[PATCH 0/1] AVDTP SRC stream send buffer size verification

[PATCH 0/1] AVDTP SRC stream send buffer size verification

[Dmitriy Paliy]

Hi,

In this patch, send buffer size for L2CAP socket is verified against
outgoing L2CAP MTU size and increased to be twice of it if it is less
than that. Such verification is done for AVDTP source transport channel
only.

Reason to do this check is that system default socket buffer size was
reduced in Meego and it affected IOP with some car-kits that use large
MTUs.

Worth to mention that send buffer size is never decreased, and can be
increased only.

BR,
Dmitriy

[PATCH] Add AVDTP SRC stream send buffer size verification

[Dmitriy Paliy]

Functions get_send_buffer_size and set_send_buffer_size are added to
avdpt.c.

get_send_buffer_size returns size of send buffer for a given socket
on success or error code on failure. set_send_buffer_size sets size
of send buffer for a given socket, and returns 0 on success or error
code on failure.

Size of send buffer for L2CAP socket for SRC AVDTP stream is verified
during establishment of a new transport channel. If the size is less
than twice of outgoing L2CAP MTU, then it is considered as being
insufficient to handle streaming data reliably.

In this case buffer size is increased to be twice of MTU size. Such
fixes some IOP problems with car-kits that use large MTU for music
playback.
---
 audio/avdtp.c |   53 +++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 files changed, 53 insertions(+), 0 deletions(-)

diff --git a/audio/avdtp.c b/audio/avdtp.c
index 1683e7c..34b95fd 100644
--- a/audio/avdtp.c
+++ b/audio/avdtp.c
@@ -838,6 +838,40 @@ static gboolean transport_cb(GIOChannel *chan, GIOCondition cond,
 	return FALSE;
 }
 
+static int get_send_buffer_size(int sk)
+{
+	int size;
+	socklen_t optlen = sizeof(size);
+
+	if (getsockopt(sk, SOL_SOCKET, SO_SNDBUF, &size, &optlen) < 0) {
+		int err = -errno;
+		error("getsockopt(SO_SNDBUF) failed: %s (%d)", strerror(-err),
+									-err);
+		return err;
+	}
+
+	/*
+	 * Doubled value is returned by getsockopt since kernel uses that
+	 * space for its own purposes (see man 7 socket, bookkeeping overhead
+	 * for SO_SNDBUF).
+	 */
+	return size / 2;
+}
+
+static int set_send_buffer_size(int sk, int size)
+{
+	socklen_t optlen = sizeof(size);
+
+	if (setsockopt(sk, SOL_SOCKET, SO_SNDBUF, &size, optlen) < 0) {
+		int err = -errno;
+		error("setsockopt(SO_SNDBUF) failed: %s (%d)", strerror(-err),
+									-err);
+		return err;
+	}
+
+	return 0;
+}
+
 static void handle_transport_connect(struct avdtp *session, GIOChannel *io,
 					uint16_t imtu, uint16_t omtu)
 {
@@ -865,6 +899,25 @@ static void handle_transport_connect(struct avdtp *session, GIOChannel *io,
 	stream->omtu = omtu;
 	stream->imtu = imtu;
 
+	/* only if local SEP is of type SRC */
+	if (sep->info.type == AVDTP_SEP_TYPE_SOURCE) {
+		int sk, buf_size, min_buf_size;
+
+		sk = g_io_channel_unix_get_fd(stream->io);
+		buf_size = get_send_buffer_size(sk);
+		if (buf_size < 0)
+			goto proceed;
+
+		DBG("sk %d, omtu %d, send buffer size %d", sk, omtu, buf_size);
+		min_buf_size = omtu * 2;
+		if (buf_size < min_buf_size) {
+			DBG("send buffer size to be increassed to %d",
+								min_buf_size);
+			set_send_buffer_size(sk, min_buf_size);
+		}
+	}
+
+proceed:
 	if (!stream->open_acp && sep->cfm && sep->cfm->open)
 		sep->cfm->open(session, sep, stream, NULL, sep->user_data);
 
-- 
1.7.0.4

Re: [PATCH] Add AVDTP SRC stream send buffer size verification

[Johan Hedberg]

Hi Dmitriy,

On Wed, Dec 15, 2010, Dmitriy Paliy wrote:
> Functions get_send_buffer_size and set_send_buffer_size are added to
> avdpt.c.
> 
> get_send_buffer_size returns size of send buffer for a given socket
> on success or error code on failure. set_send_buffer_size sets size
> of send buffer for a given socket, and returns 0 on success or error
> code on failure.
> 
> Size of send buffer for L2CAP socket for SRC AVDTP stream is verified
> during establishment of a new transport channel. If the size is less
> than twice of outgoing L2CAP MTU, then it is considered as being
> insufficient to handle streaming data reliably.
> 
> In this case buffer size is increased to be twice of MTU size. Such
> fixes some IOP problems with car-kits that use large MTU for music
> playback.
> ---
>  audio/avdtp.c |   53 +++++++++++++++++++++++++++++++++++++++++++++++++++++
>  1 files changed, 53 insertions(+), 0 deletions(-)

Thanks. The patch has been pushed upstream.

Johan