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

[Bill Knight]

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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