Re: [lwip-users] lwip: Scan through the heap searching for a free block that is big enough, beginning with the lowest free block.

[address@hidden]

Am 28.03.2019 um 09:20 schrieb vrnud:
> HI,
>
> I am very new to the tcpip world.
>
>    netif_add(&gnetif, &ipaddr, &netmask, &gw, NULL, &ethernetif_init,
> &tcpip_input);
> is called from MX_LWIP_Init() function.
>
> "But "raw" APIs functions must ONLY be called from TCPIP thread."
> I dont know how to do that. can you please provide some example for the
> same.
>
> or example for
> " tcpip_callback() can be used get called back from TCPIP thread, it is safe
> to call any "raw" APIs from there."
>
> "Use LWIP_TCPIP_CORE_LOCKING. All "raw" APIs functions can be called when
> lwIP core lock is aquired, see LOCK_TCPIP_CORE() and UNLOCK_TCPIP_CORE().
> These macros cannot be used in an interrupt context! Note the OS must
> correctly handle priority inversion for this."
> LWIP_TCPIP_CORE_LOCKING is set 1 in code.
>
> below is the code
> void tcp_echoserver_init(void)
> {
>
>    /* create new tcp pcb */
>    tcp_echoserver_pcb = tcp_new();
>
>    if (tcp_echoserver_pcb != NULL)
>    {
>      err_t err;
>
>      /* bind echo_pcb to port 7 (ECHO protocol) ;7 FOR ECHO, 502 FOR MODBUS*/
>      err = tcp_bind(tcp_echoserver_pcb, IP_ADDR_ANY, 502);
>
>      if (err == ERR_OK)
>      {
>        /* start tcp listening for echo_pcb */
>        tcp_echoserver_pcb = tcp_listen(tcp_echoserver_pcb);
>
>        /* initialize LwIP tcp_accept callback function */
>        tcp_accept(tcp_echoserver_pcb, tcp_echoserver_accept);
>      }
>      else
>      {
>        /* deallocate the pcb */
>        memp_free(MEMP_TCP_PCB, tcp_echoserver_pcb);
>      }
>    }
>
> }
>
> /**
>    * @brief  This function is the implementation of tcp_accept LwIP callback
>    * @param  arg: not used
>    * @param  newpcb: pointer on tcp_pcb struct for the newly created tcp
> connection
>    * @param  err: not used
>    * @retval err_t: error status
>    */
> static err_t tcp_echoserver_accept(void *arg, struct tcp_pcb *newpcb, err_t
> err)
> {
>    err_t ret_err;
>    struct tcp_echoserver_struct *es;
>
>    LWIP_UNUSED_ARG(arg);
>    LWIP_UNUSED_ARG(err);
>
>    /* set priority for the newly accepted tcp connection newpcb */
>    tcp_setprio(newpcb, TCP_PRIO_MIN);
>
>    /* allocate structure es to maintain tcp connection informations */
>    es = (struct tcp_echoserver_struct *)mem_malloc(sizeof(struct
> tcp_echoserver_struct));
>    if (es != NULL)
>    {
>      es->state = ES_ACCEPTED;
>      es->pcb = newpcb;
>      es->retries = 0;
>      es->p = NULL;
>
>                 if(gu8_addrs_chng_Link_break)
>                 {
>                         gu8_addrs_chng_Link_break = 0;
>                 }
>
>
>      /* pass newly allocated es structure as argument to newpcb */
>      tcp_arg(newpcb, es);
>
>      /* initialize lwip tcp_recv callback function for newpcb  */
>      tcp_recv(newpcb, tcp_echoserver_recv);
>
>      /* initialize lwip tcp_err callback function for newpcb  */
>      tcp_err(newpcb, tcp_echoserver_error);
>
>      /* initialize lwip tcp_poll callback function for newpcb */
>      tcp_poll(newpcb, tcp_echoserver_poll, 0);
>
>      ret_err = ERR_OK;
>    }
>    else
>    {
>      /*  close tcp connection */
>      tcp_echoserver_connection_close(newpcb, es);
>      /* return memory error */
>      ret_err = ERR_MEM;
>    }
>    return ret_err;
> }
>
> I am getting problem for particular this line
>    /* allocate structure es to maintain tcp connection informations */
>    es = (struct tcp_echoserver_struct *)mem_malloc(sizeof(struct
> tcp_echoserver_struct));

Sorry for taking so long to respond. If only for the archive, I'll still
reply.

If a simple 'mem_malloc' gets stuck in an endless loop, the heap is
corrupted. One reason can be threading issues (see
https://www.nongnu.org/lwip/2_1_x/pitfalls.html). Another reason could
just be plain memory corruption.

Regards,
Simon