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ipv4: Add helpers for neigh lookup for nexthop

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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: David Ahern <dsahern@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
David Ahern 2019-04-05 16:30:34 -07:00 committed by David S. Miller
parent 0353f28231
commit 5c9f7c1dfc
4 changed files with 58 additions and 22 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

10
drivers/net/vrf.c
View File

@ -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;
}

32
include/net/route.h
View File

@ -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 */

11
net/ipv4/ip_output.c
View File

@ -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;
}

27
net/ipv4/route.c
View File

@ -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();
n = __ipv4_neigh_lookup(dev, *(__force u32 *)pkey);
if (n)
return n;
return neigh_create(&arp_tbl, pkey, dev);
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();
return n;
}
static void ipv4_confirm_neigh(const struct dst_entry *dst, const void *daddr)