network: Generate TFTP config regardless of DHCP

We already allow users to provide TFTP root path in network XML
and not specify any DHCP. This makes sense, because dnsmasq is
not only DHCP server but also TFTP server and users might have
a DHCP server configured on their own, outside of libvirt's
control and want just the TFTP part.

By moving TFTP config generator out of DHCP generator and calling
it for every IPv4 range, users can finally enable just TFTP.

Resolves: https://bugzilla.redhat.com/show_bug.cgi?id=2026765
Signed-off-by: Michal Privoznik <mprivozn@redhat.com>
Reviewed-by: Ján Tomko <jtomko@redhat.com>

tests/networkxml2confdata/netboot-network.conf

@@ -10,11 +10,11 @@ expand-hosts
 except-interface=lo
 bind-dynamic
 interface=virbr1
+enable-tftp
+tftp-root=/var/lib/tftproot
 dhcp-range=192.168.122.2,192.168.122.254,255.255.255.0
 dhcp-no-override
 dhcp-authoritative
-enable-tftp
-tftp-root=/var/lib/tftproot
 dhcp-boot=pxeboot.img
 dhcp-lease-max=253
 dhcp-hostsfile=/var/lib/libvirt/dnsmasq/netboot.hostsfile

tests/networkxml2confdata/netboot-tftp.conf

@@ -0,0 +1,13 @@
+##WARNING:  THIS IS AN AUTO-GENERATED FILE. CHANGES TO IT ARE LIKELY TO BE
+##OVERWRITTEN AND LOST.  Changes to this configuration should be made using:
+##    virsh net-edit tftp-only
+## or other application using the libvirt API.
+##
+## dnsmasq conf file created by libvirt
+strict-order
+except-interface=lo
+bind-dynamic
+interface=virbr0
+enable-tftp
+tftp-root=/var/lib/tftproot
+addn-hosts=/var/lib/libvirt/dnsmasq/tftp-only.addnhosts

tests/networkxml2confdata/netboot-tftp.xml

@@ -0,0 +1,9 @@
+<network>
+  <name>tftp-only</name>
+  <uuid>eb486e5c-4df5-42ee-ae4a-ad8557998d00</uuid>
+  <forward mode='nat'/>
+  <bridge name='virbr0' stp='off' delay='1'/>
+  <ip address='192.168.122.1' netmask='255.255.255.0'>
+    <tftp root='/var/lib/tftproot'/>
+  </ip>
+</network>