17 @@ void sctp_assoc_rwnd_increase(struct sctp_association *asoc, unsigned len) asoc->rwnd += len; } + /* If we had window pressure, start recovering it + * once our rwnd had reached the accumulated pressure + * threshold. The idea is to recover slowly, but up + * to the initial advertised window. + */ + if (asoc->rwnd_press && asoc->rwnd >= asoc->rwnd_press) { + int change = min(asoc->pathmtu, asoc->rwnd_press); + asoc->rwnd += change; + asoc->rwnd_press -= change; + } + SCTP_DEBUG_PRINTK("%s: asoc %p rwnd increased by %d to (%u, %u) " "- %u\n", __func__, asoc, len, asoc->rwnd, asoc->rwnd_over, asoc->a_rwnd); @@ -1406,17 +1418,38 @@ void sctp_assoc_rwnd_increase(struct sctp_association *asoc, unsigned len) /* Decrease asoc's rwnd by len. */ void sctp_assoc_rwnd_decrease(struct sctp_association *asoc, unsigned len) { + int rx_count; + int over = 0; + SCTP_ASSERT(asoc->rwnd, "rwnd zero", return); SCTP_ASSERT(!asoc->rwnd_over, "rwnd_over not zero", return); + + if (asoc->ep->rcvbuf_policy) + rx_count = atomic_read(&asoc->rmem_alloc); + else + rx_count = atomic_read(&asoc->base.sk->sk_rmem_alloc); + + /* If we've reached or overflowed our receive buffer, announce + * a 0 rwnd if rwnd would still be positive. Store the + * the pottential pressure overflow so that the window can be restored + * back to original value. + */ + if (rx_count >= asoc->base.sk->sk_rcvbuf) + over = 1; + if (asoc->rwnd >= len) { asoc->rwnd -= len; + if (over) { + asoc->rwnd_press = asoc->rwnd; + asoc->rwnd = 0; + } } else { asoc->rwnd_over = len - asoc->rwnd; asoc->rwnd = 0; } - SCTP_DEBUG_PRINTK("%s: asoc %p rwnd decreased by %d to (%u, %u)\n", + SCTP_DEBUG_PRINTK("%s: asoc %p rwnd decreased by %d to (%u, %u, %u)\n", __func__, asoc, len, asoc->rwnd, - asoc->rwnd_over); + asoc->rwnd_over, asoc->rwnd_press); } /* Build the bind address list for the association based on info from the -- cgit v1.2.3-70-g09d2