'mdns-sd-server' and 'MG_ENABLE_TCPIP=1'

[gvanem]

I'm having troubles with running mdns-sd-server.exe under Windows with the built-in TCP/IP-stack.
I.e. MG_ENABLE_TCPIP=1.

The program crashes with a NULL-ptr reference on c->mgr->ifp. Here:

void mg_multicast_add(struct mg_connection *c, char *ip) {
  (void) ip;  // ip4/6_mcastmac(mcast_mac, &ip); ipv6 param
  // TODO(): actual IP -> MAC; check database, update
  c->mgr->ifp->update_mac_hash_table = true;  // mark dirty << !! here
}

How and where should c->mgr->ifp be set?

I would assume this sample should have some extra code like in tutorials/tcpip/pcap-driver/main.c.
But obviously not.

BTW. the tutorials/udp/mdns-sd-server/Makefile mentions -DMG_ENABLE_MDNS=1 which seems no-where.

[scaprile]

Hi Gisle, please review the TAP example and let me know. That pointer is set at driver initialization and we don't have an automated test for the pcap example. I'm the one who's more likely to test that stuff and I don't use Windows, it is possible that I forgot to incorporate some changes into the pcap example.

WRT MG_ENABLE_MDNS: yes, you're right, that has been deprecated long ago but somehow it stayed there. I'll get it removed. Thank you !

[gvanem]

please review the TAP example and let me know.

You mean tutorials/tcpip/tap-driver/main.c? Which has stuff like:

#include <linux/if.h>
#include <linux/if_tun.h>
...

Quote: This example allows the use of Mongoose's built-in TCP/IP stack in systems that support a TUN/TAP device.

This is not for Windows (allthough the Makefile has ifeq ($(OS),Windows_NT)).
Hence I cannot build it.

[scaprile]

I know, that was a pointer for you to maybe pickup something missing based on how the driver is initialized, it is pretty similar to yours.
I will check myself eventually but that might take longer than you need

[scaprile]

@gvanem I don't see anything has to be added.
Are you calling mg_mdns_listen() after mg_tcpip_init() ?

  mg_tcpip_init(&mgr, &mif);
  MG_INFO(("Init done, starting main loop"));

  // Desired name must NOT have any dots in it, nor a domain
  if (mg_mdns_listen(&mgr, fn, "Mongoose")  // Start mDNS server
       == NULL) exit(1);

  while (s_signo == 0) mg_mgr_poll(&mgr, 100);  // Infinite event loop

That struct is filled at the driver initialization and that happens after calling that function (except when you enable auto driver init, in which case it happens within mg_init() itself, thing these examples don't do)

[gvanem]

What code have you inserted above? Does look like the meat of tutorials/udp/mdns-sd-server/main.c?

I'm confused but think that since there is no MG_TCPIP_DRIVER_INIT() for my case and pcap, that's the reason. Or?

[scaprile]

That's my own version of the tutorial for the TAP interface.
You said you're running our TCP/IP stack in Windows, I assumed you were using the pcap interface, as that is the only way I know to do that, our stack needs a driver.
Then, as you are using your own driver, there are no predefined macros to initialize it, so that is manually done here:

mongoose/tutorials/tcpip/pcap-driver/main.c

Lines 276 to 286 in 988b282

	struct mg_tcpip_if mif = {.driver = &driver,
	.driver_data = ph,
	.enable_mac_check = true,
	#if defined(DISABLE_DHCP)
	.mask = MG_IPV4(255, 255, 255, 0),
	.gw = MG_IPV4(169, 254, 2, 1),
	#endif
	.fn = if_ev_handler};
	sscanf(mac, "%hhx:%hhx:%hhx:%hhx:%hhx:%hhx", &mif.mac[0], &mif.mac[1],
	&mif.mac[2], &mif.mac[3], &mif.mac[4], &mif.mac[5]);
	mg_tcpip_init(&mgr, &mif);

Listeners are started after that, in line 294, while mg_init() was called in line 272

[gvanem]

I'm confused but think that since there is no MG_TCPIP_DRIVER_INIT() for my case

So I added this for my case:

  #if defined(MG_ENABLE_TCPIP_DRIVER_INIT)
    extern struct mg_tcpip_if mg_pcap_mif;
    extern void  *mg_pcap_init (void);

    #define MG_TCPIP_DRIVER_INIT(mgr) do {            $\\
            mg_pcap_mif.driver_data = mg_pcap_init(); $\\
            mg_tcpip_init (mgr, &mg_pcap_mif);        $\\
          } while (0)
  #endif

The added mg_pcap_init() function is similar to what tutorial/tcpip/pcap-driver/main.c does.

This seems to work fine. No crash at least.

[gvanem]

I'm confused but think that since there is no MG_TCPIP_DRIVER_INIT() for my case

So I added this for my case:

  #if defined(MG_ENABLE_TCPIP_DRIVER_INIT)
    extern struct mg_tcpip_if mg_pcap_mif;
    extern void  *mg_pcap_init (void);

    #define MG_TCPIP_DRIVER_INIT(mgr) do {            $\\
            mg_pcap_mif.driver_data = mg_pcap_init(); $\\
            mg_tcpip_init (mgr, &mg_pcap_mif);        $\\
          } while (0)
  #endif

The added mg_pcap_init() function is similar to what tutorial/tcpip/pcap-driver/main.c does.

This seems to work fine. No crash at least:

...
18e32f9e 3 dns.c:564:handle_mdns_respon ignoring > 1 answers
18e32f9e 3 dns.c:574:handle_mdns_respon A response from AMD-PC.local = 10.0.0.10
18e32fdd 3 dns.c:564:handle_mdns_respon ignoring > 1 answers
...

[cpq]

@gvanem could you elaborate on your setup please? Windows and built-in stack - that's very surprising. Is that some sort of tool?

[gvanem]

Windows and built-in stack - that's very surprising.

Why? You're supposed to support libpcap on Windows, no?

Is that some sort of tool?

Not more than mdns-sd-server is a tool on Linux etc. Should work on Windows too.