[lwip-users] LWIP 1.3.2 and PPP

[Sirjee Rooplall]

Hi as stated above I am using LWIP 1.3.2 and the PPP stack.

 

I use the follwoing API's.

netconn_new

netconn_connect

netconn_delete

netconn_recv - This is called from a freeRTOS task every 10ms, to check if any data has arrived.

netbuf_data

 

I have LWIP_SO_RCVTIMEO defined as 1.

 

I am using PPP over serial through modem to sever.

 

Before I call nettcon_recv to check for data I set a receive timeout:

pxSeverConnectionHandle->recv_timeout = 10000;   // wait for incoming message 10seconds max.

 

Now here is the problem.

 

Everything works fine provided the server replies within the 10 seconds.

If netconn_recv timeout, it sets the conn->err to conn->err = ERR_TIMEOUT; //  which is -13 and referred to FATAL error.

 

The next time netconn_recev is called it encounter this piece of code which says:

if (ERR_IS_FATAL(conn->err)) {
    return NULL;
  }

 

because the conn->err is set to -13 which is fatal error, netconn_recv always returns without checking the mailbox for a message which may take more than 10 seconds to come.

 

Now the reason I am using the receive timeout in netconn_recv is because previously it wait forever for a message and if the message does not come, after 20 seconds I close the socket in another Task, and that caused my system to crash because netconn_recv was pending on that socket handle.

 

In this system using PPP and modem + GPRS it is possible that a message may not arrive, and retries are implemented etc to cater for this.

 

My question is How do I work around this ERR_IS_FATAL condition, without breaking any LWIP rules?

 

 

Kind Regards,

 

Sirjee Rooplall
Figment Design laboratories (Pty) Ltd
mailto: address@hidden
Mobile: +27 (0)83 230 8466