PCap Library

[ComtriS]

I'm able to do most everything in the PCap library successfully, except install this callback function. The line I bolded in the code below is where my program just freezes at. However, I tried using this same code in a console application, and it worked just fine. What's the deal?

void got_packet(u_char *args, const struct pcap_pkthdr *header, const u_char *packet)
{                   
	return;
}

void RawPacket::SetupFilter(pcap_if_t* Device)
{
	char Error[256];
	struct bpf_program fp;
	char filter_exp[] = "src net 128.0.27.111";
	bpf_u_int32 mask;
	bpf_u_int32 net;

	if (pcap_lookupnet(Device->name, &net, &mask, Error) == -1) {
		fprintf(stderr, "Can't get netmask for device %s\n", Device->name);
		net = 0;
		mask = 0;
	}

	handle = pcap_open_live(Device->name, BUFSIZ, FALSE, 1000, Error);
	if(!handle) {
		fprintf(stderr, "Couldn't open device %s: %s\n", Device->name, Error);
		return;
	}
	
	if (pcap_datalink(handle) != DLT_EN10MB) {
		fprintf(stderr, "%s is not an Ethernet\n", Device->name);
		return;
	}

	if (pcap_compile(handle, &fp, filter_exp, 0, net) == -1) {
		fprintf(stderr, "Couldn't parse filter %s: %s\n", filter_exp, pcap_geterr(handle));
		return;
	}
	
	if (pcap_setfilter(handle, &fp) == -1) {
		fprintf(stderr, "Couldn't install filter %s: %s\n", filter_exp, pcap_geterr(handle));
		return;
	}

	if (pcap_loop(handle, 10, got_packet, NULL) == -1) {
		fprintf(stderr, "Couldn't install callback: %s\n", pcap_geterr(handle));
		return;
	}

	pcap_freecode(&fp);
	pcap_close(handle);

	filterSetup = true;
}

Stack trace:
ntdll.dll!7d61c846()
[Frames below may be incorrect and/or missing, no symbols loaded for ntdll.dll]
kernel32.dll!7d4d8c9e()
kernel32.dll!7d4d8c0d()
Packet.dll!00d23c3a()
wpcap.dll!10016810()
> UDP Packet Test.exe!RawPacket::SetupFilter(pcap_if * Device) Line 359 + 0x14 bytes C++

[ComtriS]

So I just tried sending 10 packets, and it finally returned from that function.

Which confuses me, because I thought what pcap_loop() was supposed to do was install an asynchronous receive callback function, and then return.

Am I doing something wrong?

[jeron]

After reading this, the operation you stated seems about right as you have specified 10 as the packet count to collect prior to returning.

pcap_loop(handle, 10, got_packet, NULL)

[ComtriS]

After reading this, the operation you stated seems about right as you have specified 10 as the packet count to collect prior to returning.

pcap_loop(handle, 10, got_packet, NULL)

Yea, I realized this yesterday. I misunderstood what pcap_loop() was supposed to do. Not sure what the point of pcap_next() is. I thought pcap_next() was synchronous receive, and pcap_loop() was asynchronous receive. Turns out they're both synchronous receive.

Well whatever, I've found my solution. Thanks.