Re: Kernel network layer breakes recv_from() as the server (i think) (kernel-bug)

[linux-os (Dick Johnson)]

On Fri, 12 May 2006, [iso-8859-2] Paweł Jaworski wrote:

> $ brief-problem
> Kernel network layer breakes recv_from() as the server (i think)
>
> $ full-problem
> I am student of Jagiellonian University of Cracow. Recently I've been trying to
> write some network programs as a learning of network protocols. Everything went
> fine except for UDP. I was trying to send a structure through the UDP protocol
> to the server. Every time I was sending a packet, recv_from() returned "Invalid
> argument". As it was my homework, i brought the program to my teacher, but... it
> worked well on systems in my school.
>
> 1. It worked on Linux Mandrake (i think) 10
> 2. It worked on Debian Sarge with kernel-image-2.4.27-2-686-smp
> 3. It worked on Debian Sarge with kernel-image-2.6.8-2
> 4. It worked on IRIX (i know it's not Linux, but... it worked)
>

Not relevent.

[SNIPPED...]

>     exit(1);
>   };
>
>   while (1)
>   {
>     int rd;
>     int i;
>     socklen_t from_size;
>
>     rd = recvfrom( s, (char*)&p, sizeof(p), 0, (struct sockaddr *)&cli_address,
> &from_size);
    ^^^^^^^^______ Was NOT initialized....


Quote man pages: "The argument fromlen is a value-result parameter,
initialized to the size of the buffer associated with from...."
^^^^^^^^^^____ READ this!


recvfrom() returned -1 with errno EINVAL because you fed it
invalid parameters. If some other Unixes ignore parameters,
of if the value on the stack just happened to be okay, it
doesn't mean there is a problem with Linux or any operating
system. You must understand that millions of programs use
the O.S. (any OS). If you find a problem when coding, the
chances are millions:1 against your code!

[SNIPPED crap]


Cheers,
Dick Johnson
Penguin : Linux version 2.6.16.4 on an i686 machine (5592.89 BogoMips).
New book: http://www.lymanschool.com
_


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