From: Xie He <xie.he.0...@gmail.com> Date: Thu, 13 Aug 2020 11:17:04 -0700
> 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.ker...@gmail.com> > Cc: Martin Schiller <m...@dev.tdt.de> > Cc: Andrew Hendry <andrew.hen...@gmail.com> > Signed-off-by: Xie He <xie.he.0...@gmail.com> Applied, thanks.
