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[Bluetooth] Correct RFCOMM channel MTU for broken implementations 

Some Bluetooth RFCOMM implementations try to negotiate a bigger channel
MTU than we can support for a particular session. The maximum MTU for
a RFCOMM session is limited through the L2CAP layer. So if the other
side proposes a channel MTU that is bigger than the underlying L2CAP
MTU, we should reduce it to the L2CAP MTU of the session minus five
bytes for the RFCOMM headers.

Signed-off-by: Marcel Holtmann <marcel@holtmann.org>
This commit is contained in:
Marcel Holtmann 2006-07-14 11:42:12 +02:00 committed by David S. Miller
parent 2266d8886f
commit 98bcd08b5b
1 changed files with 17 additions and 2 deletions
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19
net/bluetooth/rfcomm/core.c
View File

@ -55,6 +55,7 @@
#define VERSION "1.8"
static int disable_cfc = 0;
static int channel_mtu = -1;
static unsigned int l2cap_mtu = RFCOMM_MAX_L2CAP_MTU;
static struct task_struct *rfcomm_thread;
@ -812,7 +813,10 @@ static int rfcomm_send_pn(struct rfcomm_session *s, int cr, struct rfcomm_dlc *d
pn->credits = 0;
}
pn->mtu = htobs(d->mtu);
if (cr && channel_mtu >= 0)
pn->mtu = htobs(channel_mtu);
else
pn->mtu = htobs(d->mtu);
*ptr = __fcs(buf); ptr++;
@ -1243,7 +1247,10 @@ static int rfcomm_apply_pn(struct rfcomm_dlc *d, int cr, struct rfcomm_pn *pn)
d->priority = pn->priority;
d->mtu = s->mtu = btohs(pn->mtu);
d->mtu = btohs(pn->mtu);
if (cr && d->mtu > s->mtu)
d->mtu = s->mtu;
return 0;
}
@ -1770,6 +1777,11 @@ static inline void rfcomm_accept_connection(struct rfcomm_session *s)
s = rfcomm_session_add(nsock, BT_OPEN);
if (s) {
rfcomm_session_hold(s);
/* We should adjust MTU on incoming sessions.
* L2CAP MTU minus UIH header and FCS. */
s->mtu = min(l2cap_pi(nsock->sk)->omtu, l2cap_pi(nsock->sk)->imtu) - 5;
rfcomm_schedule(RFCOMM_SCHED_RX);
} else
sock_release(nsock);
@ -2087,6 +2099,9 @@ module_exit(rfcomm_exit);
module_param(disable_cfc, bool, 0644);
MODULE_PARM_DESC(disable_cfc, "Disable credit based flow control");
module_param(channel_mtu, int, 0644);
MODULE_PARM_DESC(channel_mtu, "Default MTU for the RFCOMM channel");
module_param(l2cap_mtu, uint, 0644);
MODULE_PARM_DESC(l2cap_mtu, "Default MTU for the L2CAP connection");