Because i'm a stubborn dope, today i decided to have another crack at this infernal problem. Clarification: since i last posted, nothing new has gone wrong, ie, so long as i stayed with the 4.14 LTS kernel, all Suspend-Resumes have behaved just fine re networking. It's just that i decided today to have another try with the latest [Stable branch] kernel; atm = 4.19.0-1 [rc4].
Once booted into 4.19.0-1 [rc4] tonight then relying on those previously-created /etc/systemd/system/network-suspend.service & /etc/systemd/system/network-resume.service files, i Suspended then a bit later Resumed, & saw as expected that i had NO connectivity. Ie, those services somehow broke back on 9 Sept [No Ethernet Network Connection after Resume; very recent problem]. I repeated this test a few more times, with 100% failure.
After another reboot, this time i decided to revert to @tbg's manual commands [No Ethernet Network Connection after Resume; very recent problem]. These succeeded... ie, post-Resume [after said manually-run commands] i have my network .. no reboot needed... & this is with 4.19.
Finding this happy success i've now semi-kinda-sorta-almost-automated it, a bit, by making 2 bash scripts i execute, one before Suspending, then later the other after Resuming. I verified with another test that these are also working fine.
Summary
Stop_NetworkManager_service_BEFORE_Tower_Suspend.sh
#!/bin/bash
### kdemeoz 4/10/18: Manually execute this bash script immediately BEFORE i Suspend Tower, to perform an orderly closure of NetworkManager such that post-Resume, NM can be correctly restarted.
#
# Necessary in Tower [not Lappy] coz so far inexplicably, all kernels later than 4.18.3 have a broken NetworkManager post-Resume, if having done a bog-standard Suspend before. When that occurs, there's no alternative but to Reboot, in order to regain connectivity.
#
sudo systemctl stop NetworkManager.service
sudo ip link set enp2s0 down
sudo modprobe -r r8169
Start_NetworkManager_service_AFTER_Tower_Resume.sh
#!/bin/bash
### kdemeoz 4/10/18: Manually execute this bash script 15 seconds AFTER i Resume Tower, to perform an orderly launch of NetworkManager such that post-Resume, network connectivity is regained. For this to succeed, prior to Suspend i MUST *first* have run "Stop_NetworkManager_service_BEFORE_Tower_Suspend.sh".
#
# Necessary in Tower [not Lappy] coz so far inexplicably, all kernels later than 4.18.3 have a broken NetworkManager post-Resume, if having done a bog-standard Suspend before. When that occurs, there's no alternative but to Reboot, in order to regain connectivity.
#
sudo modprobe r8169
sudo ip link set enp2s0 up
sudo systemctl start NetworkManager.service
So, this seems to be a nice step forward, allowing me to again use later kernels, & still benefit from the Suspend-Resume convenience [which i much prefer compared to having to SD each night then reboot each morning] without losing network ... so long as i ensure i remember to run those scripts appropriately.
I wonder why those actual systemd service files did work correctly, for a little while, then broke [3 Sept - 9 Sept]?
