pcap_findalldevs() return codes

[Sreeram BS <sreeramabs () yahoo com>]

Hi,
     I have subscribed to the list yesterday and today I am posting one of the queries/concerns I encountered with pcap 
today.
This is related to the pcap_findalldevs() library call. This call will take a pointer-to-a-pointer-to-pcap_if_t, and an 
err-buffer. 
It returns 0 on success and -1 on failure. 
     With this information, I wrote a small program and incidentally executed it as non-root. 
The program is as follows:

#include <stdio.h>
#include <string.h>
#include <pcap.h>
#include <unistd.h>
#include <stdlib.h>

int main(int argc, char **argv) {
    pcap_if_t *devs;
    char errbuf[PCAP_ERRBUF_SIZE];
    int retn;

    /* Call the routine pcap_findalldevs() */
    retn = pcap_findalldevs(&devs, errbuf);
    if (retn < 0) {
        perror(errbuf);
        exit(-1);
    }
    /* No error - not sure yet */
    if ((devs == NULL) && *errbuf) {    <<< Is this the right way to check for errors ???
        /* This is error */
        printf("Error: %s\n", errbuf);
        exit(-2);
    } else {
        printf("pcap_findalldevs() has identified some usable interfaces !!\n");
    }

    return 0;
}

1. I found that the call to pcap_findalldevs() returned 0, meaning success, even though an error 'Permission denied' 
was filled in errbuf. 
2. Also the 'devs' was NULL, which as mentioned in the man-page could be null, if there are no openable interfaces.

Here, my question is, for the user to know that an error has occurred, he has to always rely on errbuf, irrespective of 
what pcap_findalldevs() returned.
In the above mentioned case, wouldn't it have been helpful if pcap_findalldevs() returned -1, meaning failure, setting 
the errbuf to the error string?
Also am thinking in which cases would pcap_findalldevs() return '-1' ?

Please share your thoughts/comments.

Regards,|
Sreeram
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