Subject: Re: [PATCH net-next v2] net: neighbour: Remove CONFIG_ARPD

From: [email-masked] (Eric W. Biederman)
Date: Thu, 29 Aug 2013 16:39:04 -0700

Tim Gardner <[email-masked]> writes:

> 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.

This looks good to me, and much less magic to maintain.

Eric

> Suggested-by: Eric W. Biederman <[email-masked]>
Reviewed-by: "Eric W. Biederman" <[email-masked]>

> Cc: "David S. Miller" <[email-masked]>
> Cc: Alexey Kuznetsov <[email-masked]>
> Cc: James Morris <[email-masked]>
> Cc: Hideaki YOSHIFUJI <[email-masked]>
> Cc: Patrick McHardy <[email-masked]>
> Cc: "Eric W. Biederman" <[email-masked]>
> Cc: Gao feng <[email-masked]>
> Cc: Joe Perches <[email-masked]>
> Cc: Veaceslav Falico <[email-masked]>
> Signed-off-by: Tim Gardner <[email-masked]>
> ---
>
> Eric's suggestion to simply remove the config option makes sense
> to me. If acceptable then I'll submit a patch series that also removes
> CONFIG_ARPD from the various arch defconfigs.
>
>  net/core/neighbour.c |    2 --
>  net/ipv4/Kconfig     |   16 ----------------
>  net/ipv4/arp.c       |    2 --
>  net/ipv6/ndisc.c     |    2 --
>  4 files changed, 22 deletions(-)
>
> diff --git a/net/core/neighbour.c b/net/core/neighbour.c
> index 60533db..6072610 100644
> --- a/net/core/neighbour.c
> +++ b/net/core/neighbour.c
> @@ -2759,13 +2759,11 @@ errout:
>  		rtnl_set_sk_err(net, RTNLGRP_NEIGH, err);
>  }
>  
> -#ifdef CONFIG_ARPD
>  void neigh_app_ns(struct neighbour *n)
>  {
>  	__neigh_notify(n, RTM_GETNEIGH, NLM_F_REQUEST);
>  }
>  EXPORT_SYMBOL(neigh_app_ns);
> -#endif /* CONFIG_ARPD */
>  
>  #ifdef CONFIG_SYSCTL
>  static int zero;
> diff --git a/net/ipv4/Kconfig b/net/ipv4/Kconfig
> index 37cf1a6..05c57f0 100644
> --- a/net/ipv4/Kconfig
> +++ b/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---
> diff --git a/net/ipv4/arp.c b/net/ipv4/arp.c
> index 4429b01..7808093 100644
> --- a/net/ipv4/arp.c
> +++ b/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;
>  		}
>  	}
> diff --git a/net/ipv6/ndisc.c b/net/ipv6/ndisc.c
> index 04d31c2..d5693ad 100644
> --- a/net/ipv6/ndisc.c
> +++ b/net/ipv6/ndisc.c
> @@ -663,9 +663,7 @@ static void ndisc_solicit(struct neighbour *neigh, struct sk_buff *skb)
>  		}
>  		ndisc_send_ns(dev, neigh, target, target, saddr);
>  	} else if ((probes -= neigh->parms->app_probes) < 0) {
> -#ifdef CONFIG_ARPD
>  		neigh_app_ns(neigh);
> -#endif
>  	} else {
>  		addrconf_addr_solict_mult(target, &mcaddr);
>  		ndisc_send_ns(dev, NULL, target, &mcaddr, saddr);