From: Sriram Krishnan <srirakr2@xxxxxxxxx> Date: Wed, 22 Jul 2020 21:08:44 +0530 > 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 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> Applied to net-next, thank you.
