[RFC] btio: Adjust socket buffers to be at least as big as MTU

[Luiz Augusto von Dentz <luiz.dentz@gmail.com>]

From: Luiz Augusto von Dentz <luiz.von.dentz@intel.com>

Maybe could be done in kernel automatically as it could be considered
broken in case of SOCK_SEQPACKET if socket buffer cannot hold a
write/read of MTU size.

This is not actually a new problem as there exist a workaround in
avdtp.c to adjust the socket buffer too, but it became more evident
with introduction of gobex which can use SOCK_SEQPACKET with a
considerable big MTU (up to 64k) which will fail if there is not
enough space to stuff full packets.

---
This adds checks for socket type and only adjust in case of SOCK_SEQPACKET

 btio/btio.c |   57 +++++++++++++++++++++++++++++++++++++++++++++++++++++----
 1 files changed, 53 insertions(+), 4 deletions(-)

diff --git a/btio/btio.c b/btio/btio.c
index 9781ec4..656b7e0 100644
--- a/btio/btio.c
+++ b/btio/btio.c
@@ -119,6 +119,41 @@ static gboolean check_nval(GIOChannel *io)
 	return FALSE;
 }
 
+static void adjust_buffers(GIOChannel *io)
+{
+	int sk = g_io_channel_unix_get_fd(io);
+	int type, omtu = 0, imtu = 0, sndbuf = 0, rcvbuf = 0;
+	socklen_t len = sizeof(int);
+
+	if (getsockopt(sk, SOL_SOCKET, SO_TYPE, &type, &len) < 0)
+		return;
+
+	if (type != SOCK_SEQPACKET)
+		return;
+
+	/* Checks if it is L2CAP socket otherwise ignores */
+	if (!bt_io_get(io, BT_IO_L2CAP, NULL, BT_IO_OPT_OMTU, &omtu,
+						BT_IO_OPT_IMTU, &imtu,
+						BT_IO_OPT_INVALID))
+		return;
+
+	if (getsockopt(sk, SOL_SOCKET, SO_SNDBUF, &sndbuf, &len) < 0)
+		return;
+
+	if (sndbuf < omtu) {
+		sndbuf = omtu;
+		setsockopt(sk, SOL_SOCKET, SO_SNDBUF, &sndbuf, len);
+	}
+
+	if (getsockopt(sk, SOL_SOCKET, SO_RCVBUF, &rcvbuf, &len) < 0)
+		return;
+
+	if (rcvbuf < imtu) {
+		rcvbuf = imtu;
+		setsockopt(sk, SOL_SOCKET, SO_RCVBUF, &rcvbuf, len);
+	}
+}
+
 static gboolean accept_cb(GIOChannel *io, GIOCondition cond,
 							gpointer user_data)
 {
@@ -129,10 +164,15 @@ static gboolean accept_cb(GIOChannel *io, GIOCondition cond,
 	if ((cond & G_IO_NVAL) || check_nval(io))
 		return FALSE;
 
-	if (cond & (G_IO_HUP | G_IO_ERR))
+	if (cond & (G_IO_HUP | G_IO_ERR)) {
 		g_set_error(&err, BT_IO_ERROR, BT_IO_ERROR_DISCONNECTED,
 				"HUP or ERR on socket");
+		goto done;
+	}
 
+	adjust_buffers(io);
+
+done:
 	accept->connect(io, err, accept->user_data);
 
 	g_clear_error(&err);
@@ -159,14 +199,21 @@ static gboolean connect_cb(GIOChannel *io, GIOCondition cond,
 		else
 			err = -sk_err;
 
-		if (err < 0)
+		if (err < 0) {
 			g_set_error(&gerr, BT_IO_ERROR,
 					BT_IO_ERROR_CONNECT_FAILED, "%s (%d)",
 					strerror(-err), -err);
-	} else if (cond & (G_IO_HUP | G_IO_ERR))
+			goto done;
+		}
+	} else if (cond & (G_IO_HUP | G_IO_ERR)) {
 		g_set_error(&gerr, BT_IO_ERROR, BT_IO_ERROR_CONNECT_FAILED,
 				"HUP or ERR on socket");
+		goto done;
+	}
+
+	adjust_buffers(io);
 
+done:
 	conn->connect(io, gerr, conn->user_data);
 
 	if (gerr)
@@ -199,8 +246,10 @@ static gboolean server_cb(GIOChannel *io, GIOCondition cond,
 
 	if (server->confirm)
 		server->confirm(cli_io, server->user_data);
-	else
+	else {
+		adjust_buffers(cli_io);
 		server->connect(cli_io, NULL, server->user_data);
+	}
 
 	g_io_channel_unref(cli_io);
 
-- 
1.7.7.6