ipv4: Plumb support for nexthop object in a fib_info

Add 'struct nexthop' and nh_list list_head to fib_info. nh_list is the
fib_info side of the nexthop <-> fib_info relationship.

Add fi_list list_head to 'struct nexthop' to track fib_info entries
using a nexthop instance. Add __remove_nexthop_fib and add it to
__remove_nexthop to walk the new list_head and mark those fib entries
as dead when the nexthop is deleted.

Add a few nexthop helpers for use when a nexthop is added to fib_info:
- nexthop_cmp to determine if 2 nexthops are the same
- nexthop_path_fib_result to select a path for a multipath
  'struct nexthop'
- nexthop_fib_nhc to select a specific fib_nh_common within a
  multipath 'struct nexthop'

Update existing fib_info_nhc to use nexthop_fib_nhc if a fib_info uses
a 'struct nexthop', and mark fib_info_nh as only used for the non-nexthop
case.

Update the fib_info functions to check for fi->nh and take a different
path as needed:
- free_fib_info_rcu - put the nexthop object reference
- fib_release_info - remove the fib_info from the nexthop's fi_list
- nh_comp - use nexthop_cmp when either fib_info references a nexthop
  object
- fib_info_hashfn - use the nexthop id for the hashing vs the oif of
  each fib_nh in a fib_info
- fib_nlmsg_size - add space for the RTA_NH_ID attribute
- fib_create_info - verify nexthop reference can be taken, verify
  nexthop spec is valid for fib entry, and add fib_info to fi_list for
  a nexthop
- fib_select_multipath - use the new nexthop_path_fib_result to select a
  path when nexthop objects are used
- fib_table_lookup - if the 'struct nexthop' is a blackhole nexthop, treat
  it the same as a fib entry using 'blackhole'

The bulk of the changes are in fib_semantics.c and most of that is
moving the existing change_nexthops into an else branch.

Update the nexthop code to walk fi_list on a nexthop deleted to remove
fib entries referencing it.

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

2 files changed, 52 insertions, 0 deletions

diff --git a/include/net/ip_fib.h b/include/net/ip_fib.h
index 7da8ea784029..071d280de389 100644
--- a/include/net/ip_fib.h
+++ b/include/net/ip_fib.h
@@ -129,9 +129,12 @@ struct fib_nh {
  * This structure contains data shared by many of routes.
  */
 
+struct nexthop;
+
 struct fib_info {
 	struct hlist_node	fib_hash;
 	struct hlist_node	fib_lhash;
+	struct list_head	nh_list;
 	struct net		*fib_net;
 	int			fib_treeref;
 	refcount_t		fib_clntref;
@@ -151,6 +154,7 @@ struct fib_info {
 	int			fib_nhs;
 	bool			fib_nh_is_v6;
 	bool			nh_updated;
+	struct nexthop		*nh;
 	struct rcu_head		rcu;
 	struct fib_nh		fib_nh[0];
 };
diff --git a/include/net/nexthop.h b/include/net/nexthop.h
index e501d77b82c8..2912a2d7a515 100644
--- a/include/net/nexthop.h
+++ b/include/net/nexthop.h
@@ -77,6 +77,7 @@ struct nh_group {
 
 struct nexthop {
 	struct rb_node		rb_node;    /* entry on netns rbtree */
+	struct list_head	fi_list;    /* v4 entries using nh */
 	struct list_head	grp_list;   /* nh group entries using this nh */
 	struct net		*net;
 
@@ -110,6 +111,12 @@ static inline void nexthop_put(struct nexthop *nh)
 		call_rcu(&nh->rcu, nexthop_free_rcu);
 }
 
+static inline bool nexthop_cmp(const struct nexthop *nh1,
+			       const struct nexthop *nh2)
+{
+	return nh1 == nh2;
+}
+
 static inline bool nexthop_is_multipath(const struct nexthop *nh)
 {
 	if (nh->is_group) {
@@ -193,18 +200,59 @@ static inline bool nexthop_is_blackhole(const struct nexthop *nh)
 	return nhi->reject_nh;
 }
 
+static inline void nexthop_path_fib_result(struct fib_result *res, int hash)
+{
+	struct nh_info *nhi;
+	struct nexthop *nh;
+
+	nh = nexthop_select_path(res->fi->nh, hash);
+	nhi = rcu_dereference(nh->nh_info);
+	res->nhc = &nhi->fib_nhc;
+}
+
+/* called with rcu read lock or rtnl held */
+static inline
+struct fib_nh_common *nexthop_fib_nhc(struct nexthop *nh, int nhsel)
+{
+	struct nh_info *nhi;
+
+	BUILD_BUG_ON(offsetof(struct fib_nh, nh_common) != 0);
+	BUILD_BUG_ON(offsetof(struct fib6_nh, nh_common) != 0);
+
+	if (nexthop_is_multipath(nh)) {
+		nh = nexthop_mpath_select(nh, nhsel);
+		if (!nh)
+			return NULL;
+	}
+
+	nhi = rcu_dereference_rtnl(nh->nh_info);
+	return &nhi->fib_nhc;
+}
+
 static inline unsigned int fib_info_num_path(const struct fib_info *fi)
 {
+	if (unlikely(fi->nh))
+		return nexthop_num_path(fi->nh);
+
 	return fi->fib_nhs;
 }
 
+int fib_check_nexthop(struct nexthop *nh, u8 scope,
+		      struct netlink_ext_ack *extack);
+
 static inline struct fib_nh_common *fib_info_nhc(struct fib_info *fi, int nhsel)
 {
+	if (unlikely(fi->nh))
+		return nexthop_fib_nhc(fi->nh, nhsel);
+
 	return &fi->fib_nh[nhsel].nh_common;
 }
 
+/* only used when fib_nh is built into fib_info */
 static inline struct fib_nh *fib_info_nh(struct fib_info *fi, int nhsel)
 {
+	WARN_ON(fi->nh);
+
 	return &fi->fib_nh[nhsel];
 }
 #endif