Re: [dpdk-dev] [PATCH] net: fix Tx VLAN flag for offload emulation

[Ferruh Yigit <ferruh.yigit@intel.com>]

On 3/25/2019 3:05 PM, Chas Williams wrote:
> From: Bill Hong <bhong@brocade.com>
> 
> A PMD might use rte_vlan_insert to implement Tx VLAN offload.  Typically
> the PMD will insert the VLAN header in the transmit path and then attempt
> to send the packets. If this fails, the packets are returned to
> the application which may attempt to send these packets again. If the
> PKT_TX_VLAN flag is not cleared, the transmit path may attempt to insert
> the VLAN header again.
> 
> Fixes: 47aa48b969f8 ("net: fix stripped VLAN flag for offload emulation");
> Cc: stable@dpdk.org
> 
> Signed-off-by: Bill Hong <bhong@brocade.com>
> Signed-off-by: Chas Williams <chas3@att.com>
> ---
>  lib/librte_net/rte_ether.h | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/lib/librte_net/rte_ether.h b/lib/librte_net/rte_ether.h
> index c2c5e249f..e0d831113 100644
> --- a/lib/librte_net/rte_ether.h
> +++ b/lib/librte_net/rte_ether.h
> @@ -408,7 +408,7 @@ static inline int rte_vlan_insert(struct rte_mbuf **m)
>  	vh = (struct vlan_hdr *) (nh + 1);
>  	vh->vlan_tci = rte_cpu_to_be_16((*m)->vlan_tci);
>  
> -	(*m)->ol_flags &= ~PKT_RX_VLAN_STRIPPED;
> +	(*m)->ol_flags &= ~(PKT_RX_VLAN_STRIPPED | PKT_TX_VLAN);

Hi Chas,

Looks reasonable, AFAIK, PKT_TX_VLAN flag means 'mbuf->vlan_tci' has valid value
and a request from application to driver to insert VLAN information.
After successful insertion flag can be removed.

But in mbuf header, flags documented as:
PKT_TX_VLAN: TX packet is a 802.1q VLAN packet.
PKT_TX_QINQ: TX packet with double VLAN inserted.


Hi Oliver,

Is above comments correct, or I am missing something J


Also here cleaning 'PKT_RX_VLAN_STRIPPED' looks like to say 'vlan' information
is not stripped but in the packet data, but 'RX' in this context can be
confusing, should we have a more generic 'PKT_VLAN_STRIPPED' ?