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    SubjectRe: ipv6 stack seems to forget to send ACKs


    --On Thursday, January 09, 2003 12:38:58 +0100 Rogier Wolff
    <R.E.Wolff@BitWizard.nl> wrote:

    > On Wed, Jan 08, 2003 at 02:08:50PM +0100, Wichert Akkerman wrote:
    >>

    Looked normal and then:

    >
    >> 13:57:40.282351 2001:968:1::2.8000 > tornado.wiggy.net.33035: .
    >> 9359225:9360433(1208) ack 1 win 5712 <nop,nop,timestamp 369670744 846103>
    >
    > But now: No ack! Funny.

    Might be SACK deciding not to...

    >> 13:57:40.284307 2001:968:1::2.8000 > tornado.wiggy.net.33035: .
    >> 9360433:9360653(220) ack 1 win 5712 <nop,nop,timestamp 369670744 846103>
    >
    > Another packet, no ack!
    >
    >> 13:57:40.297307 2001:968:1::2.8000 > tornado.wiggy.net.33035: .
    >> 9360653:9361861(1208) ack 1 win 5712 <nop,nop,timestamp 369670745 846104>
    >> 13:57:40.297376 tornado.wiggy.net.33035 > 2001:968:1::2.8000: . ack
    >> 9359225 win 32616 <nop,nop,timestamp 846111 369670744,nop,nop,sack sack
    >> 1 {9360653:9361861} >
    >
    > Another packet, but this time it SACKs the just-recieved packet. It looks
    > as if the two packets inbetween somehow were not recognized as belonging
    > with this connection.

    or SACK forgot about them?

    > Two more packets, and still more hints towards the other machine that
    > we're missing 9359225-9360653
    >
    >> 13:57:40.568652 2001:968:1::2.8000 > tornado.wiggy.net.33035: .
    >> 9359225:9360433(1208) ack 1 win 5712 <nop,nop,timestamp 369670773 846113>
    >
    > So, it retransmits the first. but we don't see it as beloging to
    > this connection or something, so it gets ignored.

    or we're waiting for the other one to ACK them both in one go?

    > It looks as if somehow those two packets 9359225:9360433 and
    > 9360433:9360653 get mangled in a way as to invalidate the checksum. This
    > would cause "silent drop" of these packets before they were acked....

    Could be data dependant, so there's a pattern in the packet contents that
    causes this?

    > Can you check the stats counters, to see if they are indeed dropped?
    >
    > Roger.


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