[Differential] [Commented On] D5872: tcp: Don't prematurely drop receiving-only connections

[jtl (Jonathan T. Looney)]

jtl added a comment.


  In https://reviews.freebsd.org/D5872#127063, @jtl wrote:
  
  > Doesn't tp->t_rxtshift get updated on a successful send? If not, I think that is what we should be fixing.
  
  
  Of course, tp->t_rxtshift doesn't get updated on a successful send. That's not the way this works. :-)
  
  Now that I've had more coffee...
  
  This probably amounts to the generic problem of:
  
  - When we send data, we should be setting the retransmit timer to make sure we retransmit.
  - When we are not sending data, we should be setting a different timer (DELACK, perhaps?) to make sure we send an ACK, when able.
  
  The key feature that makes the retransmit timer inappropriate for an ACK-only case is that it is only stopped when we receive input; however, in the ACK-only case, we really want to stop it as soon as we transmit a successful ACK.
  
  Of course, we could just drop the ACK and everything would "just work". But, it //probably// is still a good idea to try to re-transmit the ACK.

REVISION DETAIL
  https://reviews.freebsd.org/D5872

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To: sepherosa_gmail.com, network, glebius, hiren, lstewart, adrian, delphij, decui_microsoft.com, honzhan_microsoft.com, howard0su_gmail.com, freebsd-net-list, transport, jtl
Cc: jtl