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Subject[PATCH net-next] net/packet: Improve the comment about LL header visibility criteria
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 <>
net/packet/af_packet.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)

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.
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