Commit 5c9f7c1d authored by David Ahern's avatar David Ahern Committed by David S. Miller
Browse files

ipv4: Add helpers for neigh lookup for nexthop 



A common theme in the output path is looking up a neigh entry for a
nexthop, either the gateway in an rtable or a fallback to the daddr
in the skb:

        nexthop = (__force u32)rt_nexthop(rt, ip_hdr(skb)->daddr);
        neigh = __ipv4_neigh_lookup_noref(dev, nexthop);
        if (unlikely(!neigh))
                neigh = __neigh_create(&arp_tbl, &nexthop, dev, false);

To allow the nexthop to be an IPv6 address we need to consider the
family of the nexthop and then call __ipv{4,6}_neigh_lookup_noref based
on it.

To make this simpler, add a ip_neigh_gw4 helper similar to ip_neigh_gw6
added in an earlier patch which handles:

        neigh = __ipv4_neigh_lookup_noref(dev, nexthop);
        if (unlikely(!neigh))
                neigh = __neigh_create(&arp_tbl, &nexthop, dev, false);

And then add a second one, ip_neigh_for_gw, that calls either
ip_neigh_gw4 or ip_neigh_gw6 based on the address family of the gateway.

Update the output paths in the VRF driver and core v4 code to use
ip_neigh_for_gw simplifying the family based lookup and making both
ready for a v6 nexthop.

ipv4_neigh_lookup has a different need - the potential to resolve a
passed in address in addition to any gateway in the rtable or skb. Since
this is a one-off, add ip_neigh_gw4 and ip_neigh_gw6 diectly. The
difference between __neigh_create used by the helpers and neigh_create
called by ipv4_neigh_lookup is taking a refcount, so add rcu_read_lock_bh
and bump the refcnt on the neigh entry.

Signed-off-by: default avatarDavid Ahern <dsahern@gmail.com>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent 0353f282

drivers/net/vrf.c

+4 −6
Original line number Diff line number Diff line
@@ -549,7 +549,7 @@ static int vrf_finish_output(struct net *net, struct sock *sk, struct sk_buff *s 
	struct net_device *dev = dst->dev;

	unsigned int hh_len = LL_RESERVED_SPACE(dev);

	struct neighbour *neigh;

	u32 nexthop;

	bool is_v6gw = false;

	int ret = -EINVAL;



	nf_reset(skb);
@@ -572,13 +572,11 @@ static int vrf_finish_output(struct net *net, struct sock *sk, struct sk_buff *s 


	rcu_read_lock_bh();



	nexthop = (__force u32)rt_nexthop(rt, ip_hdr(skb)->daddr);

	neigh = __ipv4_neigh_lookup_noref(dev, nexthop);

	if (unlikely(!neigh))

		neigh = __neigh_create(&arp_tbl, &nexthop, dev, false);

	neigh = ip_neigh_for_gw(rt, skb, &is_v6gw);

	if (!IS_ERR(neigh)) {

		sock_confirm_neigh(skb, neigh);

		ret = neigh_output(neigh, skb, false);

		/* if crossing protocols, can not use the cached header */

		ret = neigh_output(neigh, skb, is_v6gw);

		rcu_read_unlock_bh();

		return ret;

	}

include/net/route.h

+32 −0
Original line number Diff line number Diff line
@@ -29,6 +29,8 @@ 
#include <net/flow.h>

#include <net/inet_sock.h>

#include <net/ip_fib.h>

#include <net/arp.h>

#include <net/ndisc.h>

#include <linux/in_route.h>

#include <linux/rtnetlink.h>

#include <linux/rcupdate.h>
@@ -350,4 +352,34 @@ static inline int ip4_dst_hoplimit(const struct dst_entry *dst) 
	return hoplimit;

}



static inline struct neighbour *ip_neigh_gw4(struct net_device *dev,

					     __be32 daddr)

{

	struct neighbour *neigh;



	neigh = __ipv4_neigh_lookup_noref(dev, daddr);

	if (unlikely(!neigh))

		neigh = __neigh_create(&arp_tbl, &daddr, dev, false);



	return neigh;

}



static inline struct neighbour *ip_neigh_for_gw(struct rtable *rt,

						struct sk_buff *skb,

						bool *is_v6gw)

{

	struct net_device *dev = rt->dst.dev;

	struct neighbour *neigh;



	if (likely(rt->rt_gw_family == AF_INET)) {

		neigh = ip_neigh_gw4(dev, rt->rt_gw4);

	} else if (rt->rt_gw_family == AF_INET6) {

		neigh = ip_neigh_gw6(dev, &rt->rt_gw6);

		*is_v6gw = true;

	} else {

		neigh = ip_neigh_gw4(dev, ip_hdr(skb)->daddr);

	}

	return neigh;

}



#endif	/* _ROUTE_H */

net/ipv4/ip_output.c

+4 −7
Original line number Diff line number Diff line
@@ -188,7 +188,7 @@ static int ip_finish_output2(struct net *net, struct sock *sk, struct sk_buff *s 
	struct net_device *dev = dst->dev;

	unsigned int hh_len = LL_RESERVED_SPACE(dev);

	struct neighbour *neigh;

	u32 nexthop;

	bool is_v6gw = false;



	if (rt->rt_type == RTN_MULTICAST) {

		IP_UPD_PO_STATS(net, IPSTATS_MIB_OUTMCAST, skb->len);
@@ -218,16 +218,13 @@ static int ip_finish_output2(struct net *net, struct sock *sk, struct sk_buff *s 
	}



	rcu_read_lock_bh();

	nexthop = (__force u32) rt_nexthop(rt, ip_hdr(skb)->daddr);

	neigh = __ipv4_neigh_lookup_noref(dev, nexthop);

	if (unlikely(!neigh))

		neigh = __neigh_create(&arp_tbl, &nexthop, dev, false);

	neigh = ip_neigh_for_gw(rt, skb, &is_v6gw);

	if (!IS_ERR(neigh)) {

		int res;



		sock_confirm_neigh(skb, neigh);

		res = neigh_output(neigh, skb, false);



		/* if crossing protocols, can not use the cached header */

		res = neigh_output(neigh, skb, is_v6gw);

		rcu_read_unlock_bh();

		return res;

	}

net/ipv4/route.c

+19 −10
Original line number Diff line number Diff line
@@ -436,18 +436,27 @@ static struct neighbour *ipv4_neigh_lookup(const struct dst_entry *dst, 
{

	const struct rtable *rt = container_of(dst, struct rtable, dst);

	struct net_device *dev = dst->dev;

	const __be32 *pkey = daddr;

	struct neighbour *n;



	if (rt->rt_gw_family == AF_INET)

		pkey = (const __be32 *) &rt->rt_gw4;

	else if (skb)

		pkey = &ip_hdr(skb)->daddr;

	rcu_read_lock_bh();



	if (likely(rt->rt_gw_family == AF_INET)) {

		n = ip_neigh_gw4(dev, rt->rt_gw4);

	} else if (rt->rt_gw_family == AF_INET6) {

		n = ip_neigh_gw6(dev, &rt->rt_gw6);

        } else {

		__be32 pkey;



		pkey = skb ? ip_hdr(skb)->daddr : *((__be32 *) daddr);

		n = ip_neigh_gw4(dev, pkey);

	}



	if (n && !refcount_inc_not_zero(&n->refcnt))

		n = NULL;



	rcu_read_unlock_bh();



	n = __ipv4_neigh_lookup(dev, *(__force u32 *)pkey);

	if (n)

	return n;

	return neigh_create(&arp_tbl, pkey, dev);

}



static void ipv4_confirm_neigh(const struct dst_entry *dst, const void *daddr)

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