Re: [lwip-users] Feeding incoming packets to lwIP

[David Haas]

Dan,

I am using an interrupt-driven multi-threaded implementation. Yes, I did 
have some problems.

You need to watch for the protection in memp.c and pbuf.c. There are 
many areas which are not protected well and do need to be. In my case, I 
am using pbuf buffers in my ISR and I found I needed to add protection 
in order to do that. If you are calling tcpip_input from another thread 
you definitely will need to add this protection and I recommend added 
protection in memp.c as well.

Please look at patch 873. This code adds this protection in the form of 
disabling and enabling interrupts through function calls in sys_arch.c.

I have had very good luck since I added this code. I am using a chargen 
server as a test program and I have run this overnight from multiple 
sources with no problems until today. Unfortunately, I did just find a 
statistics problem which I am looking into. I will issue a patch if the 
problem is in the protection code.

David.


Dan Lewis wrote:

> Dear lwIP people,
>
> What's the recommended way to feed incoming packets up to lwIP in an 
> interrupt-driven multi-threaded implmentation?
>
> The interrupt service routine in my current implementation merely signals the 
> arrival of a packet by posting to a uC/OS mailbox. I created a separate thread 
> that contains an infinite loop that pends on that mailbox, and then calls 
> ethernetif_input to read the packet from the NIC (using low_level_input) and pass 
> it on to lwIP (using netif->input, which is a call to tcpip_input).
>
> So the real question is this: Is it safe to initiate the call to tcpip_input 
> from an independent thread in a preemptive multi-threaded system? I.e., does 
> tcpip_input use kernel calls to pass the packet on to lwIP (which is running in 
> a different thread)?  Or do I need to worry about critical sections in this 
> scenario?
>
> Note that in addition to tcpip_input, ethernetif_input also calls arp_ip_input, 
> arp_arp_input, pbuf_header, and pbuf_free. Are these routines also thread-safe?
>
> Is there a better way to feed incoming packets to lwIP in this kind of 
> environment?
>
> Thanks in advance!
>
> Dan Lewis, Chair
> Computer Engineering
> Santa Clara University
>
>
>
>
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