On Tue, 2018-01-09 at 13:06 -0800, Lawrence Brakmo wrote:
> Adds field bpf_sock_ops_flags to tcp_sock and bpf_sock_ops. Its primary
> use is to determine if there should be calls to sock_ops bpf program at
> various points in the TCP code. The field is initialized to zero,
> disabling the calls. A sock_ops BPF program can set, per connection and
> as necessary, when the connection is established.
>
> It also adds support for reading and writting the field within a
> sock_ops BPF program.
>
> Examples of where to call the bpf program:
>
> 1) When RTO fires
> 2) When a packet is retransmitted
> 3) When the connection terminates
> 4) When a packet is sent
> 5) When a packet is received
>
> Signed-off-by: Lawrence Brakmo <bra...@fb.com>
> ---
> include/linux/tcp.h | 8 ++++++++
> include/uapi/linux/bpf.h | 1 +
> net/core/filter.c | 7 +++++++
> 3 files changed, 16 insertions(+)
>
> diff --git a/include/linux/tcp.h b/include/linux/tcp.h
> index 4f93f095..62f4388 100644
> --- a/include/linux/tcp.h
> +++ b/include/linux/tcp.h
> @@ -373,6 +373,14 @@ struct tcp_sock {
> */
> struct request_sock *fastopen_rsk;
> u32 *saved_syn;
> +
> +/* Sock_ops bpf program related variables */
> +#ifdef CONFIG_BPF
> + u32 bpf_sock_ops_flags; /* values defined in uapi/linux/tcp.h */
> +#define BPF_SOCK_OPS_TEST_FLAG(TP, ARG) (TP->bpf_sock_ops_flags & ARG)
> +#else
> +#define BPF_SOCK_OPS_TEST_FLAG(TP, ARG) 0
> +#endif
> };
>
It looks like we add yet another TCP socket field for some feature that
is only used by you or FB :/
At least please try to fill a hole (on 64bit kernels), instead of
adding one more.
Also, should not we reject attempts to use bits that are not yet
supported by the kernel ?
If a BPF filter expects to be called for every retransmit, but kernel
is too old, this wont work.
