dhcpcd: raw-ip support
dcbw at redhat.com
Mon Aug 19 15:34:02 UTC 2019
On Mon, 2019-08-19 at 14:57 +0200, Bjørn Mork wrote:
> Yegor Yefremov <yegorslists at googlemail.com> writes:
> > On Mon, Aug 19, 2019 at 10:49 AM Bjørn Mork <bjorn at mork.no> wrote:
> > > Yegor Yefremov <yegorslists at googlemail.com> writes:
> > >
> > > > I have a project where I'm using dhcpcd client. It is working
> > > > without
> > > > any problems with older modems like Quectel UC20 etc. But now
> > > > we want
> > > > to switch to SIM7600G-H and it is working in raw-ip mode. So
> > > > far only
> > > > udhcpc can handle such MAC address-less interfaces.
> > > >
> > > > Do you know what is so special about udhcpc compared to other
> > > > DHCP
> > > > clients?
> > >
> > > It's mostly L2 agnostic, meaning that it will work on non-
> > > ethernet
> > > interfaces.
> > >
> > > "Fixing" this for other clients isn't really that hard, if
> > > required. I
> > > did this proof-of-concept for ISC dhclient for example:
> > >
> > >
> > > https://mail.gnome.org/archives/networkmanager-list/2015-December/msg00044.html
> > Thanks for the patch. But looks like it hasn't been upstreamed yet
> > :-(
> Upstreaming anything to ISC is not possible in my experience. See
> Or at least not worth the extra effort required.
> And I don't think raw-ip support is all that useful, to be
> honest. The
> DHCP server in the modem is a hack anyway. You should use the modem
> management channel to get IP config from the modem. I.e. QMI.
> But DHCPv6 support on PPP links is something else. It's an essential
> feature for a DHCPv6 client. As you may or may not know, IPV6CP is
> different from IPCP when it comes to address negotiation. It will
> negotiate an interface-id and leave the remaining address config to
> normal autoconf protocols. I.e. you need to run SLAAC and/or DHCPv6
> the link if you want a global address.
> Somewhat off-topic here. Unless you have a modem with support for
> over PPP, which I recently learned actuall exists:
Nokia 21M-02 (Icera HSPA chipset) is what I used to develop + verify
the PPPv6 support in ModemManager and NetworkManager a number of years
ago. They do exist but in my experience are pretty rare as IPv6 only
because common with LTE networks and almost nobody should be using PPP
And yes there the procedure is to acquire the Interface ID (IID) from
IPV6CP, use that to generate the IPv6 Link-Local address and assign it
to the PPP interface, then run SLAAC to get your prefix and (if SLAAC
tells you to) DHCPv6 for DNS servers. The 21M-02 (or T-Mobile US)
didn't implement DNSSD or RDNSS options for RAs so for me static DNS or
DHCPv6 was necessary.
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