ifconfig: mtu: disallow MTU < 1280 bytes when IPv6 is enabled on the interface

Using an MTU less then the required 1280 bytes (as per RFC) on an interface
where IPv6 is not explicitly disabled by:

- set interfaces ethernet eth1 ipv6 address no-default-link-local
- not having any other IPv6 address configured

Will now trigger a commit error via verify() instead of raising
FileNotFoundError!

1 files changed, 2 insertions, 0 deletions

diff --git a/src/conf_mode/interfaces-pppoe.py b/src/conf_mode/interfaces-pppoe.py
index 1b4b9e4ee..ee3b142c8 100755
--- a/src/conf_mode/interfaces-pppoe.py
+++ b/src/conf_mode/interfaces-pppoe.py
@@ -24,6 +24,7 @@ from vyos.config import Config
 from vyos.configdict import get_interface_dict
 from vyos.configverify import verify_source_interface
 from vyos.configverify import verify_vrf
+from vyos.configverify import verify_mtu_ipv6
 from vyos.template import render
 from vyos.util import call
 from vyos import ConfigError
@@ -57,6 +58,7 @@ def verify(pppoe):
 
     verify_source_interface(pppoe)
     verify_vrf(pppoe)
+    verify_mtu_ipv6(pppoe)
 
     if {'connect_on_demand', 'vrf'} <= set(pppoe):
         raise ConfigError('On-demand dialing and VRF can not be used at the same time')