Re: [PATCH net-next v10 2/5] openvswitch: set skb protocol and mac_len when receiving on internal device

On Mon, Jun 20, 2016 at 7:25 PM, Simon Horman
[off-list ref] wrote:

[Cc Jiri Benc]

On Sat, Jun 18, 2016 at 06:38:54PM -0700, pravin shelar wrote:

quoted

On Thu, Jun 16, 2016 at 10:53 PM, Simon Horman
[off-list ref] wrote:

quoted

On Tue, Jun 07, 2016 at 03:45:27PM -0700, pravin shelar wrote:

quoted

On Mon, Jun 6, 2016 at 8:08 PM, Simon Horman [off-list ref] wrote:

quoted

On Thu, Jun 02, 2016 at 03:01:47PM -0700, pravin shelar wrote:

quoted

On Wed, Jun 1, 2016 at 11:24 PM, Simon Horman
[off-list ref] wrote:

quoted

* Set skb protocol based on contents of packet. I have observed this is
  necessary to get actual protocol of a packet when it is injected into an
  internal device e.g. by libnet in which case skb protocol will be set to
  ETH_ALL.

....
....

quoted

quoted

quoted

        eth_type = eth_type_trans(skb, skb->dev);
        skb->mac_len = skb->data - skb_mac_header(skb);
        __skb_push(skb, skb->mac_len);

        if (eth_type == htons(ETH_P_8021Q))
                skb->mac_len += VLAN_HLEN;

Perhaps that logic ought to be in a helper used by both internal_dev_xmit()
and netdev_port_receive(). Or somehow centralised in ovs_vport_receive().

This does looks bit complex. Can we use other skb metadata like
skb_mac_header_was_set()?

Yes, I think that can be made to work if skb->mac_header is unset
for l3 packets in netdev_port_receive(). The following is an incremental
patch on the entire series. Is this the kind of thing you had in mind?

diff --git a/net/openvswitch/flow.c b/net/openvswitch/flow.c
index 86f2cfb19de3..42587d5bf894 100644
--- a/net/openvswitch/flow.c
+++ b/net/openvswitch/flow.c

@@ -729,7 +729,7 @@ int ovs_flow_key_extract(const struct ip_tunnel_info *tun_info,
        key->phy.skb_mark = skb->mark;
        ovs_ct_fill_key(skb, key);
        key->ovs_flow_hash = 0;
-       key->phy.is_layer3 = skb->mac_len == 0;
+       key->phy.is_layer3 = skb_mac_header_was_set(skb) == 0;
        key->recirc_id = 0;

        err = key_extract(skb, key);

diff --git a/net/openvswitch/vport-internal_dev.c b/net/openvswitch/vport-internal_dev.c
index 484ba529c682..8973d4db509b 100644
--- a/net/openvswitch/vport-internal_dev.c
+++ b/net/openvswitch/vport-internal_dev.c

@@ -50,7 +50,6 @@ static int internal_dev_xmit(struct sk_buff *skb, struct net_device *netdev)

        skb->protocol = eth_type_trans(skb, netdev);
        skb_push(skb, ETH_HLEN);
-       skb_reset_mac_len(skb);

        len = skb->len;
        rcu_read_lock();

diff --git a/net/openvswitch/vport-netdev.c b/net/openvswitch/vport-netdev.c
index 3df36df62ee9..4cf3f12ffc99 100644
--- a/net/openvswitch/vport-netdev.c
+++ b/net/openvswitch/vport-netdev.c

@@ -60,22 +60,9 @@ static void netdev_port_receive(struct sk_buff *skb)
        if (vport->dev->type == ARPHRD_ETHER) {
                skb_push(skb, ETH_HLEN);
                skb_postpush_rcsum(skb, skb->data, ETH_HLEN);
-       } else if (vport->dev->type == ARPHRD_NONE) {
-               if (skb->protocol == htons(ETH_P_TEB)) {
-                       __be16 eth_type;
-
-                       if (unlikely(skb->len < ETH_HLEN))
-                               goto error;
-
-                       eth_type = eth_type_trans(skb, skb->dev);
-                       skb->mac_len = skb->data - skb_mac_header(skb);
-                       __skb_push(skb, skb->mac_len);
-
-                       if (eth_type == htons(ETH_P_8021Q))
-                               skb->mac_len += VLAN_HLEN;
-               } else {
-                       skb->mac_len = 0;
-               }
+       } else if (vport->dev->type == ARPHRD_NONE &&
+                  skb->protocol != htons(ETH_P_TEB)) {
+               skb->mac_header = (typeof(skb->mac_header))~0U;
        }

        ovs_vport_receive(vport, skb, skb_tunnel_info(skb));

This certainly looks better. I was wondering if we can unset the mac
header offset in L3 tunnel devices itself. So there is no need to have
this check here.

I think that might be possible for GRE by modifying the following in
__ipgre_rcv().

                if (tunnel->dev->type != ARPHRD_NONE)
                        skb_pop_mac_header(skb);
                else
                        skb_reset_mac_header(skb);

But I am unsure what side effects this might have on other users of the
code.

I think it is fine with device of type ARPHRD_NONE. metadata tunnel
devices would be of this type anyways.

Jiri, do you have any thoughts on this?

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