| Message ID | 20200902120706.3411-1-xie.he.0141@gmail.com |
|---|---|
| State | Accepted |
| Delegated to: | David Miller |
| Headers | show |
| Series | [net] drivers/net/wan/hdlc: Change the default of hard_header_len to 0 | expand |
From: Xie He <xie.he.0141@gmail.com> Date: Wed, 2 Sep 2020 05:07:06 -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> Applied, thanks.
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;
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> --- drivers/net/wan/hdlc.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)