AW: [lwip-users] DNS for socket API

[Mathias Zenger]

Dear lwIP users,

This is just to inform you that I could solve the problem. The stack was
working fine all the time!! Thank you for your help - especially Jim!

Today I figured out that the packets sent to the server didn't contain the
MAC address of my device. How could this happen?

Well just imagine you configure the hardware address registers of your
controller with 00 16 91 FF FF F5 and the netif structure with 00 16 91 FF
FF FF. You probably will get a MAC mismatch and no server replies will be
accepted!

The real problem was that ATMEL's port of a FreeRTOS/lwIP example uses a
default MAC address which they use for configuration in ethernet.c
(hardware) and in ethernetif.c (stack). So never miss to do your changes in
BOTH files when using your own MAC address!!!

Something like this could help:

ethernet.c
----------
// Pass the MAC address to MACB module (hardware)
vMACBSetMACAddress(MacAddress);

// Write same MAC address to network interface structure (netif MACB_if /
stack)
memcpy((void*)&MACB_if.hwaddr, (const void*)&MacAddress,
sizeof(MACB_if.hwaddr));


ethernetif.c
------------
Even better - delete that crap since it is the default MAC address from the
header file conf_eth.h!

// /* set MAC hardware address */
// netif->hwaddr[0] = ETHERNET_CONF_ETHADDR0;
// netif->hwaddr[1] = ETHERNET_CONF_ETHADDR1;
// netif->hwaddr[2] = ETHERNET_CONF_ETHADDR2;
// netif->hwaddr[3] = ETHERNET_CONF_ETHADDR3;
// netif->hwaddr[4] = ETHERNET_CONF_ETHADDR4;
// netif->hwaddr[5] = ETHERNET_CONF_ETHADDR5;


Enjoy your weekend!
Mathias

Only thing left: I was not able to activate lwIP's debug option or to use
stats. In my ATMEL port there is an inconsistence in lwipopts.h / debug.h /
cc.h...




-----Ursprüngliche Nachricht-----
Von: Pettinato, Jim [mailto:address@hidden
Gesendet: Freitag, 11. September 2009 16:40
An: address@hidden; address@hidden
Betreff: RE: [lwip-users] DNS for socket API




Mathais,

Without enabling stats, it is difficult to guess if a resource issue is
causing your problems. At first glance, I suspect that only having 6 pbufs
in the pool could possibly be insufficient, especially if you are on a
network with any level of broadcast traffic.

At first glance and without the benefit of any stats info, I would recommend
increasing the number of pbufs in the pool - and potentially reducing the
size of each, if memory is an issue. For me, somewhere between 128 and
256-byte pbufs seems a good balance between not wasting memory allocating
large pbufs for small packets (the majority of traffic seems to consist of
packets smaller than this range), and not wasting too much time chaining
multiple pbufs for larger packets. I use 128 byte pbufs since much of the
network traffic to our devices is Modbus/TCP or proprietary command/response
type transfers smaller than that size.

Also, I agree a static buffer is probably right - it's the safest option if
you have a finite small number of entries to populate.

Hope this helps,

- Jim


-----Original Message-----
From: Mathias Zenger [mailto:address@hidden
Sent: Thursday, September 10, 2009 11:07 AM
To: Pettinato, Jim; Mailing list for lwIP users
Subject: AW: [lwip-users] DNS for socket API

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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