ipv4: Allow routes to use nexthop objects

Add support for RTA_NH_ID attribute to allow a user to specify a
nexthop id to use with a route. fc_nh_id is added to fib_config to
hold the value passed in the RTA_NH_ID attribute. If a nexthop id
is given, the gateway, device, encap and multipath attributes can
not be set.

Update fib_nh_match to check ids on a route delete.

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

3 files changed, 35 insertions, 0 deletions

diff --git a/include/net/ip_fib.h b/include/net/ip_fib.h
index 4cdf8bc22efd..7e1e621a56df 100644
--- a/include/net/ip_fib.h
+++ b/include/net/ip_fib.h
@@ -40,6 +40,7 @@ struct fib_config {
         u32                     fc_flags;
         u32                     fc_priority;
         __be32                  fc_prefsrc;
+        u32                     fc_nh_id;
         struct nlattr           *fc_mx;
         struct rtnexthop        *fc_mp;
         int                     fc_mx_len;
diff --git a/net/ipv4/fib_frontend.c b/net/ipv4/fib_frontend.c
index 33b0dbe84aa6..108191667531 100644
--- a/net/ipv4/fib_frontend.c
+++ b/net/ipv4/fib_frontend.c
@@ -671,6 +671,7 @@ const struct nla_policy rtm_ipv4_policy[RTA_MAX + 1] = {
         [RTA_IP_PROTO]          = { .type = NLA_U8 },
         [RTA_SPORT]             = { .type = NLA_U16 },
         [RTA_DPORT]             = { .type = NLA_U16 },
+        [RTA_NH_ID]             = { .type = NLA_U32 },
 };
 
 int fib_gw_from_via(struct fib_config *cfg, struct nlattr *nla,
@@ -808,6 +809,18 @@ static int rtm_to_fib_config(struct net *net, struct sk_buff *skb,
                         if (err < 0)
                                 goto errout;
                         break;
+                case RTA_NH_ID:
+                        cfg->fc_nh_id = nla_get_u32(attr);
+                        break;
+                }
+        }
+
+        if (cfg->fc_nh_id) {
+                if (cfg->fc_oif || cfg->fc_gw_family ||
+                    cfg->fc_encap || cfg->fc_mp) {
+                        NL_SET_ERR_MSG(extack,
+                                       "Nexthop specification and nexthop id are mutually exclusive");
+                        return -EINVAL;
                 }
         }
 
@@ -834,6 +847,12 @@ static int inet_rtm_delroute(struct sk_buff *skb, struct nlmsghdr *nlh,
         if (err < 0)
                 goto errout;
 
+        if (cfg.fc_nh_id && !nexthop_find_by_id(net, cfg.fc_nh_id)) {
+                NL_SET_ERR_MSG(extack, "Nexthop id does not exist");
+                err = -EINVAL;
+                goto errout;
+        }
+
         tb = fib_get_table(net, cfg.fc_table);
         if (!tb) {
                 NL_SET_ERR_MSG(extack, "FIB table does not exist");
diff --git a/net/ipv4/fib_semantics.c b/net/ipv4/fib_semantics.c
index afa4af1f9326..2c24d8e3b126 100644
--- a/net/ipv4/fib_semantics.c
+++ b/net/ipv4/fib_semantics.c
@@ -789,6 +789,12 @@ int fib_nh_match(struct fib_config *cfg, struct fib_info *fi,
         if (cfg->fc_priority && cfg->fc_priority != fi->fib_priority)
                 return 1;
 
+        if (cfg->fc_nh_id) {
+                if (fi->nh && cfg->fc_nh_id == fi->nh->id)
+                        return 0;
+                return 1;
+        }
+
         if (cfg->fc_oif || cfg->fc_gw_family) {
                 struct fib_nh *nh = fib_info_nh(fi, 0);
 
@@ -1302,6 +1308,15 @@ struct fib_info *fib_create_info(struct fib_config *cfg,
                 goto err_inval;
         }
 
+        if (cfg->fc_nh_id) {
+                nh = nexthop_find_by_id(net, cfg->fc_nh_id);
+                if (!nh) {
+                        NL_SET_ERR_MSG(extack, "Nexthop id does not exist");
+                        goto err_inval;
+                }
+                nhs = 0;
+        }
+
 #ifdef CONFIG_IP_ROUTE_MULTIPATH
         if (cfg->fc_mp) {
                 nhs = fib_count_nexthops(cfg->fc_mp, cfg->fc_mp_len, extack);