IB/cm: Randomize starting comm ID

Randomize the starting local comm ID to avoid getting a rejected
connection due to a stale connection after a system reboot or
reloading of the ib_cm.

Signed-off-by: Sean Hefty <sean.hefty@intel.com>
Signed-off-by: Roland Dreier <rolandd@cisco.com>

1 files changed, 16 insertions, 8 deletions

diff --git a/drivers/infiniband/core/cm.c b/drivers/infiniband/core/cm.c
index 1aad33e03528..c8982b02d9b6 100644
--- a/drivers/infiniband/core/cm.c
+++ b/drivers/infiniband/core/cm.c
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2004, 2005 Intel Corporation.  All rights reserved.
+ * Copyright (c) 2004-2006 Intel Corporation.  All rights reserved.
  * Copyright (c) 2004 Topspin Corporation.  All rights reserved.
  * Copyright (c) 2004, 2005 Voltaire Corporation.  All rights reserved.
  * Copyright (c) 2005 Sun Microsystems, Inc. All rights reserved.
@@ -41,6 +41,7 @@
 #include <linux/idr.h>
 #include <linux/interrupt.h>
 #include <linux/pci.h>
+#include <linux/random.h>
 #include <linux/rbtree.h>
 #include <linux/spinlock.h>
 #include <linux/workqueue.h>
@@ -73,6 +74,7 @@ static struct ib_cm {
         struct rb_root remote_id_table;
         struct rb_root remote_sidr_table;
         struct idr local_id_table;
+        __be32 random_id_operand;
         struct workqueue_struct *wq;
 } cm;
 
@@ -299,15 +301,17 @@ static int cm_init_av_by_path(struct ib_sa_path_rec *path, struct cm_av *av)
 static int cm_alloc_id(struct cm_id_private *cm_id_priv)
 {
         unsigned long flags;
-        int ret;
+        int ret, id;
         static int next_id;
 
         do {
                 spin_lock_irqsave(&cm.lock, flags);
-                ret = idr_get_new_above(&cm.local_id_table, cm_id_priv, next_id++,
-                                        (__force int *) &cm_id_priv->id.local_id);
+                ret = idr_get_new_above(&cm.local_id_table, cm_id_priv,
+                                        next_id++, &id);
                 spin_unlock_irqrestore(&cm.lock, flags);
         } while( (ret == -EAGAIN) && idr_pre_get(&cm.local_id_table, GFP_KERNEL) );
+
+        cm_id_priv->id.local_id = (__force __be32) (id ^ cm.random_id_operand);
         return ret;
 }
 
@@ -316,7 +320,8 @@ static void cm_free_id(__be32 local_id)
         unsigned long flags;
 
         spin_lock_irqsave(&cm.lock, flags);
-        idr_remove(&cm.local_id_table, (__force int) local_id);
+        idr_remove(&cm.local_id_table,
+                   (__force int) (local_id ^ cm.random_id_operand));
         spin_unlock_irqrestore(&cm.lock, flags);
 }
 
@@ -324,7 +329,8 @@ static struct cm_id_private * cm_get_id(__be32 local_id, __be32 remote_id)
 {
         struct cm_id_private *cm_id_priv;
 
-        cm_id_priv = idr_find(&cm.local_id_table, (__force int) local_id);
+        cm_id_priv = idr_find(&cm.local_id_table,
+                              (__force int) (local_id ^ cm.random_id_operand));
         if (cm_id_priv) {
                 if (cm_id_priv->id.remote_id == remote_id)
                         atomic_inc(&cm_id_priv->refcount);
@@ -2082,8 +2088,9 @@ static struct cm_id_private * cm_acquire_rejected_id(struct cm_rej_msg *rej_msg)
                         spin_unlock_irqrestore(&cm.lock, flags);
                         return NULL;
                 }
-                cm_id_priv = idr_find(&cm.local_id_table,
-                                      (__force int) timewait_info->work.local_id);
+                cm_id_priv = idr_find(&cm.local_id_table, (__force int)
+                                      (timewait_info->work.local_id ^
+                                       cm.random_id_operand));
                 if (cm_id_priv) {
                         if (cm_id_priv->id.remote_id == remote_id)
                                 atomic_inc(&cm_id_priv->refcount);
@@ -3360,6 +3367,7 @@ static int __init ib_cm_init(void)
         cm.remote_qp_table = RB_ROOT;
         cm.remote_sidr_table = RB_ROOT;
         idr_init(&cm.local_id_table);
+        get_random_bytes(&cm.random_id_operand, sizeof cm.random_id_operand);
         idr_pre_get(&cm.local_id_table, GFP_KERNEL);
 
         cm.wq = create_workqueue("ib_cm");