Date: Tue, 7 Jul 2020 17:10:27 +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: <20200707171027.4556a126@bsd64.grem.de> In-Reply-To: <20200707120835.4834198e@bsd64.grem.de> References: <713e1f3e-4dd9-8dcf-c6d2-15c684bdce5b@daemonic.se> <a6a05909-a11d-42c9-2e62-9fc50b38c9f3@daemonic.se> <20200707120835.4834198e@bsd64.grem.de>
next in thread | previous in thread | raw e-mail | index | archive | help
On Tue, 7 Jul 2020 12:08:35 +0200 Michael Gmelin <freebsd@grem.de> wrote: > On Mon, 6 Jul 2020 22:58:54 +0200 > Niclas Zeising <zeising+freebsd@daemonic.se> wrote: >=20 > > On 2020-07-06 13:05, Niclas Zeising wrote: =20 > > > 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 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 do= es > > > 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 >=20 > > =20 >=20 > This works: >=20 > 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" >=20 > # 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> >=20 > -m >=20 This works too: ifconfig_vtnet0=3D"inet" ifconfig_vtnet0_ipv6=3D"inet6 -auto_linklocal" ifconfig_vtnet0_aliases=3D"\ inet 192.168.0.1/24 inet6 fe80::1/64 inet6 2001:6b8::/64" As well as this: ifconfig_vtnet0=3D"inet" ifconfig_vtnet0_ipv6=3D"inet6 -auto_linklocal fe80::1/64" ifconfig_vtnet0_aliases=3D"inet 192.168.0.1/24 inet6 2001:6b8::/64" Using `ifconfig_vtnet0=3D"inet 192.168.0.1/24"` adds the auto-generated link-local address (which is what you seem to try to avoid). Cheers, Michael --=20 Michael Gmelin
Want to link to this message? Use this URL: <https://mail-archive.FreeBSD.org/cgi/mid.cgi?20200707171027.4556a126>