Re: [lwip-users] help with mDNS sending a DNS_RRTYPE_SRV query

[Jens Nielsen]

Hi

Antonio, didn't you already figure out a couple of mails back that the 
problem is that your stack is too small so you get a stack overflow in 
mdns_readname? The recursive function has a max depth check so you 
shouldn't be in an infinite recursive loop.


BR /Jens

On 2018-04-10 14:14, antonio wrote:

Hi Erik,

I am using a simulation like environment, and since I am using a loopback
interface,  and I am unable to see TX/RX packets through wireshark  on the
*loopback_if *127.0.0.1.

However, I added my own hack functionality
*err_t mdns_resolve(const char* hostname, ip_addr_t *addr,
dns_found_callback fn_callback, void *cb_arg)*{
  gethostbyname(hostname, addr,.);
}
is able to correctly resolve my own hostname and also neighbor devices.  To
do so, I added an additional function do DNS
to help me resolve my own hostname.
*err_t dns_add_mdns_entry(const char* hostname, const ip_addr_t *addr, u8_t
dns_addrtype)*

So after validating my hostname with MDNS, i.e, after conflict-free
PROBING+ANNOUNCING, I call  dns_add_mdns_entry, which adds my own entry to
the LWIP DNS TABLE.










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Re: [lwip-users] help with mDNS sending a DNS_RRTYPE_SRV query

[antonio]

Hi Erik,

I am using a simulation like environment, and since I am using a loopback
interface,  and I am unable to see TX/RX packets through wireshark  on the
*loopback_if *127.0.0.1. 

However, I added my own hack functionality 
*err_t mdns_resolve(const char* hostname, ip_addr_t *addr,
dns_found_callback fn_callback, void *cb_arg)*{
 gethostbyname(hostname, addr,.);
}
is able to correctly resolve my own hostname and also neighbor devices.  To
do so, I added an additional function do DNS 
to help me resolve my own hostname. 
*err_t dns_add_mdns_entry(const char* hostname, const ip_addr_t *addr, u8_t
dns_addrtype)*

So after validating my hostname with MDNS, i.e, after conflict-free
PROBING+ANNOUNCING, I call  dns_add_mdns_entry, which adds my own entry to
the LWIP DNS TABLE. 










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Re: [lwip-users] help with mDNS sending a DNS_RRTYPE_SRV query

[Erik Ekman]

Can you record it with wireshark and send a pcap file?

/Erik

On 9 April 2018 at 10:20, antonio  wrote:

> HI Simon,
>
> Let me see if I can be clear.
>
> I have an application using loopback interface. The goal is to test mDNS
> functions and observe queries and responses.,
>
> a) My application first tries a DNS_RRTYPE_A query, and I get a response.
> here there is no problem.
>
> b) The problem happens whenever I send a DNS_RRTYPE_SRV query. Here, I
> NEVER
> get an answer, because, the receiver is unable to compose and send back an
> answer.
>
> Debugging the code, I realize that the function mdns_add_srv_answer calls
> mdns_add_answer and later function never returns :( .
>
> I hope my explanation clarifies you.
>
> Thanks in advance.
>
>
>
>
>
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Re: [lwip-users] help with mDNS sending a DNS_RRTYPE_SRV query

[antonio]

HI Simon, 

Let me see if I can be clear. 

I have an application using loopback interface. The goal is to test mDNS
functions and observe queries and responses.,

a) My application first tries a DNS_RRTYPE_A query, and I get a response.
here there is no problem.

b) The problem happens whenever I send a DNS_RRTYPE_SRV query. Here, I NEVER
get an answer, because, the receiver is unable to compose and send back an
answer. 

Debugging the code, I realize that the function mdns_add_srv_answer calls
mdns_add_answer and later function never returns :( . 

I hope my explanation clarifies you.

Thanks in advance.





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Re: [lwip-users] help with mDNS sending a DNS_RRTYPE_SRV query

[Simon Goldschmidt]

antonio wrote:
> The problem is the function that requires recursion (*mdns_readname*). The
> error is related to */Stack Overflow/.. *

So this is not related to threads? Then please describe the actual problem you 
see.
I'm getting lost in all the other things you write...

Simon

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Re: [lwip-users] help with mDNS sending a DNS_RRTYPE_SRV query

[antonio]

On 05.04.2018 16:24, antonio wrote: 
> I have a small application using MDNS, and I use the loopback interface. 
> At the beginning the Thread1 starts the MDNS process, 

Q: Wait, why are you talking about threads? You are using the callback API 
of lwIP, right? There should not be more than one thread in that case. 

Hi Simon,

The problem is the function that requires recursion (*mdns_readname*). The
error is related to */Stack Overflow/.. *
Since to build a *DNS_RRTYPE_A* responses does not use that function, then
it works perfectly. 

Inside function mdns_add_srv_answer()... setting the last input parameter of
mdns_add_answer() to NULL, 
solves this problem since it will not call mdns_write_domain, which in turn
calls *mdns_readname*. 

But I am not happy with the ack. 






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Re: [lwip-users] help with mDNS sending a DNS_RRTYPE_SRV query

[goldsi...@gmx.de]

On 05.04.2018 16:24, antonio wrote:

I have a small application using MDNS, and I use the loopback interface.
At the beginning the Thread1 starts the MDNS process,


Wait, why are you talking about threads? You are using the callback API 
of lwIP, right? There should not be more than one thread in that case.


Simon

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[lwip-users] help with mDNS sending a DNS_RRTYPE_SRV query

[antonio]

Hi all, 

I have a small problem. 

I have a small application using MDNS, and I use the loopback interface.
At the beginning the Thread1 starts the MDNS process, and I can see that it
sends 3 probes and 2 responses.
All these messages are correctly received also. 

After that I call Thread2 Is able to send a DNS_RRTYPE_A query to myself and
see the response.. 
>MDNS: thread_mdns_q Sending query... 
MDNS: Sending [PROBE] packet, len=28, unicast=0
+---MDNS--+
MDNS: Received IPv4 MDNS packet from 127.0.0.1, len 28
MDNS: Query for domain lwip.local. type 1 class 1
MDNS: Responding with A record
MDNS: Sending [RESPONSE] packet, len=38, unicast=1
+---MDNS--+
MDNS: Received IPv4 MDNS packet from 127.0.0.1, len 38
MDNS: Answer for domain lwip.local. type 1 class 1



PROBLEM:
However, when I try to send a DNS_RRTYPE_SRV query, the query is sent, and
received..
The problem is that The REPLY(RESPONSE) is never sent back, because, 
the main reason is that the function mdns_write_domain gets stuck. 

>MDNS: thread_mdns_q Sending query... 
MDNS: Sending [PROBE] packet, len=39, unicast=0
+---MDNS--+
MDNS: Received IPv4 MDNS packet from 127.0.0.1, len 39
MDNS: Query for domain mySSH._ssh._tcp.local. type 255 class 1
MDNS: Responding with SRV record

I don't know what I am doing wrong.. 

All hints and suggestions are welcome. 

Thanks in advance. 



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