Similar to 3bfd847203c6 ("net: Use passed in table for nexthop lookups")
for IPv4, if the route spec contains a table id use that to lookup the
next hop first and fall back to a full lookup if it fails (per the fix
4c9bcd117918b ("net: Fix nexthop lookups")).

Example:

    root@kenny:~# ip -6 ro ls table red
    local 2100:1::1 dev lo  proto none  metric 0  pref medium
    2100:1::/120 dev eth1  proto kernel  metric 256  pref medium
    local 2100:2::1 dev lo  proto none  metric 0  pref medium
    2100:2::/120 dev eth2  proto kernel  metric 256  pref medium
    local fe80::e0:f9ff:fe09:3cac dev lo  proto none  metric 0  pref medium
    local fe80::e0:f9ff:fe1c:b974 dev lo  proto none  metric 0  pref medium
    fe80::/64 dev eth1  proto kernel  metric 256  pref medium
    fe80::/64 dev eth2  proto kernel  metric 256  pref medium
    ff00::/8 dev red  metric 256  pref medium
    ff00::/8 dev eth1  metric 256  pref medium
    ff00::/8 dev eth2  metric 256  pref medium
    unreachable default dev lo  metric 240  error -113 pref medium

    root@kenny:~# ip -6 ro add table red 2100:3::/64 via 2100:1::64
    RTNETLINK answers: No route to host

Route add fails even though 2100:1::64 is a reachable next hop:
    root@kenny:~# ping6 -I red  2100:1::64
    ping6: Warning: source address might be selected on device other than red.
    PING 2100:1::64(2100:1::64) from 2100:1::1 red: 56 data bytes
    64 bytes from 2100:1::64: icmp_seq=1 ttl=64 time=1.33 ms

With this patch:
    root@kenny:~# ip -6 ro add table red 2100:3::/64 via 2100:1::64
    root@kenny:~# ip -6 ro ls table red
    local 2100:1::1 dev lo  proto none  metric 0  pref medium
    2100:1::/120 dev eth1  proto kernel  metric 256  pref medium
    local 2100:2::1 dev lo  proto none  metric 0  pref medium
    2100:2::/120 dev eth2  proto kernel  metric 256  pref medium
    2100:3::/64 via 2100:1::64 dev eth1  metric 1024  pref medium
    local fe80::e0:f9ff:fe09:3cac dev lo  proto none  metric 0  pref medium
    local fe80::e0:f9ff:fe1c:b974 dev lo  proto none  metric 0  pref medium
    fe80::/64 dev eth1  proto kernel  metric 256  pref medium
    fe80::/64 dev eth2  proto kernel  metric 256  pref medium
    ff00::/8 dev red  metric 256  pref medium
    ff00::/8 dev eth1  metric 256  pref medium
    ff00::/8 dev eth2  metric 256  pref medium
    unreachable default dev lo  metric 240  error -113 pref medium

Signed-off-by: David Ahern <d...@cumulusnetworks.com>
---
 net/ipv6/route.c | 35 +++++++++++++++++++++++++++++++++--
 1 file changed, 33 insertions(+), 2 deletions(-)

diff --git a/net/ipv6/route.c b/net/ipv6/route.c
index 1d8871a5ed20..3e699dc199f3 100644
--- a/net/ipv6/route.c
+++ b/net/ipv6/route.c
@@ -1928,7 +1928,7 @@ static struct rt6_info *ip6_route_info_create(struct 
fib6_config *cfg)
                rt->rt6i_gateway = *gw_addr;
 
                if (gwa_type != (IPV6_ADDR_LINKLOCAL|IPV6_ADDR_UNICAST)) {
-                       struct rt6_info *grt;
+                       struct rt6_info *grt = NULL;
 
                        /* IPv6 strictly inhibits using not link-local
                           addresses as nexthop address.
@@ -1940,7 +1940,38 @@ static struct rt6_info *ip6_route_info_create(struct 
fib6_config *cfg)
                        if (!(gwa_type & IPV6_ADDR_UNICAST))
                                goto out;
 
-                       grt = rt6_lookup(net, gw_addr, NULL, cfg->fc_ifindex, 
1);
+                       if (cfg->fc_table) {
+                               struct flowi6 fl6 = {
+                                       .flowi6_oif = cfg->fc_ifindex,
+                                       .daddr = *gw_addr,
+                                       .saddr = cfg->fc_prefsrc,
+                               };
+                               struct fib6_table *table;
+                               int flags = 0;
+
+                               err = -EHOSTUNREACH;
+                               table = fib6_get_table(net, cfg->fc_table);
+                               if (!table)
+                                       goto out;
+
+                               if (!ipv6_addr_any(&cfg->fc_prefsrc))
+                                       flags |= RT6_LOOKUP_F_HAS_SADDR;
+
+                               grt = ip6_pol_route(net, table, cfg->fc_ifindex,
+                                                   &fl6, flags);
+
+                               /* if table lookup failed, fall back
+                                * to full lookup
+                                */
+                               if (grt == net->ipv6.ip6_null_entry) {
+                                       ip6_rt_put(grt);
+                                       grt = NULL;
+                               }
+                       }
+
+                       if (!grt)
+                               grt = rt6_lookup(net, gw_addr, NULL,
+                                                cfg->fc_ifindex, 1);
 
                        err = -EHOSTUNREACH;
                        if (!grt)
-- 
2.1.4

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