Re: [lwip-users] Problem with NULL pcb->callback_arg

[Chris_S]

Yes I can confirm that you need to check for the NULL.  Arg=NULL shows up regularly in normal http processing after the connection is closed, and the alloc mem for hs (arg) gets released.  At least that's what I see in my server code, but it is somewhat dependent on how the other callback functions are of course written as well.

 

There are several problems with the httpd that is in contrib. 

Here is the code I use in my httpd for http_sent().

 

Chris.

 

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static err_t http_sent(void *arg, struct tcp_pcb *pcb, u16_t len) {
   struct http_state *hs;
   LWIP_UNUSED_ARG(len);
   hs = arg;  // assign the http_state struct
   if(hs==NULL) {
  DEBUG_PRINT("http_sent hs=NULL 0x%08x %d\n", pcb, len);
    return (ERR_OK);
  }
   DEBUG_PRINT("http_sent %s 0x%08x %d\n", hs->PFileSysEntry->name, pcb, len);
   hs->retries = 0;
   // Temporarily disable send notifications
   tcp_sent(pcb, NULL);
   // send more data
   send_data(pcb, hs);
   // Reenable notifications.
   tcp_sent(pcb, http_sent);
   return (ERR_OK);
}

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