[NETNS]: Routing cache virtualization.

Basically, this piece looks relatively easy. Namespace is already
available on the dst entry via device and the device is safe to
dereferrence. Compare it with one of a searcher and skip entry if
appropriate.

The only exception is ip_rt_frag_needed. So, add namespace parameter to it.
Signed-off-by: Denis V. Lunev <den@openvz.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

include/net/route.h

@@ -115,7 +115,7 @@ extern int		__ip_route_output_key(struct net *, struct rtable **, const struct f
 extern int		ip_route_output_key(struct net *, struct rtable **, struct flowi *flp);
 extern int		ip_route_output_flow(struct net *, struct rtable **rp, struct flowi *flp, struct sock *sk, int flags);
 extern int		ip_route_input(struct sk_buff*, __be32 dst, __be32 src, u8 tos, struct net_device *devin);
-extern unsigned short	ip_rt_frag_needed(struct iphdr *iph, unsigned short new_mtu);
+extern unsigned short	ip_rt_frag_needed(struct net *net, struct iphdr *iph, unsigned short new_mtu);
 extern void		ip_rt_send_redirect(struct sk_buff *skb);
 
 extern unsigned		inet_addr_type(struct net *net, __be32 addr);

net/ipv4/icmp.c

@@ -696,7 +696,7 @@ static void icmp_unreach(struct sk_buff *skb)
 							 "and DF set.\n",
 					       NIPQUAD(iph->daddr));
 			} else {
-				info = ip_rt_frag_needed(iph,
+				info = ip_rt_frag_needed(&init_net, iph,
 						     ntohs(icmph->un.frag.mtu));
 				if (!info)
 					goto out;

net/ipv4/route.c

@@ -648,6 +648,11 @@ static inline int compare_keys(struct flowi *fl1, struct flowi *fl2)
 		(fl1->iif ^ fl2->iif)) == 0;
 }
 
+static inline int compare_netns(struct rtable *rt1, struct rtable *rt2)
+{
+	return rt1->u.dst.dev->nd_net == rt2->u.dst.dev->nd_net;
+}
+
 /*
  * Perform a full scan of hash table and free all entries.
  * Can be called by a softirq or a process.
@@ -961,7 +966,7 @@ static int rt_intern_hash(unsigned hash, struct rtable *rt, struct rtable **rp)
 
 	spin_lock_bh(rt_hash_lock_addr(hash));
 	while ((rth = *rthp) != NULL) {
-		if (compare_keys(&rth->fl, &rt->fl)) {
+		if (compare_keys(&rth->fl, &rt->fl) && compare_netns(rth, rt)) {
 			/* Put it first */
 			*rthp = rth->u.dst.rt_next;
 			/*
@@ -1415,7 +1420,8 @@ static __inline__ unsigned short guess_mtu(unsigned short old_mtu)
 	return 68;
 }
 
-unsigned short ip_rt_frag_needed(struct iphdr *iph, unsigned short new_mtu)
+unsigned short ip_rt_frag_needed(struct net *net, struct iphdr *iph,
+				 unsigned short new_mtu)
 {
 	int i;
 	unsigned short old_mtu = ntohs(iph->tot_len);
@@ -1438,7 +1444,8 @@ unsigned short ip_rt_frag_needed(struct iphdr *iph, unsigned short new_mtu)
 			    rth->rt_dst  == daddr &&
 			    rth->rt_src  == iph->saddr &&
 			    rth->fl.iif == 0 &&
-			    !(dst_metric_locked(&rth->u.dst, RTAX_MTU))) {
+			    !(dst_metric_locked(&rth->u.dst, RTAX_MTU)) &&
+			    rth->u.dst.dev->nd_net == net) {
 				unsigned short mtu = new_mtu;
 
 				if (new_mtu < 68 || new_mtu >= old_mtu) {
@@ -2049,7 +2056,9 @@ int ip_route_input(struct sk_buff *skb, __be32 daddr, __be32 saddr,
 	struct rtable * rth;
 	unsigned	hash;
 	int iif = dev->ifindex;
+	struct net *net;
 
+	net = skb->dev->nd_net;
 	tos &= IPTOS_RT_MASK;
 	hash = rt_hash(daddr, saddr, iif);
 
@@ -2061,7 +2070,8 @@ int ip_route_input(struct sk_buff *skb, __be32 daddr, __be32 saddr,
 		    rth->fl.iif == iif &&
 		    rth->fl.oif == 0 &&
 		    rth->fl.mark == skb->mark &&
-		    rth->fl.fl4_tos == tos) {
+		    rth->fl.fl4_tos == tos &&
+		    rth->u.dst.dev->nd_net == net) {
 			dst_use(&rth->u.dst, jiffies);
 			RT_CACHE_STAT_INC(in_hit);
 			rcu_read_unlock();
@@ -2460,7 +2470,8 @@ int __ip_route_output_key(struct net *net, struct rtable **rp,
 		    rth->fl.oif == flp->oif &&
 		    rth->fl.mark == flp->mark &&
 		    !((rth->fl.fl4_tos ^ flp->fl4_tos) &
-			    (IPTOS_RT_MASK | RTO_ONLINK))) {
+			    (IPTOS_RT_MASK | RTO_ONLINK)) &&
+		    rth->u.dst.dev->nd_net == net) {
 			dst_use(&rth->u.dst, jiffies);
 			RT_CACHE_STAT_INC(out_hit);
 			rcu_read_unlock_bh();