Re: [lwip-users] lwip_sendto hanging with lwip 2.0

[Joel Cunningham]

If you want to send and receive on the same socket from two different threads, you’ll need to enable LWIP_NETCONN_FULLDUPLEX in opt.h (by default it’s not supported and feature is in alpha state):

/** LWIP_NETCONN_FULLDUPLEX==1: Enable code that allows reading from one thread,

 * writing from a 2nd thread and closing from a 3rd thread at the same time.

 * ATTENTION: This is currently really alpha! Some requirements:

 * - LWIP_NETCONN_SEM_PER_THREAD==1 is required to use one socket/netconn from

 *   multiple threads at once

 * - sys_mbox_free() has to unblock receive tasks waiting on recvmbox/acceptmbox

 *   and prevent a task pending on this during/after deletion

 */

#if !defined LWIP_NETCONN_FULLDUPLEX || defined __DOXYGEN__

#define LWIP_NETCONN_FULLDUPLEX         0

#endif

Joel

On Jan 25, 2017, at 1:02 AM, Neerav Patel <address@hidden> wrote:

Hi,

I read that same statement after I had posted and so I created another system thread (been debugging the whole day):

sys_thread_new("handle_thread", handle_thread, NULL, 400, 3);

and tried to send from it, and it also hung in the same way, seems to not return from a semaphore call deep in the bowls of lwip, still digging further into it.

Maybe this will do the same and call back from the tcpipthread.  

How would you propose structuring the code, I want one thread to receive packets and another to send out?  Is creating a system thread the right way to go?  Why would I be hanging with the code below?

Thanks for all the help!

void

handle_thread( )

{

      while ( 1 )

      {

            if ( send_actual_pkt ) 

            {

                  send_actual_pkt = 0;

                  uint8_t pkt[576];

                  // ... populate the pkt

                 uint16_t len = generate_pkt();

                 if ( lwip_sendto( s, pkt, len, 0, (struct sockaddr *)&from, sizeof(from) ) != len )   <---- hanging here!!!!

                 {

                       uart_printf( "Didnt send correctly %x\n", len );

                 }

            }

       }

}

while( 1 )

   {

      if ( (lwip_recvfrom(s, raw_buf, sizeof(raw_buf), 0, (struct sockaddr*)&from, (socklen_t*)&fromlen)) > 0 )

      {

                  send_actual_pkt = 1;

      }

   }

---

From: lwip-users <address@hidden> on behalf of Dirk Ziegelmeier <address@hidden>
Sent: January 25, 2017 6:48 AM
To: Mailing list for lwIP users
Subject: Re: [lwip-users] lwip_sendto hanging with lwip 2.0

 

Calling sys_timeout() results in send_actual_pkt being called back from TCPIP thread. You must not call sequencial style functions from TCPIP thread.

http://www.nongnu.org/lwip/2_0_0/group__sequential__api.html says: "More overhead, but can be called from any thread except TCPIP thread."

lwIP: Sequential-style APIs - nongnu.org

www.nongnu.org

Detailed Description. Sequential-style APIs, blocking functions. More overhead, but can be called from any thread except TCPIP thread.

Dirk

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