❦ 16 septembre 2016 20:36 CEST, David Ahern <d...@cumulusnetworks.com> :
>> contained a non-connected route (like a default gateway) fails while it
>> was previously working:
>>
>> $ ip link add eth0 type dummy
>> $ ip link set up dev eth0
>> $ ip addr add 2001:db8::1/64 dev eth0
>> $ ip route add ::/0 via 2001:db8::5 dev eth0 table 20
>> $ ip route add 2001:db8:cafe::1/128 via 2001:db8::6 dev eth0 table 20
>> RTNETLINK answers: No route to host
>> $ ip -6 route show table 20
>> default via 2001:db8::5 dev eth0 metric 1024 pref medium
>
> so your table 20 is not complete in that it lacks a connected route to
> resolve 2001:db8::6 as a nexthop, so you are relying on a fallback to
> other tables (main in this case).
Yes.
>> @@ -1991,33 +2015,15 @@ static struct rt6_info *ip6_route_info_create(struct
>> fib6_config *cfg)
>> if (!(gwa_type & IPV6_ADDR_UNICAST))
>> goto out;
>>
>> + err = -EHOSTUNREACH;
>> if (cfg->fc_table)
>> grt = ip6_nh_lookup_table(net, cfg, gw_addr);
>
> -----8<-----
>
>> - if (!(grt->rt6i_flags & RTF_GATEWAY))
>> - err = 0;
>
> This is the check that is failing for your use
> case. ip6_nh_lookup_table is returning the default route and nexthops
> can not rely on a gateway. Given that a simpler and more direct change
> is (whitespace mangled on paste):
>
> diff --git a/net/ipv6/route.c b/net/ipv6/route.c
> index ad4a7ff301fc..48bae2ee2e18 100644
> --- a/net/ipv6/route.c
> +++ b/net/ipv6/route.c
> @@ -1991,9 +1991,19 @@ static struct rt6_info *ip6_route_info_create(struct
> fib6_config *cfg)
> if (!(gwa_type & IPV6_ADDR_UNICAST))
> goto out;
>
> - if (cfg->fc_table)
> + if (cfg->fc_table) {
> grt = ip6_nh_lookup_table(net, cfg, gw_addr);
>
> + /* a nexthop lookup can not go through a gw.
> + * if this happens on a table based lookup
> + * then fallback to a full lookup
> + */
> + if (grt && grt->rt6i_flags & RTF_GATEWAY) {
> + ip6_rt_put(grt);
> + grt = NULL;
> + }
> + }
> +
> if (!grt)
> grt = rt6_lookup(net, gw_addr, NULL,
> cfg->fc_ifindex, 1);
OK. Should the dev check be dismissed or do we add "dev && dev !=
grt->dst.dev" just as a safety net (this would be a convulated setup,
but the correct direct route could be in an ip rule with higher priority
while the one in this table is incorrect)?
--
"... an experienced, industrious, ambitious, and often quite often
picturesque liar."
-- Mark Twain
