From c4a0ad47dd7aed257d563fbbb90e086148faf169 Mon Sep 17 00:00:00 2001
From: Coiby Xu <coxu@redhat.com>
Date: Thu, 25 May 2023 16:56:12 +0800
Subject: [PATCH] Only rename the virtual Azure Hyper-V network interface

Resolves: https://bugzilla.redhat.com/show_bug.cgi?id=1964822
Upstream: RHEL-only

Currently, vmcore dumping to remote fs gives a warning "eth0: Failed to
rename network interface 3 from 'eth0' to 'kdump-eth0': File exists" on
Azure Hyper-V VM with accelerated networking because it uses a physical
NIC for accelerated networking [1] and the backing physical NIC has the
same MAC address as the virtual NIC. In the kdump initrd, an udev rule
will try renaming NICs with the given MAC address and fails as expected
since there are two NICs having the same MAC address. This udev rule is
created automatically when specifying the dracut cmdline
"ifname=<interface>:<MAC>". For the case of Azure Hyper-V VM with
accelerated networking, only the virtual network interface need to be
renamed. So create an udev rule manually.

[1] https://learn.microsoft.com/en-us/azure/virtual-network/accelerated-networking-overview

Signed-off-by: Coiby Xu <coxu@redhat.com>
---
 dracut-module-setup.sh | 26 +++++++++++++++++++-------
 1 file changed, 19 insertions(+), 7 deletions(-)

diff --git a/dracut-module-setup.sh b/dracut-module-setup.sh
index e250703..27be84b 100755
--- a/dracut-module-setup.sh
+++ b/dracut-module-setup.sh
@@ -303,10 +303,6 @@ kdump_get_perm_addr() {
     fi
 }
 
-_get_nic_driver() {
-    ethtool -i "$1" | sed -n -E "s/driver: (.*)/\1/p"
-}
-
 # Prefix kernel assigned names with "kdump-". EX: eth0 -> kdump-eth0
 # Because kernel assigned names are not persistent between 1st and 2nd
 # kernel. We could probably end up with eth0 being eth1, eth0 being
@@ -318,7 +314,7 @@ kdump_setup_ifname() {
     # fadump to kdump. Skip prefixing 'kdump-' in this case as adding
     # another prefix may truncate the ifname. Since an ifname with
     # 'kdump-' is already persistent, this should be fine.
-    if [[ $1 =~ eth* ]] && [[ ! $1 =~ ^kdump-* ]] && [[ $(_get_nic_driver "$1") != hv_netvsc ]]; then
+    if [[ $1 =~ eth* ]] && [[ ! $1 =~ ^kdump-* ]]; then
         _ifname="kdump-$1"
     else
         _ifname="$1"
@@ -485,6 +481,18 @@ kdump_setup_znet() {
     echo rd.znet=${NETTYPE},${SUBCHANNELS}${_options} rd.znet_ifname=$(kdump_setup_ifname $_netdev):${SUBCHANNELS} > ${initdir}/etc/cmdline.d/30znet.conf
 }
 
+_get_nic_driver() {
+    ethtool -i "$1" | sed -n -E "s/driver: (.*)/\1/p"
+}
+
+_rename_hypver_netdev() {
+    local _udev_rule_dir
+
+    _udev_rule_dir=${initdir}/etc/udev/rules.d
+    mkdir -p "$_udev_rule_dir"
+    printf 'SUBSYSTEM=="net", ACTION=="add", DRIVERS=="hv_netvsc", ATTR{address}=="%s", ATTR{type}=="1", NAME="%s"\n' "$2" "$1" > "${_udev_rule_dir}/80-hv_netvsc-ifname.rules"
+}
+
 # Setup dracut to bringup a given network interface
 kdump_setup_netdev() {
     local _netdev=$1 _srcaddr=$2
@@ -533,8 +541,12 @@ kdump_setup_netdev() {
     elif kdump_is_vlan "$_netdev"; then
         kdump_setup_vlan "$_netdev"
     else
-        _ifname_opts=" ifname=$kdumpnic:$_netmac"
-        echo "$_ifname_opts" >> $_ip_conf
+        if [[ $(_get_nic_driver "$1") != hv_netvsc ]]; then
+            _ifname_opts=" ifname=$kdumpnic:$_netmac"
+            echo "$_ifname_opts" >> $_ip_conf
+        else
+            _rename_hypver_netdev "$kdumpnic" "$_netmac"
+        fi
     fi
     _save_kdump_netifs "$_netdev" "$_kdumpdev"