From 6da025fa23bb10c82f80de319c837ed2b02306e4 Mon Sep 17 00:00:00 2001
From: Eric Dumazet <edumazet@google.com>
Date: Sun, 28 Oct 2012 22:33:23 +0000
Subject: [PATCH] ipv4: avoid a test in ip_rt_put()
We can save a test in ip_rt_put(), considering dst_release() accepts
a NULL parameter, and dst is first element in rtable.
Add a BUILD_BUG_ON() to catch any change that could break this
assertion.
Signed-off-by: Eric Dumazet <edumazet@google.com>
Cc: Cong Wang <amwang@redhat.com>
Acked-by: Cong Wang <amwang@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
---
include/net/route.h | 9 ++++++---
1 file changed, 6 insertions(+), 3 deletions(-)
diff --git a/include/net/route.h b/include/net/route.h
index bc40b633a5c4..2ea40c1b5e00 100644
--- a/include/net/route.h
+++ b/include/net/route.h
@@ -198,10 +198,13 @@ struct in_ifaddr;
extern void fib_add_ifaddr(struct in_ifaddr *);
extern void fib_del_ifaddr(struct in_ifaddr *, struct in_ifaddr *);
-static inline void ip_rt_put(struct rtable * rt)
+static inline void ip_rt_put(struct rtable *rt)
{
- if (rt)
- dst_release(&rt->dst);
+ /* dst_release() accepts a NULL parameter.
+ * We rely on dst being first structure in struct rtable
+ */
+ BUILD_BUG_ON(offsetof(struct rtable, dst) != 0);
+ dst_release(&rt->dst);
}
#define IPTOS_RT_MASK (IPTOS_TOS_MASK & ~3)
--
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