On 7/7/20 9:37 PM, Xie He wrote:
> This driver is not working because of problems of its receiving code.
> This patch fixes it to make it work.
>
> When the driver receives an LAPB frame, it should first pass the frame
> to the LAPB module to process. After processing, the LAPB module passes
> the data (the packet) back to the driver, the driver should then add a
> one-byte pseudo header and pass the data to upper layers.
>
> The changes to the "x25_asy_bump" function and the
> "x25_asy_data_indication" function are to correctly implement this
> procedure.
>
> Also, the "x25_asy_unesc" function ignores any frame that is shorter
> than 3 bytes. However the shortest frames are 2-byte long. So we need
> to change it to allow 2-byte frames to pass.
>
> Signed-off-by: Xie He <xie.he.0...@gmail.com>
> ---
> drivers/net/wan/x25_asy.c | 16 +++++++++-------
> 1 file changed, 9 insertions(+), 7 deletions(-)
>
> diff --git a/drivers/net/wan/x25_asy.c b/drivers/net/wan/x25_asy.c
> index 69773d228ec1..3fd8938e591b 100644
> --- a/drivers/net/wan/x25_asy.c
> +++ b/drivers/net/wan/x25_asy.c
> @@ -183,7 +183,7 @@ static inline void x25_asy_unlock(struct x25_asy *sl)
> netif_wake_queue(sl->dev);
> }
>
> -/* Send one completely decapsulated IP datagram to the IP layer. */
> +/* Send an LAPB frame to the LAPB module to process. */
>
> static void x25_asy_bump(struct x25_asy *sl)
> {
> @@ -195,13 +195,12 @@ static void x25_asy_bump(struct x25_asy *sl)
> count = sl->rcount;
> dev->stats.rx_bytes += count;
>
> - skb = dev_alloc_skb(count+1);
> + skb = dev_alloc_skb(count);
> if (skb == NULL) {
> netdev_warn(sl->dev, "memory squeeze, dropping packet\n");
> dev->stats.rx_dropped++;
> return;
> }
> - skb_push(skb, 1); /* LAPB internal control */
> skb_put_data(skb, sl->rbuff, count);
> skb->protocol = x25_type_trans(skb, sl->dev);
> err = lapb_data_received(skb->dev, skb);
> @@ -209,7 +208,6 @@ static void x25_asy_bump(struct x25_asy *sl)
> kfree_skb(skb);
> printk(KERN_DEBUG "x25_asy: data received err - %d\n", err);
> } else {
> - netif_rx(skb);
> dev->stats.rx_packets++;
> }
> }
> @@ -356,12 +354,16 @@ static netdev_tx_t x25_asy_xmit(struct sk_buff *skb,
> */
>
> /*
> - * Called when I frame data arrives. We did the work above - throw it
> - * at the net layer.
> + * Called when I frame data arrives. We add a pseudo header for upper
> + * layers and pass it to upper layers.
> */
>
> static int x25_asy_data_indication(struct net_device *dev, struct sk_buff
> *skb)
> {
It is not clear to me what guarantee we have to have one byte of headroom in
the skb
at this point.
You might add to be safe : (as done in lapbeth_data_indication(), but after the
skb_push() which seems wrong)
if (skb_cow(skb, 1)) {
kfree_skb(skb); /* This line I am not sure, but looking at
* lapb_data_indication() this might be needed.
*/
return NET_RX_DROP;
}
> + skb_push(skb, 1);
> + skb->data[0] = X25_IFACE_DATA;
> + skb->protocol = x25_type_trans(skb, dev);
> +
> return netif_rx(skb);
> }
>
> @@ -657,7 +659,7 @@ static void x25_asy_unesc(struct x25_asy *sl, unsigned
> char s)
> switch (s) {
> case X25_END:
> if (!test_and_clear_bit(SLF_ERROR, &sl->flags) &&
> - sl->rcount > 2)
> + sl->rcount >= 2)
> x25_asy_bump(sl);
> clear_bit(SLF_ESCAPE, &sl->flags);
> sl->rcount = 0;
>
