ipv4: Don't pre-seed hoplimit metric.

Always go through a new ip4_dst_hoplimit() helper, just like ipv6.

This allowed several simplifications:

1) The interim dst_metric_hoplimit() can go as it's no longer
   userd.

2) The sysctl_ip_default_ttl entry no longer needs to use
   ipv4_doint_and_flush, since the sysctl is not cached in
   routing cache metrics any longer.

3) ipv4_doint_and_flush no longer needs to be exported and
   therefore can be marked static.

When ipv4_doint_and_flush_strategy was removed some time ago,
the external declaration in ip.h was mistakenly left around
so kill that off too.

We have to move the sysctl_ip_default_ttl declaration into
ipv4's route cache definition header net/route.h, because
currently net/ip.h (where the declaration lives now) has
a back dependency on net/route.h

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

include/net/dst.h

@@ -116,12 +116,6 @@ dst_metric(const struct dst_entry *dst, const int metric)
 	return dst_metric_raw(dst, metric);
 }
 
-static inline u32
-dst_metric_hoplimit(const struct dst_entry *dst)
-{
-	return dst_metric_raw(dst, RTAX_HOPLIMIT);
-}
-
 static inline void dst_metric_set(struct dst_entry *dst, int metric, u32 val)
 {
 	dst->_metrics[metric-1] = val;

include/net/ip.h

@@ -201,7 +201,6 @@ static inline int inet_is_reserved_local_port(int port)
 	return test_bit(port, sysctl_local_reserved_ports);
 }
 
-extern int sysctl_ip_default_ttl;
 extern int sysctl_ip_nonlocal_bind;
 
 extern struct ctl_path net_core_path[];
@@ -428,15 +427,6 @@ extern void	ip_icmp_error(struct sock *sk, struct sk_buff *skb, int err,
 extern void	ip_local_error(struct sock *sk, int err, __be32 daddr, __be16 dport,
 			       u32 info);
 
-/* sysctl helpers - any sysctl which holds a value that ends up being
- * fed into the routing cache should use these handlers.
- */
-int ipv4_doint_and_flush(ctl_table *ctl, int write,
-			 void __user *buffer,
-			 size_t *lenp, loff_t *ppos);
-int ipv4_doint_and_flush_strategy(ctl_table *table,
-				  void __user *oldval, size_t __user *oldlenp,
-				  void __user *newval, size_t newlen);
 #ifdef CONFIG_PROC_FS
 extern int ip_misc_proc_init(void);
 #endif

include/net/route.h

@@ -231,4 +231,15 @@ static inline int inet_iif(const struct sk_buff *skb)
 	return skb_rtable(skb)->rt_iif;
 }
 
+extern int sysctl_ip_default_ttl;
+
+static inline int ip4_dst_hoplimit(const struct dst_entry *dst)
+{
+	int hoplimit = dst_metric_raw(dst, RTAX_HOPLIMIT);
+
+	if (hoplimit == 0)
+		hoplimit = sysctl_ip_default_ttl;
+	return hoplimit;
+}
+
 #endif	/* _ROUTE_H */