Reviewed-by: Peter Müller <peter.mueller(a)ipfire.org>

> The DHCP server can instruct clients to configure a certain MTU.
> 
> This used to be done by setting the MTU of the interface. However,
> dhcpcd has changed this behaviour using routes to.
> 
> We used to have a modified version of the old mechanism which no longer
> works well with the new system and is therefore to be dropped.
> 
> This is the first commit in the series implementing the new behaviour
> and telling dhcpcd to use the configured MTU.
> 
> Fixes: #12563
> Signed-off-by: Michael Tremer <michael.tremer(a)ipfire.org>
> ---
>   src/initscripts/networking/functions.network | 11 ++++++++---
>   1 file changed, 8 insertions(+), 3 deletions(-)
> 
> diff --git a/src/initscripts/networking/functions.network b/src/initscripts/networking/functions.network
> index 7ec50f436..eae4a7b7c 100644
> --- a/src/initscripts/networking/functions.network
> +++ b/src/initscripts/networking/functions.network
> @@ -61,7 +61,7 @@ dhcpcd_start() {
>   	# This function will start a dhcpcd on a speciefied device.
>   
>   	local device="$1"
> -	local dhcp_start=""
> +	local dhcp_start=()
>   
>   	boot_mesg -n "Starting dhcpcd on the ${device} interface..."
>   
> @@ -76,11 +76,16 @@ dhcpcd_start() {
>   
>   	# Check if a DHCP hostname has been set.
>   	if [ -n "${RED_DHCP_HOSTNAME}" ]; then
> -		dhcp_start+="-h ${RED_DHCP_HOSTNAME}"
> +		dhcp_start+=( "-h" "${RED_DHCP_HOSTNAME}" )
> +	fi
> +
> +	# Tell dhcpcd to use the configured MTU
> +	if [ -n "${RED_DHCP_FORCE_MTU}" ]; then
> +		dhcp_start+=( "--static" "mtu=${RED_DHCP_FORCE_MTU}" )
>   	fi
>   
>   	# Start dhcpcd.
> -	/sbin/dhcpcd ${dhcp_start} ${device} >/dev/null 2>&1
> +	/sbin/dhcpcd "${dhcp_start[@]}" ${device} >/dev/null 2>&1
>   	ret="$?"
>   
>   	if [ "${ret}" -eq 0 ]; then