Re: About IFNET_PCP_NONE

> On Aug 28, 2023, at 3:54 PM, Konstantin Belousov <kostikbel@gmail.com> wrote:
> 
> On Mon, Aug 28, 2023 at 09:51:38AM +0800, Zhenlei Huang wrote:
>> Hi Konstantin,
>> 
>> 
>> I was just about going to open a PR for https://reviews.freebsd.org/D39536 and
>> realized I might made wrong assumption.
>> 
>> I thought IFNET_PCP_NONE is something like IEEE8021Q_PCP_BE but I second why not
>> use IEEE8021Q_PCP_BE but a new const IFNET_PCP_NONE.

I meant

```
int
ether_output_frame(struct ifnet *ifp, struct mbuf *m)
{
    uint8_t pcp;

    pcp = ifp->if_pcp;
    if (pcp != 0 /* IEEE8021Q_PCP_BE */ && ifp->if_type != IFT_L2VLAN &&
        !ether_set_pcp(&m, ifp, pcp))
        return (0);

...

}
```

>> 
>> So despite its naming IFNET_PCP_NONE, is it actually a flag to let specific interface
>> completely bypass (disable) PCP processing?
>> 
>> The const IFNET_PCP_NONE is defined in sys/net/if.h with 
>> ```
>> #define IFNET_PCP_NONE 0xff   /* PCP disabled */
>> ```
> I fail to understand your question.
> 
> IFNET_PCP_NONE is a value that means that no 802.1q prio is inserted into
> the packet.  Otherwise, non-vlan traffic is tagged with the priority.

Think about the following case:

1. Set interface's PCP to IFNET_PCP_NONE, application / firewall provide per-flow PCP, should
the traffic be tagged with the priority ?


> 
> IEEE8021Q_PCP_BE is a name of one of the priorities, it seems from my
> code reading.


Best regards,
Zhenlei