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Date: Sun, 28 Aug 2022 13:24:22 +0200 From: netdev@...io-technology.com To: Ido Schimmel <idosch@...dia.com> Cc: Nikolay Aleksandrov <razor@...ckwall.org>, davem@...emloft.net, kuba@...nel.org, netdev@...r.kernel.org, Florian Fainelli <f.fainelli@...il.com>, Andrew Lunn <andrew@...n.ch>, Vivien Didelot <vivien.didelot@...il.com>, Vladimir Oltean <olteanv@...il.com>, Eric Dumazet <edumazet@...gle.com>, Paolo Abeni <pabeni@...hat.com>, Kurt Kanzenbach <kurt@...utronix.de>, Hauke Mehrtens <hauke@...ke-m.de>, Woojung Huh <woojung.huh@...rochip.com>, UNGLinuxDriver@...rochip.com, Sean Wang <sean.wang@...iatek.com>, Landen Chao <Landen.Chao@...iatek.com>, DENG Qingfang <dqfext@...il.com>, Matthias Brugger <matthias.bgg@...il.com>, Claudiu Manoil <claudiu.manoil@....com>, Alexandre Belloni <alexandre.belloni@...tlin.com>, Jiri Pirko <jiri@...nulli.us>, Ivan Vecera <ivecera@...hat.com>, Roopa Prabhu <roopa@...dia.com>, Shuah Khan <shuah@...nel.org>, Christian Marangi <ansuelsmth@...il.com>, Daniel Borkmann <daniel@...earbox.net>, Yuwei Wang <wangyuweihx@...il.com>, linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org, linux-mediatek@...ts.infradead.org, bridge@...ts.linux-foundation.org, linux-kselftest@...r.kernel.org Subject: Re: [PATCH v5 net-next 1/6] net: bridge: add locked entry fdb flag to extend locked port feature On 2022-08-27 15:17, Ido Schimmel wrote: > On Sat, Aug 27, 2022 at 02:30:25PM +0300, Nikolay Aleksandrov wrote: >> On 26/08/2022 14:45, Hans Schultz wrote: >> Please add the blackhole flag in a separate patch. > > +1 > > [...] > >> > @@ -185,6 +196,9 @@ int br_handle_frame_finish(struct net *net, struct sock *sk, struct sk_buff *skb >> > if (test_bit(BR_FDB_LOCAL, &dst->flags)) >> > return br_pass_frame_up(skb); >> > >> > + if (test_bit(BR_FDB_BLACKHOLE, &dst->flags)) >> > + goto drop; >> > + >> Not happy about adding a new test in arguably the most used fast-path, >> but I don't see >> a better way to do blackhole right now. Could you please make it an >> unlikely() ? >> >> I guess the blackhole flag will be allowed for user-space to set at >> some point, why >> not do it from the start? >> >> Actually adding a BR_FDB_LOCAL and BR_FDB_BLACKHOLE would be a >> conflict above - >> the packet will be received. So you should move the blackhole check >> above the >> BR_FDB_LOCAL one if user-space is allowed to set it to any entry. > > Agree about unlikely() and making it writeable from user space from the > start. This flag is different from the "locked" flag that should only > be > ever set by the kernel. > > Regarding BR_FDB_LOCAL, I think BR_FDB_BLACKHOLE should only be allowed > with BR_FDB_LOCAL as these entries are similar in the following ways: > > 1. It doesn't make sense to associate a blackhole entry with a specific > port. The packet will never be forwarded to this port, but dropped by > the bridge. This means user space will add them on the bridge itself: > > # bridge fdb add 00:11:22:33:44:55 dev br0 self local blackhole > > 2. If you agree that these entries should not be associated with a > specific port, then it also does not make sense to subject them to > ageing and roaming, just like existing local/permanent entries. > > The above allows us to push the new check under the BR_FDB_LOCAL check: > > diff --git a/net/bridge/br_input.c b/net/bridge/br_input.c > index 68b3e850bcb9..4357445529a5 100644 > --- a/net/bridge/br_input.c > +++ b/net/bridge/br_input.c > @@ -182,8 +182,11 @@ int br_handle_frame_finish(struct net *net, > struct sock *sk, struct sk_buff *skb > if (dst) { > unsigned long now = jiffies; > > - if (test_bit(BR_FDB_LOCAL, &dst->flags)) > + if (test_bit(BR_FDB_LOCAL, &dst->flags)) { > + if (unlikely(test_bit(BR_FDB_BLACKHOLE, > &dst->flags))) > + goto drop; > return br_pass_frame_up(skb); > + } > > if (now != dst->used) > dst->used = now; It shall be so as suggested. :-)
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