Disable (?) NM random mac for shared XO wifi - USB0 / Chrome/ Pi Zero
Carrol Riddle
ebox382 at scishare.com
Thu Jul 26 10:52:06 EDT 2018
James,
Thank you for answering request for identifying resources and beyond for the
specific testing.
I had been using udevadm, but not monitor. Your point about possible racing is
supported by observations noted in previous post. The pattern of lengthening
"no-auto-default" line in NetworkManager.conf may also show varying boot paths.
A topic of interest is web discussions of failures of NetworkManager-wait-online.service as typified by:
purschel.eu/linux/centos-7-networkmanager-wait-online-service-failed/
MetworkManager-wait-online.service functions on activation of interface and does not wait for interface to obtain IP address and then come online.
NetworkManager-wait-online.service is enabled on XO (systemctl is-name). The parts in the above example fix (nohup,nm-online) are on the XO. Do not know ExecStart part. systemd-networkd-wait-online.service used by other examples is not on XO . Application machanger has been used in other examples.
My more immediate concern is bringing up the small starter network with provided Village Telco routers for these XO's in a dense inner city neighborhood.
Will have to come back to this topic later. Appreciate the kick-starter.
N. C. Riddle
> On July 25, 2018 at 6:41 AM James Cameron <quozl at laptop.org> wrote:
>
>
> In my tests just now on OLPC OS 13.2.9 and an XO-4, my USB ethernet
> adapters always come back after reconnection or reboot with the same
> MAC address. With or without Network Manager running. So that
> suggests that for adapters with a physical address ROM or
> preprogrammed flash, they will appear predictable.
>
> My tests above were not with Raspberry Pi Zero. So I now turn to
> testing with one;
>
> 1. the MAC addresses change on each boot of the Zero, and are
> unpredictable,
>
> 2. the MAC address shown on each end is different; comparing usb0 on
> the XO vs usb0 on the Zero,
>
> 3. turning off Network Manager has no effect; therefore this is not a
> Network Manager behaviour as you surmised,
>
> I've also tested with kernel v4.15 on an OLPC NL3, and the same
> unpredictable MAC address behaviour occurs.
>
> Perhaps it is udev? Using udevadm --monitor --property, shows
> several events from the kernel, and the first one to mention the
> MAC address eventually used is this one;
>
> UDEV [861.284453] add
> /devices/pci0000:00/0000:00:14.0/usb1/1-4/1-4.1/1-4.1:1.0/net/enp0s20u4u1
> (net)
> .MM_USBIFNUM=00
> ACTION=add
> DEVPATH=/devices/pci0000:00/0000:00:14.0/usb1/1-4/1-4.1/1-4.1:1.0/net/enp0s20u4u1
> ID_BUS=usb
> ID_MM_CANDIDATE=1
> ID_MODEL=RNDIS_Ethernet_Gadget
> ID_MODEL_ENC=RNDIS\x2fEthernet\x20Gadget
> ID_MODEL_FROM_DATABASE=Linux-USB Ethernet/RNDIS Gadget
> ID_MODEL_ID=a4a2
> ID_NET_DRIVER=cdc_ether
> ID_NET_LINK_FILE=/lib/systemd/network/99-default.link
> ID_NET_NAME=enp0s20u4u1
> ID_NET_NAME_MAC=enxca2a7e605b6f <-- encx followed by the address
> ID_NET_NAME_PATH=enp0s20u4u1
> ID_PATH=pci-0000:00:14.0-usb-0:4.1:1.0
> ID_PATH_TAG=pci-0000_00_14_0-usb-0_4_1_1_0
> ID_REVISION=0409
> ID_SERIAL=Linux_4.9.35+_with_20980000.usb_RNDIS_Ethernet_Gadget
> ID_TYPE=generic
> ID_USB_CLASS_FROM_DATABASE=Communications
> ID_USB_DRIVER=cdc_ether
> ID_USB_INTERFACES=:0202ff:0a0000:020600:
> ID_USB_INTERFACE_NUM=00
> ID_VENDOR=Linux_4.9.35+_with_20980000.usb
> ID_VENDOR_ENC=Linux\x204.9.35+\x20with\x2020980000.usb
> ID_VENDOR_FROM_DATABASE=Netchip Technology, Inc.
> ID_VENDOR_ID=0525
> IFINDEX=7
> INTERFACE=enp0s20u4u1
> INTERFACE_OLD=usb0
> SEQNUM=3175
> SUBSYSTEM=net
> SYSTEMD_ALIAS=/sys/subsystem/net/devices/enp0s20u4u1
> TAGS=:systemd:
> USEC_INITIALIZED=861268742
>
> So the MAC address originates from the kernel or systemd, not Network
> Manager.
>
> As there is a udev event, it should be possible to write a udev rule
> to change the MAC address when this or one of the later events
> arrives.
>
> However, perhaps we can see if this MAC address comes from the kernel
> or systemd; the event above references
> /lib/systemd/network/99-default.link which says'
>
> [Link]
> NamePolicy=kernel database onboard slot path
> MACAddressPolicy=persistent
>
> Now, setting MACAddressPolicy to none has no effect, which
> suggests the random address is coming from the kernel.
>
> My guess is that the reason why your udev rpi script fails is that it
> is triggered on more than one udev event, or races with other things
> for access to the device. Add more logging and debugging to it.
>
> Reference:
>
> https://www.freedesktop.org/software/systemd/man/systemd.link.html
>
> On Fri, Jul 20, 2018 at 11:20:57PM -0400, Carrol Riddle wrote:
> > The difficulty is that a new connection is started on each boot and starts
> > as "automatic" IPv4 instead of the desired "share with other computers" This
> > results from a randomized MAC address, which appears to be controlled by
> > Network Manager. If the MAC address persists on next boot,
> > then the connection file will persist.
> >
> > The MAC address in the cmdline.txt on Zero is vestige of efforts. It was
> > left since I suspect it will be part of the solution. Retested without and
> > it makes no difference when no other changes are made (i.e., only with
> > essentials in cmdline.txt). I have tried static IP on Zero via adding
> > ip=192.168.1.2 to cmdline.txt or in dhcpcd.config and udev rule on XO for
> > ip=198.168.1.1 . Uncertain if udev rule needs additional specification
> > (parent ATTRS ?).
> >
> > Reasoned that host_addr was telling Zero where to find existing MAC on XO
> > and udev rule then tried with hw to assure it was there. Have tried adding
> > mac-cloned-address to NetworkManager.conf
> >
> > NetworkManager randomization of MAC addresses is widely discussed in search
> > results and variety of solutions proposed. I have had periods where MAC was
> > persistent, but only have it fail a few hours later (just powered off). One
> > case of oddity was the persistence on every other boot, if the intervening
> > boot was without Zero attached. However, my work with wired links to
> > routers (TP-Link MR3020 and Village Telco MP20) shows persistence in boot of
> > router.
> >
> > A competent programmer might just modify the started connection file (using
> > awk, grep, sed ?) and restart NetworkManager. :) . I tried replacing
> > (cp) with model files, but that has problems (date stamp).
> > /etc/NetworkManger/connections
> >
> > What I see points me to NetworkManager,
> >
> > Carrol Riddle
> >
> > > On July 14, 2018 at 1:07 AM James Cameron <quozl at laptop.org> wrote:
> > >
> > >
> > > Interesting.
> > >
> > > But why do you need to give a MAC address on cmdline.txt on the RPi
> > > and in the XO udev script? g_ether should assign an address, and
> > > cdc_ether should receive it from USB descriptors.
> > >
> > > On Tue, Jul 10, 2018 at 10:50:44AM -0400, Carrol Riddle wrote:
> > > > Soliciting info or pointers to resources for disabling mac address
> > > > randomization by NetworkManager for USB0 (eth1) on XO's. Wifi mac
> > > > addresses are not randomized.
> > > >
> > > > An XO can share its Wifi over wired ethernet link (USB0) where it can be
> > > > used by
> > > > a Chromium browser on a linked Raspberry Pi Zero (not W). SSH -X on the
> > > > link
> > > > allows XO keyboard and display to be used for Chromium.
> > > >
> > > > The several setup steps are simple, but must be repeated with each boot
> > > > since
> > > > NetworkManager (version 0.9.8.* on XO's) supplies a different mac
> > > > address for
> > > > the link on each boot. To provide a simple Sugar wrapper to run
> > > > Chromium, a
> > > > consistent mac address would be needed.
> > > >
> > > > Methods from web searches have not been successful in disabling
> > > > randomization,
> > > > largely since they use features added after 0.9.8. Using a udev rule
> > > > to "ifconfig
> > > > usb0 hw ether address" has come the closest, but breaks after a few
> > > > boots and returns to
> > > > randomization.
> > > >
> > > > BACKGROUND
> > > >
> > > > For those interested, details are below, but are only peripheral to
> > > > question. This use of the XO's display, keyboard and wifi by Chromium /
> > > > Zero provides a low cost way to access a widely accepted browser. The
> > > > Zero can be plugged into XO USB for power and signals. The Zero is
> > > > available for < $10, and with SD card and plug, total cost should be $15
> > > > - 20
> > > > USD.
> > > >
> > > >
> > > > ______________________________________
> > > >
> > > >
> > > > MANUAL METHOD - XO (after Pi Zero setup)
> > > >
> > > > In Sugar, connect to wifi . This needs to be done only the first time
> > > > and is
> > > > persistent between boots. Switch to Gnome and disconnect from the
> > > > "Wired
> > > > connection ?" that just formed. Edit the connection : IPv6 to ignore,
> > > > IPv4 to
> > > > require IPv4 and "shared to other computers" and save. Connect to
> > > > this
> > > > connection. The connection info should show ip address starting with
> > > > 10: .
> > > > This link is not persistent between boots.
> > > >
> > > > systemctl enable sshd.service
> > > >
> > > > PI ZERO SETUP (prior)
> > > >
> > > > Raspberry Pi Zero with Raspbian Desktop installed. To
> > > > /boot/config.txt on Pi
> > > > SD edit and add dtoverlay=dwc2 . To /boot/cmdline.txt add after
> > > > "rootwait"
> > > > modules-load=dwc2,g_ether host_addr=00:22:82:ff:ff:20
> > > > dev_addr=00:22:82:ff:ff:22 (Substitute local mac addresses.)
> > > > To start with SSH, add dummy "ssh" file to /boot directory. On XO,
> > > > ssh pi at raspberrypi.local with password raspberry . Configure Zero to
> > > > boot to
> > > > command line (CLI) with raspi-config . To use Raspbian desktop, ssh
> > > > -X
> > > > pi at raspberry.local, and then /etc/X11/Xsession. The Pi Tool Bar
> > > > partially
> > > > overlaps the Gnome Tool Bar, but selecting "medium display size"
> > > > minimizes
> > > > affects.
> > > >
> > > > UDEV INFO FOR RULES (but not able to make work)
> > > >
> > > > DRIVERS=="cdc_ether"
> > > >
> > > > ATTRS{idVendor=1d6b}
> > > >
> > > > ATTRS{idProduct=0001}
> > > >
> > > > RUN+="/etc/udev/scripts/rpi"
> > > >
> > > >
> > > > Script rpi:
> > > >
> > > > ifconfig usb0 down
> > > >
> > > > ifconfig usb0 hw ether 00:22:82:FF:FF:20
> > > >
> > > > ifconfig usb0 up
> > > >
> > > > _____________________________
> > > >
> > > > Carrol Riddle
> > > >
> > > > ebox382 at scishare.com
> > > > _______________________________________________
> > > > Devel mailing list
> > > > Devel at lists.laptop.org
> > > > http://lists.laptop.org/listinfo/devel
> > >
> > > --
> > > James Cameron
> > > http://quozl.netrek.org/
> > > _______________________________________________
> > > Devel mailing list
> > > Devel at lists.laptop.org
> > > http://lists.laptop.org/listinfo/devel
> > _______________________________________________
> > Devel mailing list
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> > http://lists.laptop.org/listinfo/devel
>
> --
> James Cameron
> http://quozl.netrek.org/
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