Public bug reported: [Impact]
Some 4G/5G mobile networks(for ex., AT&T) requires a specific MTU setting, this setting will be exposed by the ModemManager for network- manger to configure the MTU of the modem network interface . The current modem-manager v1.22.10-1ubuntu2.2 in focal can’t pass AT&T’s modem system certification. [Fix] This upstream patch can resolve this bug: https://gitlab.freedesktop.org/NetworkManager/NetworkManager/-/merge_requests/499/diffs?commit_id=212758ea05a4c13d65f36b55c90aee7919642631 [Test Plan] 1. Use a Lenovo platform SE30 including 4G Quectel EM160 modem and an AT&T SIM card in US 2. Enable 4G modem and connect to AT&T apn $ sudo mmcli -i 0 --pin=0000 $ sudo mmcli --modem 0 --enable $ sudo mmcli -m 0 --simple-connect="pin=0000,apn=emome" $ sudo nmcli radio wwan on $ sudo nmcli connection add type gsm ifname wwan0p2MBIM con-name mymodem apn emome $ sudo nmcli connection up id mymodem 3. Check if the MTU got from the following results are the same: $ sudo mmcli --bearer 5 | mtu $ ifconfig mhi_mbim0 | grep mtu * Expected result: Both MTUs are the same value 1430 * Actual tested result: Different values (one is 1430 , another is 1500) [Where problems could occur] Very low. This is a simple fix: network-manager gets the MTU from the ModemManager then sets the MTU of the modem interface. [Other info] $ lsb_release -rd Description: Ubuntu 20.04.3 LTS Release: 20.04 ** Affects: network-manager (Ubuntu) Importance: Undecided Status: New ** Tags: oem-priority -- You received this bug notification because you are a member of Ubuntu Bugs, which is subscribed to Ubuntu. https://bugs.launchpad.net/bugs/1955797 Title: [SRU] network-manager can’t modify MTU automatically based on what ModemManager exposes for WWAN modems. To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/network-manager/+bug/1955797/+subscriptions -- ubuntu-bugs mailing list ubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs
