[lwip-devel] [task #7017] Implement DNS client

[Jonathan Larmour]

Follow-up Comment #86, task #7017 (project lwip):

Re LWIP_MAKE_ADDRWORD - a helper macro would be useful and easy to provide.
>From David's comment, it looks like it would want to be:

#define LWIP_MAKE_ADDRWORD(a,b,c,d)
htonl(((u32_t)a<<24)|((u32_t)b<<16)|(c<<8)|(d<<0)) 

Frederic wrote:
> To be honest, except "localhost", I don't see any real cases
> where a hardcoded name could be useful. Can you tell me some
> samples for such uses? 

It's analogous to /etc/hosts on Unix (or the 'hosts' file on windows,
although I can never remember where it lives). 

It can be used for fixed addresses that won't change and are important (some
sort of main server). This can be a) to save delay and network traffic by
having to look them up repeatedly; but more importantly, b) to reduce the
chance of problems when there are temporary DNS lookup failures, at least for
contacting these important servers.

The other use is to allow use of friendly names for something that won't ever
be (or won't be guaranteed to be) in the DNS server being used. For example a
private name, but in general you want to use a normal DNS server which only
resolves public addresses.


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