From: David Miller <davem@davemloft.net>
To: srirakr2@cisco.com
Cc: kys@microsoft.com, haiyangz@microsoft.com,
sthemmin@microsoft.com, wei.liu@kernel.org, mbumgard@cisco.com,
ugm@cisco.com, nimm@cisco.com, xe-linux-external@cisco.com,
kuba@kernel.org, linux-hyperv@vger.kernel.org,
netdev@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH v6] hv_netvsc: add support for vlans in AF_PACKET mode
Date: Wed, 22 Jul 2020 17:58:30 -0700 (PDT) [thread overview]
Message-ID: <20200722.175830.616952267325554952.davem@davemloft.net> (raw)
In-Reply-To: <20200722153845.79946-1-srirakr2@cisco.com>
From: Sriram Krishnan <srirakr2@cisco.com>
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@cisco.com
> Cc: Sriram Krishnan <srirakr2@cisco.com>
> Signed-off-by: Sriram Krishnan <srirakr2@cisco.com>
Applied to net-next, thank you.
prev parent reply other threads:[~2020-07-23 0:58 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-07-22 15:38 [PATCH v6] hv_netvsc: add support for vlans in AF_PACKET mode Sriram Krishnan
2020-07-22 21:06 ` Haiyang Zhang
2020-07-23 0:58 ` David Miller [this message]
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