Messages in this thread Patch in this message | | | From | Xie He <> | Subject | [PATCH net v2] drivers/net/wan/hdlc: Change the default of hard_header_len to 0 | Date | Wed, 2 Sep 2020 12:28:05 -0700 |
| |
Change the default value of hard_header_len in hdlc.c from 16 to 0.
Currently there are 6 HDLC protocol drivers. Among them:
hdlc_raw_eth, hdlc_cisco, hdlc_ppp, hdlc_x25 set hard_header_len when attaching the protocol, overriding the default. So this patch does not affect them.
hdlc_raw and hdlc_fr don't set hard_header_len when attaching the protocol. So this patch will change the hard_header_len of the HDLC device for them from 16 to 0.
This is the correct change because both hdlc_raw and hdlc_fr don't have header_ops, and the code in net/packet/af_packet.c expects the value of hard_header_len to be consistent with header_ops.
In net/packet/af_packet.c, in the packet_snd function, for AF_PACKET/DGRAM sockets it would reserve a headroom of hard_header_len and call dev_hard_header to fill in that headroom, and for AF_PACKET/RAW sockets, it does not reserve the headroom and does not call dev_hard_header, but checks if the user has provided a header of length hard_header_len (in function dev_validate_header).
Cc: Krzysztof Halasa <khc@pm.waw.pl> Cc: Martin Schiller <ms@dev.tdt.de> Signed-off-by: Xie He <xie.he.0141@gmail.com> ---
Change from v1: Small fix for the English grammar in the commit message.
--- drivers/net/wan/hdlc.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/drivers/net/wan/hdlc.c b/drivers/net/wan/hdlc.c index 386ed2aa31fd..9b00708676cf 100644 --- a/drivers/net/wan/hdlc.c +++ b/drivers/net/wan/hdlc.c @@ -229,7 +229,7 @@ static void hdlc_setup_dev(struct net_device *dev) dev->min_mtu = 68; dev->max_mtu = HDLC_MAX_MTU; dev->type = ARPHRD_RAWHDLC; - dev->hard_header_len = 16; + dev->hard_header_len = 0; dev->needed_headroom = 0; dev->addr_len = 0; dev->header_ops = &hdlc_null_ops; -- 2.25.1
| |