ipv6: add support of equal cost multipath (ECMP)

Each nexthop is added like a single route in the routing table. All routes
that have the same metric/weight and destination but not the same gateway
are considering as ECMP routes. They are linked together, through a list called
rt6i_siblings.

ECMP routes can be added in one shot, with RTA_MULTIPATH attribute or one after
the other (in both case, the flag NLM_F_EXCL should not be set).

The patch is based on a previous work from
Luc Saillard <luc.saillard@6wind.com>.

Signed-off-by: Nicolas Dichtel <nicolas.dichtel@6wind.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 10 insertions, 0 deletions

diff --git a/include/net/ip6_fib.h b/include/net/ip6_fib.h
index 8a2a203eb15d..20210d79e36a 100644
--- a/include/net/ip6_fib.h
+++ b/include/net/ip6_fib.h
@@ -47,6 +47,8 @@ struct fib6_config {
         unsigned long   fc_expires;
         struct nlattr   *fc_mx;
         int             fc_mx_len;
+        int             fc_mp_len;
+        struct nlattr   *fc_mp;
 
         struct nl_info  fc_nlinfo;
 };
@@ -99,6 +101,14 @@ struct rt6_info {
 
         struct in6_addr                 rt6i_gateway;
 
+        /* Multipath routes:
+         * siblings is a list of rt6_info that have the the same metric/weight,
+         * destination, but not the same gateway. nsiblings is just a cache
+         * to speed up lookup.
+         */
+        struct list_head                rt6i_siblings;
+        unsigned int                    rt6i_nsiblings;
+
         atomic_t                        rt6i_ref;
 
         /* These are in a separate cache line. */