linux-kernel - [PATCH] Infiniband: Randomize local port allocation.

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Message-Id: <201004140201.o3E21Aqn075978@www262.sakura.ne.jp>
Date:	Wed, 14 Apr 2010 11:01:10 +0900
From:	penguin-kernel@...ove.sakura.ne.jp
To:	rolandd@...co.com, sean.hefty@...el.com
Cc:	amwang@...hat.com, opurdila@...acom.com, eric.dumazet@...il.com,
	netdev@...r.kernel.org, nhorman@...driver.com, davem@...emloft.net,
	ebiederm@...ssion.com, linux-kernel@...r.kernel.org
Subject: [PATCH] Infiniband: Randomize local port allocation.

Sean Hefty wrote:
> Sean and Roland, is below patch correct?
> >inet_is_reserved_local_port() is the new function proposed in this patchset.
> 
> It looks correct to me.  I didn't test the patch series, but if I comment out
> the call to inet_is_reserved_local_port() in the provided below, the changes
> worked fine for me.
> 
> Acked-by: Sean Hefty <sean.hefty@...el.com>
> 
Thank you for testing.

I think it is better to split this patch into

Part 1: Make cma_alloc_any_port() to use cma_alloc_port().

Part 2: Insert "!inet_is_reserved_local_port(rover) &&" line.

for future "git bisect".

Roland, will you review below patch for part 1?
--------------------
[PATCH] Infiniband: Randomize local port allocation.

Randomize local port allocation in a way sctp_get_port_local() does.

Signed-off-by: Tetsuo Handa <penguin-kernel@...ove.SAKURA.ne.jp>
---
 drivers/infiniband/core/cma.c |   69 ++++++++++++++----------------------------
 1 file changed, 24 insertions(+), 45 deletions(-)

--- linux-2.6.34-rc4.orig/drivers/infiniband/core/cma.c
+++ linux-2.6.34-rc4/drivers/infiniband/core/cma.c
@@ -79,7 +79,6 @@ static DEFINE_IDR(sdp_ps);
 static DEFINE_IDR(tcp_ps);
 static DEFINE_IDR(udp_ps);
 static DEFINE_IDR(ipoib_ps);
-static int next_port;
 
 struct cma_device {
 	struct list_head	list;
@@ -1970,47 +1969,32 @@ err1:
 
 static int cma_alloc_any_port(struct idr *ps, struct rdma_id_private *id_priv)
 {
-	struct rdma_bind_list *bind_list;
-	int port, ret, low, high;
-
-	bind_list = kzalloc(sizeof *bind_list, GFP_KERNEL);
-	if (!bind_list)
-		return -ENOMEM;
-
-retry:
-	/* FIXME: add proper port randomization per like inet_csk_get_port */
-	do {
-		ret = idr_get_new_above(ps, bind_list, next_port, &port);
-	} while ((ret == -EAGAIN) && idr_pre_get(ps, GFP_KERNEL));
-
-	if (ret)
-		goto err1;
+	static unsigned int last_used_port;
+	int low, high, remaining;
+	unsigned int rover;
 
 	inet_get_local_port_range(&low, &high);
-	if (port > high) {
-		if (next_port != low) {
-			idr_remove(ps, port);
-			next_port = low;
-			goto retry;
+	remaining = (high - low) + 1;
+	rover = net_random() % remaining + low;
+	do {
+		rover++;
+		if ((rover < low) || (rover > high))
+			rover = low;
+		if (last_used_port != rover &&
+		    !idr_find(ps, (unsigned short) rover)) {
+			int ret = cma_alloc_port(ps, id_priv, rover);
+			/*
+			 * Remember previously used port number in order to
+			 * avoid re-using same port immediately after it is
+			 * closed.
+			 */
+			if (!ret)
+				last_used_port = rover;
+			if (ret != -EADDRNOTAVAIL)
+				return ret;
 		}
-		ret = -EADDRNOTAVAIL;
-		goto err2;
-	}
-
-	if (port == high)
-		next_port = low;
-	else
-		next_port = port + 1;
-
-	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;
+	} while (--remaining > 0);
+	return -EADDRNOTAVAIL;
 }
 
 static int cma_use_port(struct idr *ps, struct rdma_id_private *id_priv)
@@ -2995,12 +2979,7 @@ static void cma_remove_one(struct ib_dev
 
 static int __init cma_init(void)
 {
-	int ret, low, high, remaining;
-
-	get_random_bytes(&next_port, sizeof next_port);
-	inet_get_local_port_range(&low, &high);
-	remaining = (high - low) + 1;
-	next_port = ((unsigned int) next_port % remaining) + low;
+	int ret;
 
 	cma_wq = create_singlethread_workqueue("rdma_cm");
 	if (!cma_wq)
--
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