There are external event timestampers (PHCs with support for
PTP_EXTTS_REQUEST) that timestamp both event edges.

When those edges are very close (such as in the case of a short pulse),
there is a chance that the collected timestamp might be of the rising,
or of the falling edge, we never know.

There are also PHCs capable of generating periodic output with a
configurable duty cycle. This is good news, because we can space the
rising and falling edge out enough in time, that the risks to overrun
the 1-entry timestamp FIFO of the extts PHC are lower (example: the
perout PHC can be configured for a period of 1 second, and an "on" time
of 0.5 seconds, resulting in a duty cycle of 50%).

A flag is introduced for signaling that an on time is present in the
perout request structure, for preserving compatibility. Logically
speaking, the duty cycle cannot exceed 100% and the PTP core checks for
this.

PHC drivers that don't support this flag emit a periodic output of an
unspecified duty cycle, same as before.

The duty cycle is encoded as an "on" time, similar to the "start" and
"period" times, and reuses the reserved space while preserving overall
binary layout.

Pahole reported before:

struct ptp_perout_request {
        struct ptp_clock_time start;                     /*     0    16 */
        struct ptp_clock_time period;                    /*    16    16 */
        unsigned int               index;                /*    32     4 */
        unsigned int               flags;                /*    36     4 */
        unsigned int               rsv[4];               /*    40    16 */

        /* size: 56, cachelines: 1, members: 5 */
        /* last cacheline: 56 bytes */
};

And now:

struct ptp_perout_request {
        struct ptp_clock_time start;                     /*     0    16 */
        struct ptp_clock_time period;                    /*    16    16 */
        unsigned int               index;                /*    32     4 */
        unsigned int               flags;                /*    36     4 */
        union {
                struct ptp_clock_time on;                /*    40    16 */
                unsigned int       rsv[4];               /*    40    16 */
        };                                               /*    40    16 */

        /* size: 56, cachelines: 1, members: 5 */
        /* last cacheline: 56 bytes */
};
Signed-off-by: Vladimir Oltean <olteanv@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

Add setsockopt SOL_IP/IP_RECVERR_4884 to return the offset to an
extension struct if present.

ICMP messages may include an extension structure after the original
datagram. RFC 4884 standardized this behavior. It stores the offset
in words to the extension header in u8 icmphdr.un.reserved[1].

The field is valid only for ICMP types destination unreachable, time
exceeded and parameter problem, if length is at least 128 bytes and
entire packet does not exceed 576 bytes.

Return the offset to the start of the extension struct when reading an
ICMP error from the error queue, if it matches the above constraints.

Do not return the raw u8 field. Return the offset from the start of
the user buffer, in bytes. The kernel does not return the network and
transport headers, so subtract those.

Also validate the headers. Return the offset regardless of validation,
as an invalid extension must still not be misinterpreted as part of
the original datagram. Note that !invalid does not imply valid. If
the extension version does not match, no validation can take place,
for instance.

For backward compatibility, make this optional, set by setsockopt
SOL_IP/IP_RECVERR_RFC4884. For API example and feature test, see
github.com/wdebruij/kerneltools/blob/master/tests/recv_icmp_v2.c

For forward compatibility, reserve only setsockopt value 1, leaving
other bits for additional icmp extensions.

Changes
  v1->v2:
  - convert word offset to byte offset from start of user buffer
    - return in ee_data as u8 may be insufficient
  - define extension struct and object header structs
  - return len only if constraints met
  - if returning len, also validate
Signed-off-by: Willem de Bruijn <willemb@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

Lorenzo Bianconi says:

====================
rework mvneta napi_poll loop for XDP multi-buffers

Rework mvneta_rx_swbm routine in order to process all rx descriptors before
building the skb or run the xdp program attached to the interface.
Introduce xdp_get_shared_info_from_{buff,frame} utility routines to get the
skb_shared_info pointer from xdp_buff or xdp_frame.
This is a preliminary series to enable multi-buffers and jumbo frames for XDP
according to [1]

[1] https://github.com/xdp-project/xdp-project/blob/master/areas/core/xdp-multi-buffer01-design.org

Changes since v1:
- rely on skb_frag_* utility routines to access page/offset/len of the xdp multi-buffer
====================
Signed-off-by: David S. Miller <davem@davemloft.net>

Allocate rxq->left_size on mvneta_rx_swbm stack since it is used just
in sw bm napi_poll
Signed-off-by: Lorenzo Bianconi <lorenzo@kernel.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

Remove skb pointer in mvneta_rx_queue data structure since it is no
longer used
Signed-off-by: Lorenzo Bianconi <lorenzo@kernel.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

Release all consumed pages if the eBPF program returns XDP_DROP for XDP
multi-buffers
Signed-off-by: Lorenzo Bianconi <lorenzo@kernel.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

Move mvneta_run_xdp routine after all descriptor processing. This is a
preliminary patch to enable multi-buffers and JUMBO frames support for
XDP
Signed-off-by: Lorenzo Bianconi <lorenzo@kernel.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

Move skb build after all descriptors processing. This is a preliminary
patch to enable multi-buffers and JUMBO frames support for XDP.
Introduce mvneta_xdp_put_buff routine to release all pages used by a
XDP multi-buffer
Signed-off-by: Lorenzo Bianconi <lorenzo@kernel.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

Introduce xdp_get_shared_info_from_{buff,frame} utility routines to get
skb_shared_info from xdp buffer/frame pointer.
xdp_get_shared_info_from_{buff,frame} will be used to implement xdp
multi-buffer support
Signed-off-by: Lorenzo Bianconi <lorenzo@kernel.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

Christoph Hellwig says:

====================
do a single memdup_user in sctp_setsockopt v2

here is a resend of my series to lift the copy_from_user out of the
individual sctp sockopt handlers into the main sctp_setsockopt
routine.

Changes since v1:
 - fixes a few sizeof calls.
 - use memzero_explicit in sctp_setsockopt_auth_key instead of special
   casing it for a kzfree in the caller
 - remove some minor cleanups from sctp_setsockopt_autoclose to keep
   it closer to the existing version
 - add another little only vaguely related cleanup patch
====================
Signed-off-by: David S. Miller <davem@davemloft.net>

This is just used once, and a direct return for the redirect to the AF
case is much easier to follow than jumping to the end of a very long
function.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: David S. Miller <davem@davemloft.net>

Use the kernel pointer that sctp_setsockopt has available instead of
directly handling the user pointer.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: David S. Miller <davem@davemloft.net>

Use the kernel pointer that sctp_setsockopt has available instead of
directly handling the user pointer.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: David S. Miller <davem@davemloft.net>

Use the kernel pointer that sctp_setsockopt has available instead of
directly handling the user pointer.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: David S. Miller <davem@davemloft.net>

Use the kernel pointer that sctp_setsockopt has available instead of
directly handling the user pointer.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: David S. Miller <davem@davemloft.net>

Use the kernel pointer that sctp_setsockopt has available instead of
directly handling the user pointer.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: David S. Miller <davem@davemloft.net>

Use the kernel pointer that sctp_setsockopt has available instead of
directly handling the user pointer.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: David S. Miller <davem@davemloft.net>

Use the kernel pointer that sctp_setsockopt has available instead of
directly handling the user pointer.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: David S. Miller <davem@davemloft.net>

Use the kernel pointer that sctp_setsockopt has available instead of
directly handling the user pointer.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: David S. Miller <davem@davemloft.net>

Use the kernel pointer that sctp_setsockopt has available instead of
directly handling the user pointer.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: David S. Miller <davem@davemloft.net>

Use the kernel pointer that sctp_setsockopt has available instead of
directly handling the user pointer.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: David S. Miller <davem@davemloft.net>

Use the kernel pointer that sctp_setsockopt has available instead of
directly handling the user pointer.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: David S. Miller <davem@davemloft.net>

Use the kernel pointer that sctp_setsockopt has available instead of
directly handling the user pointer.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: David S. Miller <davem@davemloft.net>

Use the kernel pointer that sctp_setsockopt has available instead of
directly handling the user pointer.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: David S. Miller <davem@davemloft.net>

Use the kernel pointer that sctp_setsockopt has available instead of
directly handling the user pointer.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: David S. Miller <davem@davemloft.net>

Use the kernel pointer that sctp_setsockopt has available instead of
directly handling the user pointer.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: David S. Miller <davem@davemloft.net>

Use the kernel pointer that sctp_setsockopt has available instead of
directly handling the user pointer.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: David S. Miller <davem@davemloft.net>

Use the kernel pointer that sctp_setsockopt has available instead of
directly handling the user pointer.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: David S. Miller <davem@davemloft.net>

Use the kernel pointer that sctp_setsockopt has available instead of
directly handling the user pointer.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: David S. Miller <davem@davemloft.net>

Use the kernel pointer that sctp_setsockopt has available instead of
directly handling the user pointer.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: David S. Miller <davem@davemloft.net>

Use the kernel pointer that sctp_setsockopt has available instead of
directly handling the user pointer.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: David S. Miller <davem@davemloft.net>

Use the kernel pointer that sctp_setsockopt has available instead of
directly handling the user pointer.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: David S. Miller <davem@davemloft.net>

Use the kernel pointer that sctp_setsockopt has available instead of
directly handling the user pointer.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: David S. Miller <davem@davemloft.net>

Use the kernel pointer that sctp_setsockopt has available instead of
directly handling the user pointer.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: David S. Miller <davem@davemloft.net>

Use the kernel pointer that sctp_setsockopt has available instead of
directly handling the user pointer.  Adapt sctp_setsockopt to use a
kzfree for this case.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: David S. Miller <davem@davemloft.net>

Switch from kzfree to sctp_setsockopt_auth_key + kfree to prepare for
moving the kfree to common code.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: David S. Miller <davem@davemloft.net>

Use the kernel pointer that sctp_setsockopt has available instead of
directly handling the user pointer.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: David S. Miller <davem@davemloft.net>

Use the kernel pointer that sctp_setsockopt has available instead of
directly handling the user pointer.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: David S. Miller <davem@davemloft.net>

Use the kernel pointer that sctp_setsockopt has available instead of
directly handling the user pointer.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: David S. Miller <davem@davemloft.net>

Use the kernel pointer that sctp_setsockopt has available instead of
directly handling the user pointer.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: David S. Miller <davem@davemloft.net>