[lwip-users] Problem with lwip_select under Nucleus

[brivero]

Hello again.

I had a look at the points you mentioned to me:

First of all, I have checked that MSG_DONTWAIT in
the flags to the recv operation, and O_NONBLOCK to the socket options are
both set to zero. In fact, both flag fields are completely zero. So that
the socket should be blocking, am I right?

>Take a look at the lwip_recvfrom() function.  Can you check the
following when you call it by adding some extra debugging:
> - that sock->lastdata is NULL.
OK, it is null

> - that buf returned by netconn_recv() is NULL.
It is null too.

>If that is the case, take a look at netconn_recv().  This can
return NULL for all sorts of reasons.  Add debugging (e.g. a printf)
to each one and >see which case is failing.

Next, I specify the failing case, which shows the
reason for which the function returns NULL.

struct netbuf *
netconn_recv(struct netconn *conn)
{

...
    
  if (conn == NULL) {
    return NULL;
  }
  
  if (conn->recvmbox == SYS_MBOX_NULL) {
    conn->err = ERR_CONN;
    return NULL;
  }

  if (conn->err != ERR_OK) {
    return NULL;
  }

  if (conn->type == NETCONN_TCP) {
    if (conn->pcb.tcp->state == LISTEN)
{
      conn->err = ERR_CONN;
      return NULL;
    }

    buf = memp_malloc(MEMP_NETBUF);

    if (buf == NULL) {
      conn->err = ERR_MEM;
      return NULL;
    }
    
    sys_mbox_fetch(conn->recvmbox, (void
**)&p);

    if (p != NULL)
    {
        len = p->tot_len;
        conn->recv_avail -=
len;
    }
    else        
               
               
               
               <<<<<<<<<<<<<<<<<<<<<<<<<
IT GETS INTO THIS ELSE
        len = 0;
           
printf("\n Entra en el ELSE, Chkp1\n");
    
    /* Register event with callback */
      if (conn->callback)
        (*conn->callback)(conn,
NETCONN_EVT_RCVMINUS, len);
           
printf("\n Entra en el Callback, Chkp2\n");

    /* If we are closed, we indicate that
we no longer wish to receive
       data by setting conn->recvmbox
to SYS_MBOX_NULL. */
    if (p == NULL) {      
               
               
               
 <<<<<<<<<<<<<<<<<<<<<<<<<
IT GOES INTO THIS IF (p==NULL)
      memp_free(MEMP_NETBUF, buf);
      sys_mbox_free(conn->recvmbox);
      conn->recvmbox = SYS_MBOX_NULL;
      return NULL;      
               
               
               
 <<<<<<<<<<<<<<<<<<<<<<<<<
RETURNS NULL
    }

....
....
....

  return buf;
}

The problem seems to be that it is receiving that null p. I would thank
any advice.

Thank you very much for your help and for using your
time for this purpose.

Best regards,

Borja.