Re: [PATCH mptcp-next v9 1/3] mptcp: add subflows array in mptcp_sched_data

[Mat Martineau <mathew.j.martineau@linux.intel.com>]

On Fri, 29 Apr 2022, Geliang Tang wrote:

> This patch adds a subflow pointers array in struct mptcp_sched_data. Set
> the array before invoking get_subflow(), then get it in get_subflow() in
> the BPF contexts.
>
> Signed-off-by: Geliang Tang <geliang.tang@suse.com>
> ---
> include/net/mptcp.h                             |  3 +++
> net/mptcp/protocol.h                            | 16 ++++++++++++++++
> tools/testing/selftests/bpf/bpf_mptcp_helpers.h |  3 +++
> 3 files changed, 22 insertions(+)
>
> diff --git a/include/net/mptcp.h b/include/net/mptcp.h
> index bea7608d72d3..1a48e31f3ac7 100644
> --- a/include/net/mptcp.h
> +++ b/include/net/mptcp.h
> @@ -96,10 +96,13 @@ struct mptcp_out_options {
> };
>
> #define MPTCP_SCHED_NAME_MAX	16
> +#define MPTCP_SUBFLOWS_MAX	8
>
> struct mptcp_sched_data {
> 	struct sock	*sock;
> 	bool		call_again;
> +	u8		subflows;
> +	struct mptcp_subflow_context *array[MPTCP_SUBFLOWS_MAX];
> };
>
> struct mptcp_sched_ops {
> diff --git a/net/mptcp/protocol.h b/net/mptcp/protocol.h
> index 0da2a91ad197..95a65582f1e8 100644
> --- a/net/mptcp/protocol.h
> +++ b/net/mptcp/protocol.h
> @@ -993,7 +993,9 @@ struct sock *mptcp_subflow_get_retrans(struct mptcp_sock *msk);
>
> static inline struct sock *mptcp_sched_get_send(struct mptcp_sock *msk)
> {
> +	struct mptcp_subflow_context *subflow;
> 	struct mptcp_sched_data data;
> +	int i = 0;
>
> 	sock_owned_by_me((struct sock *)msk);
>
> @@ -1007,14 +1009,22 @@ static inline struct sock *mptcp_sched_get_send(struct mptcp_sock *msk)
> 	if (!msk->sched)
> 		return mptcp_subflow_get_send(msk);
>
> +	mptcp_for_each_subflow(msk, subflow)
> +		data.array[i++] = subflow;
> +	data.subflows = i;

As I mentioned in a previous patch, a helper function here would be good.

> 	msk->sched->get_subflow(msk, false, &data);
> +	for (i = 0; i < MPTCP_SUBFLOWS_MAX; i++)
> +		data.array[i++] = NULL;
> +	data.subflows = 0;

Why zero out this data on the stack if BPF does not have write access to 
it?

- Mat

>
> 	return data.sock;
> }
>
> static inline struct sock *mptcp_sched_get_retrans(struct mptcp_sock *msk)
> {
> +	struct mptcp_subflow_context *subflow;
> 	struct mptcp_sched_data data;
> +	int i = 0;
>
> 	sock_owned_by_me((const struct sock *)msk);
>
> @@ -1025,7 +1035,13 @@ static inline struct sock *mptcp_sched_get_retrans(struct mptcp_sock *msk)
> 	if (!msk->sched)
> 		return mptcp_subflow_get_retrans(msk);
>
> +	mptcp_for_each_subflow(msk, subflow)
> +		data.array[i++] = subflow;
> +	data.subflows = i;
> 	msk->sched->get_subflow(msk, true, &data);
> +	for (i = 0; i < MPTCP_SUBFLOWS_MAX; i++)
> +		data.array[i++] = NULL;
> +	data.subflows = 0;
>
> 	return data.sock;
> }
> diff --git a/tools/testing/selftests/bpf/bpf_mptcp_helpers.h b/tools/testing/selftests/bpf/bpf_mptcp_helpers.h
> index ee07caf978b3..1fe3d0a97429 100644
> --- a/tools/testing/selftests/bpf/bpf_mptcp_helpers.h
> +++ b/tools/testing/selftests/bpf/bpf_mptcp_helpers.h
> @@ -7,10 +7,13 @@
> #include "bpf_tcp_helpers.h"
>
> #define MPTCP_SCHED_NAME_MAX	16
> +#define MPTCP_SUBFLOWS_MAX	8
>
> struct mptcp_sched_data {
> 	struct sock	*sock;
> 	bool		call_again;
> +	__u8		subflows;
> +	struct mptcp_subflow_context *array[MPTCP_SUBFLOWS_MAX];
> };
>
> struct mptcp_sched_ops {
> -- 
> 2.34.1
>
>
>

--
Mat Martineau
Intel