Patch "packet: on direct_xmit, limit tso and csum to supported devices" has been added to the 4.4-stable tree

This is a note to let you know that I've just added the patch titled

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

to the 4.4-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
packet-on-direct_xmit-limit-tso-and-csum-to-supported-devices.patch
and it can be found in the queue-4.4 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let <[email protected]> know about it.

From: Willem de Bruijn <[email protected]>
Date: Wed, 26 Oct 2016 11:23:07 -0400
Subject: packet: on direct_xmit, limit tso and csum to supported devices

From: Willem de Bruijn <[email protected]>

[ Upstream commit 104ba78c98808ae837d1f63aae58c183db5505df ]

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)

---
 net/core/dev.c         |    1 +
 net/packet/af_packet.c |    9 ++++-----
 2 files changed, 5 insertions(+), 5 deletions(-)

@@ -2836,6 +2836,7 @@ struct sk_buff *validate_xmit_skb_list(s
 	}
 	return head;
 }
+EXPORT_SYMBOL_GPL(validate_xmit_skb_list);
 
 static void qdisc_pkt_len_init(struct sk_buff *skb)
 {

@@ -249,7 +249,7 @@ static void __fanout_link(struct sock *s
 static int packet_direct_xmit(struct sk_buff *skb)
 {
 	struct net_device *dev = skb->dev;
-	netdev_features_t features;
+	struct sk_buff *orig_skb = skb;
 	struct netdev_queue *txq;
 	int ret = NETDEV_TX_BUSY;
 

@@ -257,9 +257,8 @@ static int packet_direct_xmit(struct sk_
 		     !netif_carrier_ok(dev)))
 		goto drop;
 
-	features = netif_skb_features(skb);
-	if (skb_needs_linearize(skb, features) &&
-	    __skb_linearize(skb))
+	skb = validate_xmit_skb_list(skb, dev);
+	if (skb != orig_skb)
 		goto drop;
 
 	txq = skb_get_tx_queue(dev, skb);

@@ -279,7 +278,7 @@ static int packet_direct_xmit(struct sk_
 	return ret;
 drop:
 	atomic_long_inc(&dev->tx_dropped);
-	kfree_skb(skb);
+	kfree_skb_list(skb);
 	return NET_XMIT_DROP;
 }
 

Patches currently in stable-queue which might be from [email protected] are

queue-4.4/udp-fix-ip_checksum-handling.patch queue-4.4/packet-on-direct_xmit-limit-tso-and-csum-to-supported-devices.patch