ipv4: add support for linkdown sysctl to netconf

This kernel patch exports the value of the new
ignore_routes_with_linkdown via netconf.

v2: changes to notify userspace via netlink when sysctl values change
and proposed for 'net' since this could be considered a bugfix
Signed-off-by: Andy Gospodarek <gospo@cumulusnetworks.com>
Suggested-by: Nicolas Dichtel <nicolas.dichtel@6wind.com>
Acked-by: Nicolas Dichtel <nicolas.dichtel@6wind.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

include/uapi/linux/netconf.h

@@ -15,6 +15,7 @@ enum {
 	NETCONFA_RP_FILTER,
 	NETCONFA_MC_FORWARDING,
 	NETCONFA_PROXY_NEIGH,
+	NETCONFA_IGNORE_ROUTES_WITH_LINKDOWN,
 	__NETCONFA_MAX
 };
 #define NETCONFA_MAX	(__NETCONFA_MAX - 1)

net/ipv4/devinet.c

@@ -1740,6 +1740,8 @@ static int inet_netconf_msgsize_devconf(int type)
 		size += nla_total_size(4);
 	if (type == -1 || type == NETCONFA_PROXY_NEIGH)
 		size += nla_total_size(4);
+	if (type == -1 || type == NETCONFA_IGNORE_ROUTES_WITH_LINKDOWN)
+		size += nla_total_size(4);
 
 	return size;
 }
@@ -1780,6 +1782,10 @@ static int inet_netconf_fill_devconf(struct sk_buff *skb, int ifindex,
 	    nla_put_s32(skb, NETCONFA_PROXY_NEIGH,
 			IPV4_DEVCONF(*devconf, PROXY_ARP)) < 0)
 		goto nla_put_failure;
+	if ((type == -1 || type == NETCONFA_IGNORE_ROUTES_WITH_LINKDOWN) &&
+	    nla_put_s32(skb, NETCONFA_IGNORE_ROUTES_WITH_LINKDOWN,
+			IPV4_DEVCONF(*devconf, IGNORE_ROUTES_WITH_LINKDOWN)) < 0)
+		goto nla_put_failure;
 
 	nlmsg_end(skb, nlh);
 	return 0;
@@ -1819,6 +1825,7 @@ static const struct nla_policy devconf_ipv4_policy[NETCONFA_MAX+1] = {
 	[NETCONFA_FORWARDING]	= { .len = sizeof(int) },
 	[NETCONFA_RP_FILTER]	= { .len = sizeof(int) },
 	[NETCONFA_PROXY_NEIGH]	= { .len = sizeof(int) },
+	[NETCONFA_IGNORE_ROUTES_WITH_LINKDOWN]	= { .len = sizeof(int) },
 };
 
 static int inet_netconf_get_devconf(struct sk_buff *in_skb,
@@ -2048,6 +2055,12 @@ static int devinet_conf_proc(struct ctl_table *ctl, int write,
 			inet_netconf_notify_devconf(net, NETCONFA_PROXY_NEIGH,
 						    ifindex, cnf);
 		}
+		if (i == IPV4_DEVCONF_IGNORE_ROUTES_WITH_LINKDOWN - 1 &&
+		    new_value != old_value) {
+			ifindex = devinet_conf_ifindex(net, cnf);
+			inet_netconf_notify_devconf(net, NETCONFA_IGNORE_ROUTES_WITH_LINKDOWN,
+						    ifindex, cnf);
+		}
 	}
 
 	return ret;