Date: Tue, 7 Jul 2020 12:08:35 +0200 From: Michael Gmelin <freebsd@grem.de> To: Niclas Zeising <zeising+freebsd@daemonic.se> Cc: net@FreeBSD.org Subject: Re: Specifying link-local address in rc.conf Message-ID: <20200707120835.4834198e@bsd64.grem.de> In-Reply-To: <a6a05909-a11d-42c9-2e62-9fc50b38c9f3@daemonic.se> References: <713e1f3e-4dd9-8dcf-c6d2-15c684bdce5b@daemonic.se> <a6a05909-a11d-42c9-2e62-9fc50b38c9f3@daemonic.se>
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On Mon, 6 Jul 2020 22:58:54 +0200
Niclas Zeising <zeising+freebsd@daemonic.se> wrote:
> On 2020-07-06 13:05, Niclas Zeising wrote:
> > Hi!
> > Is it possible to specify a link-local address in rc.conf, and get
> > only that link-local address?
> >=20
> > When I add a specific link-local address, such as fe80::1/64, to an=20
> > interface from the command line, and then add a global uincast
> > address, it works as expected, I do not get an additional
> > link-local address. When I try to do the same in rc.conf however,
> > it does not work. I have added the following:
> > ifconfig_vtnet0_inet6=3D"inet6 fe80::1/64"
> > ifconfig_vtnet0_alias0=3D"2001:6b8::1/64"
> > to rc.conf, but when restarting, I get both fe80::1 and a
> > EUI64-based link-local address assigned to the interface.=C2=A0 It does
> > not matter which order I specify the entries in rc.conf.
> > I have tried changing the sysctl net.inet6.ip6.auto_linklocal to 0
> > in /etc/sysctl.conf, but that does not work (it seems it takes
> > effect too late, the interface still has the AUTO_LINKLOCAL flag
> > set according to ifconfig).
> > I tried adding -auto_linklocal to the ifconfig_* lines in
> > /etc/rc.conf, and while this removes the AUTO_LINKLOCAL flag from
> > the interface, a EUI64 based link-local address is still assigned
> > to the interface.
> >=20
> > While there might not be much of a problem having mulitple
> > link-local addresses, this is surprising.=C2=A0 Adding a specific
> > link-local address to an interface, even from rc.conf, shouldn't
> > mean that the EUI64-one is created.=C2=A0 Perhaps something like
> > ifconfig_IF_linklocal=3D"" should be added, or this is a bug in
> > rc.network.=C2=A0 I tried looking through rc.network and related rc
> > files, but I didn't find anything obvious, and I couldn't really
> > figure out how addresses are added to interfaces during boot.
> >=20
> > This is causing issues when I want for instance rtadvd to use the=20
> > fe80::1/64 address as source for router advertisements, since it
> > picks the EUI64 link-local address as source (which means this also
> > ends up in client routing tables as the default gateway).=C2=A0 I can
> > work around this problem by adding fe80::1/64 with prefer_source,
> > but I would prefer if there only was one link-local address on an
> > interface.
> >=20
> > All of this is on FreeBSD 12.1.
> >=20
> > Perhaps I'm just missing something, but this behavior feels a
> > little surprising.
> >=20
> > I can share more detailed configuration, and perhaps the whole
> > virtual machine I'm testing on, if needed.
> >=20
> > Regards =20
>=20
> I did some more digging. It only happens when there's also an=20
> ifconfig_IF for IPv4 in the /etc/rc.conf.
>=20
> Not working configuration (/etc/rc.conf)
> ifconfig_vtnet0=3D"192.168.0.1/24"
> ifconfig_vtnet0_ipv6=3D"inet6 fe80::1/64"
> ifconfig_vtnet0_alias0=3D"inet6 2001:6b8::/64"
>=20
> This configuration creates an EUI64-based link-local addess on vtnet0
> as well.
>=20
> Working configuration (apart from no IPv4)
> ifconfig_vtnet0_ipv6=3D"inet6 fe80::1/64"
> ifconfig_vtnet0_alias0=3D"inet6 2001:6b8::/64""
>=20
This works:
ifconfig_vtnet0=3D"inet6 -auto_linklocal"
ifconfig_vtnet0_ipv6=3D"up"
ifconfig_vtnet0_aliases=3D"\
inet 192.168.0.1/24 inet6 fe80::1/64 inet6 2001:6b8::/64"
# ifconfig vtnet0
vtnet0: flags=3D8943<UP,BROADCAST,RUNNING,PROMISC,SIMPLEX,MULTICAST>
metric 0 mtu 1500 options=3D80028<VLAN_MTU,JUMBO_MTU,LINKSTATE>
ether 58:9c:fc:0b:99:97
inet 192.168.0.1 netmask 0xffffff00 broadcast 192.168.0.255
inet6 fe80::1%vtnet0 prefixlen 64 scopeid 0x2
inet6 2001:6b8:: prefixlen 64
media: Ethernet 10Gbase-T <full-duplex>
status: active
nd6 options=3D1<PERFORMNUD>
-m
--=20
Michael Gmelin
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