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authorGerrit Renker <gerrit@erg.abdn.ac.uk>2007-11-24 18:40:24 -0500
committerDavid S. Miller <davem@davemloft.net>2008-01-28 17:54:53 -0500
commitd50ad163e6db2dcc365b8d02b30350220f86df04 (patch)
tree56998d89dcf4b748c09b4f5fe82bd2b7742ea3cb /include/asm-blackfin/cpumask.h
parentdf054e1d00fdafa2e2920319df326ddb3f0d0413 (diff)
[CCID2]: Deadlock and spurious timeouts when Ack Ratio > cwnd
This patch removes a bug in the current code. I agree with Andrea's comment that there is a problem here but the way it is treated does not fix it. The problem is that whenever Ack Ratio > cwnd, starvation/deadlock occurs: * the receiver will not send an Ack until (Ack Ratio - cwnd) data packets have arrived; * the sender will not send any data packet before the receipt of an Ack advances the send window. The only way that the connection then progresses was via RTO timeout. In one extreme case (bulk transfer), it was observed that this happened for every single packet; i.e. hundreds of packets, each a RTO timeout of 1..3 seconds apart: a transfer which normally would take a fraction of a second thus grew to several minutes. The solution taken by this approach is to observe the relation "Ack Ratio <= cwnd" by using the constraint (1) from RFC 4341, 6.1.2; i.e. set Ack Ratio = ceil(cwnd / 2) and update it whenever either Ack Ratio or cwnd change. This ensures that the deadlock problem can not arise. Signed-off-by: Gerrit Renker <gerrit@erg.abdn.ac.uk> Acked-by: Ian McDonald <ian.mcdonald@jandi.co.nz> Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com> Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'include/asm-blackfin/cpumask.h')
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