Calling libiptc API from a separate thread in a C program throws segmentation fault

Question

I am working on performing iptables update through a custom c program using libiptc. The requirement is to invoke iptc APIs from a separate thread every 2 seconds.

I have written a simple C program to try out invoking of iptc APIs from a separate thread. The c program is pasted below.

/*** thread_iptc.c ***/

#include <pthread.h>
#include <stdio.h>
#include <stdlib.h>

void* thread_func(void* unused)
{
        struct iptc_handle *handle = NULL;
        char *table = "filter";

        while (1)
        {
                printf("\nthread_func(): While loop.\n");
                handle = iptc_init(table);
                if (handle) {
                        printf("thread_func(): handle is not NULL.\n");
                        iptc_free(handle);
                }
                else
                        printf("thread_func(): handle is NULL.\n");

                sleep(2);
        }

        return NULL;
}


int main()
{
        struct iptc_handle *handle = NULL;
        char *table = "filter";
        pthread_t thread_id;

        handle = iptc_init(table);
        if (handle) {
                printf("main(): handle is not NULL.\n");
                iptc_free(handle);
        }
        else
                printf("main(): handle is NULL.\n");


        pthread_create(&thread_id, NULL, &thread_func, NULL);
        pthread_join(thread_id, NULL);

        return 0;
}

The problem, I am facing is that call to both iptc_init() and iptc_free() works well when called from main function. However, call to iptc_free() fails with "Segmentation Fault" when called from thread_func().

Program Output:

# ./test 
main(): handle is not NULL.

thread_func(): While loop.
thread_func(): handle is not NULL.
Segmentation fault

Compilation:

# gcc -o test thread_iptc.c -lpthread -lext4 -lext6 -lip4tc -lip6tc -liptc -lxtables -ldl

GDB Backtrace

#0  0x00007ffff79be303 in iptc_free () from /lib64/libip4tc.so.0
#1  0x00000000004007f3 in thread_func ()
#2  0x00007ffff7bc77e1 in start_thread () from /lib64/libpthread.so.0
#3  0x00007ffff6efb8ed in clone () from /lib64/libc.so.6

Am I missing something during compilation or while invoking a new thread?