On 6/3/19 12:09 PM, Wei Wang wrote:
>> diff --git a/net/ipv6/route.c b/net/ipv6/route.c
>> index fada5a13bcb2..51cb5cb027ae 100644
>> --- a/net/ipv6/route.c
>> +++ b/net/ipv6/route.c
>> @@ -432,15 +432,21 @@ void fib6_select_path(const struct net *net, struct
>> fib6_result *res,
>> struct fib6_info *sibling, *next_sibling;
>> struct fib6_info *match = res->f6i;
>>
>> - if (!match->fib6_nsiblings || have_oif_match)
>> + if ((!match->fib6_nsiblings && !match->nh) || have_oif_match)
>> goto out;
>
> So you mentioned fib6_nsiblings and nexthop is mutually exclusive. Is
> it enforced from the configuration?
It is enforced by the patch that wires up RTA_NH_ID for IPv6.
>> @@ -1982,6 +2010,14 @@ struct rt6_info *ip6_pol_route(struct net *net,
>> struct fib6_table *table,
>> rcu_read_unlock();
>> dst_hold(&rt->dst);
>> return rt;
>> + } else if (res.fib6_flags & RTF_REJECT) {
>> + rt = ip6_create_rt_rcu(&res);
>> + rcu_read_unlock();
>> + if (!rt) {
>> + rt = net->ipv6.ip6_null_entry;
>> + dst_hold(&rt->dst);
>> + }
>> + return rt;
>> }
>>
> Why do we need to call ip6_create_rt_rcu() to create a dst cache? Can
> we directly return ip6_null_entry here? This route is anyway meant to
> drop the packet. Same goes for the change in ip6_pol_route_lookup().
This is to mimic what happens if you added a route like this:
ip -6 ro add blackhole 2001:db8:99::/64
except now the blackhole target is contained in the nexthop spec.
>
> And for my education, how does this new nexthop logic interact with
> the pcpu_rt cache and the exception table? Those 2 are currently
> stored in struct fib6_nh. They are shared with fib6_siblings under the
> same fib6_info. Are they also shared with nexthop for the same
> fib6_info?
With nexthop objects IPv6 can work very similar to IPv4. Multiple IPv4
fib entries (fib_alias) can reference the same fib_info where the
fib_info contains an array of fib_nh and the cached routes and
exceptions are stored in the fib_nh.
The one IPv6 attribute that breaks the model is source routing which is
a function of the prefix. For that reason you can not use nexthop
objects with fib entries using source routing. See the note in this
patch in fib6_check_nexthop
> I don't see much changes around that area. So I assume they work as is?
Prior patch sets moved the pcpu and exception caches from fib6_info to
fib6_nh.
