with DISABLE_FILESYSTEM, no default ns server is provided.

[danielinux]

If there is no filesystem, a default nameserver should be provided. API allowing to modify the default nameserver would also be nice to have.

[cpq]

How about an overridable #define NS_DEFAULT_NAMESERVER "8.8.8.8" ?

[alashkin]

@cpq

As I see, fossa already has default NS server:

static const char *ns_default_dns_server = "udp://8.8.8.8:53";
.....
  if (nameserver == NULL && ns_dns_server[0] == '\0' &&
      ns_get_ip_address_of_nameserver(ns_dns_server, sizeof(ns_dns_server)) ==
          -1) {
    strncpy(ns_dns_server, ns_default_dns_server, sizeof(ns_dns_server));  // <- here
  }

So, the question is only about overriding it?

[cpq]

Would compile-time override be OK, e.g.

#ifndef NS_DEFAULT_NAMESERVER
#define NS_DEFAULT_NAMESERVER "8.8.8.8"
#endif

static const char *ns_default_dns_server = "udp://" NS_DEFAULT_NAMESERVER ":53";

?

[alashkin]

Who do you ask?

[cpq]

Asking @danielinux :-)

[danielinux]

I am sorry, I must have overlooked the default_ns option. Also, I think my configuration is broken because I include NS_DISABLE_RESOLVER.

It's a good idea to me to implement a compile time switch though:

#ifndef NS_DEFAULT_NAMESERVER
#define NS_DEFAULT_NAMESERVER "8.8.8.8"
#endif

[danielinux]

As @cpq suggested, there is no way to use an external DNS (e.g. from TCP/IP API). I will make some test on my target with the current codebase and removing NS_DISABLE_RESOLVER from #ifdef PICOTCP block in fossa.h.

Will keep you posted on this.

[danielinux]

OK, I am actually referring to the function

static int ns_get_ip_address_of_nameserver(char *name, size_t name_len)

Defined here:
https://github.com/cesanta/fossa/blob/master/fossa.c#L6642

This function gets called in my demo when trying to resolve the endpoint address, and does not have a valid option when !WIN32 and !NS_DISABLE_FILESYSTEM.

Perhaps this function should use the default nameserver when invoked with neither of these two options enabled?

[alashkin]

Could you use ns_resolve_async instead of ns_get_ip_address_of_nameserver?
ns_resolve_async uses default DNS if cannot find another options.

[cpq]

FYI @danielinux , Alex just pushed 561a760

[danielinux]

@alashkin ns_resolve_async calls ns_get_ip_address_of_nameserver before giving the default nameserver, and I have the feeling that the latter returns 0 erroneously, thus resulting in an invalid dns setting. At least, if this is the expected behavior, I believe that ns_get_ip_address_of_nameserver should return -1 when no options are configured.

[danielinux]

My backtrace:

#0  ns_get_ip_address_of_nameserver (name=0x20001160 "", name_len=256)
#1  0x0806c522 in ns_resolve_async_opt (mgr=0x20004134 <mgr>, name=0x2001fe64 "test.mosquitto.org", query=1, 
    cb=0x8067de5 <resolve_cb>, data=0x20004440, opts=...) at fossa.c:6584
#2  0x0806c484 in ns_resolve_async (mgr=0x20004134 <mgr>, name=0x2001fe64 "test.mosquitto.org", query=1, 
    cb=0x8067de5 <resolve_cb>, data=0x20004440) at fossa.c:6558
#3  0x08067fc6 in ns_connect_opt (mgr=0x20004134 <mgr>, address=0x8099e14 <broker_address> "test.mosquitto.org:8883", 
    callback=0x80203cd <ev_handler>, opts=...) at fossa.c:2374
#4  0x08067eca in ns_connect (mgr=0x20004134 <mgr>, address=0x8099e14 <broker_address> "test.mosquitto.org:8883", 
    callback=0x80203cd <ev_handler>) at fossa.c:2342

[danielinux]

double checked: changing the return value of ns_get_ip_address_of_nameserver to -1 when neither option is enabled, solves the issue for me and takes the path you are suggesting to assign the default nameserver.

[cpq]

Pushed, 3845872

[danielinux]

Thanks 👍