[PATCH net-next 4/4] ipv6: Add support for non-equal-cost multipath

[Ido Schimmel]

The use of hash-threshold instead of modulo-N makes it trivial to add
support for non-equal-cost multipath.

Instead of dividing the multipath hash function's output space equally
between the nexthops, each nexthop is assigned a region size which is
proportional to its weight.

Signed-off-by: Ido Schimmel <ido...@mellanox.com>
---
 include/net/ip6_fib.h |  1 +
 net/ipv6/route.c      | 11 +++++++----
 2 files changed, 8 insertions(+), 4 deletions(-)

diff --git a/include/net/ip6_fib.h b/include/net/ip6_fib.h
index 97cd05d87780..34ec321d6a03 100644
--- a/include/net/ip6_fib.h
+++ b/include/net/ip6_fib.h
@@ -171,6 +171,7 @@ struct rt6_info {
        u32                             rt6i_metric;
        u32                             rt6i_pmtu;
        /* more non-fragment space at head required */
+       int                             rt6i_nh_weight;
        unsigned short                  rt6i_nfheader_len;
        u8                              rt6i_protocol;
        u8                              exception_bucket_flushed:1,
diff --git a/net/ipv6/route.c b/net/ipv6/route.c
index 7837b8c754a3..1076ae0ea9d5 100644
--- a/net/ipv6/route.c
+++ b/net/ipv6/route.c
@@ -2594,6 +2594,7 @@ static struct rt6_info *ip6_route_info_create(struct 
fib6_config *cfg,
 #endif
 
        rt->rt6i_metric = cfg->fc_metric;
+       rt->rt6i_nh_weight = 1;
 
        /* We cannot add true routes via loopback here,
           they would result in kernel looping; promote them to reject routes
@@ -3507,11 +3508,11 @@ static int rt6_multipath_total_weight(const struct 
rt6_info *rt)
        int total = 0;
 
        if (!rt6_is_dead(rt))
-               total++;
+               total += rt->rt6i_nh_weight;
 
        list_for_each_entry(iter, &rt->rt6i_siblings, rt6i_siblings) {
                if (!rt6_is_dead(iter))
-                       total++;
+                       total += iter->rt6i_nh_weight;
        }
 
        return total;
@@ -3522,7 +3523,7 @@ static void rt6_upper_bound_set(struct rt6_info *rt, int 
*weight, int total)
        int upper_bound = -1;
 
        if (!rt6_is_dead(rt)) {
-               (*weight)++;
+               *weight += rt->rt6i_nh_weight;
                upper_bound = DIV_ROUND_CLOSEST_ULL((u64) (*weight) << 31,
                                                    total) - 1;
        }
@@ -4024,6 +4025,8 @@ static int ip6_route_multipath_add(struct fib6_config 
*cfg,
                        goto cleanup;
                }
 
+               rt->rt6i_nh_weight = rtnh->rtnh_hops + 1;
+
                err = ip6_route_info_append(&rt6_nh_list, rt, &r_cfg);
                if (err) {
                        dst_release_immediate(&rt->dst);
@@ -4246,7 +4249,7 @@ static int rt6_add_nexthop(struct sk_buff *skb, struct 
rt6_info *rt)
        if (!rtnh)
                goto nla_put_failure;
 
-       rtnh->rtnh_hops = 0;
+       rtnh->rtnh_hops = rt->rt6i_nh_weight - 1;
        rtnh->rtnh_ifindex = rt->dst.dev ? rt->dst.dev->ifindex : 0;
 
        if (rt6_nexthop_info(skb, rt, &flags, true) < 0)
-- 
2.14.3