Re: [lwip-users] tcp_write with zero-copy

[address@hidden]

Timmy Brolin wrote:
> I had a quick look at the tcp_write function, and it seems there could 
> be some problems involved. Things such as what if  the available "space" 
> in the send buffer is smaller than a pbuf. Should the pbuf be splitted 
> and reallocated, or should the entire pbuf be added to the send queue 
> anyway.
> For now I will probably look into implementing something using tcp_sent.
>   

I don't think it's that hard to implement. Just move the code that 
creates the data-pbuf from tcp_enqueue to an wrapping function and call 
the new tcp_enqueue (which then takes a pbuf pointer instead of a data 
pointer and length) directly.
Of course there have to be some checks: if the send-buffer is full, 
discard the complete pbuf and the pbufs must fit into TCP segments. 
Other than that, I think it's pretty straightforward and can help to 
speed up (might save one memcpy) and save space at least for some users.

On the other hand, it has to be well documented that users don't may 
reuse the pbufs given to TCP in this way, because they are modified by 
the stack.

Anyway, this is post-1.3.0 so it might take a while...

Simon