[lwip-devel] Problem with recv_udp and NETCONN_EVT_RCVPLUS

[Hans . Forsstrom]

Hello,
I'm using lwIP version 1.3.0 with UDP
and the netconn API. The connection is created with netconn_new_with_proto_and_callback()
and I have some problems with the callbacks. I run a test where I send
1000 UDP pakets with 160 bytes of data to the connection, and during this
tests I noticed a problem. I get more callbacks with NETCONN_EVT_RCVPLUS
then what I can read from the connection, and that result in my thread
blocking on the recv method at the end. This might not have been a real
issue if my task wasn't supervised and are required to respont to a heartbeat
at regular intervals.

I have done some simple debugging and
the problem seems to be in api_msg.c:

static void recv_udp(...)
{
......

// The last lines in the method.
  SYS_ARCH_INC(conn->recv_avail,
p->tot_len);
  /*
Register event with callback */
  API_EVENT(conn, NETCONN_EVT_RCVPLUS,
p->tot_len);

  if
(sys_mbox_trypost(conn->recvmbox, buf) != ERR_OK) {
    netbuf_delete(buf);
    return;
  }
}


The problem is that if the sys_mbox_trypost()
calls fails, then the callback will still be executed but the data is deleted
in the if statement. The implementation of the mbox doesn't have a queue,
but even if it had one the problem could still arise. The solution I tested
was to move SYS_ARCH_INC() and API_EVENT() below the if satement, and that
seems to work better.

I don't know if the change I made will
break something else, so I thought I should raise the issue to this maillinglist
instead.

Any comments on this?

Best Regards,
Hans

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