ATT_MTU_RESP shall send the original MTU value prior to the exchange. If
client sends an invalid value, the server shall use the ATT_DEFAULT_LE_MTU
value. This operation is not supported in BR/EDR, so if any client sends
this request it will be ignored by server and it will reply with
"Request not supported".
For BR/EDR, the MTU is limited to ATT_MAX_MTU (currently 256). This
avoids allocating a big buffer when most ATT PDUs are small.
Note: the kernel currently limits the minimum MTU to 48, regardless of
transport type. This limit is valid only for BR/EDR, for LE the minimum
is 23. This bug will be fixed, but it does not affect the outgoing MTU
for new created LE sockets, which are correctly set to 23.
---
src/attrib-server.c | 23 +++++++++++++++++++----
1 files changed, 19 insertions(+), 4 deletions(-)
diff --git a/src/attrib-server.c b/src/attrib-server.c
index 61db851..cc4b601 100644
--- a/src/attrib-server.c
+++ b/src/attrib-server.c
@@ -59,6 +59,7 @@ struct gatt_channel {
GSList *indicate;
GAttrib *attrib;
guint mtu;
+ gboolean le;
guint id;
gboolean encrypted;
};
@@ -759,9 +760,14 @@ static uint16_t write_value(struct gatt_channel *channel, uint16_t handle,
static uint16_t mtu_exchange(struct gatt_channel *channel, uint16_t mtu,
uint8_t *pdu, int len)
{
- channel->mtu = MIN(mtu, channel->mtu);
+ guint old_mtu = channel->mtu;
- return enc_mtu_resp(channel->mtu, pdu, len);
+ if (mtu < ATT_DEFAULT_LE_MTU)
+ channel->mtu = ATT_DEFAULT_LE_MTU;
+ else
+ channel->mtu = MIN(mtu, channel->mtu);
+
+ return enc_mtu_resp(old_mtu, pdu, len);
}
static void channel_disconnect(void *user_data)
@@ -831,6 +837,11 @@ static void channel_handler(const uint8_t *ipdu, uint16_t len,
length = read_blob(channel, start, offset, opdu, channel->mtu);
break;
case ATT_OP_MTU_REQ:
+ if (!channel->le) {
+ status = ATT_ECODE_REQ_NOT_SUPP;
+ goto done;
+ }
+
length = dec_mtu_req(ipdu, len, &mtu);
if (length == 0) {
status = ATT_ECODE_INVALID_PDU;
@@ -913,6 +924,7 @@ static void connect_event(GIOChannel *io, GError *err, void *user_data)
BT_IO_OPT_SOURCE_BDADDR, &channel->src,
BT_IO_OPT_DEST_BDADDR, &channel->dst,
BT_IO_OPT_CID, &cid,
+ BT_IO_OPT_OMTU, &channel->mtu,
BT_IO_OPT_INVALID);
if (gerr) {
error("bt_io_get: %s", gerr->message);
@@ -922,10 +934,13 @@ static void connect_event(GIOChannel *io, GError *err, void *user_data)
return;
}
+ if (channel->mtu > ATT_MAX_MTU)
+ channel->mtu = ATT_MAX_MTU;
+
if (cid != GATT_CID)
- channel->mtu = ATT_DEFAULT_L2CAP_MTU;
+ channel->le = FALSE;
else
- channel->mtu = ATT_DEFAULT_LE_MTU;
+ channel->le = TRUE;
channel->attrib = g_attrib_new(io);
g_io_channel_unref(io);
--
1.7.0.4
--
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