ofproto-dpif-xlate: Correct check for MPLS LSE

zero is a valid MPLS LSE so it is not valid check against
that value for MPLS LSE presence. Instead, check against
the flow's dl_type which should be an MPLS type if an LSE is present.

This problem appears to have been introduced by
b2dd70be133bf86c ("Native Set-Field action.").

Cc: Jarno Rajahalme <jrajahalme@nicira.com>
Signed-off-by: Simon Horman <horms@verge.net.au>
Signed-off-by: Ben Pfaff <blp@nicira.com>
netdev: Update rx_recv documentation for NULL case

Replace truncated description of when rx_recv() may be NULL
with text used for other fields of netdev_class.

Signed-off-by: Simon Horman <horms@verge.net.au>
Signed-off-by: Ben Pfaff <blp@nicira.com>
ofproto-dpif: Fix a vlan-splinter megaflow bug

When vlan-splinter is enabled, ovs receives non-vlan flows from the
kernel vlan ports, vlan tag is then added to the incoming flow before
xlating, so that they look like those received from a trunk port.

In case megaflow is enabled, xlating may set vlan masks during rule
processing as usual. If those vlan masks were serialized and downloaded
to the kernel (this bug), those mega flows will be rejected due to
unexpected vlan mask encapsulation, since the original kernel flows do
not have vlan tags. This bug does not break connectivity, but impacts
performance since all traffic received on vlan splinter ports will now
be handled by vswitchd, as no datapath flows can be successfully
installed.

This fix is to make sure no vlan mask encapsulation is generated for
the datapath flow if its in_port was re-written by vlan-splinter
receiving logic.

Bug #22567

Signed-off-by: Andy Zhou <azhou@nicira.com>
Fix !HAVE_NETLINK build

Fix a regression introduced by commit 4b97b70d
("ofproto-dpif: Enable NXAST_SAMPLE only if the datapath supports it.")

Signed-off-by: YAMAMOTO Takashi <yamamoto@valinux.co.jp>
Signed-off-by: Ben Pfaff <blp@nicira.com>