This driver didn't set hard_header_len. This patch sets hard_header_len
for it according to its header_ops->create function.
This driver's header_ops->create function (cisco_hard_header) creates
a header of (struct hdlc_header), so hard_header_len should be set to
sizeof(struct hdlc_header).
Cc: Martin Schiller <[email protected]>
Signed-off-by: Xie He <[email protected]>
---
drivers/net/wan/hdlc_cisco.c | 1 +
1 file changed, 1 insertion(+)
diff --git a/drivers/net/wan/hdlc_cisco.c b/drivers/net/wan/hdlc_cisco.c
index d8cba3625c18..444130655d8e 100644
--- a/drivers/net/wan/hdlc_cisco.c
+++ b/drivers/net/wan/hdlc_cisco.c
@@ -370,6 +370,7 @@ static int cisco_ioctl(struct net_device *dev, struct ifreq *ifr)
memcpy(&state(hdlc)->settings, &new_settings, size);
spin_lock_init(&state(hdlc)->lock);
dev->header_ops = &cisco_header_ops;
+ dev->hard_header_len = sizeof(struct hdlc_header);
dev->type = ARPHRD_CISCO;
call_netdevice_notifiers(NETDEV_POST_TYPE_CHANGE, dev);
netif_dormant_on(dev);
--
2.25.1
Hello Xie,
Xie He <[email protected]> writes:
> This driver didn't set hard_header_len. This patch sets hard_header_len
> for it according to its header_ops->create function.
BTW it's 4 bytes long:
struct hdlc_header {
u8 address;
u8 control;
__be16 protocol;
}__packed;
OTOH hdlc_setup_dev() initializes hard_header_len to 16,
but in this case I guess 4 bytes are better.
Acked-by: Krzysztof Halasa <[email protected]>
> Cc: Martin Schiller <[email protected]>
> Signed-off-by: Xie He <[email protected]>
> ---
> --- a/drivers/net/wan/hdlc_cisco.c
> +++ b/drivers/net/wan/hdlc_cisco.c
> @@ -370,6 +370,7 @@ static int cisco_ioctl(struct net_device *dev, struct ifreq *ifr)
> memcpy(&state(hdlc)->settings, &new_settings, size);
> spin_lock_init(&state(hdlc)->lock);
> dev->header_ops = &cisco_header_ops;
> + dev->hard_header_len = sizeof(struct hdlc_header);
> dev->type = ARPHRD_CISCO;
> call_netdevice_notifiers(NETDEV_POST_TYPE_CHANGE, dev);
> netif_dormant_on(dev);
--
Krzysztof Halasa
Sieć Badawcza Łukasiewicz
Przemysłowy Instytut Automatyki i Pomiarów PIAP
Al. Jerozolimskie 202, 02-486 Warszawa
On Fri, Aug 28, 2020 at 3:37 AM Krzysztof Hałasa <[email protected]> wrote:
>
> OTOH hdlc_setup_dev() initializes hard_header_len to 16,
> but in this case I guess 4 bytes are better.
>
> Acked-by: Krzysztof Halasa <[email protected]>
Thank you, Krzysztof!
Actually I'm thinking about changing the default value of 16 in hdlc.c to 0.
I think a driver should always keep its hard_header_len consistent
with its header_ops functions. If a driver doesn't have header_ops,
its hard_header_len should be set to 0. This makes the driver able to
be correctly used with AF_PACKET sockets.
In net/packet/af_packet.c, in the function packet_snd, for
AF_PACKET/DGRAM sockets, it would reserve a headroom of
hard_header_len for the skb, and call dev_hard_header (which calls the
header_ops->create function) to fill in the headroom, but for
AF_PACKET/RAW sockets, it would not reserve the headroom of
hard_header_len, and will check (in function dev_validate_header)
whether the user has provided the header of length hard_header_len. So
I think hard_header_len should be kept consistent with header_ops to
make the driver able to work correctly with af_packet.c.
If the driver really needs to use additional header space outside of
the header_ops->create function, it should request that header space
in dev->needed_headroom instead of hard_header_len. This avoids the
complex header processing in af_packet.c but still gets the header
space reserved.
Currently for the 6 HDLC protocol drivers, hdlc_ppp sets
hard_header_len and the value is consistent with its header_ops,
hdlc_raw_eth sets both hard_header_len and header_ops correctly with
the ether_setup function, hdlc_x25 has been previously changed by me
to set hard_header_len to 0 because it doesn't have header_ops, and
this patch would make hdlc_cisco set its hard_header_len to the value
consistent with its header_ops. This leaves us hdlc_raw and hdlc_fr. I
see that both of these 2 drivers don't set hard_header_len when
attaching the protocol, so they will use the default value of 16. But
because both of these drivers don't have header_ops, I think their
hard_header_len should be set to 0. So I think maybe it's better to
change the default value in hdlc.c to 0 and let them take the default
value of 0.
What do you think?
Thanks!
Xie He
From: Xie He <[email protected]>
Date: Fri, 28 Aug 2020 00:07:52 -0700
> This driver didn't set hard_header_len. This patch sets hard_header_len
> for it according to its header_ops->create function.
>
> This driver's header_ops->create function (cisco_hard_header) creates
> a header of (struct hdlc_header), so hard_header_len should be set to
> sizeof(struct hdlc_header).
>
> Cc: Martin Schiller <[email protected]>
> Signed-off-by: Xie He <[email protected]>
Applied, thanks.