net/ipv6: Add support for onlink flag

Similar to IPv4 allow routes to be added with the RTNH_F_ONLINK flag.
The onlink option requires a gateway and a nexthop device. Any unicast
gateway is allowed (including IPv4 mapped addresses and unresolved
ones) as long as the gateway is not a local address and if it resolves
it must match the given device.

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

diff --git a/net/ipv6/route.c b/net/ipv6/route.c
index db27086..fe3966a 100644 (file)
--- a/net/ipv6/route.c
+++ b/net/ipv6/route.c
@@ -2470,6 +2470,31 @@ static struct rt6_info *ip6_nh_lookup_table(struct net *net,
        return rt;
 }
 
+static int ip6_route_check_nh_onlink(struct net *net,
+                                    struct fib6_config *cfg,
+                                    struct net_device *dev,
+                                    struct netlink_ext_ack *extack)
+{
+       u32 tbid = l3mdev_fib_table(dev) ? : RT_TABLE_LOCAL;
+       const struct in6_addr *gw_addr = &cfg->fc_gateway;
+       u32 flags = RTF_LOCAL | RTF_ANYCAST | RTF_REJECT;
+       struct rt6_info *grt;
+       int err;
+
+       err = 0;
+       grt = ip6_nh_lookup_table(net, cfg, gw_addr, tbid, 0);
+       if (grt) {
+               if (grt->rt6i_flags & flags || dev != grt->dst.dev) {
+                       NL_SET_ERR_MSG(extack, "Nexthop has invalid gateway");
+                       err = -EINVAL;
+               }
+
+               ip6_rt_put(grt);
+       }
+
+       return err;
+}
+
 static int ip6_route_check_nh(struct net *net,
                              struct fib6_config *cfg,
                              struct net_device **_dev,
@@ -2572,6 +2597,21 @@ static struct rt6_info *ip6_route_info_create(struct fib6_config *cfg,
        if (cfg->fc_metric == 0)
                cfg->fc_metric = IP6_RT_PRIO_USER;
 
+       if (cfg->fc_flags & RTNH_F_ONLINK) {
+               if (!dev) {
+                       NL_SET_ERR_MSG(extack,
+                                      "Nexthop device required for onlink");
+                       err = -ENODEV;
+                       goto out;
+               }
+
+               if (!(dev->flags & IFF_UP)) {
+                       NL_SET_ERR_MSG(extack, "Nexthop device is not up");
+                       err = -ENETDOWN;
+                       goto out;
+               }
+       }
+
        err = -ENOBUFS;
        if (cfg->fc_nlinfo.nlh &&
            !(cfg->fc_nlinfo.nlh->nlmsg_flags & NLM_F_CREATE)) {
@@ -2732,7 +2772,12 @@ static struct rt6_info *ip6_route_info_create(struct fib6_config *cfg,
                                goto out;
                        }
 
-                       err = ip6_route_check_nh(net, cfg, &dev, &idev);
+                       if (cfg->fc_flags & RTNH_F_ONLINK) {
+                               err = ip6_route_check_nh_onlink(net, cfg, dev,
+                                                               extack);
+                       } else {
+                               err = ip6_route_check_nh(net, cfg, &dev, &idev);
+                       }
                        if (err)
                                goto out;
                }
@@ -2774,6 +2819,7 @@ install_route:
        if (!(rt->rt6i_flags & (RTF_LOCAL | RTF_ANYCAST)) &&
            !netif_carrier_ok(dev))
                rt->rt6i_nh_flags |= RTNH_F_LINKDOWN;
+       rt->rt6i_nh_flags |= (cfg->fc_flags & RTNH_F_ONLINK);
        rt->dst.dev = dev;
        rt->rt6i_idev = idev;
        rt->rt6i_table = table;
@@ -3843,6 +3889,8 @@ static int rtm_to_fib6_config(struct sk_buff *skb, struct nlmsghdr *nlh,
        if (rtm->rtm_flags & RTM_F_CLONED)
                cfg->fc_flags |= RTF_CACHE;
 
+       cfg->fc_flags |= (rtm->rtm_flags & RTNH_F_ONLINK);
+
        cfg->fc_nlinfo.portid = NETLINK_CB(skb).portid;
        cfg->fc_nlinfo.nlh = nlh;
        cfg->fc_nlinfo.nl_net = sock_net(skb->sk);
@@ -4248,6 +4296,7 @@ static int rt6_nexthop_info(struct sk_buff *skb, struct rt6_info *rt,
                        goto nla_put_failure;
        }
 
+       *flags |= (rt->rt6i_nh_flags & RTNH_F_ONLINK);
        if (rt->rt6i_nh_flags & RTNH_F_OFFLOAD)
                *flags |= RTNH_F_OFFLOAD;