I am new to netfilter and even linux. I just wish to try the example code in the man page of libipq (I saved it as test.c and have compiled it to test.o). But when I make it: #cc test.o -o test, the following errors showed up:

[root@kite1 netfilter]# cc test.o -o test
test.o(.text+0xf): In function `die':
: undefined reference to `ipq_perror'
test.o(.text+0x1d): In function `die':
: undefined reference to `ipq_destroy_handle'
test.o(.text+0x49): In function `main':
: undefined reference to `ipq_create_handle'
test.o(.text+0x81): In function `main':
: undefined reference to `ipq_set_mode'
test.o(.text+0xb8): In function `main':
: undefined reference to `ipq_read'
test.o(.text+0xe4): In function `main':
: undefined reference to `ipq_message_type'
test.o(.text+0x116): In function `main':
: undefined reference to `ipq_get_msgerr'
test.o(.text+0x141): In function `main':
: undefined reference to `ipq_get_packet'
test.o(.text+0x18c): In function `main':
: undefined reference to `ipq_set_verdict'
test.o(.text+0x1ce): In function `main':
: undefined reference to `ipq_set_verdict'
collect2: ld returned 1 exit status

I have installed iptables-1.2.9 following the instructions. Does it mean I have to link 'test.o' with another file (???.o or ???.so)? Thank you in advance!

Jee

Try this...

cc test.o -o test -I /usr/include/libipq -lipq

bye
Majjj

Thanks a lot!
I tried cc test.o -o test -lipq
then it works!

Oh, this time I try to compile a C++ file (test.cpp), whose content is almost the same with that in test.c. When I use 'test.o -o test -lipq', the result shows as if there were no '-lipq'. What shall I do to compile and link a C++ file? Thanks a lot!

try
extern "C"
{
#include <ipq.h>
}

or something like that :) ... I haven't compiled
C++ against C in ages, so bear with me.

The problem your facing is the fact that
name mangling in C and C++ differ, and C
functions you call from C++ need to be
declared as extern "C" ... not sure whether
it will take the entire include like that, or
whether you'll have to make a wrapper
within the include file.


Cheers,
Tink