[PATCH 0/2] tools/hv: Improve the sample hv_get_dhcp_info script

[PATCH 0/2] tools/hv: Improve the sample hv_get_dhcp_info script

[Ben Hutchings]

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The sample hv_get_dhcp_info script was originally supposed to be
replaced by downstream distributions, but:

- Network Manager and systemd-networkd are used across many
  distributions
- Debian's ifupdown is not only used in Debian derivatives but also
  Alpine and Void Linux

This adds support for all of those.

The check for DHCP in network-scripts configuration files was
also quite lax.  This makes the regex a bit more strict.

Ben.

Ben Hutchings (2):
  tools/hv: Make the sample hv_get_dhcp_info script more useful
  tools/hv: Make network-scripts DHCP status check more specific

 tools/hv/hv_get_dhcp_info.sh | 87 +++++++++++++++++++++++++++++++-----
 1 file changed, 75 insertions(+), 12 deletions(-)


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[PATCH 1/2] tools/hv: Make the sample hv_get_dhcp_info script more useful

[Ben Hutchings]

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Currently the sample hv_get_dhcp_info script only supports the old Red
Hat network-scripts configuration format and leaves everything else to
downstream distributions.

However, Network Manager and systemd-networkd are available across
many distributions, so it makes more sense to implement support for
them here.

Debian's ifupdown is also used in several distributions that are not
Debian derivatives, so I think it makes sense to implement support for
that here too.

Extend the script to support all of these:

- Add a report function that reports the status based on the result of
  the previous command
- Add a function for each configuration system that checks whether
  that system in use for the given interface, and:
  - If so, checks and reports the DHCP status
  - If not, returns failure
- Call each of those functions, exiting once one of them succeeds,
  with a final fallback to reporting 'Disabled'

The network-scripts check is placed last, because it only checks a
file and not the actual interface state and so is the least reliable
check.

Signed-off-by: Ben Hutchings <benh@debian.org>
---
 tools/hv/hv_get_dhcp_info.sh | 87 +++++++++++++++++++++++++++++++-----
 1 file changed, 75 insertions(+), 12 deletions(-)

diff --git a/tools/hv/hv_get_dhcp_info.sh b/tools/hv/hv_get_dhcp_info.sh
index 2f2a3c7df3de..310b16a2f734 100755
--- a/tools/hv/hv_get_dhcp_info.sh
+++ b/tools/hv/hv_get_dhcp_info.sh
@@ -12,18 +12,81 @@
 #	that DHCP is enabled on the interface. If DHCP is not enabled,
 #	the script prints the string "Disabled" to stdout.
 #
-# Each Distro is expected to implement this script in a distro specific
-# fashion. For instance, on Distros that ship with Network Manager enabled,
-# this script can be based on the Network Manager APIs for retrieving DHCP
-# information.
+# Distributions may need to adapt or replace this script for their
+# preferred network configuration system.
 
-if_file="/etc/sysconfig/network-scripts/ifcfg-"$1
+# Report status based on result of previous command
+report() {
+    if [ $? -eq 0 ]; then
+	echo "Enabled"
+    else
+	echo "Disabled"
+    fi
+}
 
-dhcp=$(grep "dhcp" $if_file 2>/dev/null)
+check_network_manager() {
+    local conn_name
 
-if [ "$dhcp" != "" ];
-then
-echo "Enabled"
-else
-echo "Disabled"
-fi
+    # Check that the interface has a configured connection, and get
+    # its name
+    if conn_name="$(nmcli -g GENERAL.CONNECTION device show "$1" 2>/dev/null)" &&
+       [ "$conn_name" ]; then
+	# Check whether the connection enables DHCPv4
+	test "$(nmcli -g ipv4.method connection show "$conn_name")" = auto
+	report
+    else
+	return 1
+    fi
+}
+
+check_systemd_networkd() {
+    local status
+
+    # Check that the interface is managed by networkd
+    if status="$(networkctl status --json=short -- "$1" 2>/dev/null)" &&
+       ! printf '%s' "$status" |
+	   grep -qE '"AdministrativeState":"unmanaged"'; then
+	# Check for DHCPv4 client state in the interface status
+	printf '%s' "$status" | grep -q '"DHCPv4Client":'
+	report
+    else
+	return 1
+    fi
+}
+
+check_ifupdown() {
+    local conf_name
+
+    # Check that a configuration has been applied to the interface
+    if command -v ifquery >/dev/null &&
+       conf_name="$(ifquery --state -- "$1" | sed 's/[^=]*=//')" &&
+       [ "$conf_name" ]; then
+	# Check whether that configuration enables DHCPv4.
+	# Unfortunately ifquery does not expose the method name, so we
+	# have to grep through the configuration file(s) and make an
+	# assumption about which are included.
+	find /etc/network/interfaces /etc/network/interfaces.d \
+	     -type f -regex '.*/[a-zA-Z0-9_-]+$' -print |
+	    xargs grep -qE '^\s*iface\s+'"$conf_name"'\s+inet\s+dhcp(\s|$)'
+	report
+    else
+	return 1
+    fi
+}
+
+check_network_scripts() {
+    local if_file="/etc/sysconfig/network-scripts/ifcfg-"$1
+
+    if [ -f "$if_file" ]; then
+	grep -q dhcp "$if_file"
+	report
+    else
+	return 1
+    fi
+}
+
+check_network_manager "$1" ||
+check_systemd_networkd "$1" ||
+check_ifupdown "$1" ||
+check_network_scripts "$1" ||
+report


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[PATCH 2/2] tools/hv: Make network-scripts DHCP status check more specific

[Ben Hutchings]

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We currently look for the string 'dhcp' in a network-scripts
configuration file, but this could potentially be found in a comment
line.  The variable that controls whether DHCPv4 is used is BOOTPROTO,
so check for that variable name as well as the value 'dhcp'.

Also quote the interface name when constructing the configuration
filename, just in case it contains a special character.

Signed-off-by: Ben Hutchings <benh@debian.org>
---
 tools/hv/hv_get_dhcp_info.sh | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/tools/hv/hv_get_dhcp_info.sh b/tools/hv/hv_get_dhcp_info.sh
index 310b16a2f734..7815d55a9295 100755
--- a/tools/hv/hv_get_dhcp_info.sh
+++ b/tools/hv/hv_get_dhcp_info.sh
@@ -75,10 +75,10 @@ check_ifupdown() {
 }
 
 check_network_scripts() {
-    local if_file="/etc/sysconfig/network-scripts/ifcfg-"$1
+    local if_file="/etc/sysconfig/network-scripts/ifcfg-$1"
 
     if [ -f "$if_file" ]; then
-	grep -q dhcp "$if_file"
+	grep -q '^\s*BOOTPROTO=.*dhcp' "$if_file"
 	report
     else
 	return 1

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Re: [PATCH 0/2] tools/hv: Improve the sample hv_get_dhcp_info script

[Wei Liu]

On Mon, Jun 16, 2025 at 01:04:43AM +0200, Ben Hutchings wrote:
> The sample hv_get_dhcp_info script was originally supposed to be
> replaced by downstream distributions, but:
> 
> - Network Manager and systemd-networkd are used across many
>   distributions
> - Debian's ifupdown is not only used in Debian derivatives but also
>   Alpine and Void Linux
> 
> This adds support for all of those.
> 
> The check for DHCP in network-scripts configuration files was
> also quite lax.  This makes the regex a bit more strict.
> 
> Ben.
> 
> Ben Hutchings (2):
>   tools/hv: Make the sample hv_get_dhcp_info script more useful
>   tools/hv: Make network-scripts DHCP status check more specific

Applied to hyperv-next. Thanks.