Hi all.
I'm currently trying to learn a bit more about driver programming,
therefore I'm working a little with tun.c (using the version that comes
with 2.6.7). I have some experience with C programming in general, but
I'm a newbie when it comes to kernel stuff.
Have a look at the following code (taken from the function tun_net_xmit()):
=== cut ===
/* Queue packet */
if (!(tun->flags & TUN_ONE_QUEUE)) {
/* Normal queueing mode.
* Packet scheduler handles dropping. */
if (skb_queue_len(&tun->readq) >= TUN_READQ_SIZE)
netif_stop_queue(dev);
} else {
/* Single queue mode.
* Driver handles dropping itself. */
if (skb_queue_len(&tun->readq) >= dev->tx_queue_len)
goto drop;
}
skb_queue_tail(&tun->readq, skb);
=== cut ===
Look at the code that is executed when TUN_ONE_QUEUE isn't set in
tun->flags. If the length of the queue has reached its maximum value
(given as TUN_READQ_SIZE), the current packet still is appended to the
queue, thereby exceeding the maximum length by 1.
In my eyes the simplest way to correct that would be to change
if (skb_queue_len(&tun->readq) >= TUN_READQ_SIZE)
to read
if (skb_queue_len(&tun->readq) >= TUN_READQ_SIZE - 1)
Please correct me if I'm wrong.
Bye, Mike
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