arp: Factorise ip_route_output() call in arp_req_set() and arp_req_delete().

When ioctl(SIOCDARP/SIOCSARP) is issued for non-proxy entry (no ATF_COM)
without arpreq.arp_dev[] set, arp_req_set() and arp_req_delete() looks up
dev based on IPv4 address by ip_route_output().

Let's factorise the same code as arp_req_dev().

Signed-off-by: Kuniyuki Iwashima <kuniyu@amazon.com>
Link: https://lore.kernel.org/r/20240430015813.71143-4-kuniyu@amazon.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

diff --git a/net/ipv4/arp.c b/net/ipv4/arp.c
index b20a5771d069aa325191db0b44dfb2ab42843c33..ac3e15799c2ffbcc79e858eab0c631e7f8d06f0f 100644 (file)
--- a/net/ipv4/arp.c
+++ b/net/ipv4/arp.c
@@ -1003,6 +1003,27 @@ out_of_mem:
  *     User level interface (ioctl)
  */
 
+static struct net_device *arp_req_dev(struct net *net, struct arpreq *r)
+{
+       struct net_device *dev;
+       struct rtable *rt;
+       __be32 ip;
+
+       ip = ((struct sockaddr_in *)&r->arp_pa)->sin_addr.s_addr;
+
+       rt = ip_route_output(net, ip, 0, 0, 0, RT_SCOPE_LINK);
+       if (IS_ERR(rt))
+               return ERR_CAST(rt);
+
+       dev = rt->dst.dev;
+       ip_rt_put(rt);
+
+       if (!dev)
+               return ERR_PTR(-EINVAL);
+
+       return dev;
+}
+
 /*
  *     Set (create) an ARP cache entry.
  */
@@ -1045,25 +1066,17 @@ static int arp_req_set_public(struct net *net, struct arpreq *r,
 static int arp_req_set(struct net *net, struct arpreq *r,
                       struct net_device *dev)
 {
-       __be32 ip;
        struct neighbour *neigh;
+       __be32 ip;
        int err;
 
        if (r->arp_flags & ATF_PUBL)
                return arp_req_set_public(net, r, dev);
 
-       ip = ((struct sockaddr_in *)&r->arp_pa)->sin_addr.s_addr;
-
        if (!dev) {
-               struct rtable *rt = ip_route_output(net, ip, 0, 0, 0,
-                                                   RT_SCOPE_LINK);
-
-               if (IS_ERR(rt))
-                       return PTR_ERR(rt);
-               dev = rt->dst.dev;
-               ip_rt_put(rt);
-               if (!dev)
-                       return -EINVAL;
+               dev = arp_req_dev(net, r);
+               if (IS_ERR(dev))
+                       return PTR_ERR(dev);
        }
        switch (dev->type) {
 #if IS_ENABLED(CONFIG_FDDI)
@@ -1086,6 +1099,8 @@ static int arp_req_set(struct net *net, struct arpreq *r,
                break;
        }
 
+       ip = ((struct sockaddr_in *)&r->arp_pa)->sin_addr.s_addr;
+
        neigh = __neigh_lookup_errno(&arp_tbl, &ip, dev);
        err = PTR_ERR(neigh);
        if (!IS_ERR(neigh)) {
@@ -1191,14 +1206,9 @@ static int arp_req_delete(struct net *net, struct arpreq *r,
 
        ip = ((struct sockaddr_in *)&r->arp_pa)->sin_addr.s_addr;
        if (!dev) {
-               struct rtable *rt = ip_route_output(net, ip, 0, 0, 0,
-                                                   RT_SCOPE_LINK);
-               if (IS_ERR(rt))
-                       return PTR_ERR(rt);
-               dev = rt->dst.dev;
-               ip_rt_put(rt);
-               if (!dev)
-                       return -EINVAL;
+               dev = arp_req_dev(net, r);
+               if (IS_ERR(dev))
+                       return PTR_ERR(dev);
        }
        return arp_invalidate(dev, ip, true);
 }