Re: [lwip-devel] Assertion fails in dns.c after PPP interface is down

[Sylvain Rochet]

Hello Michael,

On Wed, Jun 10, 2015 at 04:21:09PM +0200, Michael Waeber wrote:
> If the ppp netif is shut down, e.g. because of a GPRS connection loss,
> the DNS server address is set to the unspecified address (0.0.0.0) in
> ppp.c cdns(). If a client application calls dns_gethostbyname() the
> assertion in dns_send() is triggered:
> 
> >  LWIP_ASSERT("dns server has no IP address set",
> !ip_addr_isany(&dns_servers[entry->server_idx]));
> 
> I think, if no DNS server is configured, dns_gethostbyname() should
> succeed with "not found". Proposal patch attached.

There is an other option, PPP could also switch back to 
DNS_SERVER_ADDRESS, I'll let Simon decide :)

Indeed returning straight off if no DNS server is configured looks like 
better from an overall design point of view, but who cares if uplink is 
currently down ?  It might also help apps which are not designed with an 
holdoff between tries which will then loop as fast as possible on DNS 
request.

Sylvain

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