networkmanager: fix /etc/resolv.conf handling

The current handling of /etc/resolv.conf by NM has some problems.
When networkd is not configuring network, and there's 'ip=dhcp'
in kernel command line, the /run/NetworkManager/resolv.conf file
is not created, resulting in /etc/resolv.conf being a dead symlink.
This is because NM is treating the network interface as externally
configured and will not try to reconfigure it again.

This means if we want NM to work properly with /etc/resolv.conf,
we've got to either ensure there's no 'ip=dhcp' in kernel command
line, or we've got to ensure networkd is configuring network. This
is weird because normally we should not enable two network managers
at the same time. Note that NM syncs part of its codes with networkd,
which is the reason I think it happens to work when these two network
configuration tools are configuring the same interface at the same
time.

In fact, NM now works well with resolved. It sends the DNS info it
gets to resolved unconditionally by default (the behavior could be
disabled in configuration file).

Looking at the original commit that sets up the update-alternatives
mechanism, it says:
"""
  This brings the networkmanager in sync with how systemd-resolved and connman
  work. Additionally this allows it to function with a read-only rootFS.
"""
I guess the author was using systemd but disabling resolved, and the author
wanted to use read-only rootFS. In order to keep such combination still works,
change to use PACKAGECONFIG to handle things, and when 'man-resolv-conf' is
enabled, the above combination could still work.

Signed-off-by: Chen Qi <Qi.Chen@windriver.com>
Signed-off-by: Khem Raj <raj.khem@gmail.com>
(cherry picked from commit a8ebf23dde9c82dd9d1dcd0fa6de0b4467a0112b)
Signed-off-by: Armin Kuster <akuster808@gmail.com>

1 files changed, 6 insertions, 4 deletions

diff --git a/meta-networking/recipes-connectivity/networkmanager/networkmanager_1.40.0.bb b/meta-networking/recipes-connectivity/networkmanager/networkmanager_1.40.0.bb
index b9273ac89e..801739170b 100644
--- a/meta-networking/recipes-connectivity/networkmanager/networkmanager_1.40.0.bb
+++ b/meta-networking/recipes-connectivity/networkmanager/networkmanager_1.40.0.bb
@@ -107,6 +107,8 @@ PACKAGECONFIG[vala] = "-Dvapi=true,-Dvapi=false"
 PACKAGECONFIG[dhcpcd] = "-Ddhcpcd=${base_sbindir}/dhcpcd,-Ddhcpcd=no,,dhcpcd"
 PACKAGECONFIG[dhclient] = "-Ddhclient=yes,-Ddhclient=no,,dhcp"
 PACKAGECONFIG[concheck] = "-Dconcheck=true,-Dconcheck=false"
+# The following PACKAGECONFIG is used to determine whether NM is managing /etc/resolv.conf itself or not
+PACKAGECONFIG[man-resolv-conf] = ",,"
 
 
 PACKAGES =+ " \
@@ -258,9 +260,9 @@ SYSTEMD_SERVICE:${PN}-daemon = "\
 "
 RCONFLICTS:${PN}-daemon += "connman"
 ALTERNATIVE_PRIORITY = "100"
-ALTERNATIVE:${PN}-daemon = "${@bb.utils.contains('DISTRO_FEATURES','systemd','resolv-conf','',d)}"
-ALTERNATIVE_TARGET[resolv-conf] = "${@bb.utils.contains('DISTRO_FEATURES','systemd','${sysconfdir}/resolv-conf.NetworkManager','',d)}"
-ALTERNATIVE_LINK_NAME[resolv-conf] = "${@bb.utils.contains('DISTRO_FEATURES','systemd','${sysconfdir}/resolv.conf','',d)}"
+ALTERNATIVE:${PN}-daemon = "${@bb.utils.contains('PACKAGECONFIG','man-resolv-conf','resolv-conf','',d)}"
+ALTERNATIVE_TARGET[resolv-conf] = "${@bb.utils.contains('PACKAGECONFIG','man-resolv-conf','${sysconfdir}/resolv-conf.NetworkManager','',d)}"
+ALTERNATIVE_LINK_NAME[resolv-conf] = "${@bb.utils.contains('PACKAGECONFIG','man-resolv-conf','${sysconfdir}/resolv.conf','',d)}"
 
 
 # The networkmanager package is an empty meta package which weakly depends on all the compiled features.
@@ -285,7 +287,7 @@ do_install:append() {
 
     rm -rf ${D}/run ${D}${localstatedir}/run
 
-    if ${@bb.utils.contains('DISTRO_FEATURES','systemd','true','false',d)}; then
+    if ${@bb.utils.contains('PACKAGECONFIG','man-resolv-conf','true','false',d)}; then
         # For read-only filesystem, do not create links during bootup
         ln -sf ../run/NetworkManager/resolv.conf ${D}${sysconfdir}/resolv-conf.NetworkManager