packet: on direct_xmit, limit tso and csum to supported devices

commit 104ba78c98808ae837d1f63aae58c183db5505df upstream.

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.

Tested by running github.com/wdebruij/kerneltools/psock_txring_vnet.c

  ethtool -K eth0 tso off tx on
  psock_txring_vnet -d $dst -s $src -i eth0 -l 2000 -n 1 -q -v
  psock_txring_vnet -d $dst -s $src -i eth0 -l 2000 -n 1 -q -v -N

  ethtool -K eth0 tx off
  psock_txring_vnet -d $dst -s $src -i eth0 -l 1000 -n 1 -q -v -G
  psock_txring_vnet -d $dst -s $src -i eth0 -l 1000 -n 1 -q -v -G -N

v2:
  - add EXPORT_SYMBOL_GPL(validate_xmit_skb_list)

Fixes: d346a3fae3ff ("packet: introduce PACKET_QDISC_BYPASS socket option")
Signed-off-by: Willem de Bruijn <willemb@google.com>
Acked-by: Eric Dumazet <edumazet@google.com>
Acked-by: Daniel Borkmann <daniel@iogearbox.net>
Signed-off-by: David S. Miller <davem@davemloft.net>
[bwh: Backported to 3.16: open-code the necessary checks as we don't have
 validate_xmit_skb_list()]
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>

diff --git a/net/packet/af_packet.c b/net/packet/af_packet.c
index d6dfe65f4a7410f480430c87ed0a816ec8d6cd2c..620677c842cbec469ec62409a6668aefe5376024 100644 (file)
--- a/net/packet/af_packet.c
+++ b/net/packet/af_packet.c
@@ -251,9 +251,20 @@ static int packet_direct_xmit(struct sk_buff *skb)
                goto drop;
 
        features = netif_skb_features(skb);
+       if (vlan_tx_tag_present(skb) &&
+           !vlan_hw_offload_capable(features, skb->vlan_proto))
+               goto drop;
+       if (netif_needs_gso(skb, features))
+               goto drop;
        if (skb_needs_linearize(skb, features) &&
            __skb_linearize(skb))
                goto drop;
+       if (skb->ip_summed == CHECKSUM_PARTIAL) {
+               skb_set_transport_header(skb, skb_checksum_start_offset(skb));
+               if (!(features & NETIF_F_ALL_CSUM) &&
+                   skb_checksum_help(skb))
+                       goto drop;
+       }
 
        queue_map = skb_get_queue_mapping(skb);
        txq = netdev_get_tx_queue(dev, queue_map);