Data ports and maximum number of bearers
Carlo Lobrano
c.lobrano at gmail.com
Fri Sep 23 07:44:21 UTC 2016
Hi Bjørn,
thanks for this reply, it's full of information!
Carlo
On 20 September 2016 at 11:16, Bjørn Mork <bjorn at mork.no> wrote:
> Carlo Lobrano <c.lobrano at gmail.com> writes:
>
> > Initially I'd like to investigate this topic without considering the
> > protocol (AT, MBIM, QMI), and only the modem's capabilities, although
> this
> > note from the above mentioned discussion is really appealing
> >
> > MBIM modems can multiplex IP sessions over a single data port.
> >
> >
> > and as Dan said, QMI should not support this with a single data port.
>
> QMI should already work fine I think. The driver creates a cdc-wdm
> device and a NET port per QMI function, and modems with more than one
> function will therefore have more than one data port available.
>
> The driver ignores the non-functional third QMI port on the Sierra
> modems with this problem, so I believe there is no need for MM or
> anything else to be aware of that issue.
>
> > Also this note caught my attention
> >
> > There's an issue here; the port needs to be a NET port, because that
> >> is what the Bearer should export in the interface. This is, if you
> >> have 2 bearers, they should both expose "wwan0", and not
> >> "/dev/cdc-wdm...". NetworkManager needs to know which is the NET port
> >> where the IP config
> >> is to be applied.
> >
> >
> > does this mean that the required changes will touch other actors (like
> > NetworkManager and/or the driver)?
>
> I don't think so. NetworkManager only needs the NET port and address
> info. The driver already supports creating additional NET ports
> representing the multiplexed MBIM IP sessions, mapping them to VLAN
> interfaces on top of the single default port. The driver API is
> documented here:
> https://www.kernel.org/doc/Documentation/networking/cdc_mbim.txt
>
> So you can set up multiple MBIM IP sessions manually using the "ip" and
> "mbimcli" tools today. What's missing is the part that creates and
> deletes the NET ports as needed, and mapping these to bearers and MBIM
> session IDs in ModemManager.
>
> I guess an example of how to create multiple sessions can help explain
> how the existing driver and libmbim support works:
>
>
> 1) this modem supports up to 8 sessions:
>
>
> # mbimcli -p -d /dev/cdc-wdm0 --query-device-caps
> [/dev/cdc-wdm0] Device capabilities retrieved:
> Device type: 'remote'
> Cellular class: 'gsm'
> Voice class: 'no-voice'
> Sim class: 'removable'
> Data class: 'umts, hsdpa, hsupa, lte'
> SMS caps: 'pdu-receive, pdu-send'
> Ctrl caps: 'reg-manual'
> Max sessions: '8'
> Custom data class: 'unknown'
> Device ID: xxx
> Firmware info: 'SWI9X30C_02.20.03.00'
> Hardware info: 'EM7455'
>
>
> 2) the NET interface created by the driver is named wwan0. We create
> three new interfaces on top of it, representing MBIM session IDs 0,1
> and 2:
>
>
> # ip link add link wwan0 name wwan0.0 type vlan id 4094
> # ip link add link wwan0 name wwan0.1 type vlan id 1
> # ip link add link wwan0 name wwan0.2 type vlan id 2
>
> 3) and bring up the main interface and make sure we're attached to the
> network
>
> # ip link set wwan0 up
>
> # mbimcli -p -d /dev/cdc-wdm0 --attach-packet-service
> [/dev/cdc-wdm0] Successfully attached to packet service
>
> [/dev/cdc-wdm0] Packet service status:
> Network error: 'unknown'
> Packet service state: 'attached'
> Available data classes: 'lte'
> Uplink speed: '50000000 bps'
> Downlink speed: '300000000 bps'
>
>
> 4) then we connect three different sessions to different APNs, one IPv6
> only, one NATed IPv4 and one IPv4 with a public IP address:
>
>
> # mbimcli -p -d /dev/cdc-wdm0 --connect=session-id=0,apn=ims
> [/dev/cdc-wdm0] Successfully connected
>
> [/dev/cdc-wdm0] Connection status:
> Session ID: '0'
> Activation state: 'activated'
> Voice call state: 'none'
> IP type: 'ipv6'
> Context type: 'internet'
> Network error: 'unknown'
>
> [/dev/cdc-wdm0] IPv4 configuration available: 'none'
>
> [/dev/cdc-wdm0] IPv6 configuration available: 'address, gateway, mtu'
> IP [0]: '2a02:2121:105:fd6d:8887:f6a8:c14b:1dc2/64'
> Gateway: '2a02:2121:105:fd6d:31df:2343:a046:245'
> MTU: '1500'
>
> # mbimcli -p -d /dev/cdc-wdm0 --connect=session-id=1,apn=telenor.smart
> [/dev/cdc-wdm0] Successfully connected
>
> [/dev/cdc-wdm0] Connection status:
> Session ID: '1'
> Activation state: 'activated'
> Voice call state: 'none'
> IP type: 'ipv4'
> Context type: 'internet'
> Network error: 'unknown'
>
> [/dev/cdc-wdm0] IPv4 configuration available: 'address, gateway, dns, mtu'
> IP [0]: '10.130.163.117/30'
> Gateway: '10.130.163.118'
> DNS [0]: '193.213.112.4'
> DNS [1]: '130.67.15.198'
> MTU: '1500'
>
> [/dev/cdc-wdm0] IPv6 configuration available: 'none'
>
> # mbimcli -p -d /dev/cdc-wdm0 --connect=session-id=2,apn=telenor
> [/dev/cdc-wdm0] Successfully connected
>
> [/dev/cdc-wdm0] Connection status:
> Session ID: '2'
> Activation state: 'activated'
> Voice call state: 'none'
> IP type: 'ipv4'
> Context type: 'internet'
> Network error: 'unknown'
>
> [/dev/cdc-wdm0] IPv4 configuration available: 'address, gateway, dns, mtu'
> IP [0]: '46.156.97.6/30'
> Gateway: '46.156.97.5'
> DNS [0]: '193.213.112.4'
> DNS [1]: '130.67.15.198'
> MTU: '1500'
>
> [/dev/cdc-wdm0] IPv6 configuration available: 'none'
>
>
> 5) and configure the addressing (except IPv6 addresses which are
> autoconfigured using SLAAC as long as the interface is up when
> connecting):
>
> # ip addr add 10.130.163.117/32 dev wwan0.1
> # ip addr add 46.156.97.6/32 dev wwan0.2
>
>
> The MBIM related NET ports now look like this:
>
> # ip addr show|tail -22
> 10: wwan0: <BROADCAST,MULTICAST,NOARP,UP,LOWER_UP> mtu 1500 qdisc
> pfifo_fast state UNKNOWN group default qlen 1000
> link/ether 9e:81:5f:2f:36:bf brd ff:ff:ff:ff:ff:ff
> inet6 fe80::9c81:5fff:fe2f:36bf/64 scope link
> valid_lft forever preferred_lft forever
> 11: wwan0.0 at wwan0: <BROADCAST,MULTICAST,NOARP,UP,LOWER_UP> mtu 1500 qdisc
> noqueue state UP group default qlen 1000
> link/ether 9e:81:5f:2f:36:bf brd ff:ff:ff:ff:ff:ff
> inet6 2a02:2121:105:fd6d:9c81:5fff:fe2f:36bf/64 scope global
> mngtmpaddr dynamic
> valid_lft forever preferred_lft forever
> inet6 fe80::9c81:5fff:fe2f:36bf/64 scope link
> valid_lft forever preferred_lft forever
> 12: wwan0.1 at wwan0: <BROADCAST,MULTICAST,NOARP,UP,LOWER_UP> mtu 1500 qdisc
> noqueue state UP group default qlen 1000
> link/ether 9e:81:5f:2f:36:bf brd ff:ff:ff:ff:ff:ff
> inet 10.130.163.117/32 scope global wwan0.1
> valid_lft forever preferred_lft forever
> inet6 fe80::9c81:5fff:fe2f:36bf/64 scope link
> valid_lft forever preferred_lft forever
> 13: wwan0.2 at wwan0: <BROADCAST,MULTICAST,NOARP,UP,LOWER_UP> mtu 1500 qdisc
> noqueue state UP group default qlen 1000
> link/ether 9e:81:5f:2f:36:bf brd ff:ff:ff:ff:ff:ff
> inet 46.156.97.6/32 scope global wwan0.2
> valid_lft forever preferred_lft forever
> inet6 fe80::9c81:5fff:fe2f:36bf/64 scope link
> valid_lft forever preferred_lft forever
>
>
>
>
> 6) I don't know how to best demonstrate that this works, but using a
> "get public IP" service is one way:
>
> $ host api.ipify.org
> api.ipify.org is an alias for api.ipify.org.herokudns.com.
> api.ipify.org.herokudns.com has address 54.221.194.87
>
> # ip route add 54.221.194.87 dev wwan0.1
> $ curl 'https://api.ipify.org?format=json'
> {"ip":"2.150.42.73"}
>
> # ip route del 54.221.194.87 dev wwan0.1
> # ip route add 54.221.194.87 dev wwan0.2
> $ curl 'https://api.ipify.org?format=json'
> {"ip":"46.156.97.6"}r
>
>
> I can unfortunately not demonstrate this for session 0, since I have no
> idea which addresses are reachable there. It's not the Internet, but an
> IMS VPN (as you might have guessed from the APN). As you can see above,
> it doesn't even have name servers. But I currently have a shortage of
> valid APNs for testing :-(
>
> Note that it wasn't strictly necessary to create a new NET interface for
> session 0. We could have used the top level interface instead, as we
> currently do in ModemManager. But creating the VLAN is more consistent,
> and allows you to set the MTU independently for all sessions.
>
>
>
> Bjørn
>
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