> -----Original Message-----
> From: Sriram Krishnan <srirakr2@xxxxxxxxx>
> Sent: Monday, July 20, 2020 12:46 PM
> To: KY Srinivasan <kys@xxxxxxxxxxxxx>; Haiyang Zhang
> <haiyangz@xxxxxxxxxxxxx>; Stephen Hemminger <sthemmin@xxxxxxxxxxxxx>;
> Wei Liu <wei.liu@xxxxxxxxxx>
> Cc: mbumgard@xxxxxxxxx; ugm@xxxxxxxxx; nimm@xxxxxxxxx; xe-linux-
> external@xxxxxxxxx; David S. Miller <davem@xxxxxxxxxxxxx>; Jakub Kicinski
> <kuba@xxxxxxxxxx>; linux-hyperv@xxxxxxxxxxxxxxx; netdev@xxxxxxxxxxxxxxx;
> linux-kernel@xxxxxxxxxxxxxxx
> Subject: [PATCH v3] net: hyperv: add support for vlans in netvsc driver
>
> Vlan tagged packets are getting dropped when used with DPDK that uses
> the AF_PACKET interface on a hyperV guest.
>
> The packet layer uses the tpacket interface to communicate the vlans
> information to the upper layers. On Rx path, these drivers can read the
> vlan info from the tpacket header but on the Tx path, this information
> is still within the packet frame and requires the paravirtual drivers to
> push this back into the NDIS header which is then used by the host OS to
> form the packet.
>
> This transition from the packet frame to NDIS header is currently missing
> hence causing the host OS to drop the all vlan tagged packets sent by
> the drivers that use AF_PACKET (ETH_P_ALL) such as DPDK.
>
> Here is an overview of the changes in the vlan header in the packet path:
>
> The RX path (userspace handles everything):
> 1. RX VLAN packet is stripped by HOST OS and placed in NDIS header
> 2. Guest Kernel RX hv_netvsc packets and moves VLAN info from NDIS
> header into kernel SKB
> 3. Kernel shares packets with user space application with PACKET_MMAP.
> The SKB VLAN info is copied to tpacket layer and indication set
> TP_STATUS_VLAN_VALID.
> 4. The user space application will re-insert the VLAN info into the frame.
>
> The TX path:
> 1. The user space application has the VLAN info in the frame.
> 2. Guest kernel gets packets from the application with PACKET_MMAP.
> 3. The kernel later sends the frame to the hv_netvsc driver. The only way
> to send VLANs is when the SKB is setup & the VLAN is is stripped from the
> frame.
> 4. TX VLAN is re-inserted by HOST OS based on the NDIS header. If it sees
> a VLAN in the frame the packet is dropped.
>
> Cc: xe-linux-external@xxxxxxxxx
> Cc: Sriram Krishnan <srirakr2@xxxxxxxxx>
> Signed-off-by: Sriram Krishnan <srirakr2@xxxxxxxxx>
> ---
> drivers/net/hyperv/netvsc_drv.c | 23 +++++++++++++++++++++++
> 1 file changed, 23 insertions(+)
>
> diff --git a/drivers/net/hyperv/netvsc_drv.c b/drivers/net/hyperv/netvsc_drv.c
> index 6267f706e8ee..2a25b4352369 100644
> --- a/drivers/net/hyperv/netvsc_drv.c
> +++ b/drivers/net/hyperv/netvsc_drv.c
> @@ -605,6 +605,29 @@ static int netvsc_xmit(struct sk_buff *skb, struct
> net_device *net, bool xdp_tx)
> *hash_info = hash;
> }
>
> + /* When using AF_PACKET we need to remove VLAN from frame
> + * and indicate VLAN information in SKB so HOST OS will
> + * transmit the VLAN frame
> + */
> + if (skb->protocol == htons(ETH_P_8021Q)) {
> + u16 vlan_tci = 0;
> + skb_reset_mac_header(skb);
> + if (eth_type_vlan(eth_hdr(skb)->h_proto)) {
> + int pop_err;
> + pop_err = __skb_vlan_pop(skb, &vlan_tci);
> + if (likely(pop_err == 0)) {
> + __vlan_hwaccel_put_tag(skb,
> htons(ETH_P_8021Q), vlan_tci);
> +
> + /* Update the NDIS header pkt lengths */
> + packet->total_data_buflen -= VLAN_HLEN;
packet->total_bytes should be updated too.
Thanks,
- Haiyang
