[PATCH mptcp-next v7 0/5] BPF redundant scheduler

[PATCH mptcp-next v7 0/5] BPF redundant scheduler

[Geliang Tang]

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 (5):
  Squash to "mptcp: add get_subflow wrappers"
  mptcp: redundant subflows push pending
  mptcp: redundant subflows retrans support
  selftests/bpf: Add bpf_red scheduler
  selftests/bpf: Add bpf_red test

 net/mptcp/protocol.c                          | 161 +++++++++++-------
 net/mptcp/protocol.h                          |   4 +-
 net/mptcp/sched.c                             |  61 ++++---
 .../testing/selftests/bpf/prog_tests/mptcp.c  |  34 ++++
 .../selftests/bpf/progs/mptcp_bpf_red.c       |  36 ++++
 5 files changed, 203 insertions(+), 93 deletions(-)
 create mode 100644 tools/testing/selftests/bpf/progs/mptcp_bpf_red.c

-- 
2.35.3

[PATCH mptcp-next v7 1/5] Squash to "mptcp: add get_subflow wrappers"

[Geliang Tang]

Please update the commit log:

'''
This patch defines two new wrappers mptcp_sched_get_send() and
mptcp_sched_get_retrans(), invoke get_subflow() of msk->sched in them.
Use them instead of using mptcp_subflow_get_send() or
mptcp_subflow_get_retrans() directly.

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.

Check the subflow scheduled flags to test which subflow or subflows are
picked by the scheduler.

Move sock_owned_by_me() and the fallback check code from
mptcp_subflow_get_send/retrans() into the wrappers.

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 | 12 +++++----
 net/mptcp/protocol.h |  4 +--
 net/mptcp/sched.c    | 61 ++++++++++++++++++++++++++------------------
 3 files changed, 45 insertions(+), 32 deletions(-)

diff --git a/net/mptcp/protocol.c b/net/mptcp/protocol.c
index a0f9f3831509..043ac3f222ed 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
@@ -1628,13 +1628,13 @@ 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_sched_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) {
@@ -2438,7 +2438,7 @@ 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)) {
@@ -3088,11 +3088,13 @@ 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_sched_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/protocol.h b/net/mptcp/protocol.h
index bef7dea9f358..c4ce576458a2 100644
--- a/net/mptcp/protocol.h
+++ b/net/mptcp/protocol.h
@@ -634,8 +634,8 @@ 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);
+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 8858e1fc8b74..5bd96ec5da5a 100644
--- a/net/mptcp/sched.c
+++ b/net/mptcp/sched.c
@@ -117,31 +117,46 @@ 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_subflow_context *subflow;
 	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->first && sk_stream_memory_free(msk->first)) {
+			mptcp_subflow_set_scheduled(mptcp_subflow_ctx(msk->first), true);
+			*err = 0;
+			return msk->first;
+		}
+		return NULL;
 	}
 
-	if (!msk->sched)
-		return mptcp_subflow_get_send(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, 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;
+	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;
 		}
 	}
@@ -149,31 +164,27 @@ struct sock *mptcp_sched_get_send(struct mptcp_sock *msk)
 	return ssk;
 }
 
-struct sock *mptcp_sched_get_retrans(struct mptcp_sock *msk)
+int 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;
+		return -EINVAL;
 
-	if (!msk->sched)
-		return mptcp_subflow_get_retrans(msk);
+	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);
 
-	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;
+	return 0;
 }
-- 
2.35.3

[PATCH mptcp-next v7 2/5] 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 | 96 +++++++++++++++++++++++++-------------------
 1 file changed, 55 insertions(+), 41 deletions(-)

diff --git a/net/mptcp/protocol.c b/net/mptcp/protocol.c
index 043ac3f222ed..4f5e7f7fa6aa 100644
--- a/net/mptcp/protocol.c
+++ b/net/mptcp/protocol.c
@@ -1551,58 +1551,72 @@ 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_sendmsg_info info = {
-				.flags = flags,
-	};
+	struct mptcp_subflow_context *subflow;
 	struct mptcp_data_frag *dfrag;
 	int len, copied = 0;
+	int err = 0;
 
-	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;
-
-			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)
-				goto out;
+	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)) {
+			struct sock *prev_ssk = NULL, *ssk = NULL;
+			struct mptcp_sendmsg_info info = {
+				.flags = flags,
+			};
+
+			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;
+
+					prev_ssk = ssk;
+					ssk = mptcp_subflow_tcp_sock(subflow);
+
+					/* 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)
+						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);
+
+					ret = mptcp_sendmsg_frag(sk, ssk, dfrag, &info);
+					if (ret <= 0) {
+						mptcp_push_release(ssk, &info);
+						goto out;
+					}
+
+					info.sent += ret;
+					copied += ret;
+					len -= ret;
+
+					mptcp_update_post_push(msk, dfrag, ret);
+				}
+				WRITE_ONCE(msk->first_pending, mptcp_send_next(sk));
+			}
 
-			ret = mptcp_sendmsg_frag(sk, ssk, dfrag, &info);
-			if (ret <= 0) {
+			/* at this point we held the socket lock for the last subflow we used */
+			if (ssk) {
 				mptcp_push_release(ssk, &info);
-				goto out;
+				msk->last_snd = ssk;
+				mptcp_subflow_set_scheduled(subflow, false);
 			}
-
-			info.sent += ret;
-			copied += ret;
-			len -= ret;
-
-			mptcp_update_post_push(msk, dfrag, ret);
 		}
-		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))
-- 
2.35.3

[PATCH mptcp-next v7 3/5] 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 | 57 +++++++++++++++++++++++++++-----------------
 1 file changed, 35 insertions(+), 22 deletions(-)

diff --git a/net/mptcp/protocol.c b/net/mptcp/protocol.c
index 4f5e7f7fa6aa..ad1eb62a9b66 100644
--- a/net/mptcp/protocol.c
+++ b/net/mptcp/protocol.c
@@ -2443,16 +2443,17 @@ 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;
 
 	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)) {
@@ -2471,32 +2472,44 @@ 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)) {
+			ssk = mptcp_subflow_tcp_sock(subflow);
+			if (!ssk)
+				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;
+
+				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);
+			}
 
-	/* 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;
+			release_sock(ssk);
 
-		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);
+			msk->last_snd = ssk;
+			mptcp_subflow_set_scheduled(subflow, false);
+		}
 	}
 
-	release_sock(ssk);
-
 reset_timer:
 	mptcp_check_and_set_pending(sk);
 
-- 
2.35.3

[PATCH mptcp-next v7 4/5] 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",
+};
-- 
2.35.3

[PATCH mptcp-next v7 5/5] 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:
  - Success! ✅:
  - Task: https://cirrus-ci.com/task/5666112380600320
  - Summary: https://api.cirrus-ci.com/v1/artifact/task/5666112380600320/summary/summary.txt

- KVM Validation: debug:
  - Unstable: 1 failed test(s): selftest_mptcp_join 🔴:
  - Task: https://cirrus-ci.com/task/5103162427179008
  - Summary: https://api.cirrus-ci.com/v1/artifact/task/5103162427179008/summary/summary.txt

Initiator: Patchew Applier
Commits: https://github.com/multipath-tcp/mptcp_net-next/commits/ef10ef82aaa8


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 v7 2/5] mptcp: redundant subflows push pending

[Mat Martineau]

On Tue, 21 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 | 96 +++++++++++++++++++++++++-------------------
> 1 file changed, 55 insertions(+), 41 deletions(-)
>
> diff --git a/net/mptcp/protocol.c b/net/mptcp/protocol.c
> index 043ac3f222ed..4f5e7f7fa6aa 100644
> --- a/net/mptcp/protocol.c
> +++ b/net/mptcp/protocol.c
> @@ -1551,58 +1551,72 @@ 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_sendmsg_info info = {
> -				.flags = flags,
> -	};
> +	struct mptcp_subflow_context *subflow;
> 	struct mptcp_data_frag *dfrag;
> 	int len, copied = 0;
> +	int err = 0;
>
> -	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;
> -
> -			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)
> -				goto out;
> +	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)) {
> +			struct sock *prev_ssk = NULL, *ssk = NULL;
> +			struct mptcp_sendmsg_info info = {
> +				.flags = flags,
> +			};
> +
> +			while ((dfrag = mptcp_send_head(sk))) {

Hi Geliang -

Thanks for updating for v7. The changes you've made are definitely in the 
direction I was asking for, following the model of:

scheduler()
for_each_subflow():
    while(dfrag=...):
      send as much data on one subflow with one lock/unlock

I think there are some more modifications to make in order to send the 
same data on each subflow.

> +				info.sent = dfrag->already_sent;
> +				info.limit = dfrag->data_len;
> +				len = dfrag->data_len - dfrag->already_sent;
> +				while (len > 0) {
> +					int ret = 0;
> +
> +					prev_ssk = ssk;
> +					ssk = mptcp_subflow_tcp_sock(subflow);
> +
> +					/* 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)
> +						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);
> +
> +					ret = mptcp_sendmsg_frag(sk, ssk, dfrag, &info);
> +					if (ret <= 0) {
> +						mptcp_push_release(ssk, &info);
> +						goto out;
> +					}
> +
> +					info.sent += ret;
> +					copied += ret;
> +					len -= ret;
> +
> +					mptcp_update_post_push(msk, dfrag, ret);
> +				}
> +				WRITE_ONCE(msk->first_pending, mptcp_send_next(sk));

When msk->first_pending is updated here, it changes the value returned by 
mptcp_send_head() in the "while ((dfrag = mptcp_send_head(sk)))" loop for 
the next subflow.

So, when there are redundant subflows scheduled, the next subflow will 
send new data instead of redundant data. This is because of the 
modifications made to msk->first_pending and the changes made to 
dfrag->already_sent in mptcp_update_post_push().

I think the fix is to keep the loop structure the same, but modify the 
"while ((dfrag = mptcp_send_head(sk)))" loop:

* Every subflow starts sending from the same position in the same 
first dfrag

* Track the max sent data across all the subflows (similar to the 'max' 
tracking done in v6)

* Update dfrag->already_sent (for all sent dfrags) and msk->first_pending 
after all subflows have been attempted. This is currently done by 
mptcp_update_post_push() after each dfrag but I think can be delayed until 
all subflows have sent. It looks like the update to msk->snd_nxt can also 
be delayed until after all subflows have sent.

* Now that I've looked more closely at how mptcp_update_post_push() 
handles msk->snd_burst, I think msk->snd_burst should be set to 0 in 
mptcp_sched_data_init().


This could send different length mappings on each subflow, I need to 
double check the RFC to see if that's allowed.


> +			}
>
> -			ret = mptcp_sendmsg_frag(sk, ssk, dfrag, &info);
> -			if (ret <= 0) {
> +			/* at this point we held the socket lock for the last subflow we used */
> +			if (ssk) {
> 				mptcp_push_release(ssk, &info);
> -				goto out;
> +				msk->last_snd = ssk;
> +				mptcp_subflow_set_scheduled(subflow, false);
> 			}
> -
> -			info.sent += ret;
> -			copied += ret;
> -			len -= ret;
> -
> -			mptcp_update_post_push(msk, dfrag, ret);
> 		}
> -		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))
> -- 
> 2.35.3
>
>
>

--
Mat Martineau
Intel