[RFC PATCH v1 0/4] virtio/vsock: some updates for MSG_PEEK flag

[RFC PATCH v1 0/4] virtio/vsock: some updates for MSG_PEEK flag

[Arseniy Krasnov]

Hello,

This patchset does several things around MSG_PEEK flag support. In
general words it reworks MSG_PEEK test and adds support for this flag
in SOCK_SEQPACKET logic. Here is per-patch description:

1) This is cosmetic change for SOCK_STREAM implementation of MSG_PEEK:
   1) I think there is no need of "safe" mode walk here as there is no
      "unlink" of skbs inside loop (it is MSG_PEEK mode - we don't change
      queue).
   2) Nested while loop is removed: in case of MSG_PEEK we just walk
      over skbs and copy data from each one. I guess this nested loop
      even didn't behave as loop - it always executed just for single
      iteration.

2) This adds MSG_PEEK support for SOCK_SEQPACKET. It could be implemented
   be reworking MSG_PEEK callback for SOCK_STREAM to support SOCK_SEQPACKET
   also, but I think it will be more simple and clear from potential
   bugs to implemented it as separate function thus not mixing logics
   for both types of socket. So I've added it as dedicated function.

3) This is reworked MSG_PEEK test for SOCK_STREAM. Previous version just
   sent single byte, then tried to read it with MSG_PEEK flag, then read
   it in normal way. New version is more complex: now sender uses buffer
   instead of single byte and this buffer is initialized with random
   values. Receiver tests several things:
   1) Read empty socket with MSG_PEEK flag.
   2) Read part of buffer with MSG_PEEK flag.
   3) Read whole buffer with MSG_PEEK flag, then checks that it is same
      as buffer from 2) (limited by size of buffer from 2) of course).
   4) Read whole buffer without any flags, then checks that is is same
      as buffer from 3).

4) This is MSG_PEEK test for SOCK_SEQPACKET. It works in the same way
   as for SOCK_STREAM, except it also checks combination of MSG_TRUNC
   and MSG_PEEK.

Head is:
https://git.kernel.org/pub/scm/linux/kernel/git/netdev/net-next.git/commit/?id=d20dd0ea14072e8a90ff864b2c1603bd68920b4b

Arseniy Krasnov (4):
  virtio/vsock: rework MSG_PEEK for SOCK_STREAM
  virtio/vsock: support MSG_PEEK for SOCK_SEQPACKET
  vsock/test: rework MSG_PEEK test for SOCK_STREAM
  vsock/test: MSG_PEEK test for SOCK_SEQPACKET

 net/vmw_vsock/virtio_transport_common.c | 104 +++++++++++++++-----
 tools/testing/vsock/vsock_test.c        | 124 ++++++++++++++++++++++--
 2 files changed, 196 insertions(+), 32 deletions(-)

-- 
2.25.1

[RFC PATCH v1 1/4] virtio/vsock: rework MSG_PEEK for SOCK_STREAM

[Arseniy Krasnov]

This reworks current implementation of MSG_PEEK logic:
1) Replaces 'skb_queue_walk_safe()' with 'skb_queue_walk()'. There is
   no need in the first one, as there are no removes of skb in loop.
2) Removes nested while loop - MSG_PEEK logic could be implemented
   without it: just iterate over skbs without removing it and copy
   data from each until destination buffer is not full.

Signed-off-by: Arseniy Krasnov <AVKrasnov@sberdevices.ru>
---
 net/vmw_vsock/virtio_transport_common.c | 41 ++++++++++++-------------
 1 file changed, 19 insertions(+), 22 deletions(-)

diff --git a/net/vmw_vsock/virtio_transport_common.c b/net/vmw_vsock/virtio_transport_common.c
index b769fc258931..2ee40574c339 100644
--- a/net/vmw_vsock/virtio_transport_common.c
+++ b/net/vmw_vsock/virtio_transport_common.c
@@ -348,37 +348,34 @@ virtio_transport_stream_do_peek(struct vsock_sock *vsk,
 				size_t len)
 {
 	struct virtio_vsock_sock *vvs = vsk->trans;
-	size_t bytes, total = 0, off;
-	struct sk_buff *skb, *tmp;
-	int err = -EFAULT;
+	struct sk_buff *skb;
+	size_t total = 0;
+	int err;
 
 	spin_lock_bh(&vvs->rx_lock);
 
-	skb_queue_walk_safe(&vvs->rx_queue, skb,  tmp) {
-		off = 0;
+	skb_queue_walk(&vvs->rx_queue, skb) {
+		size_t bytes;
 
-		if (total == len)
-			break;
+		bytes = len - total;
+		if (bytes > skb->len)
+			bytes = skb->len;
 
-		while (total < len && off < skb->len) {
-			bytes = len - total;
-			if (bytes > skb->len - off)
-				bytes = skb->len - off;
+		spin_unlock_bh(&vvs->rx_lock);
 
-			/* sk_lock is held by caller so no one else can dequeue.
-			 * Unlock rx_lock since memcpy_to_msg() may sleep.
-			 */
-			spin_unlock_bh(&vvs->rx_lock);
+		/* sk_lock is held by caller so no one else can dequeue.
+		 * Unlock rx_lock since memcpy_to_msg() may sleep.
+		 */
+		err = memcpy_to_msg(msg, skb->data, bytes);
+		if (err)
+			goto out;
 
-			err = memcpy_to_msg(msg, skb->data + off, bytes);
-			if (err)
-				goto out;
+		total += bytes;
 
-			spin_lock_bh(&vvs->rx_lock);
+		spin_lock_bh(&vvs->rx_lock);
 
-			total += bytes;
-			off += bytes;
-		}
+		if (total == len)
+			break;
 	}
 
 	spin_unlock_bh(&vvs->rx_lock);
-- 
2.25.1

[RFC PATCH v1 2/4] virtio/vsock: support MSG_PEEK for SOCK_SEQPACKET

[Arseniy Krasnov]

This adds support of MSG_PEEK flag for SOCK_SEQPACKET type of socket.
Difference with SOCK_STREAM is that this callback returns either length
of the message or error.

Signed-off-by: Arseniy Krasnov <AVKrasnov@sberdevices.ru>
---
 net/vmw_vsock/virtio_transport_common.c | 63 +++++++++++++++++++++++--
 1 file changed, 60 insertions(+), 3 deletions(-)

diff --git a/net/vmw_vsock/virtio_transport_common.c b/net/vmw_vsock/virtio_transport_common.c
index 2ee40574c339..352d042b130b 100644
--- a/net/vmw_vsock/virtio_transport_common.c
+++ b/net/vmw_vsock/virtio_transport_common.c
@@ -460,6 +460,63 @@ virtio_transport_stream_do_dequeue(struct vsock_sock *vsk,
 	return err;
 }
 
+static ssize_t
+virtio_transport_seqpacket_do_peek(struct vsock_sock *vsk,
+				   struct msghdr *msg)
+{
+	struct virtio_vsock_sock *vvs = vsk->trans;
+	struct sk_buff *skb;
+	size_t total, len;
+
+	spin_lock_bh(&vvs->rx_lock);
+
+	if (!vvs->msg_count) {
+		spin_unlock_bh(&vvs->rx_lock);
+		return 0;
+	}
+
+	total = 0;
+	len = msg_data_left(msg);
+
+	skb_queue_walk(&vvs->rx_queue, skb) {
+		struct virtio_vsock_hdr *hdr;
+
+		if (total < len) {
+			size_t bytes;
+			int err;
+
+			bytes = len - total;
+			if (bytes > skb->len)
+				bytes = skb->len;
+
+			spin_unlock_bh(&vvs->rx_lock);
+
+			/* sk_lock is held by caller so no one else can dequeue.
+			 * Unlock rx_lock since memcpy_to_msg() may sleep.
+			 */
+			err = memcpy_to_msg(msg, skb->data, bytes);
+			if (err)
+				return err;
+
+			spin_lock_bh(&vvs->rx_lock);
+		}
+
+		total += skb->len;
+		hdr = virtio_vsock_hdr(skb);
+
+		if (le32_to_cpu(hdr->flags) & VIRTIO_VSOCK_SEQ_EOM) {
+			if (le32_to_cpu(hdr->flags) & VIRTIO_VSOCK_SEQ_EOR)
+				msg->msg_flags |= MSG_EOR;
+
+			break;
+		}
+	}
+
+	spin_unlock_bh(&vvs->rx_lock);
+
+	return total;
+}
+
 static int virtio_transport_seqpacket_do_dequeue(struct vsock_sock *vsk,
 						 struct msghdr *msg,
 						 int flags)
@@ -554,9 +611,9 @@ virtio_transport_seqpacket_dequeue(struct vsock_sock *vsk,
 				   int flags)
 {
 	if (flags & MSG_PEEK)
-		return -EOPNOTSUPP;
-
-	return virtio_transport_seqpacket_do_dequeue(vsk, msg, flags);
+		return virtio_transport_seqpacket_do_peek(vsk, msg);
+	else
+		return virtio_transport_seqpacket_do_dequeue(vsk, msg, flags);
 }
 EXPORT_SYMBOL_GPL(virtio_transport_seqpacket_dequeue);
 
-- 
2.25.1

[RFC PATCH v1 3/4] vsock/test: rework MSG_PEEK test for SOCK_STREAM

[Arseniy Krasnov]

This new version makes test more complicated by adding empty read,
partial read and data comparisons between MSG_PEEK and normal reads.

Signed-off-by: Arseniy Krasnov <AVKrasnov@sberdevices.ru>
---
 tools/testing/vsock/vsock_test.c | 66 ++++++++++++++++++++++++++++++--
 1 file changed, 63 insertions(+), 3 deletions(-)

diff --git a/tools/testing/vsock/vsock_test.c b/tools/testing/vsock/vsock_test.c
index ac1bd3ac1533..104ac102e411 100644
--- a/tools/testing/vsock/vsock_test.c
+++ b/tools/testing/vsock/vsock_test.c
@@ -255,9 +255,13 @@ static void test_stream_multiconn_server(const struct test_opts *opts)
 		close(fds[i]);
 }
 
+#define MSG_PEEK_BUF_LEN 64
+
 static void test_stream_msg_peek_client(const struct test_opts *opts)
 {
+	unsigned char buf[MSG_PEEK_BUF_LEN];
 	int fd;
+	int i;
 
 	fd = vsock_stream_connect(opts->peer_cid, 1234);
 	if (fd < 0) {
@@ -265,12 +269,21 @@ static void test_stream_msg_peek_client(const struct test_opts *opts)
 		exit(EXIT_FAILURE);
 	}
 
-	send_byte(fd, 1, 0);
+	for (i = 0; i < sizeof(buf); i++)
+		buf[i] = rand() & 0xFF;
+
+	control_expectln("SRVREADY");
+
+	send(fd, buf, sizeof(buf), 0);
 	close(fd);
 }
 
 static void test_stream_msg_peek_server(const struct test_opts *opts)
 {
+	unsigned char buf_half[MSG_PEEK_BUF_LEN / 2];
+	unsigned char buf_normal[MSG_PEEK_BUF_LEN];
+	unsigned char buf_peek[MSG_PEEK_BUF_LEN];
+	ssize_t res;
 	int fd;
 
 	fd = vsock_stream_accept(VMADDR_CID_ANY, 1234, NULL);
@@ -279,8 +292,55 @@ static void test_stream_msg_peek_server(const struct test_opts *opts)
 		exit(EXIT_FAILURE);
 	}
 
-	recv_byte(fd, 1, MSG_PEEK);
-	recv_byte(fd, 1, 0);
+	/* Peek from empty socket. */
+	res = recv(fd, buf_peek, sizeof(buf_peek), MSG_PEEK | MSG_DONTWAIT);
+	if (res != -1) {
+		fprintf(stderr, "expected recv(2) failure, got %zi\n", res);
+		exit(EXIT_FAILURE);
+	}
+
+	if (errno != EAGAIN) {
+		perror("EAGAIN expected");
+		exit(EXIT_FAILURE);
+	}
+
+	control_writeln("SRVREADY");
+
+	/* Peek part of data. */
+	res = recv(fd, buf_half, sizeof(buf_half), MSG_PEEK);
+	if (res != sizeof(buf_half)) {
+		fprintf(stderr, "recv(2) + MSG_PEEK, expected %zu, got %zi\n",
+			sizeof(buf_half), res);
+		exit(EXIT_FAILURE);
+	}
+
+	/* Peek whole data. */
+	res = recv(fd, buf_peek, sizeof(buf_peek), MSG_PEEK);
+	if (res != sizeof(buf_peek)) {
+		fprintf(stderr, "recv(2) + MSG_PEEK, expected %zu, got %zi\n",
+			sizeof(buf_peek), res);
+		exit(EXIT_FAILURE);
+	}
+
+	/* Compare partial and full peek. */
+	if (memcmp(buf_half, buf_peek, sizeof(buf_half))) {
+		fprintf(stderr, "Partial peek data mismatch\n");
+		exit(EXIT_FAILURE);
+	}
+
+	res = recv(fd, buf_normal, sizeof(buf_normal), 0);
+	if (res != sizeof(buf_normal)) {
+		fprintf(stderr, "recv(2), expected %zu, got %zi\n",
+			sizeof(buf_normal), res);
+		exit(EXIT_FAILURE);
+	}
+
+	/* Compare full peek and normal read. */
+	if (memcmp(buf_peek, buf_normal, sizeof(buf_peek))) {
+		fprintf(stderr, "Full peek data mismatch\n");
+		exit(EXIT_FAILURE);
+	}
+
 	close(fd);
 }
 
-- 
2.25.1

[RFC PATCH v1 4/4] vsock/test: MSG_PEEK test for SOCK_SEQPACKET

[Arseniy Krasnov]

This adds MSG_PEEK test for SOCK_SEQPACKET. It works in the same way as
SOCK_STREAM test, except it also tests MSG_TRUNC flag.

Signed-off-by: Arseniy Krasnov <AVKrasnov@sberdevices.ru>
---
 tools/testing/vsock/vsock_test.c | 58 +++++++++++++++++++++++++++++---
 1 file changed, 54 insertions(+), 4 deletions(-)

diff --git a/tools/testing/vsock/vsock_test.c b/tools/testing/vsock/vsock_test.c
index 104ac102e411..2bacd0ea1195 100644
--- a/tools/testing/vsock/vsock_test.c
+++ b/tools/testing/vsock/vsock_test.c
@@ -257,13 +257,18 @@ static void test_stream_multiconn_server(const struct test_opts *opts)
 
 #define MSG_PEEK_BUF_LEN 64
 
-static void test_stream_msg_peek_client(const struct test_opts *opts)
+static void __test_msg_peek_client(const struct test_opts *opts,
+				   bool seqpacket)
 {
 	unsigned char buf[MSG_PEEK_BUF_LEN];
 	int fd;
 	int i;
 
-	fd = vsock_stream_connect(opts->peer_cid, 1234);
+	if (seqpacket)
+		fd = vsock_seqpacket_connect(opts->peer_cid, 1234);
+	else
+		fd = vsock_stream_connect(opts->peer_cid, 1234);
+
 	if (fd < 0) {
 		perror("connect");
 		exit(EXIT_FAILURE);
@@ -278,7 +283,8 @@ static void test_stream_msg_peek_client(const struct test_opts *opts)
 	close(fd);
 }
 
-static void test_stream_msg_peek_server(const struct test_opts *opts)
+static void __test_msg_peek_server(const struct test_opts *opts,
+				   bool seqpacket)
 {
 	unsigned char buf_half[MSG_PEEK_BUF_LEN / 2];
 	unsigned char buf_normal[MSG_PEEK_BUF_LEN];
@@ -286,7 +292,11 @@ static void test_stream_msg_peek_server(const struct test_opts *opts)
 	ssize_t res;
 	int fd;
 
-	fd = vsock_stream_accept(VMADDR_CID_ANY, 1234, NULL);
+	if (seqpacket)
+		fd = vsock_seqpacket_accept(VMADDR_CID_ANY, 1234, NULL);
+	else
+		fd = vsock_stream_accept(VMADDR_CID_ANY, 1234, NULL);
+
 	if (fd < 0) {
 		perror("accept");
 		exit(EXIT_FAILURE);
@@ -328,6 +338,21 @@ static void test_stream_msg_peek_server(const struct test_opts *opts)
 		exit(EXIT_FAILURE);
 	}
 
+	if (seqpacket) {
+		/* This type of socket supports MSG_TRUNC flag,
+		 * so check it with MSG_PEEK. We must get length
+		 * of the message.
+		 */
+		res = recv(fd, buf_half, sizeof(buf_half), MSG_PEEK |
+			   MSG_TRUNC);
+		if (res != sizeof(buf_peek)) {
+			fprintf(stderr,
+				"recv(2) + MSG_PEEK | MSG_TRUNC, exp %zu, got %zi\n",
+				sizeof(buf_half), res);
+			exit(EXIT_FAILURE);
+		}
+	}
+
 	res = recv(fd, buf_normal, sizeof(buf_normal), 0);
 	if (res != sizeof(buf_normal)) {
 		fprintf(stderr, "recv(2), expected %zu, got %zi\n",
@@ -344,6 +369,16 @@ static void test_stream_msg_peek_server(const struct test_opts *opts)
 	close(fd);
 }
 
+static void test_stream_msg_peek_client(const struct test_opts *opts)
+{
+	return __test_msg_peek_client(opts, false);
+}
+
+static void test_stream_msg_peek_server(const struct test_opts *opts)
+{
+	return __test_msg_peek_server(opts, false);
+}
+
 #define SOCK_BUF_SIZE (2 * 1024 * 1024)
 #define MAX_MSG_SIZE (32 * 1024)
 
@@ -1113,6 +1148,16 @@ static void test_stream_virtio_skb_merge_server(const struct test_opts *opts)
 	close(fd);
 }
 
+static void test_seqpacket_msg_peek_client(const struct test_opts *opts)
+{
+	return __test_msg_peek_client(opts, true);
+}
+
+static void test_seqpacket_msg_peek_server(const struct test_opts *opts)
+{
+	return __test_msg_peek_server(opts, true);
+}
+
 static struct test_case test_cases[] = {
 	{
 		.name = "SOCK_STREAM connection reset",
@@ -1188,6 +1233,11 @@ static struct test_case test_cases[] = {
 		.run_client = test_stream_virtio_skb_merge_client,
 		.run_server = test_stream_virtio_skb_merge_server,
 	},
+	{
+		.name = "SOCK_SEQPACKET MSG_PEEK",
+		.run_client = test_seqpacket_msg_peek_client,
+		.run_server = test_seqpacket_msg_peek_server,
+	},
 	{},
 };
 
-- 
2.25.1

Re: [RFC PATCH v1 1/4] virtio/vsock: rework MSG_PEEK for SOCK_STREAM

[Stefano Garzarella]

On Sun, Jun 18, 2023 at 09:24:48AM +0300, Arseniy Krasnov wrote:
>This reworks current implementation of MSG_PEEK logic:
>1) Replaces 'skb_queue_walk_safe()' with 'skb_queue_walk()'. There is
>   no need in the first one, as there are no removes of skb in loop.
>2) Removes nested while loop - MSG_PEEK logic could be implemented
>   without it: just iterate over skbs without removing it and copy
>   data from each until destination buffer is not full.
>
>Signed-off-by: Arseniy Krasnov <AVKrasnov@sberdevices.ru>
>---
> net/vmw_vsock/virtio_transport_common.c | 41 ++++++++++++-------------
> 1 file changed, 19 insertions(+), 22 deletions(-)

Great clean up!

LGTM, but @Bobby can you also take a look?

Thanks,
Stefano

>
>diff --git a/net/vmw_vsock/virtio_transport_common.c b/net/vmw_vsock/virtio_transport_common.c
>index b769fc258931..2ee40574c339 100644
>--- a/net/vmw_vsock/virtio_transport_common.c
>+++ b/net/vmw_vsock/virtio_transport_common.c
>@@ -348,37 +348,34 @@ virtio_transport_stream_do_peek(struct vsock_sock *vsk,
> 				size_t len)
> {
> 	struct virtio_vsock_sock *vvs = vsk->trans;
>-	size_t bytes, total = 0, off;
>-	struct sk_buff *skb, *tmp;
>-	int err = -EFAULT;
>+	struct sk_buff *skb;
>+	size_t total = 0;
>+	int err;
>
> 	spin_lock_bh(&vvs->rx_lock);
>
>-	skb_queue_walk_safe(&vvs->rx_queue, skb,  tmp) {
>-		off = 0;
>+	skb_queue_walk(&vvs->rx_queue, skb) {
>+		size_t bytes;
>
>-		if (total == len)
>-			break;
>+		bytes = len - total;
>+		if (bytes > skb->len)
>+			bytes = skb->len;
>
>-		while (total < len && off < skb->len) {
>-			bytes = len - total;
>-			if (bytes > skb->len - off)
>-				bytes = skb->len - off;
>+		spin_unlock_bh(&vvs->rx_lock);
>
>-			/* sk_lock is held by caller so no one else can dequeue.
>-			 * Unlock rx_lock since memcpy_to_msg() may sleep.
>-			 */
>-			spin_unlock_bh(&vvs->rx_lock);
>+		/* sk_lock is held by caller so no one else can dequeue.
>+		 * Unlock rx_lock since memcpy_to_msg() may sleep.
>+		 */
>+		err = memcpy_to_msg(msg, skb->data, bytes);
>+		if (err)
>+			goto out;
>
>-			err = memcpy_to_msg(msg, skb->data + off, bytes);
>-			if (err)
>-				goto out;
>+		total += bytes;
>
>-			spin_lock_bh(&vvs->rx_lock);
>+		spin_lock_bh(&vvs->rx_lock);
>
>-			total += bytes;
>-			off += bytes;
>-		}
>+		if (total == len)
>+			break;
> 	}
>
> 	spin_unlock_bh(&vvs->rx_lock);
>-- 
>2.25.1
>

Re: [RFC PATCH v1 2/4] virtio/vsock: support MSG_PEEK for SOCK_SEQPACKET

[Stefano Garzarella]

On Sun, Jun 18, 2023 at 09:24:49AM +0300, Arseniy Krasnov wrote:
>This adds support of MSG_PEEK flag for SOCK_SEQPACKET type of socket.
>Difference with SOCK_STREAM is that this callback returns either length
>of the message or error.
>
>Signed-off-by: Arseniy Krasnov <AVKrasnov@sberdevices.ru>
>---
> net/vmw_vsock/virtio_transport_common.c | 63 +++++++++++++++++++++++--
> 1 file changed, 60 insertions(+), 3 deletions(-)
>
>diff --git a/net/vmw_vsock/virtio_transport_common.c b/net/vmw_vsock/virtio_transport_common.c
>index 2ee40574c339..352d042b130b 100644
>--- a/net/vmw_vsock/virtio_transport_common.c
>+++ b/net/vmw_vsock/virtio_transport_common.c
>@@ -460,6 +460,63 @@ virtio_transport_stream_do_dequeue(struct vsock_sock *vsk,
> 	return err;
> }
>
>+static ssize_t
>+virtio_transport_seqpacket_do_peek(struct vsock_sock *vsk,
>+				   struct msghdr *msg)
>+{
>+	struct virtio_vsock_sock *vvs = vsk->trans;
>+	struct sk_buff *skb;
>+	size_t total, len;
>+
>+	spin_lock_bh(&vvs->rx_lock);
>+
>+	if (!vvs->msg_count) {
>+		spin_unlock_bh(&vvs->rx_lock);
>+		return 0;
>+	}
>+
>+	total = 0;
>+	len = msg_data_left(msg);
>+
>+	skb_queue_walk(&vvs->rx_queue, skb) {
>+		struct virtio_vsock_hdr *hdr;
>+
>+		if (total < len) {
>+			size_t bytes;
>+			int err;
>+
>+			bytes = len - total;
>+			if (bytes > skb->len)
>+				bytes = skb->len;
>+
>+			spin_unlock_bh(&vvs->rx_lock);
>+
>+			/* sk_lock is held by caller so no one else can dequeue.
>+			 * Unlock rx_lock since memcpy_to_msg() may sleep.
>+			 */
>+			err = memcpy_to_msg(msg, skb->data, bytes);
>+			if (err)
>+				return err;
>+
>+			spin_lock_bh(&vvs->rx_lock);
>+		}
>+
>+		total += skb->len;
>+		hdr = virtio_vsock_hdr(skb);
>+
>+		if (le32_to_cpu(hdr->flags) & VIRTIO_VSOCK_SEQ_EOM) {
>+			if (le32_to_cpu(hdr->flags) & VIRTIO_VSOCK_SEQ_EOR)
>+				msg->msg_flags |= MSG_EOR;
>+
>+			break;
>+		}
>+	}
>+
>+	spin_unlock_bh(&vvs->rx_lock);
>+
>+	return total;

Should we return the minimum between total and len?

Thanks,
Stefano

>+}
>+
> static int virtio_transport_seqpacket_do_dequeue(struct vsock_sock *vsk,
> 						 struct msghdr *msg,
> 						 int flags)
>@@ -554,9 +611,9 @@ virtio_transport_seqpacket_dequeue(struct vsock_sock *vsk,
> 				   int flags)
> {
> 	if (flags & MSG_PEEK)
>-		return -EOPNOTSUPP;
>-
>-	return virtio_transport_seqpacket_do_dequeue(vsk, msg, flags);
>+		return virtio_transport_seqpacket_do_peek(vsk, msg);
>+	else
>+		return virtio_transport_seqpacket_do_dequeue(vsk, msg, flags);
> }
> EXPORT_SYMBOL_GPL(virtio_transport_seqpacket_dequeue);
>
>-- 
>2.25.1
>

Re: [RFC PATCH v1 0/4] virtio/vsock: some updates for MSG_PEEK flag

[Stefano Garzarella]

On Sun, Jun 18, 2023 at 09:24:47AM +0300, Arseniy Krasnov wrote:
>Hello,
>
>This patchset does several things around MSG_PEEK flag support. In
>general words it reworks MSG_PEEK test and adds support for this flag
>in SOCK_SEQPACKET logic. Here is per-patch description:
>
>1) This is cosmetic change for SOCK_STREAM implementation of MSG_PEEK:
>   1) I think there is no need of "safe" mode walk here as there is no
>      "unlink" of skbs inside loop (it is MSG_PEEK mode - we don't change
>      queue).
>   2) Nested while loop is removed: in case of MSG_PEEK we just walk
>      over skbs and copy data from each one. I guess this nested loop
>      even didn't behave as loop - it always executed just for single
>      iteration.
>
>2) This adds MSG_PEEK support for SOCK_SEQPACKET. It could be implemented
>   be reworking MSG_PEEK callback for SOCK_STREAM to support SOCK_SEQPACKET
>   also, but I think it will be more simple and clear from potential
>   bugs to implemented it as separate function thus not mixing logics
>   for both types of socket. So I've added it as dedicated function.
>
>3) This is reworked MSG_PEEK test for SOCK_STREAM. Previous version just
>   sent single byte, then tried to read it with MSG_PEEK flag, then read
>   it in normal way. New version is more complex: now sender uses buffer
>   instead of single byte and this buffer is initialized with random
>   values. Receiver tests several things:
>   1) Read empty socket with MSG_PEEK flag.
>   2) Read part of buffer with MSG_PEEK flag.
>   3) Read whole buffer with MSG_PEEK flag, then checks that it is same
>      as buffer from 2) (limited by size of buffer from 2) of course).
>   4) Read whole buffer without any flags, then checks that is is same
>      as buffer from 3).
>
>4) This is MSG_PEEK test for SOCK_SEQPACKET. It works in the same way
>   as for SOCK_STREAM, except it also checks combination of MSG_TRUNC
>   and MSG_PEEK.
>
>Head is:
>https://git.kernel.org/pub/scm/linux/kernel/git/netdev/net-next.git/commit/?id=d20dd0ea14072e8a90ff864b2c1603bd68920b4b

Nice cleanup, LGTM, but I'd like a comment from Bobby.

Thanks,
Stefano

Re: [RFC PATCH v1 1/4] virtio/vsock: rework MSG_PEEK for SOCK_STREAM

[Bobby Eshleman]

On Sun, Jun 18, 2023 at 09:24:48AM +0300, Arseniy Krasnov wrote:
> This reworks current implementation of MSG_PEEK logic:
> 1) Replaces 'skb_queue_walk_safe()' with 'skb_queue_walk()'. There is
>    no need in the first one, as there are no removes of skb in loop.
> 2) Removes nested while loop - MSG_PEEK logic could be implemented
>    without it: just iterate over skbs without removing it and copy
>    data from each until destination buffer is not full.
> 
> Signed-off-by: Arseniy Krasnov <AVKrasnov@sberdevices.ru>
> ---
>  net/vmw_vsock/virtio_transport_common.c | 41 ++++++++++++-------------
>  1 file changed, 19 insertions(+), 22 deletions(-)
> 
> diff --git a/net/vmw_vsock/virtio_transport_common.c b/net/vmw_vsock/virtio_transport_common.c
> index b769fc258931..2ee40574c339 100644
> --- a/net/vmw_vsock/virtio_transport_common.c
> +++ b/net/vmw_vsock/virtio_transport_common.c
> @@ -348,37 +348,34 @@ virtio_transport_stream_do_peek(struct vsock_sock *vsk,
>  				size_t len)
>  {
>  	struct virtio_vsock_sock *vvs = vsk->trans;
> -	size_t bytes, total = 0, off;
> -	struct sk_buff *skb, *tmp;
> -	int err = -EFAULT;
> +	struct sk_buff *skb;
> +	size_t total = 0;
> +	int err;
>  
>  	spin_lock_bh(&vvs->rx_lock);
>  
> -	skb_queue_walk_safe(&vvs->rx_queue, skb,  tmp) {
> -		off = 0;
> +	skb_queue_walk(&vvs->rx_queue, skb) {
> +		size_t bytes;
>  
> -		if (total == len)
> -			break;
> +		bytes = len - total;
> +		if (bytes > skb->len)
> +			bytes = skb->len;
>  
> -		while (total < len && off < skb->len) {
> -			bytes = len - total;
> -			if (bytes > skb->len - off)
> -				bytes = skb->len - off;
> +		spin_unlock_bh(&vvs->rx_lock);
>  
> -			/* sk_lock is held by caller so no one else can dequeue.
> -			 * Unlock rx_lock since memcpy_to_msg() may sleep.
> -			 */
> -			spin_unlock_bh(&vvs->rx_lock);
> +		/* sk_lock is held by caller so no one else can dequeue.
> +		 * Unlock rx_lock since memcpy_to_msg() may sleep.
> +		 */
> +		err = memcpy_to_msg(msg, skb->data, bytes);
> +		if (err)
> +			goto out;
>  
> -			err = memcpy_to_msg(msg, skb->data + off, bytes);
> -			if (err)
> -				goto out;
> +		total += bytes;
>  
> -			spin_lock_bh(&vvs->rx_lock);
> +		spin_lock_bh(&vvs->rx_lock);
>  
> -			total += bytes;
> -			off += bytes;
> -		}
> +		if (total == len)
> +			break;
>  	}
>  
>  	spin_unlock_bh(&vvs->rx_lock);
> -- 
> 2.25.1
> 

That cleans up nicely!

LGTM.

Reviewed-by: Bobby Eshleman <bobby.eshleman@bytedance.com>

Re: [RFC PATCH v1 2/4] virtio/vsock: support MSG_PEEK for SOCK_SEQPACKET

[Arseniy Krasnov]

On 26.06.2023 19:28, Stefano Garzarella wrote:
> On Sun, Jun 18, 2023 at 09:24:49AM +0300, Arseniy Krasnov wrote:
>> This adds support of MSG_PEEK flag for SOCK_SEQPACKET type of socket.
>> Difference with SOCK_STREAM is that this callback returns either length
>> of the message or error.
>>
>> Signed-off-by: Arseniy Krasnov <AVKrasnov@sberdevices.ru>
>> ---
>> net/vmw_vsock/virtio_transport_common.c | 63 +++++++++++++++++++++++--
>> 1 file changed, 60 insertions(+), 3 deletions(-)
>>
>> diff --git a/net/vmw_vsock/virtio_transport_common.c b/net/vmw_vsock/virtio_transport_common.c
>> index 2ee40574c339..352d042b130b 100644
>> --- a/net/vmw_vsock/virtio_transport_common.c
>> +++ b/net/vmw_vsock/virtio_transport_common.c
>> @@ -460,6 +460,63 @@ virtio_transport_stream_do_dequeue(struct vsock_sock *vsk,
>>     return err;
>> }
>>
>> +static ssize_t
>> +virtio_transport_seqpacket_do_peek(struct vsock_sock *vsk,
>> +                   struct msghdr *msg)
>> +{
>> +    struct virtio_vsock_sock *vvs = vsk->trans;
>> +    struct sk_buff *skb;
>> +    size_t total, len;
>> +
>> +    spin_lock_bh(&vvs->rx_lock);
>> +
>> +    if (!vvs->msg_count) {
>> +        spin_unlock_bh(&vvs->rx_lock);
>> +        return 0;
>> +    }
>> +
>> +    total = 0;
>> +    len = msg_data_left(msg);
>> +
>> +    skb_queue_walk(&vvs->rx_queue, skb) {
>> +        struct virtio_vsock_hdr *hdr;
>> +
>> +        if (total < len) {
>> +            size_t bytes;
>> +            int err;
>> +
>> +            bytes = len - total;
>> +            if (bytes > skb->len)
>> +                bytes = skb->len;
>> +
>> +            spin_unlock_bh(&vvs->rx_lock);
>> +
>> +            /* sk_lock is held by caller so no one else can dequeue.
>> +             * Unlock rx_lock since memcpy_to_msg() may sleep.
>> +             */
>> +            err = memcpy_to_msg(msg, skb->data, bytes);
>> +            if (err)
>> +                return err;
>> +
>> +            spin_lock_bh(&vvs->rx_lock);
>> +        }
>> +
>> +        total += skb->len;
>> +        hdr = virtio_vsock_hdr(skb);
>> +
>> +        if (le32_to_cpu(hdr->flags) & VIRTIO_VSOCK_SEQ_EOM) {
>> +            if (le32_to_cpu(hdr->flags) & VIRTIO_VSOCK_SEQ_EOR)
>> +                msg->msg_flags |= MSG_EOR;
>> +
>> +            break;
>> +        }
>> +    }
>> +
>> +    spin_unlock_bh(&vvs->rx_lock);
>> +
>> +    return total;
> 
> Should we return the minimum between total and len?

I guess no, because seqpacket dequeue callback always returns length of message,
then, in af_vsock.c we return either number of bytes read or length of message
depending on MSG_TRUNC flags.

Thanks, Arseniy

> 
> Thanks,
> Stefano
> 
>> +}
>> +
>> static int virtio_transport_seqpacket_do_dequeue(struct vsock_sock *vsk,
>>                          struct msghdr *msg,
>>                          int flags)
>> @@ -554,9 +611,9 @@ virtio_transport_seqpacket_dequeue(struct vsock_sock *vsk,
>>                    int flags)
>> {
>>     if (flags & MSG_PEEK)
>> -        return -EOPNOTSUPP;
>> -
>> -    return virtio_transport_seqpacket_do_dequeue(vsk, msg, flags);
>> +        return virtio_transport_seqpacket_do_peek(vsk, msg);
>> +    else
>> +        return virtio_transport_seqpacket_do_dequeue(vsk, msg, flags);
>> }
>> EXPORT_SYMBOL_GPL(virtio_transport_seqpacket_dequeue);
>>
>> -- 
>> 2.25.1
>>
> 

Re: [RFC PATCH v1 2/4] virtio/vsock: support MSG_PEEK for SOCK_SEQPACKET

[Stefano Garzarella]

On Tue, Jun 27, 2023 at 07:34:29AM +0300, Arseniy Krasnov wrote:
>
>
>On 26.06.2023 19:28, Stefano Garzarella wrote:
>> On Sun, Jun 18, 2023 at 09:24:49AM +0300, Arseniy Krasnov wrote:
>>> This adds support of MSG_PEEK flag for SOCK_SEQPACKET type of socket.
>>> Difference with SOCK_STREAM is that this callback returns either length
>>> of the message or error.
>>>
>>> Signed-off-by: Arseniy Krasnov <AVKrasnov@sberdevices.ru>
>>> ---
>>> net/vmw_vsock/virtio_transport_common.c | 63 +++++++++++++++++++++++--
>>> 1 file changed, 60 insertions(+), 3 deletions(-)
>>>
>>> diff --git a/net/vmw_vsock/virtio_transport_common.c b/net/vmw_vsock/virtio_transport_common.c
>>> index 2ee40574c339..352d042b130b 100644
>>> --- a/net/vmw_vsock/virtio_transport_common.c
>>> +++ b/net/vmw_vsock/virtio_transport_common.c
>>> @@ -460,6 +460,63 @@ virtio_transport_stream_do_dequeue(struct vsock_sock *vsk,
>>>     return err;
>>> }
>>>
>>> +static ssize_t
>>> +virtio_transport_seqpacket_do_peek(struct vsock_sock *vsk,
>>> +                   struct msghdr *msg)
>>> +{
>>> +    struct virtio_vsock_sock *vvs = vsk->trans;
>>> +    struct sk_buff *skb;
>>> +    size_t total, len;
>>> +
>>> +    spin_lock_bh(&vvs->rx_lock);
>>> +
>>> +    if (!vvs->msg_count) {
>>> +        spin_unlock_bh(&vvs->rx_lock);
>>> +        return 0;
>>> +    }
>>> +
>>> +    total = 0;
>>> +    len = msg_data_left(msg);
>>> +
>>> +    skb_queue_walk(&vvs->rx_queue, skb) {
>>> +        struct virtio_vsock_hdr *hdr;
>>> +
>>> +        if (total < len) {
>>> +            size_t bytes;
>>> +            int err;
>>> +
>>> +            bytes = len - total;
>>> +            if (bytes > skb->len)
>>> +                bytes = skb->len;
>>> +
>>> +            spin_unlock_bh(&vvs->rx_lock);
>>> +
>>> +            /* sk_lock is held by caller so no one else can dequeue.
>>> +             * Unlock rx_lock since memcpy_to_msg() may sleep.
>>> +             */
>>> +            err = memcpy_to_msg(msg, skb->data, bytes);
>>> +            if (err)
>>> +                return err;
>>> +
>>> +            spin_lock_bh(&vvs->rx_lock);
>>> +        }
>>> +
>>> +        total += skb->len;
>>> +        hdr = virtio_vsock_hdr(skb);
>>> +
>>> +        if (le32_to_cpu(hdr->flags) & VIRTIO_VSOCK_SEQ_EOM) {
>>> +            if (le32_to_cpu(hdr->flags) & VIRTIO_VSOCK_SEQ_EOR)
>>> +                msg->msg_flags |= MSG_EOR;
>>> +
>>> +            break;
>>> +        }
>>> +    }
>>> +
>>> +    spin_unlock_bh(&vvs->rx_lock);
>>> +
>>> +    return total;
>>
>> Should we return the minimum between total and len?
>
>I guess no, because seqpacket dequeue callback always returns length of message,
>then, in af_vsock.c we return either number of bytes read or length of message
>depending on MSG_TRUNC flags.

Right! We should always return the total lenght of the packet.

Thanks,
Stefano

>
>Thanks, Arseniy
>
>>
>> Thanks,
>> Stefano
>>
>>> +}
>>> +
>>> static int virtio_transport_seqpacket_do_dequeue(struct vsock_sock *vsk,
>>>                          struct msghdr *msg,
>>>                          int flags)
>>> @@ -554,9 +611,9 @@ virtio_transport_seqpacket_dequeue(struct vsock_sock *vsk,
>>>                    int flags)
>>> {
>>>     if (flags & MSG_PEEK)
>>> -        return -EOPNOTSUPP;
>>> -
>>> -    return virtio_transport_seqpacket_do_dequeue(vsk, msg, flags);
>>> +        return virtio_transport_seqpacket_do_peek(vsk, msg);
>>> +    else
>>> +        return virtio_transport_seqpacket_do_dequeue(vsk, msg, flags);
>>> }
>>> EXPORT_SYMBOL_GPL(virtio_transport_seqpacket_dequeue);
>>>
>>> -- 
>>> 2.25.1
>>>
>>
>

Re: [RFC PATCH v1 0/4] virtio/vsock: some updates for MSG_PEEK flag

[Arseniy Krasnov]

On 26.06.2023 19:30, Stefano Garzarella wrote:
> On Sun, Jun 18, 2023 at 09:24:47AM +0300, Arseniy Krasnov wrote:
>> Hello,
>>
>> This patchset does several things around MSG_PEEK flag support. In
>> general words it reworks MSG_PEEK test and adds support for this flag
>> in SOCK_SEQPACKET logic. Here is per-patch description:
>>
>> 1) This is cosmetic change for SOCK_STREAM implementation of MSG_PEEK:
>>   1) I think there is no need of "safe" mode walk here as there is no
>>      "unlink" of skbs inside loop (it is MSG_PEEK mode - we don't change
>>      queue).
>>   2) Nested while loop is removed: in case of MSG_PEEK we just walk
>>      over skbs and copy data from each one. I guess this nested loop
>>      even didn't behave as loop - it always executed just for single
>>      iteration.
>>
>> 2) This adds MSG_PEEK support for SOCK_SEQPACKET. It could be implemented
>>   be reworking MSG_PEEK callback for SOCK_STREAM to support SOCK_SEQPACKET
>>   also, but I think it will be more simple and clear from potential
>>   bugs to implemented it as separate function thus not mixing logics
>>   for both types of socket. So I've added it as dedicated function.
>>
>> 3) This is reworked MSG_PEEK test for SOCK_STREAM. Previous version just
>>   sent single byte, then tried to read it with MSG_PEEK flag, then read
>>   it in normal way. New version is more complex: now sender uses buffer
>>   instead of single byte and this buffer is initialized with random
>>   values. Receiver tests several things:
>>   1) Read empty socket with MSG_PEEK flag.
>>   2) Read part of buffer with MSG_PEEK flag.
>>   3) Read whole buffer with MSG_PEEK flag, then checks that it is same
>>      as buffer from 2) (limited by size of buffer from 2) of course).
>>   4) Read whole buffer without any flags, then checks that is is same
>>      as buffer from 3).
>>
>> 4) This is MSG_PEEK test for SOCK_SEQPACKET. It works in the same way
>>   as for SOCK_STREAM, except it also checks combination of MSG_TRUNC
>>   and MSG_PEEK.
>>
>> Head is:
>> https://git.kernel.org/pub/scm/linux/kernel/git/netdev/net-next.git/commit/?id=d20dd0ea14072e8a90ff864b2c1603bd68920b4b
> 
> Nice cleanup, LGTM, but I'd like a comment from Bobby.

Got it, thanks!

Thanks, Arseniy

> 
> Thanks,
> Stefano
>