[PATCH mptcp-next v21 0/7] BPF redundant scheduler

[PATCH mptcp-next v21 0/7] BPF redundant scheduler

[Geliang Tang]

v21:
- address Mat's comments in v20.
- redundant sends on retransmit code path.

v20:
- rebased on "Squash to "mptcp: refactor push_pending logic" v19"

v19:
- patch 1, use 'continue' instead of 'goto again'.

v18:
 - some cleanups
 - update commit logs.

v17:
 - address to Mat's comments in v16
 - rebase to export/20221108T055508.

v16:
- keep last_snd and snd_burst in struct mptcp_sock.
- drop "mptcp: register default scheduler".
- drop "mptcp: add scheduler wrappers", move it into "mptcp: use
get_send wrapper" and "mptcp: use get_retrans wrapper".
- depends on 'v2, Revert "mptcp: add get_subflow wrappers" - fix
divide error in mptcp_subflow_get_send'

v15:
 1: "refactor push pending" v10
 2-11: "register default scheduler" v3
  - move last_snd and snd_burst into struct mptcp_sched_ops
 12-19: "BPF redundant scheduler" v15
  - split "use get_send wrapper" into two patches
 - rebase to export/20221021T061837.

v14:
- add "mptcp: refactor push_pending logic" v10 as patch 1
- drop update_first_pending in patch 4
- drop update_already_sent in patch 5

v13:
- deponds on "refactor push pending" v9.
- Simply 'goto out' after invoking mptcp_subflow_delegate in patch 1.
- All selftests (mptcp_connect.sh, mptcp_join.sh and simult_flows.sh) passed.

v12:
 - fix WARN_ON_ONCE(reuse_skb) and WARN_ON_ONCE(!msk->recovery) errors
   in kernel logs.

v11:
 - address to Mat's comments in v10.
 - rebase to export/20220908T063452

v10:
 - send multiple dfrags in __mptcp_push_pending().

v9:
 - drop the extra *err paramenter of mptcp_sched_get_send() as Florian
   suggested.

v8:
 - update __mptcp_push_pending(), send the same data on each subflow.
 - update __mptcp_retrans, track the max sent data.
 = add a new patch.

v7:
 - drop redundant flag in v6
 - drop __mptcp_subflows_push_pending in v6
 - update redundant subflows support in __mptcp_push_pending
 - update redundant subflows support in __mptcp_retrans

v6:
 - Add redundant flag for struct mptcp_sched_ops.
 - add a dedicated function __mptcp_subflows_push_pending() to deal with
   redundat subflows push pending.

v5:
 - address to Paolo's comment, keep the optimization to
mptcp_subflow_get_send() for the non eBPF case.
 - merge mptcp_sched_get_send() and __mptcp_sched_get_send() in v4 into one.
 - depends on "cleanups for bpf sched selftests".

v4:
 - small cleanups in patch 1, 2.
 - add TODO in patch 3.
 - rebase patch 5 on 'cleanups for bpf sched selftests'.

v3:
 - use new API.
 - fix the link failure tests issue mentioned in ("https://patchwork.kernel.org/project/mptcp/cover/cover.1653033459.git.geliang.tang@suse.com/").

v2:
 - add MPTCP_SUBFLOWS_MAX limit to avoid infinite loops when the
   scheduler always sets call_again to true.
 - track the largest copied amount.
 - deal with __mptcp_subflow_push_pending() and the retransmit loop.
 - depends on "BPF round-robin scheduler" v14.

v1:

Implements the redundant BPF MPTCP scheduler, which sends all packets
redundantly on all available subflows.

Geliang Tang (7):
  mptcp: add scheduler wrappers
  mptcp: use get_send wrapper
  mptcp: use get_retrans wrapper
  mptcp: retrans for redundant sends
  mptcp: add mptcp_update_dfrags
  selftests/bpf: Add bpf_red scheduler
  selftests/bpf: Add bpf_red test

 net/mptcp/protocol.c                          | 237 ++++++++++++------
 net/mptcp/protocol.h                          |  17 +-
 net/mptcp/sched.c                             |  69 +++++
 .../testing/selftests/bpf/prog_tests/mptcp.c  |  34 +++
 .../selftests/bpf/progs/mptcp_bpf_red.c       |  45 ++++
 5 files changed, 320 insertions(+), 82 deletions(-)
 create mode 100644 tools/testing/selftests/bpf/progs/mptcp_bpf_red.c

-- 
2.35.3

[PATCH mptcp-next v21 1/7] mptcp: add scheduler wrappers

[Geliang Tang]

This patch defines two packet scheduler wrappers mptcp_sched_get_send()
and mptcp_sched_get_retrans(), invoke data_init() and get_subflow() of
msk->sched in them.

Set data->reinject to true in mptcp_sched_get_retrans(), set it false in
mptcp_sched_get_send().

If msk->sched is NULL, use default functions mptcp_subflow_get_send()
and mptcp_subflow_get_retrans() to send data.

Signed-off-by: Geliang Tang <geliang.tang@suse.com>
---
 net/mptcp/protocol.c |  4 ++--
 net/mptcp/protocol.h |  4 ++++
 net/mptcp/sched.c    | 50 ++++++++++++++++++++++++++++++++++++++++++++
 3 files changed, 56 insertions(+), 2 deletions(-)

diff --git a/net/mptcp/protocol.c b/net/mptcp/protocol.c
index 99f5e51d5ca4..d8ad68dd504a 100644
--- a/net/mptcp/protocol.c
+++ b/net/mptcp/protocol.c
@@ -1397,7 +1397,7 @@ bool mptcp_subflow_active(struct mptcp_subflow_context *subflow)
  * returns the subflow that will transmit the next DSS
  * additionally updates the rtx timeout
  */
-static struct sock *mptcp_subflow_get_send(struct mptcp_sock *msk)
+struct sock *mptcp_subflow_get_send(struct mptcp_sock *msk)
 {
 	struct subflow_send_info send_info[SSK_MODE_MAX];
 	struct mptcp_subflow_context *subflow;
@@ -2213,7 +2213,7 @@ static void mptcp_timeout_timer(struct timer_list *t)
  *
  * A backup subflow is returned only if that is the only kind available.
  */
-static struct sock *mptcp_subflow_get_retrans(struct mptcp_sock *msk)
+struct sock *mptcp_subflow_get_retrans(struct mptcp_sock *msk)
 {
 	struct sock *backup = NULL, *pick = NULL;
 	struct mptcp_subflow_context *subflow;
diff --git a/net/mptcp/protocol.h b/net/mptcp/protocol.h
index 224f03a899c5..adfb758a842f 100644
--- a/net/mptcp/protocol.h
+++ b/net/mptcp/protocol.h
@@ -657,6 +657,10 @@ void mptcp_subflow_set_scheduled(struct mptcp_subflow_context *subflow,
 				 bool scheduled);
 void mptcp_sched_data_set_contexts(const struct mptcp_sock *msk,
 				   struct mptcp_sched_data *data);
+struct sock *mptcp_subflow_get_send(struct mptcp_sock *msk);
+struct sock *mptcp_subflow_get_retrans(struct mptcp_sock *msk);
+int mptcp_sched_get_send(struct mptcp_sock *msk);
+int mptcp_sched_get_retrans(struct mptcp_sock *msk);
 
 static inline bool __tcp_can_send(const struct sock *ssk)
 {
diff --git a/net/mptcp/sched.c b/net/mptcp/sched.c
index 0d7c73e9562e..c4006f142f10 100644
--- a/net/mptcp/sched.c
+++ b/net/mptcp/sched.c
@@ -112,3 +112,53 @@ void mptcp_sched_data_set_contexts(const struct mptcp_sock *msk,
 	for (; i < MPTCP_SUBFLOWS_MAX; i++)
 		data->contexts[i] = NULL;
 }
+
+int mptcp_sched_get_send(struct mptcp_sock *msk)
+{
+	struct mptcp_subflow_context *subflow;
+	struct mptcp_sched_data data;
+
+	mptcp_for_each_subflow(msk, subflow) {
+		if (READ_ONCE(subflow->scheduled))
+			return 0;
+	}
+
+	if (!msk->sched) {
+		struct sock *ssk;
+
+		ssk = mptcp_subflow_get_send(msk);
+		if (!ssk)
+			return -EINVAL;
+		mptcp_subflow_set_scheduled(mptcp_subflow_ctx(ssk), true);
+		return 0;
+	}
+
+	data.reinject = false;
+	msk->sched->data_init(msk, &data);
+	return msk->sched->get_subflow(msk, &data);
+}
+
+int mptcp_sched_get_retrans(struct mptcp_sock *msk)
+{
+	struct mptcp_subflow_context *subflow;
+	struct mptcp_sched_data data;
+
+	mptcp_for_each_subflow(msk, subflow) {
+		if (READ_ONCE(subflow->scheduled))
+			return 0;
+	}
+
+	if (!msk->sched) {
+		struct sock *ssk;
+
+		ssk = mptcp_subflow_get_retrans(msk);
+		if (!ssk)
+			return -EINVAL;
+		mptcp_subflow_set_scheduled(mptcp_subflow_ctx(ssk), true);
+		return 0;
+	}
+
+	data.reinject = true;
+	msk->sched->data_init(msk, &data);
+	return msk->sched->get_subflow(msk, &data);
+}
-- 
2.35.3

[PATCH mptcp-next v21 2/7] mptcp: use get_send wrapper

[Geliang Tang]

This patch adds the multiple subflows support for __mptcp_push_pending
and __mptcp_subflow_push_pending. Use get_send() wrapper instead of
mptcp_subflow_get_send() in them.

Check the subflow scheduled flags to test which subflow or subflows are
picked by the scheduler, use them to send data.

Move sock_owned_by_me() check and fallback check into get_send() wrapper
from mptcp_subflow_get_send().

This commit allows the scheduler to set the subflow->scheduled bit in
multiple subflows, but it does not allow for sending redundant data.
Multiple scheduled subflows will send sequential data on each subflow.

Signed-off-by: Geliang Tang <geliang.tang@suse.com>
---
 net/mptcp/protocol.c | 118 ++++++++++++++++++++++++++-----------------
 net/mptcp/sched.c    |  13 +++++
 2 files changed, 84 insertions(+), 47 deletions(-)

diff --git a/net/mptcp/protocol.c b/net/mptcp/protocol.c
index d8ad68dd504a..65eaf59c9a6f 100644
--- a/net/mptcp/protocol.c
+++ b/net/mptcp/protocol.c
@@ -1408,15 +1408,6 @@ struct sock *mptcp_subflow_get_send(struct mptcp_sock *msk)
 	u64 linger_time;
 	long tout = 0;
 
-	sock_owned_by_me(sk);
-
-	if (__mptcp_check_fallback(msk)) {
-		if (!msk->first)
-			return NULL;
-		return __tcp_can_send(msk->first) &&
-		       sk_stream_memory_free(msk->first) ? msk->first : NULL;
-	}
-
 	/* pick the subflow with the lower wmem/wspace ratio */
 	for (i = 0; i < SSK_MODE_MAX; ++i) {
 		send_info[i].ssk = NULL;
@@ -1563,47 +1554,58 @@ void __mptcp_push_pending(struct sock *sk, unsigned int flags)
 {
 	struct sock *prev_ssk = NULL, *ssk = NULL;
 	struct mptcp_sock *msk = mptcp_sk(sk);
+	struct mptcp_subflow_context *subflow;
 	struct mptcp_sendmsg_info info = {
 				.flags = flags,
 	};
 	bool do_check_data_fin = false;
+	bool err = false;
 
-	while (mptcp_send_head(sk)) {
+	while (mptcp_send_head(sk) && !err) {
 		int ret = 0;
 
-		prev_ssk = ssk;
-		ssk = mptcp_subflow_get_send(msk);
-
-		/* First check. If the ssk has changed since
-		 * the last round, release prev_ssk
-		 */
-		if (ssk != prev_ssk && prev_ssk)
-			mptcp_push_release(prev_ssk, &info);
-		if (!ssk)
+		if (mptcp_sched_get_send(msk))
 			goto out;
 
-		/* Need to lock the new subflow only if different
-		 * from the previous one, otherwise we are still
-		 * helding the relevant lock
-		 */
-		if (ssk != prev_ssk)
-			lock_sock(ssk);
+		mptcp_for_each_subflow(msk, subflow) {
+			if (READ_ONCE(subflow->scheduled)) {
+				prev_ssk = ssk;
+				ssk = mptcp_subflow_tcp_sock(subflow);
 
-		ret = __subflow_push_pending(sk, ssk, &info);
-		if (ret <= 0) {
-			if (ret == -EAGAIN)
-				continue;
-			mptcp_push_release(ssk, &info);
-			goto out;
+				if (ssk != prev_ssk) {
+					/* First check. If the ssk has changed since
+					 * the last round, release prev_ssk
+					 */
+					if (prev_ssk)
+						mptcp_push_release(prev_ssk, &info);
+
+					/* Need to lock the new subflow only if different
+					 * from the previous one, otherwise we are still
+					 * helding the relevant lock
+					 */
+					lock_sock(ssk);
+				}
+
+				ret = __subflow_push_pending(sk, ssk, &info);
+				if (ret <= 0) {
+					if (ret != -EAGAIN ||
+					    (1 << ssk->sk_state) &
+					     (TCPF_FIN_WAIT1 | TCPF_FIN_WAIT2 | TCPF_CLOSE))
+						err = true;
+					continue;
+				}
+				do_check_data_fin = true;
+				msk->last_snd = ssk;
+				mptcp_subflow_set_scheduled(subflow, false);
+			}
 		}
-		do_check_data_fin = true;
 	}
 
+out:
 	/* at this point we held the socket lock for the last subflow we used */
 	if (ssk)
 		mptcp_push_release(ssk, &info);
 
-out:
 	/* ensure the rtx timer is running */
 	if (!mptcp_timer_pending(sk))
 		mptcp_reset_timer(sk);
@@ -1614,33 +1616,55 @@ void __mptcp_push_pending(struct sock *sk, unsigned int flags)
 static void __mptcp_subflow_push_pending(struct sock *sk, struct sock *ssk, bool first)
 {
 	struct mptcp_sock *msk = mptcp_sk(sk);
+	struct mptcp_subflow_context *subflow;
 	struct mptcp_sendmsg_info info = {
 		.data_lock_held = true,
 	};
-	struct sock *xmit_ssk;
+	bool err = false;
 	int copied = 0;
 
 	info.flags = 0;
-	while (mptcp_send_head(sk)) {
+	while (mptcp_send_head(sk) && !err) {
 		int ret = 0;
 
 		/* check for a different subflow usage only after
 		 * spooling the first chunk of data
 		 */
-		xmit_ssk = first ? ssk : mptcp_subflow_get_send(msk);
-		if (!xmit_ssk)
-			goto out;
-		if (xmit_ssk != ssk) {
-			mptcp_subflow_delegate(mptcp_subflow_ctx(xmit_ssk),
-					       MPTCP_DELEGATE_SEND);
-			goto out;
+		if (first) {
+			ret = __subflow_push_pending(sk, ssk, &info);
+			first = false;
+			if (ret <= 0)
+				break;
+			copied += ret;
+			msk->last_snd = ssk;
+			continue;
 		}
 
-		ret = __subflow_push_pending(sk, ssk, &info);
-		first = false;
-		if (ret <= 0)
-			break;
-		copied += ret;
+		if (mptcp_sched_get_send(msk))
+			goto out;
+
+		mptcp_for_each_subflow(msk, subflow) {
+			if (READ_ONCE(subflow->scheduled)) {
+				struct sock *xmit_ssk = mptcp_subflow_tcp_sock(subflow);
+
+				if (xmit_ssk != ssk) {
+					mptcp_subflow_delegate(subflow,
+							       MPTCP_DELEGATE_SEND);
+					msk->last_snd = ssk;
+					mptcp_subflow_set_scheduled(subflow, false);
+					goto out;
+				}
+
+				ret = __subflow_push_pending(sk, ssk, &info);
+				if (ret <= 0) {
+					err = true;
+					continue;
+				}
+				copied += ret;
+				msk->last_snd = ssk;
+				mptcp_subflow_set_scheduled(subflow, false);
+			}
+		}
 	}
 
 out:
diff --git a/net/mptcp/sched.c b/net/mptcp/sched.c
index c4006f142f10..18518a81afb3 100644
--- a/net/mptcp/sched.c
+++ b/net/mptcp/sched.c
@@ -118,6 +118,19 @@ int mptcp_sched_get_send(struct mptcp_sock *msk)
 	struct mptcp_subflow_context *subflow;
 	struct mptcp_sched_data data;
 
+	sock_owned_by_me((const struct sock *)msk);
+
+	/* the following check is moved out of mptcp_subflow_get_send */
+	if (__mptcp_check_fallback(msk)) {
+		if (msk->first &&
+		    __tcp_can_send(msk->first) &&
+		    sk_stream_memory_free(msk->first)) {
+			mptcp_subflow_set_scheduled(mptcp_subflow_ctx(msk->first), true);
+			return 0;
+		}
+		return -EINVAL;
+	}
+
 	mptcp_for_each_subflow(msk, subflow) {
 		if (READ_ONCE(subflow->scheduled))
 			return 0;
-- 
2.35.3

[PATCH mptcp-next v21 3/7] mptcp: use get_retrans wrapper

[Geliang Tang]

This patch adds the multiple subflows support for __mptcp_retrans(). Use
get_retrans() wrapper instead of mptcp_subflow_get_retrans() in it.

Check the subflow scheduled flags to test which subflow or subflows are
picked by the scheduler, use them to send data.

Move sock_owned_by_me() check and fallback check into get_retrans()
wrapper from mptcp_subflow_get_retrans().

Signed-off-by: Geliang Tang <geliang.tang@suse.com>
---
 net/mptcp/protocol.c | 67 ++++++++++++++++++++++++++------------------
 net/mptcp/sched.c    |  6 ++++
 2 files changed, 45 insertions(+), 28 deletions(-)

diff --git a/net/mptcp/protocol.c b/net/mptcp/protocol.c
index 65eaf59c9a6f..f8c95affaade 100644
--- a/net/mptcp/protocol.c
+++ b/net/mptcp/protocol.c
@@ -2243,11 +2243,6 @@ struct sock *mptcp_subflow_get_retrans(struct mptcp_sock *msk)
 	struct mptcp_subflow_context *subflow;
 	int min_stale_count = INT_MAX;
 
-	sock_owned_by_me((const struct sock *)msk);
-
-	if (__mptcp_check_fallback(msk))
-		return NULL;
-
 	mptcp_for_each_subflow(msk, subflow) {
 		struct sock *ssk = mptcp_subflow_tcp_sock(subflow);
 
@@ -2517,16 +2512,17 @@ static void mptcp_check_fastclose(struct mptcp_sock *msk)
 static void __mptcp_retrans(struct sock *sk)
 {
 	struct mptcp_sock *msk = mptcp_sk(sk);
+	struct mptcp_subflow_context *subflow;
 	struct mptcp_sendmsg_info info = {};
 	struct mptcp_data_frag *dfrag;
-	size_t copied = 0;
 	struct sock *ssk;
-	int ret;
+	int ret, err;
+	u16 len = 0;
 
 	mptcp_clean_una_wakeup(sk);
 
 	/* first check ssk: need to kick "stale" logic */
-	ssk = mptcp_subflow_get_retrans(msk);
+	err = mptcp_sched_get_retrans(msk);
 	dfrag = mptcp_rtx_head(sk);
 	if (!dfrag) {
 		if (mptcp_data_fin_enabled(msk)) {
@@ -2545,31 +2541,46 @@ static void __mptcp_retrans(struct sock *sk)
 		goto reset_timer;
 	}
 
-	if (!ssk)
+	if (err)
 		goto reset_timer;
 
-	lock_sock(ssk);
+	mptcp_for_each_subflow(msk, subflow) {
+		if (READ_ONCE(subflow->scheduled)) {
+			u16 copied = 0;
 
-	/* limit retransmission to the bytes already sent on some subflows */
-	info.sent = 0;
-	info.limit = READ_ONCE(msk->csum_enabled) ? dfrag->data_len : dfrag->already_sent;
-	while (info.sent < info.limit) {
-		ret = mptcp_sendmsg_frag(sk, ssk, dfrag, &info);
-		if (ret <= 0)
-			break;
+			ssk = mptcp_subflow_tcp_sock(subflow);
+			if (!ssk)
+				goto reset_timer;
 
-		MPTCP_INC_STATS(sock_net(sk), MPTCP_MIB_RETRANSSEGS);
-		copied += ret;
-		info.sent += ret;
-	}
-	if (copied) {
-		dfrag->already_sent = max(dfrag->already_sent, info.sent);
-		tcp_push(ssk, 0, info.mss_now, tcp_sk(ssk)->nonagle,
-			 info.size_goal);
-		WRITE_ONCE(msk->allow_infinite_fallback, false);
-	}
+			lock_sock(ssk);
 
-	release_sock(ssk);
+			/* limit retransmission to the bytes already sent on some subflows */
+			info.sent = 0;
+			info.limit = READ_ONCE(msk->csum_enabled) ? dfrag->data_len :
+								    dfrag->already_sent;
+			while (info.sent < info.limit) {
+				ret = mptcp_sendmsg_frag(sk, ssk, dfrag, &info);
+				if (ret <= 0)
+					break;
+
+				MPTCP_INC_STATS(sock_net(sk), MPTCP_MIB_RETRANSSEGS);
+				copied += ret;
+				info.sent += ret;
+			}
+			if (copied) {
+				len = max(copied, len);
+				tcp_push(ssk, 0, info.mss_now, tcp_sk(ssk)->nonagle,
+					 info.size_goal);
+				WRITE_ONCE(msk->allow_infinite_fallback, false);
+			}
+
+			release_sock(ssk);
+
+			msk->last_snd = ssk;
+			mptcp_subflow_set_scheduled(subflow, false);
+		}
+	}
+	dfrag->already_sent = max(dfrag->already_sent, len);
 
 reset_timer:
 	mptcp_check_and_set_pending(sk);
diff --git a/net/mptcp/sched.c b/net/mptcp/sched.c
index 18518a81afb3..c55f2f1cb7ac 100644
--- a/net/mptcp/sched.c
+++ b/net/mptcp/sched.c
@@ -156,6 +156,12 @@ int mptcp_sched_get_retrans(struct mptcp_sock *msk)
 	struct mptcp_subflow_context *subflow;
 	struct mptcp_sched_data data;
 
+	sock_owned_by_me((const struct sock *)msk);
+
+	/* the following check is moved out of mptcp_subflow_get_retrans */
+	if (__mptcp_check_fallback(msk))
+		return -EINVAL;
+
 	mptcp_for_each_subflow(msk, subflow) {
 		if (READ_ONCE(subflow->scheduled))
 			return 0;
-- 
2.35.3

[PATCH mptcp-next v21 4/7] mptcp: retrans for redundant sends

[Geliang Tang]

Redundant sends need to work more like the MPTCP retransmit code path.
When the scheduler selects multiple subflows, the first subflow to send
is a "normal" transmit, and any other subflows would act like a retransmit
when accessing the dfrags.

Signed-off-by: Geliang Tang <geliang.tang@suse.com>
---
 net/mptcp/protocol.c | 22 +++++++++++++++++++---
 1 file changed, 19 insertions(+), 3 deletions(-)

diff --git a/net/mptcp/protocol.c b/net/mptcp/protocol.c
index f8c95affaade..3fcd6af96721 100644
--- a/net/mptcp/protocol.c
+++ b/net/mptcp/protocol.c
@@ -1562,13 +1562,19 @@ void __mptcp_push_pending(struct sock *sk, unsigned int flags)
 	bool err = false;
 
 	while (mptcp_send_head(sk) && !err) {
-		int ret = 0;
+		int ret = 0, i = 0;
 
 		if (mptcp_sched_get_send(msk))
 			goto out;
 
 		mptcp_for_each_subflow(msk, subflow) {
 			if (READ_ONCE(subflow->scheduled)) {
+				if (i > 0) {
+					if (!test_and_set_bit(MPTCP_WORK_RTX, &msk->flags))
+						mptcp_schedule_work(sk);
+					goto out;
+				}
+
 				prev_ssk = ssk;
 				ssk = mptcp_subflow_tcp_sock(subflow);
 
@@ -1594,6 +1600,7 @@ void __mptcp_push_pending(struct sock *sk, unsigned int flags)
 						err = true;
 					continue;
 				}
+				i++;
 				do_check_data_fin = true;
 				msk->last_snd = ssk;
 				mptcp_subflow_set_scheduled(subflow, false);
@@ -1625,7 +1632,7 @@ static void __mptcp_subflow_push_pending(struct sock *sk, struct sock *ssk, bool
 
 	info.flags = 0;
 	while (mptcp_send_head(sk) && !err) {
-		int ret = 0;
+		int ret = 0, i = 0;
 
 		/* check for a different subflow usage only after
 		 * spooling the first chunk of data
@@ -1647,12 +1654,20 @@ static void __mptcp_subflow_push_pending(struct sock *sk, struct sock *ssk, bool
 			if (READ_ONCE(subflow->scheduled)) {
 				struct sock *xmit_ssk = mptcp_subflow_tcp_sock(subflow);
 
+				if (i > 0) {
+					if (!test_and_set_bit(MPTCP_WORK_RTX, &msk->flags))
+						mptcp_schedule_work(sk);
+					goto out;
+				}
+
 				if (xmit_ssk != ssk) {
 					mptcp_subflow_delegate(subflow,
 							       MPTCP_DELEGATE_SEND);
+					i++;
 					msk->last_snd = ssk;
 					mptcp_subflow_set_scheduled(subflow, false);
-					goto out;
+					err = true;
+					continue;
 				}
 
 				ret = __subflow_push_pending(sk, ssk, &info);
@@ -1660,6 +1675,7 @@ static void __mptcp_subflow_push_pending(struct sock *sk, struct sock *ssk, bool
 					err = true;
 					continue;
 				}
+				i++;
 				copied += ret;
 				msk->last_snd = ssk;
 				mptcp_subflow_set_scheduled(subflow, false);
-- 
2.35.3

[PATCH mptcp-next v21 5/7] mptcp: add mptcp_update_dfrags

[Geliang Tang]

Add a new helper mptcp_next_frag() to get the next dfrag of the given
dfrag.

Add new members first and last in struct mptcp_sendmsg_info, to point
to the first and last sent dfrag in the dfrags iteration loop in
__subflow_push_pending().

Invoke the new helper mptcp_update_dfrags() to iterate the dfrags from
info->first to info->last to update already_sent of every dfrag to 0
in the redundant sends retrans path.

Signed-off-by: Geliang Tang <geliang.tang@suse.com>
---
 net/mptcp/protocol.c | 28 ++++++++++++++++++++++++++++
 net/mptcp/protocol.h | 13 ++++++++++---
 2 files changed, 38 insertions(+), 3 deletions(-)

diff --git a/net/mptcp/protocol.c b/net/mptcp/protocol.c
index 3fcd6af96721..23116b0840ad 100644
--- a/net/mptcp/protocol.c
+++ b/net/mptcp/protocol.c
@@ -992,6 +992,12 @@ static void __mptcp_clean_una(struct sock *sk)
 		msk->snd_una = READ_ONCE(msk->snd_nxt);
 
 	snd_una = msk->snd_una;
+	/* Fix this:
+	 * ------------[ cut here ]------------
+	 * WARNING: CPU: 6 PID: 3007 at net/mptcp/protocol.c:1003 __mptcp_clean_una+0x243/0x2b0
+	 */
+	if (msk->first_pending)
+		goto out;
 	list_for_each_entry_safe(dfrag, dtmp, &msk->rtx_queue, list) {
 		if (after64(dfrag->data_seq + dfrag->data_len, snd_una))
 			break;
@@ -1112,6 +1118,7 @@ struct mptcp_sendmsg_info {
 	u16 sent;
 	unsigned int flags;
 	bool data_lock_held;
+	struct mptcp_data_frag *first, *last;
 };
 
 static int mptcp_check_allowed_size(const struct mptcp_sock *msk, struct sock *ssk,
@@ -1502,6 +1509,23 @@ static void mptcp_update_post_push(struct mptcp_sock *msk,
 		msk->snd_nxt = snd_nxt_new;
 }
 
+static void mptcp_update_dfrags(struct sock *sk, struct mptcp_sendmsg_info *info)
+{
+	struct mptcp_data_frag *dfrag = info->first;
+	struct mptcp_sock *msk = mptcp_sk(sk);
+
+	if (!dfrag)
+		return;
+
+	do {
+		dfrag->already_sent = 0;
+		if (dfrag == info->last)
+			break;
+	} while ((dfrag = mptcp_next_frag(sk, dfrag)));
+
+	WRITE_ONCE(msk->first_pending, info->first);
+}
+
 void mptcp_check_and_set_pending(struct sock *sk)
 {
 	if (mptcp_send_head(sk))
@@ -1515,10 +1539,12 @@ static int __subflow_push_pending(struct sock *sk, struct sock *ssk,
 	struct mptcp_data_frag *dfrag;
 	int len, copied = 0, err = 0;
 
+	info->first = mptcp_send_head(sk);
 	while ((dfrag = mptcp_send_head(sk))) {
 		info->sent = dfrag->already_sent;
 		info->limit = dfrag->data_len;
 		len = dfrag->data_len - dfrag->already_sent;
+		info->last = dfrag;
 		while (len > 0) {
 			int ret = 0;
 
@@ -1572,6 +1598,7 @@ void __mptcp_push_pending(struct sock *sk, unsigned int flags)
 				if (i > 0) {
 					if (!test_and_set_bit(MPTCP_WORK_RTX, &msk->flags))
 						mptcp_schedule_work(sk);
+					mptcp_update_dfrags(sk, &info);
 					goto out;
 				}
 
@@ -1657,6 +1684,7 @@ static void __mptcp_subflow_push_pending(struct sock *sk, struct sock *ssk, bool
 				if (i > 0) {
 					if (!test_and_set_bit(MPTCP_WORK_RTX, &msk->flags))
 						mptcp_schedule_work(sk);
+					mptcp_update_dfrags(sk, &info);
 					goto out;
 				}
 
diff --git a/net/mptcp/protocol.h b/net/mptcp/protocol.h
index adfb758a842f..782dcfd55429 100644
--- a/net/mptcp/protocol.h
+++ b/net/mptcp/protocol.h
@@ -358,16 +358,23 @@ static inline struct mptcp_data_frag *mptcp_send_head(const struct sock *sk)
 	return READ_ONCE(msk->first_pending);
 }
 
-static inline struct mptcp_data_frag *mptcp_send_next(struct sock *sk)
+static inline struct mptcp_data_frag *mptcp_next_frag(const struct sock *sk,
+						      struct mptcp_data_frag *cur)
 {
 	struct mptcp_sock *msk = mptcp_sk(sk);
-	struct mptcp_data_frag *cur;
 
-	cur = msk->first_pending;
+	if (!cur)
+		return NULL;
+
 	return list_is_last(&cur->list, &msk->rtx_queue) ? NULL :
 						     list_next_entry(cur, list);
 }
 
+static inline struct mptcp_data_frag *mptcp_send_next(const struct sock *sk)
+{
+	return mptcp_next_frag(sk, mptcp_send_head(sk));
+}
+
 static inline struct mptcp_data_frag *mptcp_pending_tail(const struct sock *sk)
 {
 	struct mptcp_sock *msk = mptcp_sk(sk);
-- 
2.35.3

[PATCH mptcp-next v21 6/7] selftests/bpf: Add bpf_red scheduler

[Geliang Tang]

This patch implements the redundant BPF MPTCP scheduler, named bpf_red,
which sends all packets redundantly on all available subflows.

Signed-off-by: Geliang Tang <geliang.tang@suse.com>
---
 .../selftests/bpf/progs/mptcp_bpf_red.c       | 45 +++++++++++++++++++
 1 file changed, 45 insertions(+)
 create mode 100644 tools/testing/selftests/bpf/progs/mptcp_bpf_red.c

diff --git a/tools/testing/selftests/bpf/progs/mptcp_bpf_red.c b/tools/testing/selftests/bpf/progs/mptcp_bpf_red.c
new file mode 100644
index 000000000000..30dd6f521b7f
--- /dev/null
+++ b/tools/testing/selftests/bpf/progs/mptcp_bpf_red.c
@@ -0,0 +1,45 @@
+// SPDX-License-Identifier: GPL-2.0
+/* Copyright (c) 2022, SUSE. */
+
+#include <linux/bpf.h>
+#include "bpf_tcp_helpers.h"
+
+char _license[] SEC("license") = "GPL";
+
+SEC("struct_ops/mptcp_sched_red_init")
+void BPF_PROG(mptcp_sched_red_init, const struct mptcp_sock *msk)
+{
+}
+
+SEC("struct_ops/mptcp_sched_red_release")
+void BPF_PROG(mptcp_sched_red_release, const struct mptcp_sock *msk)
+{
+}
+
+void BPF_STRUCT_OPS(bpf_red_data_init, const struct mptcp_sock *msk,
+		    struct mptcp_sched_data *data)
+{
+	mptcp_sched_data_set_contexts(msk, data);
+}
+
+int BPF_STRUCT_OPS(bpf_red_get_subflow, const struct mptcp_sock *msk,
+		   struct mptcp_sched_data *data)
+{
+	for (int i = 0; i < MPTCP_SUBFLOWS_MAX; i++) {
+		if (!data->contexts[i])
+			break;
+
+		mptcp_subflow_set_scheduled(data->contexts[i], true);
+	}
+
+	return 0;
+}
+
+SEC(".struct_ops")
+struct mptcp_sched_ops red = {
+	.init		= (void *)mptcp_sched_red_init,
+	.release	= (void *)mptcp_sched_red_release,
+	.data_init	= (void *)bpf_red_data_init,
+	.get_subflow	= (void *)bpf_red_get_subflow,
+	.name		= "bpf_red",
+};
-- 
2.35.3

[PATCH mptcp-next v21 7/7] selftests/bpf: Add bpf_red test

[Geliang Tang]

This patch adds the redundant BPF MPTCP scheduler test: test_red(). Use
sysctl to set net.mptcp.scheduler to use this sched. Add two veth net
devices to simulate the multiple addresses case. Use 'ip mptcp endpoint'
command to add the new endpoint ADDR_2 to PM netlink. Send data and check
bytes_sent of 'ss' output after it to make sure the data has been
redundantly sent on both net devices.

Signed-off-by: Geliang Tang <geliang.tang@suse.com>
---
 .../testing/selftests/bpf/prog_tests/mptcp.c  | 34 +++++++++++++++++++
 1 file changed, 34 insertions(+)

diff --git a/tools/testing/selftests/bpf/prog_tests/mptcp.c b/tools/testing/selftests/bpf/prog_tests/mptcp.c
index 647d313475bc..8426a5aba721 100644
--- a/tools/testing/selftests/bpf/prog_tests/mptcp.c
+++ b/tools/testing/selftests/bpf/prog_tests/mptcp.c
@@ -9,6 +9,7 @@
 #include "mptcp_bpf_first.skel.h"
 #include "mptcp_bpf_bkup.skel.h"
 #include "mptcp_bpf_rr.skel.h"
+#include "mptcp_bpf_red.skel.h"
 
 #ifndef TCP_CA_NAME_MAX
 #define TCP_CA_NAME_MAX	16
@@ -381,6 +382,37 @@ static void test_rr(void)
 	mptcp_bpf_rr__destroy(rr_skel);
 }
 
+static void test_red(void)
+{
+	struct mptcp_bpf_red *red_skel;
+	int server_fd, client_fd;
+	struct bpf_link *link;
+
+	red_skel = mptcp_bpf_red__open_and_load();
+	if (!ASSERT_OK_PTR(red_skel, "bpf_red__open_and_load"))
+		return;
+
+	link = bpf_map__attach_struct_ops(red_skel->maps.red);
+	if (!ASSERT_OK_PTR(link, "bpf_map__attach_struct_ops")) {
+		mptcp_bpf_red__destroy(red_skel);
+		return;
+	}
+
+	sched_init("subflow", "bpf_red");
+	server_fd = start_mptcp_server(AF_INET, ADDR_1, 0, 0);
+	client_fd = connect_to_fd(server_fd, 0);
+
+	send_data(server_fd, client_fd);
+	ASSERT_OK(has_bytes_sent(ADDR_1), "has_bytes_sent addr 1");
+	ASSERT_OK(has_bytes_sent(ADDR_2), "has_bytes_sent addr 2");
+
+	close(client_fd);
+	close(server_fd);
+	sched_cleanup();
+	bpf_link__destroy(link);
+	mptcp_bpf_red__destroy(red_skel);
+}
+
 void test_mptcp(void)
 {
 	if (test__start_subtest("base"))
@@ -391,4 +423,6 @@ void test_mptcp(void)
 		test_bkup();
 	if (test__start_subtest("rr"))
 		test_rr();
+	if (test__start_subtest("red"))
+		test_red();
 }
-- 
2.35.3

Re: selftests/bpf: Add bpf_red test: Tests Results

[MPTCP CI]

Hi Geliang,

Thank you for your modifications, that's great!

Our CI did some validations and here is its report:

- KVM Validation: normal:
  - Unstable: 1 failed test(s): selftest_simult_flows 🔴:
  - Task: https://cirrus-ci.com/task/6078049075068928
  - Summary: https://api.cirrus-ci.com/v1/artifact/task/6078049075068928/summary/summary.txt

- KVM Validation: debug:
  - Unstable: 2 failed test(s): selftest_mptcp_join selftest_simult_flows 🔴:
  - Task: https://cirrus-ci.com/task/5515099121647616
  - Summary: https://api.cirrus-ci.com/v1/artifact/task/5515099121647616/summary/summary.txt

Initiator: Patchew Applier
Commits: https://github.com/multipath-tcp/mptcp_net-next/commits/f53d9d553d2e


If there are some issues, you can reproduce them using the same environment as
the one used by the CI thanks to a docker image, e.g.:

    $ cd [kernel source code]
    $ docker run -v "${PWD}:${PWD}:rw" -w "${PWD}" --privileged --rm -it \
        --pull always mptcp/mptcp-upstream-virtme-docker:latest \
        auto-debug

For more details:

    https://github.com/multipath-tcp/mptcp-upstream-virtme-docker


Please note that despite all the efforts that have been already done to have a
stable tests suite when executed on a public CI like here, it is possible some
reported issues are not due to your modifications. Still, do not hesitate to
help us improve that ;-)

Cheers,
MPTCP GH Action bot
Bot operated by Matthieu Baerts (Tessares)

Re: [PATCH mptcp-next v21 2/7] mptcp: use get_send wrapper

[Mat Martineau]

On Mon, 28 Nov 2022, Geliang Tang wrote:

> This patch adds the multiple subflows support for __mptcp_push_pending
> and __mptcp_subflow_push_pending. Use get_send() wrapper instead of
> mptcp_subflow_get_send() in them.
>
> Check the subflow scheduled flags to test which subflow or subflows are
> picked by the scheduler, use them to send data.
>
> Move sock_owned_by_me() check and fallback check into get_send() wrapper
> from mptcp_subflow_get_send().
>
> This commit allows the scheduler to set the subflow->scheduled bit in
> multiple subflows, but it does not allow for sending redundant data.
> Multiple scheduled subflows will send sequential data on each subflow.
>
> Signed-off-by: Geliang Tang <geliang.tang@suse.com>
> ---
> net/mptcp/protocol.c | 118 ++++++++++++++++++++++++++-----------------
> net/mptcp/sched.c    |  13 +++++
> 2 files changed, 84 insertions(+), 47 deletions(-)
>
> diff --git a/net/mptcp/protocol.c b/net/mptcp/protocol.c
> index d8ad68dd504a..65eaf59c9a6f 100644
> --- a/net/mptcp/protocol.c
> +++ b/net/mptcp/protocol.c
> @@ -1408,15 +1408,6 @@ struct sock *mptcp_subflow_get_send(struct mptcp_sock *msk)
> 	u64 linger_time;
> 	long tout = 0;
>
> -	sock_owned_by_me(sk);
> -
> -	if (__mptcp_check_fallback(msk)) {
> -		if (!msk->first)
> -			return NULL;
> -		return __tcp_can_send(msk->first) &&
> -		       sk_stream_memory_free(msk->first) ? msk->first : NULL;
> -	}
> -
> 	/* pick the subflow with the lower wmem/wspace ratio */
> 	for (i = 0; i < SSK_MODE_MAX; ++i) {
> 		send_info[i].ssk = NULL;
> @@ -1563,47 +1554,58 @@ void __mptcp_push_pending(struct sock *sk, unsigned int flags)
> {
> 	struct sock *prev_ssk = NULL, *ssk = NULL;
> 	struct mptcp_sock *msk = mptcp_sk(sk);
> +	struct mptcp_subflow_context *subflow;
> 	struct mptcp_sendmsg_info info = {
> 				.flags = flags,
> 	};
> 	bool do_check_data_fin = false;
> +	bool err = false;

The code below will still quit the "while (mptcp send_head() && !err)" 
loop if the previous iteration had an error on one subflow (even if 
multiple subflows were scheduled and there were successful sends).

I suggest removing the "bool err" and instead add

 	int push_count = -1;

(more info below)

>
> -	while (mptcp_send_head(sk)) {
> +	while (mptcp_send_head(sk) && !err) {

Change to

 	while (mptcp_send_head(sk) && (push_count == 0)) {

> 		int ret = 0;
>
> -		prev_ssk = ssk;
> -		ssk = mptcp_subflow_get_send(msk);
> -
> -		/* First check. If the ssk has changed since
> -		 * the last round, release prev_ssk
> -		 */
> -		if (ssk != prev_ssk && prev_ssk)
> -			mptcp_push_release(prev_ssk, &info);
> -		if (!ssk)
> +		if (mptcp_sched_get_send(msk))
> 			goto out;
>
> -		/* Need to lock the new subflow only if different
> -		 * from the previous one, otherwise we are still
> -		 * helding the relevant lock
> -		 */
> -		if (ssk != prev_ssk)
> -			lock_sock(ssk);

add:

 		push_count = 0;

> +		mptcp_for_each_subflow(msk, subflow) {
> +			if (READ_ONCE(subflow->scheduled)) {
> +				prev_ssk = ssk;
> +				ssk = mptcp_subflow_tcp_sock(subflow);
>
> -		ret = __subflow_push_pending(sk, ssk, &info);
> -		if (ret <= 0) {
> -			if (ret == -EAGAIN)
> -				continue;
> -			mptcp_push_release(ssk, &info);
> -			goto out;
> +				if (ssk != prev_ssk) {
> +					/* First check. If the ssk has changed since
> +					 * the last round, release prev_ssk
> +					 */
> +					if (prev_ssk)
> +						mptcp_push_release(prev_ssk, &info);
> +
> +					/* Need to lock the new subflow only if different
> +					 * from the previous one, otherwise we are still
> +					 * helding the relevant lock
> +					 */
> +					lock_sock(ssk);
> +				}
> +

add:

 				push_count++;

> +				ret = __subflow_push_pending(sk, ssk, &info);
> +				if (ret <= 0) {
> +					if (ret != -EAGAIN ||
> +					    (1 << ssk->sk_state) &
> +					     (TCPF_FIN_WAIT1 | TCPF_FIN_WAIT2 | TCPF_CLOSE))
> +						err = true;

replace with:

 						push_count--;

This way push_count will be a positive number at the end of the loop 
iteration if any __subflow_push_pending() calls succeeded, and the loop 
will continue sending on the working subflow(s).

- Mat

> +					continue;
> +				}
> +				do_check_data_fin = true;
> +				msk->last_snd = ssk;
> +				mptcp_subflow_set_scheduled(subflow, false);
> +			}
> 		}
> -		do_check_data_fin = true;
> 	}
>
> +out:
> 	/* at this point we held the socket lock for the last subflow we used */
> 	if (ssk)
> 		mptcp_push_release(ssk, &info);
>
> -out:
> 	/* ensure the rtx timer is running */
> 	if (!mptcp_timer_pending(sk))
> 		mptcp_reset_timer(sk);
> @@ -1614,33 +1616,55 @@ void __mptcp_push_pending(struct sock *sk, unsigned int flags)
> static void __mptcp_subflow_push_pending(struct sock *sk, struct sock *ssk, bool first)
> {
> 	struct mptcp_sock *msk = mptcp_sk(sk);
> +	struct mptcp_subflow_context *subflow;
> 	struct mptcp_sendmsg_info info = {
> 		.data_lock_held = true,
> 	};
> -	struct sock *xmit_ssk;
> +	bool err = false;
> 	int copied = 0;
>
> 	info.flags = 0;
> -	while (mptcp_send_head(sk)) {
> +	while (mptcp_send_head(sk) && !err) {
> 		int ret = 0;
>
> 		/* check for a different subflow usage only after
> 		 * spooling the first chunk of data
> 		 */
> -		xmit_ssk = first ? ssk : mptcp_subflow_get_send(msk);
> -		if (!xmit_ssk)
> -			goto out;
> -		if (xmit_ssk != ssk) {
> -			mptcp_subflow_delegate(mptcp_subflow_ctx(xmit_ssk),
> -					       MPTCP_DELEGATE_SEND);
> -			goto out;
> +		if (first) {
> +			ret = __subflow_push_pending(sk, ssk, &info);
> +			first = false;
> +			if (ret <= 0)
> +				break;
> +			copied += ret;
> +			msk->last_snd = ssk;
> +			continue;
> 		}
>
> -		ret = __subflow_push_pending(sk, ssk, &info);
> -		first = false;
> -		if (ret <= 0)
> -			break;
> -		copied += ret;
> +		if (mptcp_sched_get_send(msk))
> +			goto out;
> +
> +		mptcp_for_each_subflow(msk, subflow) {
> +			if (READ_ONCE(subflow->scheduled)) {
> +				struct sock *xmit_ssk = mptcp_subflow_tcp_sock(subflow);
> +
> +				if (xmit_ssk != ssk) {
> +					mptcp_subflow_delegate(subflow,
> +							       MPTCP_DELEGATE_SEND);
> +					msk->last_snd = ssk;
> +					mptcp_subflow_set_scheduled(subflow, false);
> +					goto out;
> +				}
> +
> +				ret = __subflow_push_pending(sk, ssk, &info);
> +				if (ret <= 0) {
> +					err = true;
> +					continue;
> +				}
> +				copied += ret;
> +				msk->last_snd = ssk;
> +				mptcp_subflow_set_scheduled(subflow, false);
> +			}
> +		}
> 	}
>
> out:
> diff --git a/net/mptcp/sched.c b/net/mptcp/sched.c
> index c4006f142f10..18518a81afb3 100644
> --- a/net/mptcp/sched.c
> +++ b/net/mptcp/sched.c
> @@ -118,6 +118,19 @@ int mptcp_sched_get_send(struct mptcp_sock *msk)
> 	struct mptcp_subflow_context *subflow;
> 	struct mptcp_sched_data data;
>
> +	sock_owned_by_me((const struct sock *)msk);
> +
> +	/* the following check is moved out of mptcp_subflow_get_send */
> +	if (__mptcp_check_fallback(msk)) {
> +		if (msk->first &&
> +		    __tcp_can_send(msk->first) &&
> +		    sk_stream_memory_free(msk->first)) {
> +			mptcp_subflow_set_scheduled(mptcp_subflow_ctx(msk->first), true);
> +			return 0;
> +		}
> +		return -EINVAL;
> +	}
> +
> 	mptcp_for_each_subflow(msk, subflow) {
> 		if (READ_ONCE(subflow->scheduled))
> 			return 0;
> -- 
> 2.35.3
>
>
>

--
Mat Martineau
Intel

Re: [PATCH mptcp-next v21 5/7] mptcp: add mptcp_update_dfrags

[Mat Martineau]

On Mon, 28 Nov 2022, Geliang Tang wrote:

> Add a new helper mptcp_next_frag() to get the next dfrag of the given
> dfrag.
>
> Add new members first and last in struct mptcp_sendmsg_info, to point
> to the first and last sent dfrag in the dfrags iteration loop in
> __subflow_push_pending().
>
> Invoke the new helper mptcp_update_dfrags() to iterate the dfrags from
> info->first to info->last to update already_sent of every dfrag to 0
> in the redundant sends retrans path.
>
> Signed-off-by: Geliang Tang <geliang.tang@suse.com>
> ---
> net/mptcp/protocol.c | 28 ++++++++++++++++++++++++++++
> net/mptcp/protocol.h | 13 ++++++++++---
> 2 files changed, 38 insertions(+), 3 deletions(-)
>
> diff --git a/net/mptcp/protocol.c b/net/mptcp/protocol.c
> index 3fcd6af96721..23116b0840ad 100644
> --- a/net/mptcp/protocol.c
> +++ b/net/mptcp/protocol.c
> @@ -992,6 +992,12 @@ static void __mptcp_clean_una(struct sock *sk)
> 		msk->snd_una = READ_ONCE(msk->snd_nxt);
>
> 	snd_una = msk->snd_una;
> +	/* Fix this:
> +	 * ------------[ cut here ]------------
> +	 * WARNING: CPU: 6 PID: 3007 at net/mptcp/protocol.c:1003 __mptcp_clean_una+0x243/0x2b0
> +	 */
> +	if (msk->first_pending)
> +		goto out;

Is this triggered by WARN_ON_ONCE(!msk->recovery)?


I looked at my v20 comment on this patch again, and I could have been 
clearer about the issues with modifying dfrag->already_sent:

When called from __mptcp_push_pending() (with the msk lock held), dfrags 
can be modified more freely because the call to __mptcp_clean_una() is 
deferred using msk->cb_flags.

The tricky part is handling dfrag updates when using 
__mptcp_subflow_push_pending(). On this code path, the msk lock is not 
held continuously when doing a redundant send on multiple subflows. This 
means __mptcp_clean_una() can run between each subflow send. When this 
happens, if dfrag->already_sent == 0 then __mptcp_clean_una() doesn't know 
what to do.

I think it's important to find a way to do redundant sends with 
__mptcp_subflow_push_pending() without having to change 
dfrag->already_sent. After the data is sent for the first time and the msk 
lock is released, dfrag->already_sent should not be set back to 0 so 
__mptcp_clean_una() can work correctly if a DATA_ACK arrives.

One way to solve this is to have the scheduler set sequence numbers to 
limit the payload sent on the scheduled subflows. Right now, the scheduler 
tells the MPTCP core which subflows to send on, but does not have any 
limit on how much data to send. If you replaced msk->snd_burst with 
msk->sched_seq_start and msk->sched_seq_end and have the scheduler set 
those values for the current scheduled transmits, that could be used 
instead of dfrag->already_sent. If a DATA_ACK has already cleared the 
received and acknowledged dfrags, then the redundant sends on the 
__mptcp_subflow_push_pending() code path don't even need to transmit the 
data.

What do you think? I am very open to better ideas too!

Thanks,

Mat



> 	list_for_each_entry_safe(dfrag, dtmp, &msk->rtx_queue, list) {
> 		if (after64(dfrag->data_seq + dfrag->data_len, snd_una))
> 			break;
> @@ -1112,6 +1118,7 @@ struct mptcp_sendmsg_info {
> 	u16 sent;
> 	unsigned int flags;
> 	bool data_lock_held;
> +	struct mptcp_data_frag *first, *last;
> };
>
> static int mptcp_check_allowed_size(const struct mptcp_sock *msk, struct sock *ssk,
> @@ -1502,6 +1509,23 @@ static void mptcp_update_post_push(struct mptcp_sock *msk,
> 		msk->snd_nxt = snd_nxt_new;
> }
>
> +static void mptcp_update_dfrags(struct sock *sk, struct mptcp_sendmsg_info *info)
> +{
> +	struct mptcp_data_frag *dfrag = info->first;
> +	struct mptcp_sock *msk = mptcp_sk(sk);
> +
> +	if (!dfrag)
> +		return;
> +
> +	do {
> +		dfrag->already_sent = 0;
> +		if (dfrag == info->last)
> +			break;
> +	} while ((dfrag = mptcp_next_frag(sk, dfrag)));
> +
> +	WRITE_ONCE(msk->first_pending, info->first);
> +}
> +
> void mptcp_check_and_set_pending(struct sock *sk)
> {
> 	if (mptcp_send_head(sk))
> @@ -1515,10 +1539,12 @@ static int __subflow_push_pending(struct sock *sk, struct sock *ssk,
> 	struct mptcp_data_frag *dfrag;
> 	int len, copied = 0, err = 0;
>
> +	info->first = mptcp_send_head(sk);
> 	while ((dfrag = mptcp_send_head(sk))) {
> 		info->sent = dfrag->already_sent;
> 		info->limit = dfrag->data_len;
> 		len = dfrag->data_len - dfrag->already_sent;
> +		info->last = dfrag;
> 		while (len > 0) {
> 			int ret = 0;
>
> @@ -1572,6 +1598,7 @@ void __mptcp_push_pending(struct sock *sk, unsigned int flags)
> 				if (i > 0) {
> 					if (!test_and_set_bit(MPTCP_WORK_RTX, &msk->flags))
> 						mptcp_schedule_work(sk);
> +					mptcp_update_dfrags(sk, &info);
> 					goto out;
> 				}
>
> @@ -1657,6 +1684,7 @@ static void __mptcp_subflow_push_pending(struct sock *sk, struct sock *ssk, bool
> 				if (i > 0) {
> 					if (!test_and_set_bit(MPTCP_WORK_RTX, &msk->flags))
> 						mptcp_schedule_work(sk);
> +					mptcp_update_dfrags(sk, &info);
> 					goto out;
> 				}
>
> diff --git a/net/mptcp/protocol.h b/net/mptcp/protocol.h
> index adfb758a842f..782dcfd55429 100644
> --- a/net/mptcp/protocol.h
> +++ b/net/mptcp/protocol.h
> @@ -358,16 +358,23 @@ static inline struct mptcp_data_frag *mptcp_send_head(const struct sock *sk)
> 	return READ_ONCE(msk->first_pending);
> }
>
> -static inline struct mptcp_data_frag *mptcp_send_next(struct sock *sk)
> +static inline struct mptcp_data_frag *mptcp_next_frag(const struct sock *sk,
> +						      struct mptcp_data_frag *cur)
> {
> 	struct mptcp_sock *msk = mptcp_sk(sk);
> -	struct mptcp_data_frag *cur;
>
> -	cur = msk->first_pending;
> +	if (!cur)
> +		return NULL;
> +
> 	return list_is_last(&cur->list, &msk->rtx_queue) ? NULL :
> 						     list_next_entry(cur, list);
> }
>
> +static inline struct mptcp_data_frag *mptcp_send_next(const struct sock *sk)
> +{
> +	return mptcp_next_frag(sk, mptcp_send_head(sk));
> +}
> +
> static inline struct mptcp_data_frag *mptcp_pending_tail(const struct sock *sk)
> {
> 	struct mptcp_sock *msk = mptcp_sk(sk);
> -- 
> 2.35.3
>
>
>

--
Mat Martineau
Intel