[PATCH v2 08/11] reduce kdump memory consumption by not letting NetworkManager manage unneeded network interfaces

[Coiby Xu]

By default, NetworkManger will manage all the network interfaces and
try to set interface IFF_UP to get carrier state. Regardless of whether
the network interface is connected to a cable or not, the NIC driver
will allocate memory resources for e.g. ring buffers when setting IFF_UP.
This could be a waste of memory. For example it's found i40e consumes ~15GB
on a power machine. On this machine, i40e manages four interfaces but only
one interface is valid. This patch use "managed=false" to tell
NetworkManager to not manage network interfaces that are not needed by
kdump by putting /etc/NetworkManager/conf.d/10-kdump-netif.conf in the
initramfs.

Signed-off-by: Coiby Xu <coxu(a)redhat.com&gt;
---
 dracut-module-setup.sh | 34 +++++++++++++++++++++++++++++++++-
 1 file changed, 33 insertions(+), 1 deletion(-)

diff --git a/dracut-module-setup.sh b/dracut-module-setup.sh
index b72a8e1..f861d3b 100755
--- a/dracut-module-setup.sh
+++ b/dracut-module-setup.sh
@@ -1,6 +1,7 @@
 #!/bin/bash
 
 _DRACUT_KDUMP_NM_TMP_DIR="/tmp/$$-DRACUT_KDUMP_NM"
+_TMP_KDUMP_NETIFS="$_DRACUT_KDUMP_NM_TMP_DIR/kdump_netifs"
 
 cleanup() {
     rm -rf "$_DRACUT_KDUMP_NM_TMP_DIR"
@@ -16,6 +17,7 @@ kdump_module_init() {
     fi
 
     mkdir -p "$_DRACUT_KDUMP_NM_TMP_DIR"
+    echo -n > "$_TMP_KDUMP_NETIFS"
 
     . /lib/kdump/kdump-lib.sh
 }
@@ -299,6 +301,31 @@ kdump_copy_nmconnection_file() {
     # wait-device-timeout=60000 is inserted after "[connection]" so the
     # user's custom value could overwrite it
     sed -i '/\[connection\]/a wait-device-timeout=60000'
"${initdir}/$_initrd_nmconnection_file_path"
+
+    echo -n " $_dev" >> "$_TMP_KDUMP_NETIFS"
+}
+
+kdump_install_nm_netif_allowlist() {
+    local _netif _except_netif _netif_allowlist _netif_allowlist_nm_conf
+
+    for _netif in $1; do
+        _per_mac=$(kdump_get_perm_addr "$_netif")
+        if [[ "$_per_mac" != 'not set' ]]; then
+            _except_netif="mac:$_per_mac"
+        else
+            _except_netif="interface-name:$_netif"
+        fi
+        _netif_allowlist="${_netif_allowlist}except:${_except_netif};"
+    done
+
+    _netif_allowlist_nm_conf=$_DRACUT_KDUMP_NM_TMP_DIR/netif_allowlist_nm_conf
+    cat <<- EOF > "$_netif_allowlist_nm_conf"
+		[device-others]
+		match-device=${_netif_allowlist}
+		managed=false
+	EOF
+
+    inst "$_netif_allowlist_nm_conf"
"/etc/NetworkManager/conf.d/10-kdump-netif.conf"
 }
 
 kdump_setup_bridge() {
@@ -915,7 +942,7 @@ remove_cpu_online_rule() {
 }
 
 install() {
-    local arch
+    local arch _netifs
 
     kdump_module_init
     kdump_install_conf
@@ -976,6 +1003,11 @@ install() {
         inst "ip"
     fi
 
+    _netifs=$(cat "$_TMP_KDUMP_NETIFS")
+    if [[ -n "$_netifs" ]]; then
+        kdump_install_nm_netif_allowlist "$_netifs"
+    fi
+
     # For the lvm type target under kdump, in /etc/lvm/lvm.conf we can
     # safely replace "reserved_memory=XXXX"(default value is 8192) with
     # "reserved_memory=1024" to lower memory pressure under kdump. We do
-- 
2.37.1