Re: [lwip-users] LWIP PPP - When connecting, int sifup(ppp_pcb *pcb) is called multiple times

[Sylvain Rochet]

Hi,

On Fri, Oct 30, 2015 at 11:42:14PM +0300, Gennady Shmakov wrote:
> I would agree with Sylvain.
> If we introduce something that will make lwip drop packets and let higher
> protocols to handle that then it might be ok with TCP, but with UDP and
> such it will not.
> My point here is that solution needs to be in driver code or maybe in some
> configuration of lwip to handle slower hardware.

Yes, UDP is even worse, there is no callback to tell you when a UDP 
packet is sent so there is no clean way in user code to only have one 
(or two) pbuf at a time allocated in the stack to do a I/O bound UDP 
flow on a slow netif.

I've been thinking about this issue for the last three months and I 
couln't find anothing appropriate to handle multiple and unbalanced (one 
fast and one slow) netif in lwIP without adding queueing disciplines.

Maybe the recently proposed scheduling disciplines by Russ Dill is the 
proper way :-)

Sylvain

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