Re: How to tell an application to use a custom tcp/ip stack instead of tcp/ip stack from linux?

gds_at_best.cut.here.com
Date: 07/05/05 

Date: Tue, 05 Jul 2005 19:52:46 GMT

>John-Paul Stewart wrote:
>> CDP wrote:
>> >
>> >
>> > I tried it , by setting the LD_PRELOAD environement variable to
>> > the path of the shared library of lwip I have with me , which I already
>> > compiled on my linux system. By setting it I started my tftp
>> > application , but I did not observe any change... its like ,its using
>> > the normal tcp/ip stack from linux , but not lwip. If the standard
>> > functions are replaced with this , I should observe some change
>> > ..right?
>>
>> I don't quite know what you'd expect to observe. TCP/IP stacks don't
>> typically display a lot of output on screen telling you what is going
>> on. What did *you* expect to see? Why did you expect that? (E.g., did
>> the makers of the alternate stack tell you "expect to see X happen"?)
>>
>> It's possible that the lack of observed difference means the alternate
>> stack was running just fine. There might only be observable differences
>> when things go wrong, if one stack is meant to be a drop-in replacement
>> for the other.
>
> Hi John,
>
> The makers of alternate tcp/ip stack (lwip) did not mention
>anything to happen after the replacement.So do you think that the
>alternate stack is working fine with my tftp application? I can not
>even see a single difference b/w the linux tcp/ip stack and lwip , may
>be I might have done wrong with my LD_PRELOAD environment variable . I
>cross checked the LD_PRELOAD environment variable , its set to the path
>of shared library gen erated by means of compiling the stack. Do you
>know any other means of cross checking ? whether what I have done is
>right?

Just a shot in the dark ... can you do netstats or sockstats that show
the packets that used to use the default tcp/ip stack don't use it any
more?

--gregbo
gds at best dot com

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