RDMA/cma: Increment port number after close to avoid re-use

Randomize the starting port number and avoid re-using port values
immediately after they are closed.  Instead keep track of the last
port value used and increment it every time a new port number is
assigned, to better replicate other port spaces.

Signed-off-by: Roland Dreier <rolandd@cisco.com>

1 files changed, 56 insertions, 10 deletions

diff --git a/drivers/infiniband/core/cma.c b/drivers/infiniband/core/cma.c
index 9e0ab048c878..bc31b54e9cac 100644
--- a/drivers/infiniband/core/cma.c
+++ b/drivers/infiniband/core/cma.c
@@ -71,6 +71,7 @@ static struct workqueue_struct *cma_wq;
 static DEFINE_IDR(sdp_ps);
 static DEFINE_IDR(tcp_ps);
 static DEFINE_IDR(udp_ps);
+static int next_port;
 
 struct cma_device {
         struct list_head        list;
@@ -1722,33 +1723,74 @@ static int cma_alloc_port(struct idr *ps, struct rdma_id_private *id_priv,
                           unsigned short snum)
 {
         struct rdma_bind_list *bind_list;
-        int port, start, ret;
+        int port, ret;
 
         bind_list = kzalloc(sizeof *bind_list, GFP_KERNEL);
         if (!bind_list)
                 return -ENOMEM;
 
-        start = snum ? snum : sysctl_local_port_range[0];
+        do {
+                ret = idr_get_new_above(ps, bind_list, snum, &port);
+        } while ((ret == -EAGAIN) && idr_pre_get(ps, GFP_KERNEL));
+
+        if (ret)
+                goto err1;
+
+        if (port != snum) {
+                ret = -EADDRNOTAVAIL;
+                goto err2;
+        }
+
+        bind_list->ps = ps;
+        bind_list->port = (unsigned short) port;
+        cma_bind_port(bind_list, id_priv);
+        return 0;
+err2:
+        idr_remove(ps, port);
+err1:
+        kfree(bind_list);
+        return ret;
+}
 
+static int cma_alloc_any_port(struct idr *ps, struct rdma_id_private *id_priv)
+{
+        struct rdma_bind_list *bind_list;
+        int port, ret;
+
+        bind_list = kzalloc(sizeof *bind_list, GFP_KERNEL);
+        if (!bind_list)
+                return -ENOMEM;
+
+retry:
         do {
-                ret = idr_get_new_above(ps, bind_list, start, &port);
+                ret = idr_get_new_above(ps, bind_list, next_port, &port);
         } while ((ret == -EAGAIN) && idr_pre_get(ps, GFP_KERNEL));
 
         if (ret)
-                goto err;
+                goto err1;
 
-        if ((snum && port != snum) ||
-            (!snum && port > sysctl_local_port_range[1])) {
-                idr_remove(ps, port);
+        if (port > sysctl_local_port_range[1]) {
+                if (next_port != sysctl_local_port_range[0]) {
+                        idr_remove(ps, port);
+                        next_port = sysctl_local_port_range[0];
+                        goto retry;
+                }
                 ret = -EADDRNOTAVAIL;
-                goto err;
+                goto err2;
         }
 
+        if (port == sysctl_local_port_range[1])
+                next_port = sysctl_local_port_range[0];
+        else
+                next_port = port + 1;
+
         bind_list->ps = ps;
         bind_list->port = (unsigned short) port;
         cma_bind_port(bind_list, id_priv);
         return 0;
-err:
+err2:
+        idr_remove(ps, port);
+err1:
         kfree(bind_list);
         return ret;
 }
@@ -1811,7 +1853,7 @@ static int cma_get_port(struct rdma_id_private *id_priv)
 
         mutex_lock(&lock);
         if (cma_any_port(&id_priv->id.route.addr.src_addr))
-                ret = cma_alloc_port(ps, id_priv, 0);
+                ret = cma_alloc_any_port(ps, id_priv);
         else
                 ret = cma_use_port(ps, id_priv);
         mutex_unlock(&lock);
@@ -2448,6 +2490,10 @@ static int cma_init(void)
 {
         int ret;
 
+        get_random_bytes(&next_port, sizeof next_port);
+        next_port = (next_port % (sysctl_local_port_range[1] -
+                                  sysctl_local_port_range[0])) +
+                    sysctl_local_port_range[0];
         cma_wq = create_singlethread_workqueue("rdma_cm_wq");
         if (!cma_wq)
                 return -ENOMEM;