[lwip-devel] [bug #28106] duplicate acknowledge for fast retransmit could have not null length

[Kieran Mansley]

Follow-up Comment #3, bug #28106 (project lwip):

Linux has:

#define FLAG_NOT_DUP (FLAG_DATA|FLAG_WIN_UPDATE|FLAG_ACKED)

i.e. if the packet has data, updates the window, or acks new data, it is not
a duplicate.  The first of these is the point in question.  Looks like other
stacks all consider a packet with data in as not a duplicate, so the change
brings us in line with everyone else.

You are quite right that if packets carrying data get interleaved with the
duplicate ACKs it will fail to do fast retransmission due to the dup ack count
being reset, but for most network stacks that would be an unusual case because
received packets would normal be processed in batches.  That might not be the
case for users of lwIP, particularly where there are small windows and so not
many packets in flight, but it's better that we're compatible with other
stacks than with older versions of lwIP.

    _______________________________________________________

Reply to this item at:

  <http://savannah.nongnu.org/bugs/?28106>

_______________________________________________
  Message sent via/by Savannah
  http://savannah.nongnu.org/