Re: pcap_loop

[Eloy Paris <peloy () chapus net>]

On Tue, Jun 03, 2008 at 10:13:49AM +0200, m. kh  wrote:

> how to use a the last argument of pcap_loop ?
> in my program i use :
>                      u_char *user;
>                       user="the message ";
>                       pcap_loop(handle, -1, (pcap_handler) callback , user);
>
> but not succe ,help me
> give me example ?

Using the example you started:

void
mycallback(u_char *user, const struct pcap_pkthdr *h, const u_char *bytes)
{
    printf("mycallback() called. \"user\" pointer is '%s'\n", user);
}

void
f(void)
{
    u_char *user = "the message ";

    pcap_loop(handle, -1, mycallback, user);
}

The last argument to pcap_loop() is a pointer that will be passed to
your callback function. The pointer points to any variable or structure
of your choosing. It's just a standard way of passing data to callback
functions.

Here's another example:

void
mycallback(u_char *user, const struct pcap_pkthdr *h, const u_char *bytes)
{
    int *counter = (int *) user;

    printf("Packet #%d: %u bytes.\n", *counter++, h->caplen);
}

void
f(void)
{
    int pktcounter = 0;

    pcap_loop(handle, -1, mycallback, (u_char *) &pktcounter);
}

Cheers,

Eloy Paris.-
-
This is the tcpdump-workers list.
Visit https://cod.sandelman.ca/ to unsubscribe.