[RESEND PATCH net 0/4] net: hsr: fix GRO/GSO super-packet handling

[resend: the previous cover letter was silently dropped by the
sender's mail provider after SMTP acceptance; the four patches
themselves are byte-identical.]

HSR/PRP forward frames one by one: each wire frame gets its own tag
or RCT and sequence number, and duplicate discard is per frame. Two
aggregation mechanisms break that per-frame assumption:

* On RX, a lower device that aggregates frames into a GRO
  super-packet feeds the HSR receive and forward paths something
  they cannot handle: frames are dropped, and on memory-constrained
  devices processing super-skbs in softirq context also pressures
  atomic allocation.

* At the forward entry, a GSO super-packet (locally generated on
  the master, or delivered intact by software NICs such as veth)
  would be tagged and forwarded as a single frame, violating
  per-frame wire semantics.

Patch 1 adds netif_disable_gro() and dev_disable_gro() alongside
the existing LRO helpers.  HSR calls the public wrapper at
enslavement time, while the networking core handles the generic
feature update and recursive lower-device traversal. Enslavement to
an HSR/PRP master therefore strips NETIF_F_GRO and NETIF_F_GRO_HW
on the lower device.

Patch 2 is a preparatory locking change with forwarding semantics
unchanged: it shrinks hsr->seqnr_lock from whole hsr_forward_skb()
calls to the individual sequence counter updates, so that the
segmentation work of patch 3 (per-segment allocation, checksums and
forwarding) never runs with BH disabled under the global sequence
lock. Patch 3 depends on patch 2; please keep them together for
stable.

Patch 3 unfolds the remaining GSO super-packets at the forward
entry with the top-level GSO dispatch (__skb_gso_segment()), so
each wire frame still gets its own tag and sequence number.
Segmentation is offered only for ingress roles whose frames are
known to be plain Ethernet: the master (locally generated) and the
interlink (SAN side, untagged). A super-packet from a LAN slave may
carry per-frame HSR tags or PRP RCT trailers that software
segmentation cannot recover, and an already-tagged HSR/PRP
super-packet violates per-frame wire semantics; both are rejected
by ingress-port policy. The HSR master also stops advertising
NETIF_F_GSO_MASK so locally generated traffic is segmented as
early as possible.

Patch 4 adds a kselftest covering the above: GRO disabled on
enslaved devices, no GSO/TSO advertised by the HSR master, and a
TCP stream from a TSO-enabled SAN through an HSR DUT completing
with zero retransmits.

Validation:
* build: W=1 allmodconfig and allyesconfig, base vs patched - no
  new warnings.
* selftests: hsr_gro_superpacket (new), hsr_ping, prp_ping and
  hsr_redbox pass on QEMU x86_64 and on physical igb lower devices.
* functional: SAN TSO streams unfold per-frame with zero
  retransmits (IPv4, IPv6, VLAN); LAN-slave and GRO-merged
  super-packets are dropped by policy; master/interlink concurrency
  under PROVE_LOCKING is clean.
* physical igb lower devices: GRO stripped at enslavement;
  force-enabled generic GRO super-packets unfold at line rate with
  a clean dmesg.

Xin Xie (4):
  net: hsr: fix packet drops caused by GRO superpackets
  net: hsr: shrink seqnr_lock to sequence counter updates
  net: hsr: unfold GSO super-packets at the forward entry
  selftests: net: hsr: add GRO super-packet forwarding test

 include/linux/netdevice.h                     |   2 +
 net/core/dev.c                                |  18 ++
 net/core/dev_api.c                            |  16 ++
 net/hsr/hsr_device.c                          |  17 +-
 net/hsr/hsr_forward.c                         |  53 +++-
 net/hsr/hsr_slave.c                           |  12 +-
 tools/testing/selftests/net/hsr/Makefile      |   1 +
 .../selftests/net/hsr/hsr_gro_superpacket.sh  | 249 ++++++++++++++++++
 8 files changed, 344 insertions(+), 24 deletions(-)
 create mode 100755 tools/testing/selftests/net/hsr/hsr_gro_superpacket.sh


base-commit: ba712ecfd942b68b21a4b0a5daaf72f6616cc66d
-- 
2.43.0