ipv4: Refactor fib_check_nh

fib_check_nh is currently huge covering multiple uses cases - device only,
device + gateway, and device + gateway with ONLINK. The next patch adds
validation checks for IPv6 which only further complicates it. So, break
fib_check_nh into 2 helpers - one for gateway validation and one for device
only.

Signed-off-by: David Ahern <dsahern@gmail.com>
Reviewed-by: Ido Schimmel <idosch@mellanox.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 125 insertions, 109 deletions

diff --git a/net/ipv4/fib_semantics.c b/net/ipv4/fib_semantics.c
index 680b5a9a911a..32ce6e6202d2 100644
--- a/net/ipv4/fib_semantics.c
+++ b/net/ipv4/fib_semantics.c
@@ -885,134 +885,150 @@ bool fib_metrics_match(struct fib_config *cfg, struct fib_info *fi)
  *                                      |
  *                                      |-> {local prefix} (terminal node)
  */
-static int fib_check_nh(struct fib_config *cfg, struct fib_nh *nh,
-                        struct netlink_ext_ack *extack)
+static int fib_check_nh_v4_gw(struct net *net, struct fib_nh *nh, u32 table,
+                              u8 scope, struct netlink_ext_ack *extack)
 {
-        int err = 0;
-        struct net *net;
         struct net_device *dev;
+        struct fib_result res;
+        int err;
 
-        net = cfg->fc_nlinfo.nl_net;
-        if (nh->fib_nh_gw4) {
-                struct fib_result res;
-
-                if (nh->fib_nh_flags & RTNH_F_ONLINK) {
-                        unsigned int addr_type;
+        if (nh->fib_nh_flags & RTNH_F_ONLINK) {
+                unsigned int addr_type;
 
-                        if (cfg->fc_scope >= RT_SCOPE_LINK) {
-                                NL_SET_ERR_MSG(extack,
-                                               "Nexthop has invalid scope");
-                                return -EINVAL;
-                        }
-                        dev = __dev_get_by_index(net, nh->fib_nh_oif);
-                        if (!dev) {
-                                NL_SET_ERR_MSG(extack, "Nexthop device required for onlink");
-                                return -ENODEV;
-                        }
-                        if (!(dev->flags & IFF_UP)) {
-                                NL_SET_ERR_MSG(extack,
-                                               "Nexthop device is not up");
-                                return -ENETDOWN;
-                        }
-                        addr_type = inet_addr_type_dev_table(net, dev,
-                                                             nh->fib_nh_gw4);
-                        if (addr_type != RTN_UNICAST) {
-                                NL_SET_ERR_MSG(extack,
-                                               "Nexthop has invalid gateway");
-                                return -EINVAL;
-                        }
-                        if (!netif_carrier_ok(dev))
-                                nh->fib_nh_flags |= RTNH_F_LINKDOWN;
-                        nh->fib_nh_dev = dev;
-                        dev_hold(dev);
-                        nh->fib_nh_scope = RT_SCOPE_LINK;
-                        return 0;
+                if (scope >= RT_SCOPE_LINK) {
+                        NL_SET_ERR_MSG(extack, "Nexthop has invalid scope");
+                        return -EINVAL;
                 }
-                rcu_read_lock();
-                {
-                        struct fib_table *tbl = NULL;
-                        struct flowi4 fl4 = {
-                                .daddr = nh->fib_nh_gw4,
-                                .flowi4_scope = cfg->fc_scope + 1,
-                                .flowi4_oif = nh->fib_nh_oif,
-                                .flowi4_iif = LOOPBACK_IFINDEX,
-                        };
-
-                        /* It is not necessary, but requires a bit of thinking */
-                        if (fl4.flowi4_scope < RT_SCOPE_LINK)
-                                fl4.flowi4_scope = RT_SCOPE_LINK;
-
-                        if (cfg->fc_table)
-                                tbl = fib_get_table(net, cfg->fc_table);
-
-                        if (tbl)
-                                err = fib_table_lookup(tbl, &fl4, &res,
-                                                       FIB_LOOKUP_IGNORE_LINKSTATE |
-                                                       FIB_LOOKUP_NOREF);
-
-                        /* on error or if no table given do full lookup. This
-                         * is needed for example when nexthops are in the local
-                         * table rather than the given table
-                         */
-                        if (!tbl || err) {
-                                err = fib_lookup(net, &fl4, &res,
-                                                 FIB_LOOKUP_IGNORE_LINKSTATE);
-                        }
-
-                        if (err) {
-                                NL_SET_ERR_MSG(extack,
-                                               "Nexthop has invalid gateway");
-                                rcu_read_unlock();
-                                return err;
-                        }
+                dev = __dev_get_by_index(net, nh->fib_nh_oif);
+                if (!dev) {
+                        NL_SET_ERR_MSG(extack, "Nexthop device required for onlink");
+                        return -ENODEV;
                 }
-                err = -EINVAL;
-                if (res.type != RTN_UNICAST && res.type != RTN_LOCAL) {
-                        NL_SET_ERR_MSG(extack, "Nexthop has invalid gateway");
-                        goto out;
+                if (!(dev->flags & IFF_UP)) {
+                        NL_SET_ERR_MSG(extack, "Nexthop device is not up");
+                        return -ENETDOWN;
                 }
-                nh->fib_nh_scope = res.scope;
-                nh->fib_nh_oif = FIB_RES_OIF(res);
-                nh->fib_nh_dev = dev = FIB_RES_DEV(res);
-                if (!dev) {
-                        NL_SET_ERR_MSG(extack,
-                                       "No egress device for nexthop gateway");
-                        goto out;
+                addr_type = inet_addr_type_dev_table(net, dev, nh->fib_nh_gw4);
+                if (addr_type != RTN_UNICAST) {
+                        NL_SET_ERR_MSG(extack, "Nexthop has invalid gateway");
+                        return -EINVAL;
                 }
-                dev_hold(dev);
                 if (!netif_carrier_ok(dev))
                         nh->fib_nh_flags |= RTNH_F_LINKDOWN;
-                err = (dev->flags & IFF_UP) ? 0 : -ENETDOWN;
-        } else {
-                struct in_device *in_dev;
-
-                if (nh->fib_nh_flags & (RTNH_F_PERVASIVE | RTNH_F_ONLINK)) {
-                        NL_SET_ERR_MSG(extack,
-                                       "Invalid flags for nexthop - PERVASIVE and ONLINK can not be set");
-                        return -EINVAL;
+                nh->fib_nh_dev = dev;
+                dev_hold(dev);
+                nh->fib_nh_scope = RT_SCOPE_LINK;
+                return 0;
+        }
+        rcu_read_lock();
+        {
+                struct fib_table *tbl = NULL;
+                struct flowi4 fl4 = {
+                        .daddr = nh->fib_nh_gw4,
+                        .flowi4_scope = scope + 1,
+                        .flowi4_oif = nh->fib_nh_oif,
+                        .flowi4_iif = LOOPBACK_IFINDEX,
+                };
+
+                /* It is not necessary, but requires a bit of thinking */
+                if (fl4.flowi4_scope < RT_SCOPE_LINK)
+                        fl4.flowi4_scope = RT_SCOPE_LINK;
+
+                if (table)
+                        tbl = fib_get_table(net, table);
+
+                if (tbl)
+                        err = fib_table_lookup(tbl, &fl4, &res,
+                                               FIB_LOOKUP_IGNORE_LINKSTATE |
+                                               FIB_LOOKUP_NOREF);
+
+                /* on error or if no table given do full lookup. This
+                 * is needed for example when nexthops are in the local
+                 * table rather than the given table
+                 */
+                if (!tbl || err) {
+                        err = fib_lookup(net, &fl4, &res,
+                                         FIB_LOOKUP_IGNORE_LINKSTATE);
                 }
-                rcu_read_lock();
-                err = -ENODEV;
-                in_dev = inetdev_by_index(net, nh->fib_nh_oif);
-                if (!in_dev)
-                        goto out;
-                err = -ENETDOWN;
-                if (!(in_dev->dev->flags & IFF_UP)) {
-                        NL_SET_ERR_MSG(extack, "Device for nexthop is not up");
+
+                if (err) {
+                        NL_SET_ERR_MSG(extack, "Nexthop has invalid gateway");
                         goto out;
                 }
-                nh->fib_nh_dev = in_dev->dev;
-                dev_hold(nh->fib_nh_dev);
-                nh->fib_nh_scope = RT_SCOPE_HOST;
-                if (!netif_carrier_ok(nh->fib_nh_dev))
-                        nh->fib_nh_flags |= RTNH_F_LINKDOWN;
-                err = 0;
         }
+
+        err = -EINVAL;
+        if (res.type != RTN_UNICAST && res.type != RTN_LOCAL) {
+                NL_SET_ERR_MSG(extack, "Nexthop has invalid gateway");
+                goto out;
+        }
+        nh->fib_nh_scope = res.scope;
+        nh->fib_nh_oif = FIB_RES_OIF(res);
+        nh->fib_nh_dev = dev = FIB_RES_DEV(res);
+        if (!dev) {
+                NL_SET_ERR_MSG(extack,
+                               "No egress device for nexthop gateway");
+                goto out;
+        }
+        dev_hold(dev);
+        if (!netif_carrier_ok(dev))
+                nh->fib_nh_flags |= RTNH_F_LINKDOWN;
+        err = (dev->flags & IFF_UP) ? 0 : -ENETDOWN;
 out:
         rcu_read_unlock();
         return err;
 }
 
+static int fib_check_nh_nongw(struct net *net, struct fib_nh *nh,
+                              struct netlink_ext_ack *extack)
+{
+        struct in_device *in_dev;
+        int err;
+
+        if (nh->fib_nh_flags & (RTNH_F_PERVASIVE | RTNH_F_ONLINK)) {
+                NL_SET_ERR_MSG(extack,
+                               "Invalid flags for nexthop - PERVASIVE and ONLINK can not be set");
+                return -EINVAL;
+        }
+
+        rcu_read_lock();
+
+        err = -ENODEV;
+        in_dev = inetdev_by_index(net, nh->fib_nh_oif);
+        if (!in_dev)
+                goto out;
+        err = -ENETDOWN;
+        if (!(in_dev->dev->flags & IFF_UP)) {
+                NL_SET_ERR_MSG(extack, "Device for nexthop is not up");
+                goto out;
+        }
+
+        nh->fib_nh_dev = in_dev->dev;
+        dev_hold(nh->fib_nh_dev);
+        nh->fib_nh_scope = RT_SCOPE_HOST;
+        if (!netif_carrier_ok(nh->fib_nh_dev))
+                nh->fib_nh_flags |= RTNH_F_LINKDOWN;
+        err = 0;
+out:
+        rcu_read_unlock();
+        return err;
+}
+
+static int fib_check_nh(struct fib_config *cfg, struct fib_nh *nh,
+                        struct netlink_ext_ack *extack)
+{
+        struct net *net = cfg->fc_nlinfo.nl_net;
+        u32 table = cfg->fc_table;
+        int err;
+
+        if (nh->fib_nh_gw_family == AF_INET)
+                err = fib_check_nh_v4_gw(net, nh, table, cfg->fc_scope, extack);
+        else
+                err = fib_check_nh_nongw(net, nh, extack);
+
+        return err;
+}
+
 static inline unsigned int fib_laddr_hashfn(__be32 val)
 {
         unsigned int mask = (fib_info_hash_size - 1);