From: Stefano Brivio <sbrivio@redhat.com>
To: Martin Lau <kafai@fb.com>
Cc: David Miller <davem@davemloft.net>,
Jianlin Shi <jishi@redhat.com>, "Wei Wang" <weiwan@google.com>,
David Ahern <dsahern@gmail.com>,
Eric Dumazet <edumazet@google.com>,
"netdev@vger.kernel.org" <netdev@vger.kernel.org>
Subject: Re: [PATCH net 1/2] ipv6: Dump route exceptions too in rt6_dump_route()
Date: Fri, 7 Jun 2019 00:58:52 +0200 [thread overview]
Message-ID: <20190607005852.2aee8784@redhat.com> (raw)
In-Reply-To: <20190606223707.s2fyhnqnt3ygdtdj@kafai-mbp.dhcp.thefacebook.com>
On Thu, 6 Jun 2019 22:37:11 +0000
Martin Lau <kafai@fb.com> wrote:
> On Fri, Jun 07, 2019 at 12:17:47AM +0200, Stefano Brivio wrote:
> > On Thu, 6 Jun 2019 21:44:58 +0000
> > Martin Lau <kafai@fb.com> wrote:
> >
> > > > + if (!(filter->flags & RTM_F_CLONED)) {
> > > > + err = rt6_fill_node(net, arg->skb, rt, NULL, NULL, NULL, 0,
> > > > + RTM_NEWROUTE,
> > > > + NETLINK_CB(arg->cb->skb).portid,
> > > > + arg->cb->nlh->nlmsg_seq, flags);
> > > > + if (err)
> > > > + return err;
> > > > + } else {
> > > > + flags |= NLM_F_DUMP_FILTERED;
> > > > + }
> > > > +
> > > > + bucket = rcu_dereference(rt->rt6i_exception_bucket);
> > > > + if (!bucket)
> > > > + return 0;
> > > > +
> > > > + for (i = 0; i < FIB6_EXCEPTION_BUCKET_SIZE; i++) {
> > > > + hlist_for_each_entry(rt6_ex, &bucket->chain, hlist) {
> > > > + if (rt6_check_expired(rt6_ex->rt6i))
> > > > + continue;
> > > > +
> > > > + err = rt6_fill_node(net, arg->skb, rt,
> > > > + &rt6_ex->rt6i->dst,
> > > > + NULL, NULL, 0, RTM_NEWROUTE,
> > > > + NETLINK_CB(arg->cb->skb).portid,
> > > > + arg->cb->nlh->nlmsg_seq, flags);
> > > Thanks for the patch.
> > >
> > > A question on when rt6_fill_node() returns -EMSGSIZE while dumping the
> > > exception bucket here. Where will the next inet6_dump_fib() start?
> >
> > And thanks for reviewing.
> >
> > It starts again from the same node, see fib6_dump_node(): w->leaf = rt;
> > where rt is the fib6_info where we failed dumping, so we won't skip
> > dumping any node.
> If the same node will be dumped, does it mean that it will go through this
> loop and iterate all exceptions again?
Yes (well, all the exceptions for that node).
> > This also means that to avoid sending duplicates in the case where at
> > least one rt6_fill_node() call goes through and one fails, we would
> > need to track the last bucket and entry sent, or, alternatively, to
> > make sure we can fit the whole node before dumping.
> My another concern is the dump may never finish.
That's not a guarantee in general, even without this, because in theory
the skb passed might be small enough that we can't even fit a single
node without exceptions.
We could add a guard on w->leaf not being the same before and after the
walk in inet6_dump_fib() and, if it is, terminate the dump. I just
wonder if we have to do this at all -- I can't find this being done
anywhere else (at a quick look at least).
By the way, we can also trigger a never-ending dump by touching the
tree frequently enough during a dump: it would always start again from
the root, see fib6_dump_table().
--
Stefano
next prev parent reply other threads:[~2019-06-06 22:59 UTC|newest]
Thread overview: 25+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-06-06 20:13 [PATCH net 0/2] ipv6: Fix listing and flushing of cached route exceptions Stefano Brivio
2019-06-06 20:13 ` [PATCH net 1/2] ipv6: Dump route exceptions too in rt6_dump_route() Stefano Brivio
2019-06-06 20:57 ` David Ahern
2019-06-06 21:18 ` Stefano Brivio
2019-06-06 22:47 ` David Ahern
2019-06-06 23:07 ` Stefano Brivio
2019-06-08 5:40 ` Martin Lau
2019-06-08 5:59 ` Stefano Brivio
2019-06-08 7:19 ` Martin Lau
2019-06-08 15:02 ` Stefano Brivio
2019-06-08 15:47 ` Stefano Brivio
2019-06-10 19:42 ` Martin Lau
2019-06-10 21:01 ` Stefano Brivio
2019-06-10 5:56 ` Vaittinen, Matti
2019-06-10 19:01 ` Stefano Brivio
2019-06-06 21:44 ` Martin Lau
2019-06-06 22:17 ` Stefano Brivio
2019-06-06 22:37 ` Martin Lau
2019-06-06 22:48 ` David Ahern
2019-06-07 1:54 ` Stefano Brivio
2019-06-06 22:58 ` Stefano Brivio [this message]
2019-06-06 23:15 ` Stefano Brivio
2019-06-06 23:19 ` David Ahern
2019-06-06 23:31 ` Martin Lau
2019-06-06 20:13 ` [PATCH net 2/2] ip6_fib: Don't discard nodes with valid routing information in fib6_locate_1() Stefano Brivio
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