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Message-ID: <CAA1TwFC8h318B5BPq7a58tBRBwy1KwVbZztXHxc9s4_7TwCiWg@mail.gmail.com>
Date: Mon, 18 Jul 2022 12:58:33 -0400
From: Jaehee <jhpark1013@...il.com>
To: nicolas.dichtel@...nd.com
Cc: netdev@...r.kernel.org, "David S. Miller" <davem@...emloft.net>,
yoshfuji@...ux-ipv6.org, dsahern@...nel.org,
David Ahern <dsahern@...il.com>,
Eric Dumazet <edumazet@...gle.com>,
Jakub Kicinski <kuba@...nel.org>,
Paolo Abeni <pabeni@...hat.com>, shuah@...nel.org,
linux-kernel@...r.kernel.org, Arun Ajith S <aajith@...sta.com>,
Roopa Prabhu <roopa@...dia.com>,
Roopa Prabhu <roopa.prabhu@...il.com>,
Andy Roulin <aroulin@...dia.com>,
Stefano Brivio <sbrivio@...hat.com>
Subject: Re: [PATCH v3 net-next 2/3] net: ipv6: new accept_untracked_na option
to accept na only if in-network
On Mon, Jul 18, 2022 at 4:35 AM Nicolas Dichtel
<nicolas.dichtel@...nd.com> wrote:
>
>
> Le 14/07/2022 à 01:40, Jaehee Park a écrit :
> > This patch adds a third knob, '2', which extends the
> > accept_untracked_na option to learn a neighbor only if the src ip is
> > in the same subnet as an address configured on the interface that
> > received the neighbor advertisement. This is similar to the arp_accept
> > configuration for ipv4.
> >
> > Signed-off-by: Jaehee Park <jhpark1013@...il.com>
> > Suggested-by: Roopa Prabhu <roopa@...dia.com>
> > ---
> > Documentation/networking/ip-sysctl.rst | 51 +++++++++++++++-----------
> > net/ipv6/addrconf.c | 2 +-
> > net/ipv6/ndisc.c | 29 ++++++++++++---
> > 3 files changed, 55 insertions(+), 27 deletions(-)
> >
> > diff --git a/Documentation/networking/ip-sysctl.rst b/Documentation/networking/ip-sysctl.rst
> > index 5c017fc1e24d..722ec4f491db 100644
> > --- a/Documentation/networking/ip-sysctl.rst
> > +++ b/Documentation/networking/ip-sysctl.rst
> > @@ -2483,27 +2483,36 @@ drop_unsolicited_na - BOOLEAN
> >
> > By default this is turned off.
> >
> > -accept_untracked_na - BOOLEAN
> > - Add a new neighbour cache entry in STALE state for routers on receiving a
> > - neighbour advertisement (either solicited or unsolicited) with target
> > - link-layer address option specified if no neighbour entry is already
> > - present for the advertised IPv6 address. Without this knob, NAs received
> > - for untracked addresses (absent in neighbour cache) are silently ignored.
> > -
> > - This is as per router-side behaviour documented in RFC9131.
> > -
> > - This has lower precedence than drop_unsolicited_na.
> > -
> > - This will optimize the return path for the initial off-link communication
> > - that is initiated by a directly connected host, by ensuring that
> > - the first-hop router which turns on this setting doesn't have to
> > - buffer the initial return packets to do neighbour-solicitation.
> > - The prerequisite is that the host is configured to send
> > - unsolicited neighbour advertisements on interface bringup.
> > - This setting should be used in conjunction with the ndisc_notify setting
> > - on the host to satisfy this prerequisite.
> > -
> > - By default this is turned off.
> > +accept_untracked_na - INTEGER
> > + Define behavior for accepting neighbor advertisements from devices that
> > + are absent in the neighbor cache:
> > +
> > + - 0 - (default) Do not accept unsolicited and untracked neighbor
> > + advertisements.
> > +
> > + - 1 - Add a new neighbor cache entry in STALE state for routers on
> > + receiving a neighbor advertisement (either solicited or unsolicited)
> > + with target link-layer address option specified if no neighbor entry
> > + is already present for the advertised IPv6 address. Without this knob,
> > + NAs received for untracked addresses (absent in neighbor cache) are
> > + silently ignored.
> > +
> > + This is as per router-side behavior documented in RFC9131.
> > +
> > + This has lower precedence than drop_unsolicited_na.
> > +
> > + This will optimize the return path for the initial off-link
> > + communication that is initiated by a directly connected host, by
> > + ensuring that the first-hop router which turns on this setting doesn't
> > + have to buffer the initial return packets to do neighbor-solicitation.
> > + The prerequisite is that the host is configured to send unsolicited
> > + neighbor advertisements on interface bringup. This setting should be
> > + used in conjunction with the ndisc_notify setting on the host to
> > + satisfy this prerequisite.
> > +
> > + - 2 - Extend option (1) to add a new neighbor cache entry only if the
> > + source IP address is in the same subnet as an address configured on
> > + the interface that received the neighbor advertisement.
> >
> > enhanced_dad - BOOLEAN
> > Include a nonce option in the IPv6 neighbor solicitation messages used for
> > diff --git a/net/ipv6/addrconf.c b/net/ipv6/addrconf.c
> > index 88becb037eb6..6ed807b6c647 100644
> > --- a/net/ipv6/addrconf.c
> > +++ b/net/ipv6/addrconf.c
> > @@ -7042,7 +7042,7 @@ static const struct ctl_table addrconf_sysctl[] = {
> > .data = &ipv6_devconf.accept_untracked_na,
> > .maxlen = sizeof(int),
> > .mode = 0644,
> > - .proc_handler = proc_dointvec_minmax,
> > + .proc_handler = proc_dointvec,
> > .extra1 = (void *)SYSCTL_ZERO,
> > .extra2 = (void *)SYSCTL_ONE,
> Maybe keeping proc_dointvec_minmax with SYSCTL_TWO for extra2 is better to avoid
> accepting all values. It enables to add another value later.
>
Hi Nicolas, your suggested fix seems to work well in helping us avoid
accepting values >2. When I applied this change, and try to set
accept_untracked_na=3, it gives me a warning: "invalid argument" which
is the desired behavior, thanks! There might be a similar way for arp;
i'm looking for this now.
>
> Regards,
> Nicolas
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