Return-Path: From: Szymon Janc To: Lukasz Rymanowski Cc: linux-bluetooth@vger.kernel.org Subject: Re: [PATCH v2 1/2] android/gatt: Fix initial setting of MTU Date: Tue, 03 Feb 2015 12:45:49 +0100 Message-ID: <1432325.UU2MSNSUEs@uw000953> In-Reply-To: <1422564649-32210-1-git-send-email-lukasz.rymanowski@tieto.com> References: <1422564649-32210-1-git-send-email-lukasz.rymanowski@tieto.com> MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Sender: linux-bluetooth-owner@vger.kernel.org List-ID: Hi Łukasz, On Thursday 29 of January 2015 21:50:48 Lukasz Rymanowski wrote: > Initial setting of MTU should be IMTU. This is actually our assumption > in other part of code, that IMTU is something we start with and change > if needed after exchange MTU procedure. > > If we are not able to get IMTU from the socket just disconnect, there is > something wrong going on. > > Without this patch you can face the issue with following scenario: > 1. On connection complete MTU is set to 23 > 2. BfA sends Exchange MTU Request with MTU set to IMTU > 3. Remote device response with MTU equal to what BfA sends > 4. In that case, since remote MTU is equal to ours, there is no > update in bt_att, so bt_att keep using MTU = 23 > 5. Remote sends packets highier then 23 and bt_att start to drop not > complete packets. > > Issue found and fix tested on UPF50 > --- > v2: Use local GError instead the one provided as a function parameter > > android/gatt.c | 12 +++++++++--- > 1 file changed, 9 insertions(+), 3 deletions(-) > > diff --git a/android/gatt.c b/android/gatt.c > index 466c1ea..23ffb9e 100644 > --- a/android/gatt.c > +++ b/android/gatt.c > @@ -1488,6 +1488,7 @@ static void connect_cb(GIOChannel *io, GError *gerr, gpointer user_data) > struct connect_data data; > struct att_range range; > uint32_t status; > + GError *err = NULL; > GAttrib *attrib; > uint16_t mtu; > uint16_t cid; > @@ -1510,9 +1511,14 @@ static void connect_cb(GIOChannel *io, GError *gerr, gpointer user_data) > goto reply; > } > > - if (!bt_io_get(io, &gerr, BT_IO_OPT_IMTU, &mtu, BT_IO_OPT_CID, &cid, > - BT_IO_OPT_INVALID) || cid == ATT_CID) > - mtu = ATT_DEFAULT_LE_MTU; > + if (!bt_io_get(io, &err, BT_IO_OPT_IMTU, &mtu, BT_IO_OPT_CID, &cid, > + BT_IO_OPT_INVALID)) { > + error("gatt: Could not get imtu: %s", err->message); > + device_set_state(dev, DEVICE_DISCONNECTED); > + status = GATT_FAILURE; > + g_error_free(err); > + goto reply; > + } > > attrib = g_attrib_new(io, mtu); > if (!attrib) { > Both patches applied, thanks. -- Best regards, Szymon Janc