AW: [lwip-users] DNS for socket API

[Mathias Zenger]

I am afraid I need your help again. My call to gethostbyname() still doesn't
return the desired IP address. The DNS request was sent out to the DNS
server and it returned a correct packet with the resolved address. However,
this reply doesn't seem to arrive in my application. At least dns_recv() is
never called. After three more tries gethostbyname() returns with the
error -8 because there was no address available (timeout).

Unfortunately I am not that familiar with lwIP's debug options and with
stats. As far as I see stats and some of the debug helps are enabled in my
port. Where could I see the results if something would have been stated?

My application uses UDP, DHCP, IGMP and DNS with the socket API. Because it
could be a problem with the available ressources here are some of my
definitions in lwipopts.h:

#define MEMP_NUM_PBUF           6
#define MEMP_NUM_RAW_PCB        1

#define LWIP_UDP                1
#define UDP_TTL                 255

#define MEMP_NUM_UDP_PCB        6

#define MEMP_NUM_SYS_TIMEOUT    6

#define MEMP_NUM_NETBUF         3
#define MEMP_NUM_NETCONN        4

#define PBUF_POOL_SIZE          6
#define PBUF_POOL_BUFSIZE       500
#define PBUF_LINK_HLEN          16

The following definition is in opt.h (probably right):

/** DNS use a local buffer if DNS_USES_STATIC_BUF=0, a static one if
    DNS_USES_STATIC_BUF=1, or a dynamic one if DNS_USES_STATIC_BUF=2.
    The buffer will be of size DNS_MSG_SIZE */
#ifndef DNS_USES_STATIC_BUF
#define DNS_USES_STATIC_BUF             1
#endif






-----Ursprüngliche Nachricht-----
Von: Pettinato, Jim [mailto:address@hidden
Gesendet: Dienstag, 8. September 2009 16:53
An: address@hidden; Mailing list for lwIP users
Betreff: RE: [lwip-users] DNS for socket API



Sorry for assuming the simplest source of your problem - I pretty much
strictly use the raw API, so am less familiar with the socket / netconn API.

Can you verify that the DHCP-returned DNS server IP is being stored
properly? It should be stuffed into dns.c's static array variable
dns_servers[0].

There are at minimum the following memory requirements for DNS to work...
You need an available UDP pcb, one open entry in the DNS table (i.e.
DNS_TABLE_SIZE large enough for all resolved names) and some free pbufs in
the pool to send the packet.

Is dns_send() getting called or is it not getting that far?

Do you have stats enabled? Any allocation errors should show up in the
associated memory structure's stats.


-----Original Message-----
From: address@hidden
[mailto:address@hidden On Behalf Of
Mathias Zenger
Sent: Tuesday, September 08, 2009 10:33 AM
To: address@hidden
Subject: WG: [lwip-users] DNS for socket API

Thanks for your hint. I dug even deeper but still wasn't successful. At the
end I was able to break in

do_dns_found(const char *name, struct ip_addr *ipaddr, void *arg)

This method returns ERR_VAL (-8) which says "timeout or memory error" or
"illegal value" or "dns server response was invalid" respectively (depending
on different method comments).

I guess that my name argument is OK. At least my debugger resolves the name
pointer to "ntpbmt01.dyndns.org" which is the desired server. The second
argument (addr) gets defined in netconn_gethostbyname(). I am only passing
the name pointer to gethostbyname(). Could there anyway be a problem with
the memory (e.g. a missing memory allocation / lwIP configuration setting)?
Still there is no DNS packet output which I would expect to see after the
call of dns_enqueue()...



-----Ursprüngliche Nachricht-----
Von: Pettinato, Jim [mailto:address@hidden
Gesendet: Freitag, 4. September 2009 17:27
An: address@hidden; Mailing list for lwIP users
Betreff: RE: [lwip-users] DNS for socket API



-8 (ERR_ARG) would appear to indicate that the netconn_gethostbyname()
function is being passed either a NULL pointer for the name to look up, or a
NULL pointer for the destination to write the resolved IP address. Check
your arguments to the call; my guess would be perhaps you are a level of
indirection off on your addr argument (i.e. passing the value instead of the
address of your ip_addr variable).


-----Original Message-----
From: address@hidden
[mailto:address@hidden On Behalf Of
Mathias Zenger
Sent: Friday, September 04, 2009 10:40 AM
To: Mailing list for lwIP users
Subject: AW: [lwip-users] DNS for socket API

Hi,

I am working on my 'problem' again.

My call of gethostbyname() after a few seconds always returns NULL. I set a
breakpoint within this function and saw that

err = netconn_gethostbyname(name, &addr);

returns the error code -8. Unfortunately I still don't know what I am doing
wrong. DHCP works fine and gives the correct DNS server address. LWIP_DNS is
set to 1. There is no packet output from my device to the DNS server at all
(no packet captured with Wireshark). Is there a special need to 'somehow
handle' the DNS server address?

To solve my previous problems I replaced the netdb.c/h files in my stack.
Afterwards the compiler errors/warnings disappeared. Was it a bad idea to
just replace the two 1.3.0 files by the 1.3.1 version?

Any other ideas? Thanks.
Regards,
Mathias


-----Ursprüngliche Nachricht-----
Von: address@hidden
[mailto:address@hidden Auftrag von
address@hidden
Gesendet: Dienstag, 11. August 2009 16:41
An: Mailing list for lwIP users
Betreff: Re: [lwip-users] DNS for socket API


Simon Goldschmidt wrote:
>> In netdb.c I get some warnings for implicit declarations of strlen(),
>> memcpy() and memset(). This probably could indicate a missing
>> string.h include.
>>
> That could well be as I think the example ports include string.h in
> their
port-defined cc.h file. Just try to add the missing include in netdb.c until
we added it to CVS.
>
I've just added #include <string.h> to netdb.c in CVS.
>> The error in netdb.c says 'conflicting types for lwip_gethostbyname_r'.
In
>> netdb.h I get the error messages 'previous declaration of
>> lwip_gethostbyname_r was here' and 'expected declaration specifiers
>> or '...'
>> before size_t'
>>
>
> That would mean another standard include is missing in netdb.h. I'll
> check
that.
>
#include <stddef.h> was added to netdb.h 2 weeks ago.

Simon


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