On Mon, 2009-05-18 at 15:17 -0400, Claude Robitaille wrote: > That is another solution; which function do you call to transmit: > dev_queue_xmit? Do you handle fragmentation, and hence need to receive > ICMP replies? i have both packet split and scatter gather dma. do not use dev_queue_xmit but dev->hard_start_xmit. u have a light udp stack examples: pktgen.c and kute. > Claude > > raz ben yehuda wrote: > > i have the same issue in my modules. I created a light udp stack and i > > am transmitting in softirq context. > > On Mon, 2009-05-18 at 13:07 -0400, Claude Robitaille wrote: > > > >> Thanks Mulyadi, > >> > >> this is what I was suspecting would be the way to go. But I am more > >> familiar, still, with 2.4 but I found interesting reading about work queues. > >> > >> Someone else is also suggesting to use netfilter and create a module of > >> my own. Any one knows how to compare the 2 solutions? > >> > >> In the packet handler, running in softirq, I will have to handle sk_buff > >> list, or lists. This list will be used by both the packet handler and > >> the work job so there is a need to atomatically manipulate it. I am sure > >> there are quit a bit of list manipulation define or function in 2.6 but > >> I do not know where to look. Any pointers? Or names? > >> > >> Claude > >> > >> Mulyadi Santosa wrote: > >> > >>> Hi Claude.... > >>> > >>> Just trying to give you idea... > >>> > >>> On Mon, May 18, 2009 at 4:35 AM, Claude Robitaille <clauder@xxxxxxxxxxxx> wrote: > >>> > >>> > >>>> Hi all, > >>>> > >>>> i am trying to create a module that will receive frames from a physical > >>>> interface, using a packet handler registered via dev_add_pack, mangle the > >>>> frame content and send it over a UDP socket. To transmit over UDP I created > >>>> a socket and I am sending the frame using sock_sendmsg. It is mostly working > >>>> except that I am getting some error and, above all, the kernel is crashing > >>>> :-( > >>>> > >>>> The error message that I get the most is "scheduling while atomic". This > >>>> leads me to believe that sock_sendmsg cannot be used while in softirq > >>>> context, which, as per my understanding, is the context when the packet > >>>> handlers are called. > >>>> > >>>> So, I am a little puzzled as to what are my options. Should I use some > >>>> queuing and then dispatch something that will execute in the proper context? > >>>> Or try to find a lower entry point into UDP that would work in softirq > >>>> context? Any suggestions? > >>>> > >>>> > >>> As you know, the tcp/ip code path is quite long, IIRC it could reach > >>> 10-15 level deep. So, I think you'll agree we can call it "fast path". > >>> Furthermore, we shouldn't make it slower with unnecessary work. > >>> > >>> Therefore, IMO, if you could somehow copy or move your mangled frame > >>> into separate queue and process it in process context (probably using > >>> workqueue), I think it's the way to go. > >>> > >>> regards, > >>> > >>> Mulyadi. > >>> > >>> > >>> > > > > > > > -- To unsubscribe from this list: send an email with "unsubscribe kernelnewbies" to ecartis@xxxxxxxxxxxx Please read the FAQ at http://kernelnewbies.org/FAQ
