Messages in this thread |  | | | Date | Sat, 05 Apr 2008 12:26:57 -0500 | | From | Anthony Liguori <> | | Subject | Re: [PATCH RFC 3/5] tun: vringfd receive support. | |
Rusty Russell wrote:
> This patch modifies tun to allow a vringfd to specify the receive
> buffer. Because we can't copy to userspace in bh context, we queue
> like normal then use the "pull" hook to actually do the copy.
>
> More thought needs to be put into the possible races with ring
> registration and a simultaneous close, for example (see FIXME).
>
> We use struct virtio_net_hdr prepended to packets in the ring to allow
> userspace to receive GSO packets in future (at the moment, the tun
> driver doesn't tell the stack it can handle them, so these cases are
> never taken).
>
> Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
<snip>
> +> +#ifdef CONFIG_VRINGFD
I think the rest of the code needs these for it to actually work without
VRINGFD.
> +static void unset_recv(void *_tun)> +{> + struct tun_struct *tun = _tun;> +> + tun->inring = NULL;> +}> +> +/* Returns number of used buffers, or negative errno. */
> +static int pull_recv_skbs(void *_tun)> +{> + struct tun_struct *tun = _tun;> + int err = 0, num_copied = 0;> + struct sk_buff *skb;> +> + while ((skb = skb_dequeue(&tun->readq)) != NULL) {
> + struct iovec iov[1+MAX_SKB_FRAGS];> + struct virtio_net_hdr gso = { 0 }; /* no info leak */
> + unsigned int iovnum = ARRAY_SIZE(iov);> + unsigned long len;> + int id;> +> + id = vring_get_buffer(tun->inring, iov, &iovnum, &len,
> + NULL, NULL, NULL);> + if (id <= 0) {> + err = id;> + break;> + }
Ah, I see now why you're passing something from the stack.
Regards,
Anthony Liguori
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