Linux Kernels

ipv4: Calling ->cow_metrics() now is a bug.

This change “ipv4: Calling ->cow_metrics() now is a bug.” (commit 3124873) in Linux kernel is authored by David S. Miller <davem [at] davemloft.net> on Tue Jul 10 07:08:18 2012 -0700.

Description of "ipv4: Calling ->cow_metrics() now is a bug."

The change “ipv4: Calling →cow_metrics() now is a bug.” introduces changes as follows.

ipv4: Calling ->cow_metrics() now is a bug.

Nothing every writes to ipv4 metrics any longer.

PMTU is stored in rt->rt_pmtu.

Dynamic TCP metrics are stored in a special TCP metrics cache,
completely outside of the routes.

Therefore ->cow_metrics() can simply nothing more than a WARN_ON
trigger so we can catch anyone who tries to add new writes to
ipv4 route metrics.

Signed-off-by: David S. Miller <davem@davemloft.net>

Linux kernel releases containing commit 3124873

The Linux kernel releases containing this commit are as follows.

Linux kernel code changes from "ipv4: Calling ->cow_metrics() now is a bug."

There are 30 lines of Linux source code added/deleted in this change. Code changes to Linux kernel are as follows.

 net/ipv4/route.c | 30 ++----------------------------
 1 file changed, 2 insertions(+), 28 deletions(-)
 
diff --git a/net/ipv4/route.c b/net/ipv4/route.c
index a967df54a423..9cc00f8a6ee5 100644
--- a/net/ipv4/route.c
+++ b/net/ipv4/route.c
@@ -158,34 +158,8 @@ static void ipv4_dst_ifdown(struct dst_entry *dst, struct net_device *dev,
 
 static u32 *ipv4_cow_metrics(struct dst_entry *dst, unsigned long old)
 {
-	struct rtable *rt = (struct rtable *) dst;
-	struct inet_peer *peer;
-	u32 *p = NULL;
-
-	peer = rt_get_peer_create(rt, rt->rt_dst);
-	if (peer) {
-		u32 *old_p = __DST_METRICS_PTR(old);
-		unsigned long prev, new;
-
-		p = peer->metrics;
-		if (inet_metrics_new(peer))
-			memcpy(p, old_p, sizeof(u32) * RTAX_MAX);
-
-		new = (unsigned long) p;
-		prev = cmpxchg(&dst->_metrics, old, new);
-
-		if (prev != old) {
-			p = __DST_METRICS_PTR(prev);
-			if (prev & DST_METRICS_READ_ONLY)
-				p = NULL;
-		} else {
-			if (rt->fi) {
-				fib_info_put(rt->fi);
-				rt->fi = NULL;
-			}
-		}
-	}
-	return p;
+	WARN_ON(1);
+	return NULL;
 }
 
 static struct neighbour *ipv4_neigh_lookup(const struct dst_entry *dst,

The commit for this change in Linux stable tree is 3124873 (patch).

Last modified: 2020/01/11 09:38