On Tue, Oct 31, 2017 at 9:41 PM, Björn Töpel <bjorn.to...@gmail.com> wrote:
> From: Björn Töpel <bjorn.to...@intel.com>
>
> This patch adds the necessary AF_PACKET V4 structures for usage from
> userspace. AF_PACKET V4 is a new interface optimized for high
> performance packet processing.
>
> Signed-off-by: Björn Töpel <bjorn.to...@intel.com>
> ---
> include/uapi/linux/if_packet.h | 65
> +++++++++++++++++++++++++++++++++++++++++-
> 1 file changed, 64 insertions(+), 1 deletion(-)
>
> +struct tpacket4_queue {
> + struct tpacket4_desc *ring;
> +
> + unsigned int avail_idx;
> + unsigned int last_used_idx;
> + unsigned int num_free;
> + unsigned int ring_mask;
> +};
>
> struct packet_mreq {
> @@ -294,6 +335,28 @@ struct packet_mreq {
> unsigned char mr_address[8];
> };
>
> +/*
> + * struct tpacket_memreg_req is used in conjunction with PACKET_MEMREG
> + * to register user memory which should be used to store the packet
> + * data.
> + *
> + * There are some constraints for the memory being registered:
> + * - The memory area has to be memory page size aligned.
> + * - The frame size has to be a power of 2.
> + * - The frame size cannot be smaller than 2048B.
> + * - The frame size cannot be larger than the memory page size.
> + *
> + * Corollary: The number of frames that can be stored is
> + * len / frame_size.
> + *
> + */
> +struct tpacket_memreg_req {
> + unsigned long addr; /* Start of packet data area */
> + unsigned long len; /* Length of packet data area */
> + unsigned int frame_size; /* Frame size */
> + unsigned int data_headroom; /* Frame head room */
> +};
Existing packet sockets take a tpacket_req, allocate memory and let the
user process mmap this. I understand that TPACKET_V4 distinguishes
the descriptor from packet pools, but could both use the existing structs
and logic (packet_mmap)? That would avoid introducing a lot of new code
just for granting user pages to the kernel.
Also, use of unsigned long can cause problems on 32/64 bit compat
environments. Prefer fixed width types in uapi. Same for pointer in
tpacket4_queue.
