Re: [lwip-users] Init - how to deal with static IP ?

[address@hidden]

Micael (abc) wrote:
> Hi Guys,
>
> I have a problem with init of lwip, in conjunction with FreeRTOS.
>
> The thing is that the example startup looks similar to this;
>
> -------8<-------8<-------8<-------8<-------8<----
> tcpip_init(NULL, NULL);
>
> IP4_ADDR(&ip_address, 192,168,1,47 );
> IP4_ADDR(&net_mask,255,255,255,0 );
> IP4_ADDR(&gateway, 192,168,1,151 );
>
> netif_add(&ether_if,&ip_address,&net_mask,&gateway, NULL, ethernetif_init, 
> tcpip_input );
> netif_set_default(&ether_if );
> netif_set_up(&ether_if );
> -------8<-------8<-------8<-------8<-------8<----
>    
The above example violates threading constraints: the netif_*() 
functions may only be called from the tcpip_thread. To do this, create a 
new functions that calls netif_add/_set_default/_set_up and pass a 
pointer to this function to tcpip_init. See the win32 example port for 
how to do this (I'm currently at fixing the unix port, which violates 
threading, too).
> This is all (in the example code) done prior to OS has started.
> Now the problem I have, is that if I want to get hold of the IP address 
> (instead of hard coded
> as above) of this node, I need to have the OS up and running.
>
> So therefore, can I simply move the three netif_* lines later on, when the OS 
> has started?
> If so, what happens if a thread tries to open a connection (socket layer)? Will 
> the stack give
> appropriate (error) return codes on e.g. socket() and brothers.
> OR do I need to protect the whole socket layer with some mutex or similar, 
> until I have set-up
> netif?
>    
You can either call tcpip_init from one of your threads (so it gets 
called after the OS has started) or call netif_add (etc.) later. For 
that latter, you have to create a function that can be called in 
tcpip_thread via tcpip_callback() to prevent threading issues.

In both cases, sockets will not work before netif_add has been called: 
in the first case, you will get an error (as none of the lwip init 
functions have been called, yet), in the second case, you can create a 
socket but cannot bind it to a specific (ANY will work) and cannot 
send/connect before netif_add has been called.

Simon