[lwip-users] Bug on recv_udp function?

[Muhamad Ikhwan Ismail]

Hi guys.

On my implementation of the lwip 1.3.0, i had a high frequency input and output of UDP packets on multiple sockets in a single task.
So all the sockets read and write are done with select since none of them can be blocking. The problem was it still blocked despite select
said something was in the mailbox. Select checks out the recvevent variable of the sockets, and it was 1 despite the fact
nothing was available in mailbox and hence the recv call blocked. So i checked out the recv_udp() function and found this :

  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, if the posting failed, the recvevent variable was not subtracted hence it stayed one despite the mailbox posting failed. I only found this
with high frequency packet sending. Should this be a bug ?

Greetings

M Ikhwan Ismail

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