Use bitmap instead of sock in struct mptcp_sched_data.

Please update the commit log:

'''
This patch defines struct mptcp_sched_ops, which has three struct members,
name, owner and list, and three function pointers, init, release and
get_subflow.

Add the scheduler registering, unregistering and finding functions to add,
delete and find a packet scheduler on the global list mptcp_sched_list.

The BPF scheduler function get_subflow() has a struct mptcp_sched_data
parameter, which contains a subflow pointers array. It returns a bitmap of
which subflow or subflows in the array are picked by the scheduler to
send data.
'''

Signed-off-by: Geliang Tang <geliang.tang@suse.com>
---
 include/net/mptcp.h                           |  8 ++++----
 tools/testing/selftests/bpf/bpf_tcp_helpers.h | 12 ++++++++----
 2 files changed, 12 insertions(+), 8 deletions(-)

diff --git a/include/net/mptcp.h b/include/net/mptcp.h
index 6456ea26e4c7..24a9eb32c1dd 100644
--- a/include/net/mptcp.h
+++ b/include/net/mptcp.h
@@ -97,15 +97,15 @@ 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;
+	struct mptcp_subflow_context *contexts[MPTCP_SUBFLOWS_MAX];
 };
 
 struct mptcp_sched_ops {
-	void (*get_subflow)(const struct mptcp_sock *msk, bool reinject,
-			    struct mptcp_sched_data *data);
+	unsigned long (*get_subflow)(const struct mptcp_sock *msk, bool reinject,
+				     struct mptcp_sched_data *data);
 
 	char			name[MPTCP_SCHED_NAME_MAX];
 	struct module		*owner;
diff --git a/tools/testing/selftests/bpf/bpf_tcp_helpers.h b/tools/testing/selftests/bpf/bpf_tcp_helpers.h
index aca4e3c6ac48..17d97e21b1ea 100644
--- a/tools/testing/selftests/bpf/bpf_tcp_helpers.h
+++ b/tools/testing/selftests/bpf/bpf_tcp_helpers.h
@@ -231,10 +231,14 @@ extern __u32 tcp_slow_start(struct tcp_sock *tp, __u32 acked) __ksym;
 extern void tcp_cong_avoid_ai(struct tcp_sock *tp, __u32 w, __u32 acked) __ksym;
 
 #define MPTCP_SCHED_NAME_MAX	16
+#define MPTCP_SUBFLOWS_MAX	8
+
+struct mptcp_subflow_context {
+	struct	sock *tcp_sock;	    /* tcp sk backpointer */
+} __attribute__((preserve_access_index));
 
 struct mptcp_sched_data {
-	struct sock	*sock;
-	bool		call_again;
+	struct mptcp_subflow_context *contexts[MPTCP_SUBFLOWS_MAX];
 };
 
 struct mptcp_sched_ops {
@@ -243,8 +247,8 @@ struct mptcp_sched_ops {
 	void (*init)(const struct mptcp_sock *msk);
 	void (*release)(const struct mptcp_sock *msk);
 
-	void (*get_subflow)(const struct mptcp_sock *msk, bool reinject,
-			    struct mptcp_sched_data *data);
+	unsigned long (*get_subflow)(const struct mptcp_sock *msk, bool reinject,
+				     struct mptcp_sched_data *data);
 	void *owner;
 };
 
-- 
2.34.1