datapath: flow_netlink: Fix a bug.

Commit 62974663fe (datapath/flow_netlink: Create right mask with
disabled megaflows) introduced the bug which caused
ovs_nla_get_match() returns immediately after parsing the flow
mask for OVS_KEY_ATTR_ENCAP.  Consequently, when vlan encapsulated
packets are present, the corresponding datapath flows will have
incorrect mask like below.  And the incorrect flows could affect
other non-vlan packets.

~/ovs# ovs-dpctl dump-flows
in_port(3/0xffff0000),eth_type(0x8100),encap(), packets:0,
bytes:0, used:never, actions:2

This commit fixes the bug by checking and handling the return
value of the parsing function correctly.

Signed-off-by: Alex Wang <alexw@nicira.com>
Acked-by: Pravin B Shelar <pshelar@nicira.com>
datapath/flow_netlink: Avoid wildcarding tunnel key with disabled megaflows

If the userspace wants to match on a flow with some tunnel attributesset to 0,
it simply omits them in the netlink attributes stream.
Since our wildcarding logic (when megaflows are disabled) is based on the
attributes in the netlink stream, we set our mask incorrectly.

This commit adds a check to detect if the userspace wants to match on a tunnel,
in which case we simply unwildcard the whole tun_key

Reported-by: Andy Zhou <azhou@nicira.com>
Signed-off-by: Daniele Di Proietto <ddiproietto@vmware.com>
Signed-off-by: Andy Zhou <azhou@nicira.com>
userspace: add support for pop_eth and push_eth actions

These actions will allow L2->L3 and L3->L2 switching, and are supposed
to be added to flows installed in the datapath transparently by
ovs-vswitchd.

Signed-off-by: Lorand Jakab <lojakab@cisco.com>
userspace: add layer 3 flow and switching support

This commit relaxes the assumption that all packets have an Ethernet
header, and adds support for layer 3 flows.  For each packet received on
the Linux kernel datapath the l2 and l3 members of struct ofpbuf are
intialized appropriately, and some functions now expect this (notably
flow_extract()), in order to differentiate between layer 2 and layer 3
packets.  struct flow has now a new 'base_layer' member, because we
cannot assume that a flow has no Ethernet header when eth_src and
eth_dst are 0.  For layer 3 packets, the protocol type is still stored
in the eth_type member.

Switching L2->L3 and L3->L2 are both implemented by adding the pop_eth
and push_eth actions respectively when a transition is detected.  The
push_eth action puts 0s on both source and destination MACs.  These
addresses can be modified with mod_dl_dst and mod_dl_src actions.

Added new prerequisite MFP_ETHERNET for fields MFF_ETH_SRC, MFF_ETH_DST,
MFF_VLAN_TCI, MFF_DL_VLAN, MFF_VLAN_VID and MFF_DL_VLAN_PCP.

Signed-off-by: Lorand Jakab <lojakab@cisco.com>
datapath: add layer 3 flow/port support

Implementation of the pop_eth and push_eth actions in the kernel, and
layer 3 flow support.

Signed-off-by: Lorand Jakab <lojakab@cisco.com>