Re: [lwip-users] TCP behaviour with Zero Copy API using Raw API interface

[Sathya Thammanur]

Thanks Peter and others. Let me check on this one and get back to this
list if things work out fine.

Sathya


On 6/8/05, Peter Jolasson <address@hidden> wrote:
> ... or maybe it should be optimized a bit for speed performance
> 
> --8<------------
> 
> #if MEM_ALIGNMENT >= 2
>   if( (int)dataptr & 1 ) { /* odd address */
> 
>     for(acc = 0; len > 1; len -= 2) {
>       /*    acc = acc + *((u16_t *)dataptr)++;*/
>       acc += htons( ((u16_t)(((u8_t *)dataptr)[0])<<8) | ((u8_t *)dataptr)[1] 
> );
>       dataptr += 2;
>     }
> 
>   } else
> #endif
>   for(acc = 0; len > 1; len -= 2) {
>       /*    acc = acc + *((u16_t *)dataptr)++;*/
>     acc += *(u16_t *)dataptr;
>     dataptr = (void *)((u16_t *)dataptr + 1);
>   }
> 
> --8<------------
> 
> On 6/8/05, Peter Jolasson <address@hidden> wrote:
> > Hi,
> >
> > My problem was the lwip_standard_chksum() routine in the inet.c module.
> > I wasn't aware that it might need to be rewritten/ported. (I don't
> > remember seeing it in any documentation.)
> >
> > I just included a compile directive when MEM_ALIGNMENT >= 2.
> > Maybe this could/should be put into the code repository?
> >
> > //Peter
> >
> >
> >
> > static u16_t
> > lwip_standard_chksum(void *dataptr, int len)
> > {
> >  u32_t acc;
> >
> >  LWIP_DEBUGF(INET_DEBUG, ("lwip_chksum(%p, %d)\n", (void *)dataptr, len));
> >  for(acc = 0; len > 1; len -= 2) {
> >      /*    acc = acc + *((u16_t *)dataptr)++;*/
> > #if MEM_ALIGNMENT >= 2
> >    acc += htons( ((u16_t)(((u8_t *)dataptr)[0])<<8) | ((u8_t *)dataptr)[1] 
> > );
> >    dataptr += 2;
> > #else
> >    acc += *(u16_t *)dataptr;
> >    dataptr = (void *)((u16_t *)dataptr + 1);
> > #endif
> >  }
> >
> >  /* add up any odd byte */
> >  if (len == 1) {
> >    acc += htons((u16_t)((*(u8_t *)dataptr) & 0xff) << 8);
> >    LWIP_DEBUGF(INET_DEBUG, ("inet: chksum: odd byte %d\n", (unsigned
> > int)(*(u8_t *)dataptr)));
> >  } else {
> >    LWIP_DEBUGF(INET_DEBUG, ("inet: chksum: no odd byte\n"));
> >  }
> >  acc = (acc >> 16) + (acc & 0xffffUL);
> >
> >  if ((acc & 0xffff0000) != 0) {
> >    acc = (acc >> 16) + (acc & 0xffffUL);
> >  }
> >
> >  return (u16_t)acc;
> > }
> >
> >
> >
> >
> >
> > On 6/8/05, Bill Knight <address@hidden> wrote:
> > > This is possibly a problem with the ip checksum routine running
> > > on a 16 or 32 bit cpu.
> > >
> > > Regards
> > > -Bill Knight
> > > R O SOftWare &
> > > http://www.theARMPatch.com
> > >
> > >
> > >
> > > On Wed, 8 Jun 2005 10:46:29 +0200, Peter Jolasson wrote:
> > >
> > > >Hi again,
> > >
> > > >To correct myself.
> > > >It's not when there is an odd number of bytes to transfer that it fails.
> > > >It fails when the data is located at an odd address.
> > >
> > > >But as said before my workaround is to set "copy" to 1 and then it works 
> > > >OK.
> > >
> > > >My target cpu is ARM and I've set MEM_ALIGNMENT to 4.
> > > >//Peter
> > >
> > > >On 6/8/05, Peter Jolasson <address@hidden> wrote:
> > > >> Hi,
> > > >>
> > > >> I dont have a solution to your problem but I can describe a 'funny' 
> > > >> behavior
> > > >> that I've noticed with tcp_write().
> > > >> When I send an even number of bytes I can set "copy" to 0.
> > > >> But when sending an odd number of bytes I must set "copy" to 1 
> > > >> otherwise
> > > >> it will fail.
> > > >>
> > > >> I'm using lwIP 1.1.0
> > > >> //Peter
> > > >>
> > > >> On 6/7/05, Sathya Thammanur <address@hidden> wrote:
> > > >> > Hi all,
> > > >> > I have a client program that connects to a server on PC. The client 
> > > >> > is
> > > >> > a simple program that sends data to PC. What I notice is that when I
> > > >> > call  tcp_write() with "copy" argument 1, then my program works
> > > >> > without any issues. However, if I change "copy" to 0 then I notice
> > > >> > that the TCP connection is not established completely. The following
> > > >> > happens :
> > > >> >
> > > >> > Client                            Server
> > > >> > SYN ---------->
> > > >> >       <---------             SYN, ACK
> > > >> >
> > > >> > Junk packet sent from client. The Server resends the SYN, ACK and 
> > > >> > then
> > > >> > closes the connection. TCP client sends a lost ACK with incorrect
> > > >> > sequence number after couple of junk packets.
> > > >> >
> > > >> > I do notice that my application call back that is registered with
> > > >> > tcp_connected() is called. Here is where I start to send data. I am
> > > >> > using lwip version 0.7.2.  Am I using the tcp_write() in the right 
> > > >> > way
> > > >> > as intended ? Any correct usage of this function will be very useful.
> > > >> >
> > > >> > Any help would be greatly appreciated.
> > > >> >
> > > >> > Thanks,
> > > >> > Sathya
> > > >> >
> > > >> >
> > > >> > _______________________________________________
> > > >> > lwip-users mailing list
> > > >> > address@hidden
> > > >> > http://lists.nongnu.org/mailman/listinfo/lwip-users
> > > >> >
> > > >>
> > >
> > >
> > > >_______________________________________________
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> > > >http://lists.nongnu.org/mailman/listinfo/lwip-users
> > >
> > >
> > >
> > >
> > >
> > > _______________________________________________
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> > >
> >
> 
> 
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