Re: [lwip-users] DNS client for lwIP raw API

[Winformatik Info]

Hi Jim,

I have tested the resolver code from you. It is working great... after a 
little debugging. I always had the problem if the domain name to resolve 
had an odd number of bytes. If this was the case, the resolver did not 
work (I use a 16-bit CPU with an alignment of 2).
To solve the problem I think we should surround the struct 
"s_dns_answer" by the two macros PACK_STRUCT_BEGIN and PACK_STRUCT_END 
(please see below). This handles a mapping of the struct "s_dns_answer" 
starting on an odd address the right way.

/* The DNS answer message structure */
PACK_STRUCT_BEGIN
typedef struct s_dns_answer {
 /* DNS answer record starts with either a domain name or a pointer
 to a name already present somewhere in the packet. */
 u16_t type;
 u16_t class;
 u16_t ttl[2];
 u16_t len;
 struct ip_addr ipaddr;
} DNS_ANSWER;
PACK_STRUCT_END

Hope this also helps others...

Roland


Pettinato, Jim schrieb:
> You're welcome... Hopefully more sweet stuff to follow. ;)
>
> -----Original Message-----
> From: address@hidden
> [mailto:address@hidden On Behalf
> Of Taranowski, Thomas (SWCOE)
> Sent: Wednesday, June 27, 2007 2:31 PM
> To: Mailing list for lwIP users
> Subject: RE: [lwip-users] DNS client for lwIP raw API
>
>
> This is sweet.  I've been wanting some DNS functionality for awhile.
> Thanks.
>
>   
> > -----Original Message-----
> > From: address@hidden
> > [mailto:address@hidden
> >     
> On
>   
> > Behalf Of Pettinato, Jim
> > Sent: Tuesday, June 19, 2007 5:30 AM
> > To: Mailing list for lwIP users
> > Subject: [lwip-users] DNS client for lwIP raw API
> >
> >
> > All:
> >
> > As mentioned here before, I have ported Adam Dunkel's original uIP DNS
> >     
>
>   
> > client (resolv.c) to something that works for raw API apps. There has 
> > been some interest expressed recently in this code by others, and
> >     
> since
>   
> > I don't want to keep everyone who might benefit waiting until we
> >     
> decide
>   
> > whether to integrate this into the core or maintain it as a separate 
> > application, I have attached the module here.
> >
> > In the nature of the raw API, this DNS client has been implemented
> >     
> using
>   
> > the callback scheme - there is a gethostbyname() function that accepts
> >     
> a
>   
> > callback argument that is stored away if a query is required for the 
> > requested host, and then is called when the DNS query completes or
> >     
> times
>   
> > out. See the header file for more details.
> >
> > The only requirements to use it (other than including the module in
> >     
> the
>   
> > build and calling gethostbyname() with an appropriate callback
> >     
> function)
>   
> > is to call resolv_init() with an appropriate DNS server IP address,
> >     
> and
>   
> > adding a call to the resolve_tmr() function approximately once a
> >     
> second
>   
> > in your timer routine.
> >
> > Let me know if you 1. can't access the attachment and 2. need this
> >     
> code
>   
> > immediately; and I'll post it as inline text or forward it to your 
> > specific email address.
> >
> > - Jim
> >
> > __
> >
> >
> > James M. Pettinato, Jr.
> > Software Engineer
> > E: address@hidden | P: 814 898 5250
> >
> > FMC Technologies Measurement Solutions Inc.
> > 1602 Wagner Avenue | Erie PA | 16510 USA
> > Phone: 814 898 5000 | Fax: 814 899-3414 www.fmctechnologies.com
> >     
>
>
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