| Message ID | 20210205224124.21345-1-xie.he.0141@gmail.com |
|---|---|
| State | New |
| Headers | show |
| Series | [net-next] net/packet: Improve the comment about LL header visibility criteria | expand |
Hi, On Sat, Feb 6, 2021 at 4:52 AM Willem de Bruijn <willemdebruijn.kernel@gmail.com> wrote: > > On Fri, Feb 5, 2021 at 5:42 PM Xie He <xie.he.0141@gmail.com> wrote: > > > > The "dev_has_header" function, recently added in > > commit d549699048b4 ("net/packet: fix packet receive on L3 devices > > without visible hard header"), > > is more accurate as criteria for determining whether a device exposes > > the LL header to upper layers, because in addition to dev->header_ops, > > it also checks for dev->header_ops->create. > > > > When transmitting an skb on a device, dev_hard_header can be called to > > generate an LL header. dev_hard_header will only generate a header if > > dev->header_ops->create is present. > > > > Signed-off-by: Xie He <xie.he.0141@gmail.com> > > Acked-by: Willem de Bruijn <willemb@google.com> > > Indeed, existence of dev->header_ops->create is the deciding factor. Thanks Xie. As such, may I suggest making this explicit by making dev_hard_header() use dev_has_header()? Eyal.
On Sat, Feb 6, 2021 at 7:43 AM Eyal Birger <eyal.birger@gmail.com> wrote: > > As such, may I suggest making this explicit by making > dev_hard_header() use dev_has_header()? That is a good idea. We may submit another patch for that.
On Fri, 5 Feb 2021 21:51:36 -0500 Willem de Bruijn wrote: > On Fri, Feb 5, 2021 at 5:42 PM Xie He <xie.he.0141@gmail.com> wrote: > > > > The "dev_has_header" function, recently added in > > commit d549699048b4 ("net/packet: fix packet receive on L3 devices > > without visible hard header"), > > is more accurate as criteria for determining whether a device exposes > > the LL header to upper layers, because in addition to dev->header_ops, > > it also checks for dev->header_ops->create. > > > > When transmitting an skb on a device, dev_hard_header can be called to > > generate an LL header. dev_hard_header will only generate a header if > > dev->header_ops->create is present. > > > > Signed-off-by: Xie He <xie.he.0141@gmail.com> > > Acked-by: Willem de Bruijn <willemb@google.com> > > Indeed, existence of dev->header_ops->create is the deciding factor. Thanks Xie. Applied, thanks!
diff --git a/net/packet/af_packet.c b/net/packet/af_packet.c index 6bbc7a448593..e24b2841c643 100644 --- a/net/packet/af_packet.c +++ b/net/packet/af_packet.c @@ -132,17 +132,17 @@ Resume because it is invisible to us. On transmit: ------------ -dev->header_ops != NULL +dev_has_header(dev) == true mac_header -> ll header data -> ll header -dev->header_ops == NULL (ll header is invisible to us) +dev_has_header(dev) == false (ll header is invisible to us) mac_header -> data data -> data We should set network_header on output to the correct position, packet classifier depends on it. */
The "dev_has_header" function, recently added in commit d549699048b4 ("net/packet: fix packet receive on L3 devices without visible hard header"), is more accurate as criteria for determining whether a device exposes the LL header to upper layers, because in addition to dev->header_ops, it also checks for dev->header_ops->create. When transmitting an skb on a device, dev_hard_header can be called to generate an LL header. dev_hard_header will only generate a header if dev->header_ops->create is present. Signed-off-by: Xie He <xie.he.0141@gmail.com> --- net/packet/af_packet.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-)