Cross-merge networking fixes after downstream PR (net-6.19-rc9).

No adjacent changes, conflicts:

drivers/net/ethernet/spacemit/k1_emac.c
  3125fc1701694 ("net: spacemit: k1-emac: fix jumbo frame support")
  f66086798f91f ("net: spacemit: Remove broken flow control support")
https://lore.kernel.org/aYIysFIE9ooavWia@sirena.org.uk

Signed-off-by: Jakub Kicinski <kuba@kernel.org>

To remove the private CAN bus skb headroom infrastructure 8 bytes need to
be stored in the skb. The skb extensions are a common pattern and an easy
and efficient way to hold private data travelling along with the skb. We
only need the skb_ext_add() and skb_ext_find() functions to allocate and
access CAN specific content as the skb helpers to copy/clone/free skbs
automatically take care of skb extensions and their final removal.

This patch introduces the complete CAN skb extensions infrastructure:
- add struct can_skb_ext in new file include/net/can.h
- add include/net/can.h in MAINTAINERS
- add SKB_EXT_CAN to skbuff.c and skbuff.h
- select SKB_EXTENSIONS in Kconfig when CONFIG_CAN is enabled
- check for existing CAN skb extensions in can_rcv() in af_can.c
- add CAN skb extensions allocation at every skb_alloc() location
- duplicate the skb extensions if cloning outgoing skbs (framelen/gw_hops)
- introduce can_skb_ext_add() and can_skb_ext_find() helpers

The patch also corrects an indention issue in the original code from 2018:
Reported-by: kernel test robot <lkp@intel.com>
Closes: https://lore.kernel.org/oe-kbuild-all/202602010426.PnGrYAk3-lkp@intel.com/
Signed-off-by: Marc Kleine-Budde <mkl@pengutronix.de>
Signed-off-by: Oliver Hartkopp <socketcan@hartkopp.net>
Link: https://patch.msgid.link/20260201-can_skb_ext-v8-2-3635d790fe8b@hartkopp.net
Signed-off-by: Paolo Abeni <pabeni@redhat.com>

Add the following check, to detect bugs sooner for CONFIG_DEBUG_NET=y
builds.

	DEBUG_NET_WARN_ON_ONCE(skb->data < skb->head);

Signed-off-by: Eric Dumazet <edumazet@google.com>
Link: https://patch.msgid.link/20260130160253.2936789-1-edumazet@google.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

This variant of skb_header_pointer() should be used in contexts
where @offset argument is user-controlled and could be negative.

Negative offsets are supported, as long as the zone starts
between skb->head and skb->data.

Signed-off-by: Eric Dumazet <edumazet@google.com>
Link: https://patch.msgid.link/20260128141539.3404400-2-edumazet@google.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

clang does not inline this helper in GRO fast path.

We can save space and cpu cycles.

$ scripts/bloat-o-meter -t vmlinux.0 vmlinux.1
add/remove: 0/2 grow/shrink: 2/0 up/down: 156/-218 (-62)
Function                                     old     new   delta
tcp6_gro_complete                            227     311     +84
tcp4_gro_complete                            325     397     +72
__pfx___skb_incr_checksum_unnecessary         32       -     -32
__skb_incr_checksum_unnecessary              186       -    -186
Total: Before=22592724, After=22592662, chg -0.00%

Signed-off-by: Eric Dumazet <edumazet@google.com>
Link: https://patch.msgid.link/20260120164903.1912995-2-edumazet@google.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

Convert all the legacy code directly accessing the pp fields in net_iov
to access them through @desc in net_iov.

Signed-off-by: Byungchul Park <byungchul@sk.com>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

Lay groundwork for fixing BPF helpers available to TC(X) programs.

When skb_push() or skb_pull() is called in a TC(X) ingress BPF program, the
skb metadata must be kept in front of the MAC header. Otherwise, BPF
programs using the __sk_buff->data_meta pseudo-pointer lose access to it.

Introduce a helper that moves both metadata and a specified number of
packet data bytes together, suitable as a drop-in replacement for
memmove().

Signed-off-by: Jakub Sitnicki <jakub@cloudflare.com>
Signed-off-by: Martin KaFai Lau <martin.lau@kernel.org>
Link: https://patch.msgid.link/20251105-skb-meta-rx-path-v4-1-5ceb08a9b37b@cloudflare.com

Some protocols using TCP encapsulation (e.g., espintcp, openvpn) deliver
userspace-bound packets through a custom skb queue rather than the
standard sk_receive_queue.

Introduce datagram_poll_queue that accepts an explicit receive queue,
and convert datagram_poll into a wrapper around datagram_poll_queue.
This allows protocols with custom skb queues to reuse the core polling
logic without relying on sk_receive_queue.

Cc: Sabrina Dubroca <sd@queasysnail.net>
Cc: Antonio Quartulli <antonio@openvpn.net>
Signed-off-by: Ralf Lici <ralf@mandelbit.com>
Reviewed-by: Sabrina Dubroca <sd@queasysnail.net>
Reviewed-by: Antonio Quartulli <antonio@openvpn.net>
Link: https://patch.msgid.link/20251021100942.195010-2-ralf@mandelbit.com
Signed-off-by: Paolo Abeni <pabeni@redhat.com>

Currently, NETIF_F_TSO_MANGLEID indicates that the inner-most ID can
be mangled. Outer IDs can always be mangled.

Make GSO preserve outer IDs by default, with NETIF_F_TSO_MANGLEID allowing
both inner and outer IDs to be mangled.

This commit also modifies a few drivers that use SKB_GSO_FIXEDID directly.

Signed-off-by: Richard Gobert <richardbgobert@gmail.com>
Reviewed-by: Edward Cree <ecree.xilinx@gmail.com> # for sfc
Reviewed-by: Willem de Bruijn <willemb@google.com>
Link: https://patch.msgid.link/20250923085908.4687-4-richardbgobert@gmail.com
Signed-off-by: Paolo Abeni <pabeni@redhat.com>

Add pointers to psp data structures to core networking structs,
and an SKB extension to carry the PSP information from the drivers
to the socket layer.

Reviewed-by: Willem de Bruijn <willemb@google.com>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Co-developed-by: Daniel Zahka <daniel.zahka@gmail.com>
Signed-off-by: Daniel Zahka <daniel.zahka@gmail.com>
Reviewed-by: Eric Dumazet <edumazet@google.com>
Link: https://patch.msgid.link/20250917000954.859376-4-daniel.zahka@gmail.com
Signed-off-by: Paolo Abeni <pabeni@redhat.com>