Commit 77b981c8 authored by Xie He's avatar Xie He Committed by David S. Miller

drivers/net/wan/hdlc_x25: Added needed_headroom and a skb->len check

1. Added a skb->len check

This driver expects upper layers to include a pseudo header of 1 byte
when passing down a skb for transmission. This driver will read this
1-byte header. This patch added a skb->len check before reading the
header to make sure the header exists.

2. Added needed_headroom and set hard_header_len to 0

When this driver transmits data,
  first this driver will remove a pseudo header of 1 byte,
  then the lapb module will prepend the LAPB header of 2 or 3 bytes.
So the value of needed_headroom in this driver should be 3 - 1.

Because this driver has no header_ops, according to the logic of
af_packet.c, the value of hard_header_len should be 0.

Reason of setting needed_headroom and hard_header_len at this place:

This driver is written using the API of the hdlc module, the hdlc
module enables this driver (the protocol driver) to run on any hardware
that has a driver (the hardware driver) written using the API of the
hdlc module.

Two other hdlc protocol drivers - hdlc_ppp and hdlc_raw_eth, also set
things like hard_header_len at this place. In hdlc_ppp, it sets
hard_header_len after attach_hdlc_protocol and before setting dev->type.
In hdlc_raw_eth, it sets hard_header_len by calling ether_setup after
attach_hdlc_protocol and after memcpy the settings.

3. Reset needed_headroom when detaching protocols (in hdlc.c)

When detaching a protocol from a hardware device, the hdlc module will
reset various parameters of the device (including hard_header_len) to
the default values. We add needed_headroom here so that needed_headroom
will also be reset.

Cc: Willem de Bruijn <willemdebruijn.kernel@gmail.com>
Cc: Martin Schiller <ms@dev.tdt.de>
Cc: Andrew Hendry <andrew.hendry@gmail.com>
Signed-off-by: default avatarXie He <xie.he.0141@gmail.com>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent 4ca0d9ac
...@@ -230,6 +230,7 @@ static void hdlc_setup_dev(struct net_device *dev) ...@@ -230,6 +230,7 @@ static void hdlc_setup_dev(struct net_device *dev)
dev->max_mtu = HDLC_MAX_MTU; dev->max_mtu = HDLC_MAX_MTU;
dev->type = ARPHRD_RAWHDLC; dev->type = ARPHRD_RAWHDLC;
dev->hard_header_len = 16; dev->hard_header_len = 16;
dev->needed_headroom = 0;
dev->addr_len = 0; dev->addr_len = 0;
dev->header_ops = &hdlc_null_ops; dev->header_ops = &hdlc_null_ops;
} }
......
...@@ -107,8 +107,14 @@ static netdev_tx_t x25_xmit(struct sk_buff *skb, struct net_device *dev) ...@@ -107,8 +107,14 @@ static netdev_tx_t x25_xmit(struct sk_buff *skb, struct net_device *dev)
{ {
int result; int result;
/* There should be a pseudo header of 1 byte added by upper layers.
* Check to make sure it is there before reading it.
*/
if (skb->len < 1) {
kfree_skb(skb);
return NETDEV_TX_OK;
}
/* X.25 to LAPB */
switch (skb->data[0]) { switch (skb->data[0]) {
case X25_IFACE_DATA: /* Data to be transmitted */ case X25_IFACE_DATA: /* Data to be transmitted */
skb_pull(skb, 1); skb_pull(skb, 1);
...@@ -294,6 +300,15 @@ static int x25_ioctl(struct net_device *dev, struct ifreq *ifr) ...@@ -294,6 +300,15 @@ static int x25_ioctl(struct net_device *dev, struct ifreq *ifr)
return result; return result;
memcpy(&state(hdlc)->settings, &new_settings, size); memcpy(&state(hdlc)->settings, &new_settings, size);
/* There's no header_ops so hard_header_len should be 0. */
dev->hard_header_len = 0;
/* When transmitting data:
* first we'll remove a pseudo header of 1 byte,
* then we'll prepend an LAPB header of at most 3 bytes.
*/
dev->needed_headroom = 3 - 1;
dev->type = ARPHRD_X25; dev->type = ARPHRD_X25;
call_netdevice_notifiers(NETDEV_POST_TYPE_CHANGE, dev); call_netdevice_notifiers(NETDEV_POST_TYPE_CHANGE, dev);
netif_dormant_off(dev); netif_dormant_off(dev);
......
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