ipv4: Flag fib_info with a fib_nh using IPv6 gateway

Until support is added to the offload drivers, they need to be able to
reject routes with an IPv6 gateway. To that end add a flag to fib_info
that indicates if any fib_nh has a v6 gateway. The flag allows the drivers
to efficiently know the use of a v6 gateway without walking all fib_nh
tied to a fib_info each time a route is added.

Update mlxsw and rocker to reject the routes with extack message as to why.
Signed-off-by: NDavid Ahern <dsahern@gmail.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

drivers/net/ethernet/mellanox/mlxsw/spectrum_router.c

@@ -6092,6 +6092,14 @@ static int mlxsw_sp_router_fib_event(struct notifier_block *nb,
 			NL_SET_ERR_MSG_MOD(info->extack, "FIB offload was aborted. Not configuring route");
 			return notifier_from_errno(-EINVAL);
 		}
+		if (info->family == AF_INET) {
+			struct fib_entry_notifier_info *fen_info = ptr;
+
+			if (fen_info->fi->fib_nh_is_v6) {
+				NL_SET_ERR_MSG_MOD(info->extack, "IPv6 gateway with IPv4 route is not supported");
+				return notifier_from_errno(-EINVAL);
+			}
+		}
 		break;
 	}
 

drivers/net/ethernet/rocker/rocker_main.c

@@ -2207,6 +2207,15 @@ static int rocker_router_fib_event(struct notifier_block *nb,
 	switch (event) {
 	case FIB_EVENT_ENTRY_ADD: /* fall through */
 	case FIB_EVENT_ENTRY_DEL:
+		if (info->family == AF_INET) {
+			struct fib_entry_notifier_info *fen_info = ptr;
+
+			if (fen_info->fi->fib_nh_is_v6) {
+				NL_SET_ERR_MSG_MOD(info->extack, "IPv6 gateway with IPv4 route is not supported");
+				return notifier_from_errno(-EINVAL);
+			}
+		}
+
 		memcpy(&fib_work->fen_info, ptr, sizeof(fib_work->fen_info));
 		/* Take referece on fib_info to prevent it from being
 		 * freed while work is queued. Release it afterwards.

include/net/ip_fib.h

@@ -147,6 +147,7 @@ struct fib_info {
 #define fib_rtt fib_metrics->metrics[RTAX_RTT-1]
 #define fib_advmss fib_metrics->metrics[RTAX_ADVMSS-1]
 	int			fib_nhs;
+	bool			fib_nh_is_v6;
 	struct rcu_head		rcu;
 	struct fib_nh		fib_nh[0];
 #define fib_dev		fib_nh[0].fib_nh_dev

net/ipv4/fib_semantics.c

@@ -1349,6 +1349,8 @@ struct fib_info *fib_create_info(struct fib_config *cfg,
 
 	change_nexthops(fi) {
 		fib_info_update_nh_saddr(net, nexthop_nh);
+		if (nexthop_nh->fib_nh_gw_family == AF_INET6)
+			fi->fib_nh_is_v6 = true;
 	} endfor_nexthops(fi)
 
 	fib_rebalance(fi);