net: Set strict_start_type for routes and rules

New userspace on an older kernel can send unknown and unsupported
attributes resulting in an incompelete config which is almost
always wrong for routing (few exceptions are passthrough settings
like the protocol that installed the route).

Set strict_start_type in the policies for IPv4 and IPv6 routes and
rules to detect new, unsupported attributes and fail the route add.

Signed-off-by: David Ahern <dsahern@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

include/net/fib_rules.h

@@ -103,6 +103,7 @@ struct fib_rule_notifier_info {
 };
 
 #define FRA_GENERIC_POLICY \
+	[FRA_UNSPEC]	= { .strict_start_type = FRA_DPORT_RANGE + 1 }, \
 	[FRA_IIFNAME]	= { .type = NLA_STRING, .len = IFNAMSIZ - 1 }, \
 	[FRA_OIFNAME]	= { .type = NLA_STRING, .len = IFNAMSIZ - 1 }, \
 	[FRA_PRIORITY]	= { .type = NLA_U32 }, \

net/ipv4/fib_frontend.c

@@ -645,6 +645,7 @@ int ip_rt_ioctl(struct net *net, unsigned int cmd, struct rtentry *rt)
 }
 
 const struct nla_policy rtm_ipv4_policy[RTA_MAX + 1] = {
+	[RTA_UNSPEC]		= { .strict_start_type = RTA_DPORT + 1 },
 	[RTA_DST]		= { .type = NLA_U32 },
 	[RTA_SRC]		= { .type = NLA_U32 },
 	[RTA_IIF]		= { .type = NLA_U32 },

net/ipv6/route.c

@@ -4221,6 +4221,7 @@ void rt6_mtu_change(struct net_device *dev, unsigned int mtu)
 }
 
 static const struct nla_policy rtm_ipv6_policy[RTA_MAX+1] = {
+	[RTA_UNSPEC]		= { .strict_start_type = RTA_DPORT + 1 },
 	[RTA_GATEWAY]           = { .len = sizeof(struct in6_addr) },
 	[RTA_PREFSRC]		= { .len = sizeof(struct in6_addr) },
 	[RTA_OIF]               = { .type = NLA_U32 },