netdev - Re: [RFC] net: ipv4 -- Introduce ifa limit per net

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Message-Id: <20160304.231109.1838919633640757059.davem@davemloft.net>
Date:	Fri, 04 Mar 2016 23:11:09 -0500 (EST)
From:	David Miller <davem@...emloft.net>
To:	eric.dumazet@...il.com
Cc:	gorcunov@...il.com, netdev@...r.kernel.org, solar@...nwall.com,
	vvs@...tuozzo.com, avagin@...tuozzo.com, xemul@...tuozzo.com,
	vdavydov@...tuozzo.com, khorenko@...tuozzo.com
Subject: Re: [RFC] net: ipv4 -- Introduce ifa limit per net

From: Eric Dumazet <eric.dumazet@...il.com>
Date: Fri, 04 Mar 2016 16:08:30 -0800

> __inet_del_ifa() should probably take into account in_dev->dead (no
> promotion, no list scan...)

Indeed, that is the real problem:

diff --git a/net/ipv4/devinet.c b/net/ipv4/devinet.c
index 8c3df2c..7412feb 100644
--- a/net/ipv4/devinet.c
+++ b/net/ipv4/devinet.c
@@ -334,6 +334,12 @@ static void __inet_del_ifa(struct in_device *in_dev, struct in_ifaddr **ifap,
 
 	ASSERT_RTNL();
 
+	/* None of these potentially quadratic scans matter if the
+	 * device is being destroyed.
+	 */
+	if (in_dev->dead)
+		goto no_promotions;
+
 	/* 1. Deleting primary ifaddr forces deletion all secondaries
 	 * unless alias promotion is set
 	 **/
@@ -380,6 +386,7 @@ static void __inet_del_ifa(struct in_device *in_dev, struct in_ifaddr **ifap,
 			fib_del_ifaddr(ifa, ifa1);
 	}
 
+no_promotions:
 	/* 2. Unlink it */
 
 	*ifap = ifa1->ifa_next;