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[irda-users] [PATCH] : ir258_irnet_simult_race-2.diff
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From: Jean T. <jt...@bo...> - 2002-04-19 02:34:28
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ir258_irnet_simult_race-2.diff :
------------------------------
o [CORRECT] Prevent dealock on simultaneous peer IrNET connections
Only the primary peer will accept the IrNET connection
--------------------------------------
diff -u -p linux/include/net/irda/irlap.d7.h linux/include/net/irda/irlap.h
--- linux/include/net/irda/irlap.d7.h Wed Apr 10 18:36:27 2002
+++ linux/include/net/irda/irlap.h Wed Apr 10 19:36:28 2002
@@ -31,8 +31,6 @@
#include <linux/types.h>
#include <linux/skbuff.h>
#include <linux/netdevice.h>
-#include <linux/ppp_defs.h>
-#include <linux/ppp-comp.h>
#include <linux/timer.h>
#include <net/irda/irlap_event.h>
@@ -239,5 +237,25 @@ void irlap_apply_connection_parameters(s
#define IRLAP_GET_HEADER_SIZE(self) (LAP_MAX_HEADER)
#define IRLAP_GET_TX_QUEUE_LEN(self) skb_queue_len(&self->txq)
+
+/* Return TRUE if the node is in primary mode (i.e. master)
+ * - Jean II */
+static inline int irlap_is_primary(struct irlap_cb *self)
+{
+ int ret;
+ switch(self->state) {
+ case LAP_XMIT_P:
+ case LAP_NRM_P:
+ ret = 1;
+ break;
+ case LAP_XMIT_S:
+ case LAP_NRM_S:
+ ret = 0;
+ break;
+ default:
+ ret = -1;
+ }
+ return(ret);
+}
#endif
diff -u -p linux/include/net/irda/irttp.d7.h linux/include/net/irda/irttp.h
--- linux/include/net/irda/irttp.d7.h Wed Apr 10 18:45:50 2002
+++ linux/include/net/irda/irttp.h Fri Apr 12 09:57:29 2002
@@ -197,6 +197,18 @@ static inline void irttp_listen(struct t
self->dtsap_sel = LSAP_ANY;
}
+/* Return TRUE if the node is in primary mode (i.e. master)
+ * - Jean II */
+static inline int irttp_is_primary(struct tsap_cb *self)
+{
+ if ((self == NULL) ||
+ (self->lsap == NULL) ||
+ (self->lsap->lap == NULL) ||
+ (self->lsap->lap->irlap == NULL))
+ return -2;
+ return(irlap_is_primary(self->lsap->lap->irlap));
+}
+
extern struct irttp_cb *irttp;
#endif /* IRTTP_H */
diff -u -p linux/net/irda/irnet/irnet.d7.h linux/net/irda/irnet/irnet.h
--- linux/net/irda/irnet/irnet.d7.h Wed Apr 10 18:53:59 2002
+++ linux/net/irda/irnet/irnet.h Fri Apr 12 14:22:36 2002
@@ -217,6 +217,11 @@
* Better fix in irnet_disconnect_indication() :
* - if connected, kill pppd via hangup.
* - if not connected, reenable ppp Tx, which trigger IrNET retry.
+ *
+ * v12 - 10.4.02 - Jean II
+ * o Fix race condition in irnet_connect_indication().
+ * If the socket was already trying to connect, drop old connection
+ * and use new one only if acting as primary. See comments.
*/
/***************************** INCLUDES *****************************/
diff -u -p linux/net/irda/irnet/irnet_irda.d7.c linux/net/irda/irnet/irnet_irda.c
--- linux/net/irda/irnet/irnet_irda.d7.c Wed Apr 10 18:53:52 2002
+++ linux/net/irda/irnet/irnet_irda.c Fri Apr 12 14:20:35 2002
@@ -1340,46 +1340,80 @@ irnet_connect_indication(void * instanc
return;
}
- /* Socket connecting ?
- * Clear up flag : prevent irnet_disconnect_indication() to mess up tsap */
- if(test_and_clear_bit(0, &new->ttp_connect))
- {
- /* The socket is trying to connect to the other end and may have sent
- * a IrTTP connection request and is waiting for a connection response
- * (that may never come).
- * Now, the pain is that the socket may have opened a tsap and is
- * waiting on it, while the other end is trying to connect to it on
- * another tsap.
- */
- DERROR(IRDA_CB_ERROR, "Socket already connecting. Ouch !\n");
+ /* The following code is a bit tricky, so need comments ;-)
+ */
+ /* If ttp_connect is set, the socket is trying to connect to the other
+ * end and may have sent a IrTTP connection request and is waiting for
+ * a connection response (that may never come).
+ * Now, the pain is that the socket may have opened a tsap and is
+ * waiting on it, while the other end is trying to connect to it on
+ * another tsap.
+ * Because IrNET can be peer to peer, we need to workaround this.
+ * Furthermore, the way the irnetd script is implemented, the
+ * target will create a second IrNET connection back to the
+ * originator and expect the originator to bind this new connection
+ * to the original PPPD instance.
+ * And of course, if we don't use irnetd, we can have a race when
+ * both side try to connect simultaneously, which could leave both
+ * connections half closed (yuck).
+ * Conclusions :
+ * 1) The "originator" must accept the new connection and get rid
+ * of the old one so that irnetd works
+ * 2) One side must deny the new connection to avoid races,
+ * but both side must agree on which side it is...
+ * Most often, the originator is primary at the LAP layer.
+ * Jean II
+ */
+ /* Now, let's look at the way I wrote the test...
+ * We need to clear up the ttp_connect flag atomically to prevent
+ * irnet_disconnect_indication() to mess up the tsap we are going to close.
+ * We want to clear the ttp_connect flag only if we close the tsap,
+ * otherwise we will never close it, so we need to check for primary
+ * *before* doing the test on the flag.
+ * And of course, ALLOW_SIMULT_CONNECT can disable this entirely...
+ * Jean II
+ */
+
+ /* Socket already connecting ? On primary ? */
+ if(0
#ifdef ALLOW_SIMULT_CONNECT
- /* Cleanup the TSAP if necessary - IrIAP will be cleaned up later */
+ || ((irttp_is_primary(server->tsap) == 1) /* primary */
+ && (test_and_clear_bit(0, &new->ttp_connect)))
+#endif /* ALLOW_SIMULT_CONNECT */
+ )
+ {
+ DERROR(IRDA_CB_ERROR, "Socket already connecting, but going to reuse it !\n");
+
+ /* Cleanup the old TSAP if necessary - IrIAP will be cleaned up later */
if(new->tsap != NULL)
{
- /* Close the connection the new socket was attempting.
- * This seems to be safe... */
+ /* Close the old connection the new socket was attempting,
+ * so that we can hook it up to the new connection.
+ * It's now safe to do it... */
irttp_close_tsap(new->tsap);
new->tsap = NULL;
}
- /* Note : no return, fall through... */
-#else /* ALLOW_SIMULT_CONNECT */
- irnet_disconnect_server(server, skb);
- return;
-#endif /* ALLOW_SIMULT_CONNECT */
}
else
- /* If socket is not connecting or connected, tsap should be NULL */
- if(new->tsap != NULL)
- {
- /* If we are here, we are also in irnet_disconnect_indication(),
- * and it's a nice race condition... On the other hand, we can't be
- * in irda_irnet_destroy() otherwise we would not have found the
- * socket in the hashbin. */
- /* Better get out of here, otherwise we will mess up tsaps ! */
- DERROR(IRDA_CB_ERROR, "Race condition detected, abort connect...\n");
- irnet_disconnect_server(server, skb);
- return;
- }
+ {
+ /* Three options :
+ * 1) socket was not connecting or connected : ttp_connect should be 0.
+ * 2) we don't want to connect the socket because we are secondary or
+ * ALLOW_SIMULT_CONNECT is undefined. ttp_connect should be 1.
+ * 3) we are half way in irnet_disconnect_indication(), and it's a
+ * nice race condition... Fortunately, we can detect that by checking
+ * if tsap is still alive. On the other hand, we can't be in
+ * irda_irnet_destroy() otherwise we would not have found this
+ * socket in the hashbin.
+ * Jean II */
+ if((test_bit(0, &new->ttp_connect)) || (new->tsap != NULL))
+ {
+ /* Don't mess this socket, somebody else in in charge... */
+ DERROR(IRDA_CB_ERROR, "Race condition detected, socket in use, abort connect...\n");
+ irnet_disconnect_server(server, skb);
+ return;
+ }
+ }
/* So : at this point, we have a socket, and it is idle. Good ! */
irnet_connect_socket(server, new, qos, max_sdu_size, max_header_size);
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