RE: [lwip-users] tcp_write and dynamic data (was: Optimizing TCPwrites)

[Bill Auerbach]

I see I can use TCP_WRITE_FLAG_COPY with tcp_write when the data is dynamic.
There won't be a lot to copy.  It's not very efficient but the problem is
solvable.

Bill

> -----Original Message-----
> From: address@hidden
> [mailto:address@hidden On Behalf
> Of Bill Auerbach
> Sent: Friday, March 07, 2008 9:56 AM
> To: 'Mailing list for lwIP users'
> Subject: RE: [lwip-users] tcp_write and dynamic data (was: Optimizing
> TCPwrites)
> 
> Jonathan,
> 
> While debugging this, I found a much more serious problem to now deal
> with.
> Once resolved, I'll continue on the original problem because I don't want
> to
> have this new problem be causing the original.
> 
> In my tcp_sent callback, I see that I have no remaining data to send.  It
> was recommended that this is the time that I can deallocate the memory
> passed to tcp_write (because presumably it's been sent).  The problem is,
> this data is still in the send queue and cannot be deallocated at this
> time.
> The data cannot be deallocated until it is ACKed, which I have no way of
> knowing (I think).
> 
> This makes me wonder, how is anyone handling calling tcp_write with
> dynamically allocated memory and freeing it at the time when it is safe
> to?
> 
> Do I really need a custom version that tracks segments that have dynamic
> memory, sees the ACK and then frees those that are marked dynamic?  Or as
> I've done in the past, have I made this a much bigger problem than is
> really
> there?
> 
> Thank you,
> Bill
> 
> > -----Original Message-----
> > I can only assume that your subsequent tcp_writes are not matching the
> > 'if'
> > condition. Maybe you could debug it (or add a little print statement) to
> > find out why. It is possible there may be a bug around.
> >
> > Jifl
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