> I have most of the lwip stack running in a "tcpip" thread, and stack
> users in various threads synchronise with it using the netconn* API.
But
> there is a problem with netconn_delete and netconn_recv when they
delete
> mboxes. A packet, or a connection to a listening socket, may arrive in
> the gap between removing mbox items, and deleting the mboxes. For
> example:
>
> /* Drain the recvmbox. */
> if (conn->recvmbox != SYS_MBOX_NULL) {
> while (sys_arch_mbox_fetch(conn->recvmbox, &mem, 1) !=
SYS_ARCH_TIMEOUT) {
> if (conn->type == NETCONN_TCP) {
> if(mem != NULL)
> pbuf_free((struct pbuf *)mem);
> } else {
> netbuf_delete((struct netbuf *)mem);
> }
> }
>
> *** PACKET CAN ARRIVE HERE ***
> sys_mbox_free(conn->recvmbox);
> conn->recvmbox = SYS_MBOX_NULL;
> }
>
> In that case a sys_mbox_free can be called on a non-empty mbox. This
may
> either leak a pbuf, or cause an assertion in the OS from the
underlying
> mbox implementation. I've been thinking about how to fix this. Either
> new sys_arch primitives could be added. Or, better, we could try to
use
> SYS_LIGHTWEIGHT_PROT, but this seems a bit dubious as we need to
protect
> from before the sys_arch_mbox_fetch, until the conn->recvmbox =
> SYS_MBOX_NULL.
Doesn't the API_MSG_DELCONN message posted just prior to the above code
already prevent any further packets from being placed in the recvmbox?
Don Krueger
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