net: neighbour: Remove CONFIG_ARPD

This config option is superfluous in that it only guards a call
to neigh_app_ns(). Enabling CONFIG_ARPD by default has no
change in behavior. There will now be call to __neigh_notify()
for each ARP resolution, which has no impact unless there is a
user space daemon waiting to receive the notification, i.e.,
the case for which CONFIG_ARPD was designed anyways.

Suggested-by: Eric W. Biederman <[email protected]>
Cc: "David S. Miller" <[email protected]>
Cc: Alexey Kuznetsov <[email protected]>
Cc: James Morris <[email protected]>
Cc: Hideaki YOSHIFUJI <[email protected]>
Cc: Patrick McHardy <[email protected]>
Cc: "Eric W. Biederman" <[email protected]>
Cc: Gao feng <[email protected]>
Cc: Joe Perches <[email protected]>
Cc: Veaceslav Falico <[email protected]>
Signed-off-by: Tim Gardner <[email protected]>
Reviewed-by: "Eric W. Biederman" <[email protected]>
Signed-off-by: David S. Miller <[email protected]>

net/ipv4/Kconfig

@@ -259,22 +259,6 @@ config IP_PIMSM_V2
 	  gated-5). This routing protocol is not used widely, so say N unless
 	  you want to play with it.
 
-config ARPD
-	bool "IP: ARP daemon support"
-	---help---
-	  The kernel maintains an internal cache which maps IP addresses to
-	  hardware addresses on the local network, so that Ethernet
-	  frames are sent to the proper address on the physical networking
-	  layer. Normally, kernel uses the ARP protocol to resolve these
-	  mappings.
-
-	  Saying Y here adds support to have an user space daemon to do this
-	  resolution instead. This is useful for implementing an alternate
-	  address resolution protocol (e.g. NHRP on mGRE tunnels) and also for
-	  testing purposes.
-
-	  If unsure, say N.
-
 config SYN_COOKIES
 	bool "IP: TCP syncookie support"
 	---help---

net/ipv4/arp.c

@@ -368,9 +368,7 @@ static void arp_solicit(struct neighbour *neigh, struct sk_buff *skb)
 	} else {
 		probes -= neigh->parms->app_probes;
 		if (probes < 0) {
-#ifdef CONFIG_ARPD
 			neigh_app_ns(neigh);
-#endif
 			return;
 		}
 	}