On 10/26/2016 02:28 AM, Willem de Bruijn wrote:
From: Willem de Bruijn <will...@google.com>
When transmitting on a packet socket with PACKET_VNET_HDR and
PACKET_QDISC_BYPASS, validate device support for features requested
in vnet_hdr.
Drop TSO packets sent to devices that do not support TSO or have the
feature disabled. Note that the latter currently do process those
packets correctly, regardless of not advertising the feature.
Because of SKB_GSO_DODGY, it is not sufficient to test device features
with netif_needs_gso. Full validate_xmit_skb is needed.
Switch to software checksum for non-TSO packets that request checksum
offload if that device feature is unsupported or disabled. Note that
similar to the TSO case, device drivers may perform checksum offload
correctly even when not advertising it.
When switching to software checksum, packets hit skb_checksum_help,
which has two BUG_ON checksum not in linear segment. Packet sockets
always allocate at least up to csum_start + csum_off + 2 as linear.
Ok, for the tpacket_fill_skb() case with SOCK_RAW, it's guaranteed,
because if we have a vnet header, then copylen would cover that here
(as opposed to just dev->hard_header_len). With Eric's suggestion,
looks good to me. Thanks, Willem!
