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:Xie He <xie.he.0141@gmail.com> Signed-off-by:
David S. Miller <davem@davemloft.net>
parent
4ca0d9ac
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