Add test_pop_vlan() to verify OVS kernel datapath pop_vlan action
correctly strips 802.1Q VLAN tags from frames.

Patch 1 extends ovs-dpctl.py with vlan(vid=X,pcp=Y,cfi=Z) formatting
and parsing, plus an encap_ovskey subclass for safe ENCAP NLA decoding.
It also adds push_vlan action support (parse/format with range
validation) and removes the unnecessary MAX_ENCAP_DEPTH limit.
Patch 2 adds the selftest using purely ping-based verification with
a push_vlan return flow for symmetric bidirectional testing.

Tested with vng on x86_64, all OVS selftests pass (including new
test_pop_vlan).

v5:
  - add push_vlan action class, dpstr format and parse with range
    validation (vid 0-4095, pcp 0-7, tpid 0-0xFFFF, CFI forced to 1)
  - remove MAX_ENCAP_DEPTH constant and depth tracking (bracket-depth
    counter in encap parser already handles nesting)
  - remove start_capture/stop_capture helpers and tcpdump/pcap
    verification — use ping success/failure instead
  - remove modprobe/netns pre-flight checks (other tests don't do this)
  - remove ethtool VLAN offload disable (unnecessary for veth)
  - add push_vlan return flow for symmetric bidirectional ping
  - use ovs_sbx wrapper for ping commands (consistent with siblings)
v4: https://lore.kernel.org/netdev/20260504123713.555461-1-houminxi@gmail.com/ (local)
  - fix all checkpatch line-length warnings in new code
  - fix pylint W0707: use explicit exception chaining (from exc)
v3: https://lore.kernel.org/netdev/20260503120946.51869-1-houminxi@gmail.com/ (local)
  - encap_ovskey: MPLS type "ovs_key_mpls" -> "array(ovs_key_mpls)"
  - encap_ovskey: PRIORITY/IN_PORT set to "none" (metadata, not in ENCAP)
  - _vlan_dpstr: cfi=0 falls back to tci=0x%04x for round-trip safety
  - encap parse(): check return value for unrecognized trailing content
  - vlan parser: boundary check + raise-from for exception chaining
  - start_capture: || return $? to propagate ksft_skip correctly
  - on_exit: moved after resource creation, not before
  - ping success: changed from NOTE to FAIL + return 1
  - VLAN interface creation: added || return 1 error propagation
  - netns probe: distinguish EEXIST from missing CONFIG_NET_NS
  - sbx_add: || return $ksft_skip -> || return $? (match sibling tests)
v2: https://lore.kernel.org/netdev/20260501133924.3100680-1-houminxi@gmail.com/ (local)

Minxi Hou (2):
  selftests: openvswitch: add vlan() and encap() flow string parsing
  selftests: openvswitch: add pop_vlan test

 .../selftests/net/openvswitch/openvswitch.sh  |  77 +++++
 .../selftests/net/openvswitch/ovs-dpctl.py    | 322 +++++++++++++++++-
 2 files changed, 389 insertions(+), 10 deletions(-)

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2.53.0