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

[Andreas Becker]

Hi Peter,

did your inet.c / lwip_xxx_checksum() functions deal with odd/even 
byteaddresses? This may be an problem of an ARM target.

MfG,

> 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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