[PATCH mptcp-next v5 0/7] BPF redundant scheduler

[PATCH mptcp-next v5 0/7] BPF redundant scheduler

[Geliang Tang]

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):
  Squash to "mptcp: add get_subflow wrappers"
  mptcp: redundant subflows push pending
  mptcp: placeholder for subflow_push_pending
  mptcp: add sched_get_retrans wrapper
  mptcp: redundant subflows retrans support
  selftests/bpf: Add bpf_red scheduler
  selftests/bpf: Add bpf_red test

 net/mptcp/protocol.c                          | 116 ++++++++++--------
 net/mptcp/protocol.h                          |   4 +-
 net/mptcp/sched.c                             |  62 ++++++----
 net/mptcp/subflow.c                           |   1 -
 .../testing/selftests/bpf/prog_tests/mptcp.c  |  34 +++++
 .../selftests/bpf/progs/mptcp_bpf_red.c       |  36 ++++++
 6 files changed, 177 insertions(+), 76 deletions(-)
 create mode 100644 tools/testing/selftests/bpf/progs/mptcp_bpf_red.c

-- 
2.34.1

[PATCH mptcp-next v5 1/7] Squash to "mptcp: add get_subflow wrappers"

[Geliang Tang]

'''
mptcp: add sched_get_send wrapper

This patch defines a wrapper named mptcp_sched_get_send(), invoke
mptcp_subflow_get_send() or get_subflow() of msk->sched in it.

Set the subflow pointers array in struct mptcp_sched_data before invoking
get_subflow(), then it can be used in get_subflow() in the BPF contexts.

Move sock_owned_by_me() and the fallback check code from
mptcp_subflow_get_send() into this wrapper.
'''

Signed-off-by: Geliang Tang <geliang.tang@suse.com>
---
 net/mptcp/protocol.c | 15 +++++++----
 net/mptcp/protocol.h |  4 +--
 net/mptcp/sched.c    | 60 ++++++++++++--------------------------------
 3 files changed, 27 insertions(+), 52 deletions(-)

diff --git a/net/mptcp/protocol.c b/net/mptcp/protocol.c
index d6aef4b13b8a..8d93df73a9e3 100644
--- a/net/mptcp/protocol.c
+++ b/net/mptcp/protocol.c
@@ -1567,7 +1567,7 @@ void __mptcp_push_pending(struct sock *sk, unsigned int flags)
 			int ret = 0;
 
 			prev_ssk = ssk;
-			ssk = mptcp_sched_get_send(msk);
+			ssk = mptcp_subflow_get_send(msk);
 
 			/* First check. If the ssk has changed since
 			 * the last round, release prev_ssk
@@ -1634,7 +1634,7 @@ static void __mptcp_subflow_push_pending(struct sock *sk, struct sock *ssk)
 			 * check for a different subflow usage only after
 			 * spooling the first chunk of data
 			 */
-			xmit_ssk = first ? ssk : mptcp_sched_get_send(mptcp_sk(sk));
+			xmit_ssk = first ? ssk : mptcp_subflow_get_send(mptcp_sk(sk));
 			if (!xmit_ssk)
 				goto out;
 			if (xmit_ssk != ssk) {
@@ -2195,12 +2195,17 @@ static void mptcp_timeout_timer(struct timer_list *t)
  *
  * A backup subflow is returned only if that is the only kind available.
  */
-struct sock *mptcp_subflow_get_retrans(struct mptcp_sock *msk)
+static struct sock *mptcp_subflow_get_retrans(struct mptcp_sock *msk)
 {
 	struct sock *backup = NULL, *pick = NULL;
 	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);
 
@@ -2453,7 +2458,7 @@ static void __mptcp_retrans(struct sock *sk)
 	mptcp_clean_una_wakeup(sk);
 
 	/* first check ssk: need to kick "stale" logic */
-	ssk = mptcp_sched_get_retrans(msk);
+	ssk = mptcp_subflow_get_retrans(msk);
 	dfrag = mptcp_rtx_head(sk);
 	if (!dfrag) {
 		if (mptcp_data_fin_enabled(msk)) {
@@ -3107,7 +3112,7 @@ void __mptcp_check_push(struct sock *sk, struct sock *ssk)
 		return;
 
 	if (!sock_owned_by_user(sk)) {
-		struct sock *xmit_ssk = mptcp_sched_get_send(mptcp_sk(sk));
+		struct sock *xmit_ssk = mptcp_subflow_get_send(mptcp_sk(sk));
 
 		if (xmit_ssk == ssk)
 			__mptcp_subflow_push_pending(sk, ssk);
diff --git a/net/mptcp/protocol.h b/net/mptcp/protocol.h
index d406b5afbee4..0fb2970a7a2d 100644
--- a/net/mptcp/protocol.h
+++ b/net/mptcp/protocol.h
@@ -632,9 +632,7 @@ void mptcp_release_sched(struct mptcp_sock *msk);
 void mptcp_subflow_set_scheduled(struct mptcp_subflow_context *subflow,
 				 bool scheduled);
 struct sock *mptcp_subflow_get_send(struct mptcp_sock *msk);
-struct sock *mptcp_subflow_get_retrans(struct mptcp_sock *msk);
-struct sock *mptcp_sched_get_send(struct mptcp_sock *msk);
-struct sock *mptcp_sched_get_retrans(struct mptcp_sock *msk);
+struct sock *mptcp_sched_get_send(struct mptcp_sock *msk, int *err);
 
 static inline bool __mptcp_subflow_active(struct mptcp_subflow_context *subflow)
 {
diff --git a/net/mptcp/sched.c b/net/mptcp/sched.c
index 8858e1fc8b74..a0585182a2b1 100644
--- a/net/mptcp/sched.c
+++ b/net/mptcp/sched.c
@@ -117,63 +117,35 @@ static int mptcp_sched_data_init(struct mptcp_sock *msk, bool reinject,
 	return 0;
 }
 
-struct sock *mptcp_sched_get_send(struct mptcp_sock *msk)
+struct sock *mptcp_sched_get_send(struct mptcp_sock *msk, int *err)
 {
 	struct mptcp_sched_data data;
 	struct sock *ssk = NULL;
-	int i;
 
+	*err = -EINVAL;
 	sock_owned_by_me((struct sock *)msk);
 
 	/* the following check is moved out of mptcp_subflow_get_send */
 	if (__mptcp_check_fallback(msk)) {
-		if (!msk->first)
-			return NULL;
-		return sk_stream_memory_free(msk->first) ? msk->first : NULL;
-	}
-
-	if (!msk->sched)
-		return mptcp_subflow_get_send(msk);
-
-	mptcp_sched_data_init(msk, false, &data);
-	msk->sched->get_subflow(msk, &data);
-
-	for (i = 0; i < MPTCP_SUBFLOWS_MAX; i++) {
-		if (data.contexts[i] && READ_ONCE(data.contexts[i]->scheduled)) {
-			ssk = data.contexts[i]->tcp_sock;
-			msk->last_snd = ssk;
-			break;
+		if (msk->first && sk_stream_memory_free(msk->first)) {
+			mptcp_subflow_set_scheduled(mptcp_subflow_ctx(msk->first), true);
+			*err = 0;
+			return msk->first;
 		}
-	}
-
-	return ssk;
-}
-
-struct sock *mptcp_sched_get_retrans(struct mptcp_sock *msk)
-{
-	struct mptcp_sched_data data;
-	struct sock *ssk = NULL;
-	int i;
-
-	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 NULL;
+	}
 
-	if (!msk->sched)
-		return mptcp_subflow_get_retrans(msk);
+	if (!msk->sched) {
+		ssk = mptcp_subflow_get_send(msk);
+		if (!ssk)
+			return NULL;
+		mptcp_subflow_set_scheduled(mptcp_subflow_ctx(ssk), true);
+		*err = 0;
+		return ssk;
+	}
 
-	mptcp_sched_data_init(msk, true, &data);
+	mptcp_sched_data_init(msk, false, &data);
 	msk->sched->get_subflow(msk, &data);
 
-	for (i = 0; i < MPTCP_SUBFLOWS_MAX; i++) {
-		if (data.contexts[i] && READ_ONCE(data.contexts[i]->scheduled)) {
-			ssk = data.contexts[i]->tcp_sock;
-			msk->last_snd = ssk;
-			break;
-		}
-	}
-
 	return ssk;
 }
-- 
2.34.1

Re: [PATCH mptcp-next v5 1/7] Squash to "mptcp: add get_subflow wrappers"

[Mat Martineau]

On Mon, 6 Jun 2022, Geliang Tang wrote:

> '''
> mptcp: add sched_get_send wrapper
>
> This patch defines a wrapper named mptcp_sched_get_send(), invoke
> mptcp_subflow_get_send() or get_subflow() of msk->sched in it.
>
> Set the subflow pointers array in struct mptcp_sched_data before invoking
> get_subflow(), then it can be used in get_subflow() in the BPF contexts.
>
> Move sock_owned_by_me() and the fallback check code from
> mptcp_subflow_get_send() into this wrapper.
> '''
>
> Signed-off-by: Geliang Tang <geliang.tang@suse.com>
> ---
> net/mptcp/protocol.c | 15 +++++++----
> net/mptcp/protocol.h |  4 +--
> net/mptcp/sched.c    | 60 ++++++++++++--------------------------------
> 3 files changed, 27 insertions(+), 52 deletions(-)
>
> diff --git a/net/mptcp/protocol.c b/net/mptcp/protocol.c
> index d6aef4b13b8a..8d93df73a9e3 100644
> --- a/net/mptcp/protocol.c
> +++ b/net/mptcp/protocol.c
> @@ -1567,7 +1567,7 @@ void __mptcp_push_pending(struct sock *sk, unsigned int flags)
> 			int ret = 0;
>
> 			prev_ssk = ssk;
> -			ssk = mptcp_sched_get_send(msk);
> +			ssk = mptcp_subflow_get_send(msk);
>
> 			/* First check. If the ssk has changed since
> 			 * the last round, release prev_ssk
> @@ -1634,7 +1634,7 @@ static void __mptcp_subflow_push_pending(struct sock *sk, struct sock *ssk)
> 			 * check for a different subflow usage only after
> 			 * spooling the first chunk of data
> 			 */
> -			xmit_ssk = first ? ssk : mptcp_sched_get_send(mptcp_sk(sk));
> +			xmit_ssk = first ? ssk : mptcp_subflow_get_send(mptcp_sk(sk));
> 			if (!xmit_ssk)
> 				goto out;
> 			if (xmit_ssk != ssk) {
> @@ -2195,12 +2195,17 @@ static void mptcp_timeout_timer(struct timer_list *t)
>  *
>  * A backup subflow is returned only if that is the only kind available.
>  */
> -struct sock *mptcp_subflow_get_retrans(struct mptcp_sock *msk)
> +static struct sock *mptcp_subflow_get_retrans(struct mptcp_sock *msk)
> {
> 	struct sock *backup = NULL, *pick = NULL;
> 	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);
>
> @@ -2453,7 +2458,7 @@ static void __mptcp_retrans(struct sock *sk)
> 	mptcp_clean_una_wakeup(sk);
>
> 	/* first check ssk: need to kick "stale" logic */
> -	ssk = mptcp_sched_get_retrans(msk);
> +	ssk = mptcp_subflow_get_retrans(msk);
> 	dfrag = mptcp_rtx_head(sk);
> 	if (!dfrag) {
> 		if (mptcp_data_fin_enabled(msk)) {
> @@ -3107,7 +3112,7 @@ void __mptcp_check_push(struct sock *sk, struct sock *ssk)
> 		return;
>
> 	if (!sock_owned_by_user(sk)) {
> -		struct sock *xmit_ssk = mptcp_sched_get_send(mptcp_sk(sk));
> +		struct sock *xmit_ssk = mptcp_subflow_get_send(mptcp_sk(sk));
>
> 		if (xmit_ssk == ssk)
> 			__mptcp_subflow_push_pending(sk, ssk);
> diff --git a/net/mptcp/protocol.h b/net/mptcp/protocol.h
> index d406b5afbee4..0fb2970a7a2d 100644
> --- a/net/mptcp/protocol.h
> +++ b/net/mptcp/protocol.h
> @@ -632,9 +632,7 @@ void mptcp_release_sched(struct mptcp_sock *msk);
> void mptcp_subflow_set_scheduled(struct mptcp_subflow_context *subflow,
> 				 bool scheduled);
> struct sock *mptcp_subflow_get_send(struct mptcp_sock *msk);
> -struct sock *mptcp_subflow_get_retrans(struct mptcp_sock *msk);
> -struct sock *mptcp_sched_get_send(struct mptcp_sock *msk);
> -struct sock *mptcp_sched_get_retrans(struct mptcp_sock *msk);
> +struct sock *mptcp_sched_get_send(struct mptcp_sock *msk, int *err);
>
> static inline bool __mptcp_subflow_active(struct mptcp_subflow_context *subflow)
> {
> diff --git a/net/mptcp/sched.c b/net/mptcp/sched.c
> index 8858e1fc8b74..a0585182a2b1 100644
> --- a/net/mptcp/sched.c
> +++ b/net/mptcp/sched.c
> @@ -117,63 +117,35 @@ static int mptcp_sched_data_init(struct mptcp_sock *msk, bool reinject,
> 	return 0;
> }
>
> -struct sock *mptcp_sched_get_send(struct mptcp_sock *msk)
> +struct sock *mptcp_sched_get_send(struct mptcp_sock *msk, int *err)
> {
> 	struct mptcp_sched_data data;
> 	struct sock *ssk = NULL;
> -	int i;
>
> +	*err = -EINVAL;
> 	sock_owned_by_me((struct sock *)msk);
>
> 	/* the following check is moved out of mptcp_subflow_get_send */
> 	if (__mptcp_check_fallback(msk)) {
> -		if (!msk->first)
> -			return NULL;
> -		return sk_stream_memory_free(msk->first) ? msk->first : NULL;
> -	}
> -
> -	if (!msk->sched)
> -		return mptcp_subflow_get_send(msk);
> -
> -	mptcp_sched_data_init(msk, false, &data);
> -	msk->sched->get_subflow(msk, &data);
> -
> -	for (i = 0; i < MPTCP_SUBFLOWS_MAX; i++) {
> -		if (data.contexts[i] && READ_ONCE(data.contexts[i]->scheduled)) {
> -			ssk = data.contexts[i]->tcp_sock;
> -			msk->last_snd = ssk;
> -			break;
> +		if (msk->first && sk_stream_memory_free(msk->first)) {
> +			mptcp_subflow_set_scheduled(mptcp_subflow_ctx(msk->first), true);
> +			*err = 0;
> +			return msk->first;
> 		}
> -	}
> -
> -	return ssk;
> -}
> -
> -struct sock *mptcp_sched_get_retrans(struct mptcp_sock *msk)
> -{
> -	struct mptcp_sched_data data;
> -	struct sock *ssk = NULL;
> -	int i;
> -
> -	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 NULL;
> +	}
>
> -	if (!msk->sched)
> -		return mptcp_subflow_get_retrans(msk);
> +	if (!msk->sched) {
> +		ssk = mptcp_subflow_get_send(msk);
> +		if (!ssk)
> +			return NULL;
> +		mptcp_subflow_set_scheduled(mptcp_subflow_ctx(ssk), true);
> +		*err = 0;
> +		return ssk;
> +	}
>
> -	mptcp_sched_data_init(msk, true, &data);
> +	mptcp_sched_data_init(msk, false, &data);
> 	msk->sched->get_subflow(msk, &data);

Need to add *err = 0 here.

>
> -	for (i = 0; i < MPTCP_SUBFLOWS_MAX; i++) {
> -		if (data.contexts[i] && READ_ONCE(data.contexts[i]->scheduled)) {
> -			ssk = data.contexts[i]->tcp_sock;
> -			msk->last_snd = ssk;
> -			break;
> -		}
> -	}
> -
> 	return ssk;
> }
> -- 
> 2.34.1
>
>
>

--
Mat Martineau
Intel

[PATCH mptcp-next v5 2/7] mptcp: redundant subflows push pending

[Geliang Tang]

This patch adds the redundant subflows support for __mptcp_push_pending().
Use mptcp_sched_get_send() wrapper instead of mptcp_subflow_get_send()
in it.

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

Signed-off-by: Geliang Tang <geliang.tang@suse.com>
---
 net/mptcp/protocol.c | 63 ++++++++++++++++++++++----------------------
 net/mptcp/subflow.c  |  1 -
 2 files changed, 32 insertions(+), 32 deletions(-)

diff --git a/net/mptcp/protocol.c b/net/mptcp/protocol.c
index 8d93df73a9e3..8bf48387f9d8 100644
--- a/net/mptcp/protocol.c
+++ b/net/mptcp/protocol.c
@@ -1551,58 +1551,59 @@ void mptcp_check_and_set_pending(struct sock *sk)
 
 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,
+		.flags = flags,
 	};
 	struct mptcp_data_frag *dfrag;
-	int len, copied = 0;
+	int len, copied = 0, err = 0;
+	struct sock *ssk = NULL;
 
 	while ((dfrag = mptcp_send_head(sk))) {
 		info.sent = dfrag->already_sent;
 		info.limit = dfrag->data_len;
 		len = dfrag->data_len - dfrag->already_sent;
 		while (len > 0) {
-			int ret = 0;
+			int ret = 0, max = 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)
+			mptcp_sched_get_send(msk, &err);
+			if (err)
 				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)) {
+					ssk = mptcp_subflow_tcp_sock(subflow);
+					if (!ssk)
+						goto out;
 
-			ret = mptcp_sendmsg_frag(sk, ssk, dfrag, &info);
-			if (ret <= 0) {
-				mptcp_push_release(ssk, &info);
-				goto out;
+					lock_sock(ssk);
+
+					ret = mptcp_sendmsg_frag(sk, ssk, dfrag, &info);
+					if (ret <= 0) {
+						mptcp_push_release(ssk, &info);
+						goto out;
+					}
+
+					if (ret > max)
+						max = ret;
+
+					mptcp_push_release(ssk, &info);
+
+					msk->last_snd = ssk;
+					mptcp_subflow_set_scheduled(subflow, false);
+				}
 			}
 
-			info.sent += ret;
-			copied += ret;
-			len -= ret;
+			info.sent += max;
+			copied += max;
+			len -= max;
 
-			mptcp_update_post_push(msk, dfrag, ret);
+			mptcp_update_post_push(msk, dfrag, max);
 		}
 		WRITE_ONCE(msk->first_pending, mptcp_send_next(sk));
 	}
 
-	/* 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))
diff --git a/net/mptcp/subflow.c b/net/mptcp/subflow.c
index 8841e8cd9ad8..e7864a413192 100644
--- a/net/mptcp/subflow.c
+++ b/net/mptcp/subflow.c
@@ -881,7 +881,6 @@ static bool validate_mapping(struct sock *ssk, struct sk_buff *skb)
 				  subflow->map_data_len))) {
 		/* Mapping does covers past subflow data, invalid */
 		dbg_bad_map(subflow, ssn);
-		return false;
 	}
 	return true;
 }
-- 
2.34.1

Re: [PATCH mptcp-next v5 2/7] mptcp: redundant subflows push pending

[Mat Martineau]

On Mon, 6 Jun 2022, Geliang Tang wrote:

> This patch adds the redundant subflows support for __mptcp_push_pending().
> Use mptcp_sched_get_send() wrapper instead of mptcp_subflow_get_send()
> in it.
>
> Check the subflow scheduled flags to test which subflow or subflows are
> picked by the scheduler, use them to send data.
>
> Signed-off-by: Geliang Tang <geliang.tang@suse.com>
> ---
> net/mptcp/protocol.c | 63 ++++++++++++++++++++++----------------------
> net/mptcp/subflow.c  |  1 -
> 2 files changed, 32 insertions(+), 32 deletions(-)
>
> diff --git a/net/mptcp/protocol.c b/net/mptcp/protocol.c
> index 8d93df73a9e3..8bf48387f9d8 100644
> --- a/net/mptcp/protocol.c
> +++ b/net/mptcp/protocol.c
> @@ -1551,58 +1551,59 @@ void mptcp_check_and_set_pending(struct sock *sk)
>
> 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,
> +		.flags = flags,
> 	};
> 	struct mptcp_data_frag *dfrag;
> -	int len, copied = 0;
> +	int len, copied = 0, err = 0;
> +	struct sock *ssk = NULL;
>
> 	while ((dfrag = mptcp_send_head(sk))) {
> 		info.sent = dfrag->already_sent;
> 		info.limit = dfrag->data_len;
> 		len = dfrag->data_len - dfrag->already_sent;
> 		while (len > 0) {
> -			int ret = 0;
> +			int ret = 0, max = 0;
>
> -			prev_ssk = ssk;

Removing prev_ssk and the optimizations related to it will affect the 
performance of non-redundant schedulers (which is most of them). It forces 
a separate lock and tcp_push call for every dfrag. The optimization is 
important to keep, but using it with a redundant scheduler means changing 
this transmit loop.

There are some options for how to handle redundant schedulers and 
optimization:

1. Only optimize non-redundant schedulers. Redundant schedulers will 
require lock/tcp_push/unlock for each scheduled subflow.

2. Change the transmit loop to instead call the scheduler first, and then 
send multiple fragments on each scheduled subflow.


Option 2 would need more information from the scheduler I think: for 
example, the number of bytes to schedule. Instead of just the 'scheduled' 
flag, the subflow context could store more information about the range of 
sequence numbers to send.

Another approach could be to use something like the current code to send 
as much data as possible on the first selected subflow, then for redundant 
subflows use the retransmit code to send data again.


There's a lot of complexity here: changing the (re)transmit and scheduler 
loops, modifying the BPF API, keeping or improving existing performance. I 
think it's worth talking about at the meeting again.


- Mat

> -			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)
> +			mptcp_sched_get_send(msk, &err);
> +			if (err)
> 				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)) {
> +					ssk = mptcp_subflow_tcp_sock(subflow);
> +					if (!ssk)
> +						goto out;
>
> -			ret = mptcp_sendmsg_frag(sk, ssk, dfrag, &info);
> -			if (ret <= 0) {
> -				mptcp_push_release(ssk, &info);
> -				goto out;
> +					lock_sock(ssk);
> +
> +					ret = mptcp_sendmsg_frag(sk, ssk, dfrag, &info);
> +					if (ret <= 0) {
> +						mptcp_push_release(ssk, &info);
> +						goto out;
> +					}
> +
> +					if (ret > max)
> +						max = ret;
> +
> +					mptcp_push_release(ssk, &info);
> +
> +					msk->last_snd = ssk;
> +					mptcp_subflow_set_scheduled(subflow, false);
> +				}
> 			}
>
> -			info.sent += ret;
> -			copied += ret;
> -			len -= ret;
> +			info.sent += max;
> +			copied += max;
> +			len -= max;
>
> -			mptcp_update_post_push(msk, dfrag, ret);
> +			mptcp_update_post_push(msk, dfrag, max);
> 		}
> 		WRITE_ONCE(msk->first_pending, mptcp_send_next(sk));
> 	}
>
> -	/* 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))
> diff --git a/net/mptcp/subflow.c b/net/mptcp/subflow.c
> index 8841e8cd9ad8..e7864a413192 100644
> --- a/net/mptcp/subflow.c
> +++ b/net/mptcp/subflow.c
> @@ -881,7 +881,6 @@ static bool validate_mapping(struct sock *ssk, struct sk_buff *skb)
> 				  subflow->map_data_len))) {
> 		/* Mapping does covers past subflow data, invalid */
> 		dbg_bad_map(subflow, ssn);
> -		return false;
> 	}
> 	return true;
> }
> -- 
> 2.34.1
>
>
>

--
Mat Martineau
Intel

[PATCH mptcp-next v5 3/7] mptcp: placeholder for subflow_push_pending

[Geliang Tang]

Redundant subflows are not supported in __mptcp_subflow_push_pending()
yet. This patch adds a placeholder in mptcp_sched_get_send() to pick the
first subflow for the redundant subflows case.

Signed-off-by: Geliang Tang <geliang.tang@suse.com>
---
 net/mptcp/protocol.c |  8 +++++---
 net/mptcp/sched.c    | 15 +++++++++++++++
 2 files changed, 20 insertions(+), 3 deletions(-)

diff --git a/net/mptcp/protocol.c b/net/mptcp/protocol.c
index 8bf48387f9d8..bcaf91562e2b 100644
--- a/net/mptcp/protocol.c
+++ b/net/mptcp/protocol.c
@@ -1629,13 +1629,13 @@ static void __mptcp_subflow_push_pending(struct sock *sk, struct sock *ssk)
 		info.limit = dfrag->data_len;
 		len = dfrag->data_len - dfrag->already_sent;
 		while (len > 0) {
-			int ret = 0;
+			int ret = 0, err = 0;
 
 			/* the caller already invoked the packet scheduler,
 			 * check for a different subflow usage only after
 			 * spooling the first chunk of data
 			 */
-			xmit_ssk = first ? ssk : mptcp_subflow_get_send(mptcp_sk(sk));
+			xmit_ssk = first ? ssk : mptcp_sched_get_send(mptcp_sk(sk), &err);
 			if (!xmit_ssk)
 				goto out;
 			if (xmit_ssk != ssk) {
@@ -3109,11 +3109,13 @@ void __mptcp_data_acked(struct sock *sk)
 
 void __mptcp_check_push(struct sock *sk, struct sock *ssk)
 {
+	int err = 0;
+
 	if (!mptcp_send_head(sk))
 		return;
 
 	if (!sock_owned_by_user(sk)) {
-		struct sock *xmit_ssk = mptcp_subflow_get_send(mptcp_sk(sk));
+		struct sock *xmit_ssk = mptcp_sched_get_send(mptcp_sk(sk), &err);
 
 		if (xmit_ssk == ssk)
 			__mptcp_subflow_push_pending(sk, ssk);
diff --git a/net/mptcp/sched.c b/net/mptcp/sched.c
index a0585182a2b1..527ea07982c5 100644
--- a/net/mptcp/sched.c
+++ b/net/mptcp/sched.c
@@ -119,6 +119,7 @@ static int mptcp_sched_data_init(struct mptcp_sock *msk, bool reinject,
 
 struct sock *mptcp_sched_get_send(struct mptcp_sock *msk, int *err)
 {
+	struct mptcp_subflow_context *subflow;
 	struct mptcp_sched_data data;
 	struct sock *ssk = NULL;
 
@@ -147,5 +148,19 @@ struct sock *mptcp_sched_get_send(struct mptcp_sock *msk, int *err)
 	mptcp_sched_data_init(msk, false, &data);
 	msk->sched->get_subflow(msk, &data);
 
+	mptcp_for_each_subflow(msk, subflow) {
+		if (READ_ONCE(subflow->scheduled)) {
+			/*
+			 * TODO: Redundant subflows are not supported in
+			 * __mptcp_subflow_push_pending() yet. Here's a
+			 * placeholder to pick the first subflow for the
+			 * redundant subflows case.
+			 */
+			ssk = subflow->tcp_sock;
+			*err = 0;
+			break;
+		}
+	}
+
 	return ssk;
 }
-- 
2.34.1

[PATCH mptcp-next v5 4/7] mptcp: add sched_get_retrans wrapper

[Geliang Tang]

This patch defines a wrapper named mptcp_sched_get_retrans(), invoke
mptcp_subflow_get_retrans() or get_subflow() of msk->sched in it.

Move sock_owned_by_me() and the fallback check code from
mptcp_subflow_get_retans() into this wrapper.

Signed-off-by: Geliang Tang <geliang.tang@suse.com>
---
 net/mptcp/protocol.c |  7 +------
 net/mptcp/protocol.h |  2 ++
 net/mptcp/sched.c    | 25 +++++++++++++++++++++++++
 3 files changed, 28 insertions(+), 6 deletions(-)

diff --git a/net/mptcp/protocol.c b/net/mptcp/protocol.c
index bcaf91562e2b..b583454cfc91 100644
--- a/net/mptcp/protocol.c
+++ b/net/mptcp/protocol.c
@@ -2196,17 +2196,12 @@ 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;
 	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);
 
diff --git a/net/mptcp/protocol.h b/net/mptcp/protocol.h
index 0fb2970a7a2d..3b6b9e43e261 100644
--- a/net/mptcp/protocol.h
+++ b/net/mptcp/protocol.h
@@ -632,7 +632,9 @@ void mptcp_release_sched(struct mptcp_sock *msk);
 void mptcp_subflow_set_scheduled(struct mptcp_subflow_context *subflow,
 				 bool scheduled);
 struct sock *mptcp_subflow_get_send(struct mptcp_sock *msk);
+struct sock *mptcp_subflow_get_retrans(struct mptcp_sock *msk);
 struct sock *mptcp_sched_get_send(struct mptcp_sock *msk, int *err);
+int mptcp_sched_get_retrans(struct mptcp_sock *msk);
 
 static inline bool __mptcp_subflow_active(struct mptcp_subflow_context *subflow)
 {
diff --git a/net/mptcp/sched.c b/net/mptcp/sched.c
index 527ea07982c5..0ac80eb9a428 100644
--- a/net/mptcp/sched.c
+++ b/net/mptcp/sched.c
@@ -164,3 +164,28 @@ struct sock *mptcp_sched_get_send(struct mptcp_sock *msk, int *err)
 
 	return ssk;
 }
+
+int mptcp_sched_get_retrans(struct mptcp_sock *msk)
+{
+	struct mptcp_sched_data data;
+	struct sock *ssk = NULL;
+
+	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;
+
+	if (!msk->sched) {
+		ssk = mptcp_subflow_get_retrans(msk);
+		if (!ssk)
+			return -EINVAL;
+		mptcp_subflow_set_scheduled(mptcp_subflow_ctx(ssk), true);
+		return 0;
+	}
+
+	mptcp_sched_data_init(msk, true, &data);
+	msk->sched->get_subflow(msk, &data);
+
+	return 0;
+}
-- 
2.34.1

[PATCH mptcp-next v5 5/7] mptcp: redundant subflows retrans support

[Geliang Tang]

This patch adds the redundant subflows support for __mptcp_retrans(). In
it, use sched_get_retrans() wrapper instead of mptcp_subflow_get_retrans().

Iterate each subflow of msk, check the scheduled flag to test if it is
picked by the scheduler. If so, use it to send data.

Signed-off-by: Geliang Tang <geliang.tang@suse.com>
---
 net/mptcp/protocol.c | 45 ++++++++++++++++++++++++++++++--------------
 1 file changed, 31 insertions(+), 14 deletions(-)

diff --git a/net/mptcp/protocol.c b/net/mptcp/protocol.c
index b583454cfc91..f39318f5a21e 100644
--- a/net/mptcp/protocol.c
+++ b/net/mptcp/protocol.c
@@ -2445,16 +2445,17 @@ 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 err;
 
 	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)) {
@@ -2473,32 +2474,48 @@ static void __mptcp_retrans(struct sock *sk)
 		goto reset_timer;
 	}
 
-	if (!ssk)
+	if (err)
 		goto reset_timer;
 
-	lock_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;
+		int ret = 0, max = 0;
+
+		mptcp_for_each_subflow(msk, subflow) {
+			if (READ_ONCE(subflow->scheduled)) {
+				ssk = mptcp_subflow_tcp_sock(subflow);
+				if (!ssk)
+					goto reset_timer;
+
+				lock_sock(ssk);
 
+				ret = mptcp_sendmsg_frag(sk, ssk, dfrag, &info);
+				if (ret <= 0)
+					break;
+
+				if (ret > max)
+					max = ret;
+
+				tcp_push(ssk, 0, info.mss_now, tcp_sk(ssk)->nonagle,
+					 info.size_goal);
+
+				release_sock(ssk);
+
+				msk->last_snd = ssk;
+				mptcp_subflow_set_scheduled(subflow, false);
+			}
+		}
 		MPTCP_INC_STATS(sock_net(sk), MPTCP_MIB_RETRANSSEGS);
-		copied += ret;
-		info.sent += ret;
+		copied += max;
+		info.sent += max;
 	}
 	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);
 	}
 
-	release_sock(ssk);
-
 reset_timer:
 	mptcp_check_and_set_pending(sk);
 
-- 
2.34.1

[PATCH mptcp-next v5 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       | 36 +++++++++++++++++++
 1 file changed, 36 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..58f90473e495
--- /dev/null
+++ b/tools/testing/selftests/bpf/progs/mptcp_bpf_red.c
@@ -0,0 +1,36 @@
+// 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_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);
+	}
+}
+
+SEC(".struct_ops")
+struct mptcp_sched_ops red = {
+	.init		= (void *)mptcp_sched_red_init,
+	.release	= (void *)mptcp_sched_red_release,
+	.get_subflow	= (void *)bpf_red_get_subflow,
+	.name		= "bpf_red",
+};
-- 
2.34.1

[PATCH mptcp-next v5 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 8b2fe1004323..9f3242c7920a 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();
 }
-- 
2.34.1

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_mptcp_join - Critical: 59 Call Trace(s) - Critical: Global Timeout ❌:
  - Task: https://cirrus-ci.com/task/4759088235020288
  - Summary: https://api.cirrus-ci.com/v1/artifact/task/4759088235020288/summary/summary.txt

- KVM Validation: debug:
  - Unstable: 2 failed test(s): selftest_diag selftest_mptcp_join - Critical: 80 Call Trace(s) - Critical: Global Timeout ❌:
  - Task: https://cirrus-ci.com/task/5884988141862912
  - Summary: https://api.cirrus-ci.com/v1/artifact/task/5884988141862912/summary/summary.txt

Initiator: Patchew Applier
Commits: https://github.com/multipath-tcp/mptcp_net-next/commits/e8e0daeb0d12


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)