On 6/4/19 3:06 PM, Martin Lau wrote:
> On Tue, Jun 04, 2019 at 02:17:28PM -0600, David Ahern wrote:
>> On 6/3/19 11:29 PM, Martin Lau wrote:
>>> On Mon, Jun 03, 2019 at 07:36:06PM -0600, David Ahern wrote:
>>>> On 6/3/19 6:58 PM, Martin Lau wrote:
>>>>> I have concern on calling ip6_create_rt_rcu() in general which seems
>>>>> to trace back to this commit
>>>>> dec9b0e295f6 ("net/ipv6: Add rt6_info create function for
>>>>> ip6_pol_route_lookup")
>>>>>
>>>>> This rt is not tracked in pcpu_rt, rt6_uncached_list or exception bucket.
>>>>> In particular, how to react to NETDEV_UNREGISTER/DOWN like
>>>>> the rt6_uncached_list_flush_dev() does and calls dev_put()?
>>>>>
>>>>> The existing callers seem to do dst_release() immediately without
>>>>> caching it, but still concerning.
>>>>
>>>> those are the callers that don't care about the dst_entry, but are
>>>> forced to deal with it. Removing the tie between fib lookups an
>>>> dst_entry is again the right solution.
>>> Great to know that there will be a solution. It would be great
>>> if there is patch (or repo) to show how that may look like on
>>> those rt6_lookup() callers.
>>
>> Not 'will be', 'there is' a solution now. Someone just needs to do the
>> conversions and devise the tests for the impacted users.
> I don't think everyone will convert to the new nexthop solution
> immediately.
>
> How about ensuring the existing usage stays solid first?
Use of nexthop objects has nothing to do with separating fib lookups
from dst_entries, but with the addition of fib6_result it Just Works.
Wei converted ipv6 to use exception caches instead of adding them to the
FIB.
I converted ipv6 to use separate data structures for fib entries, added
direct fib6 lookup functions and added fib6_result. See the
net/core/filter.c.
The stage is set for converting users.
For example, ip6_nh_lookup_table does not care about the dst entry, only
the fib entry. This converts it:
static int ip6_nh_lookup_table(struct net *net, struct fib6_config *cfg,
const struct in6_addr *gw_addr, u32 tbid,
int flags, struct fib6_result *res)
{
struct flowi6 fl6 = {
.flowi6_oif = cfg->fc_ifindex,
.daddr = *gw_addr,
.saddr = cfg->fc_prefsrc,
};
struct fib6_table *table;
struct rt6_info *rt;
table = fib6_get_table(net, tbid);
if (!table)
return -EINVAL;
if (!ipv6_addr_any(&cfg->fc_prefsrc))
flags |= RT6_LOOKUP_F_HAS_SADDR;
flags |= RT6_LOOKUP_F_IGNORE_LINKSTATE;
fib6_table_lookup(net, table, cfg->fc_ifindex, fl6, res, flags);
if (res.f6i == net->ipv6.fib6_null_entry)
return -ENETUNREACH;
fib6_select_path(net, &res, fl6, oif, false, NULL, flags);
return 0;
}
