vrf: T8320: only allow alpha numerical characters, - and _ as VRF name

This prevents the Kernel to error out. VRF names are limited within the Linux
kernal as any other network interface name. See net/core/dev.c:dev_valid_name()!

vyos@vyos# set vrf name MGM>T table 1000
vyos@vyos# commit
[ vrf ]
Traceback (most recent call last):
  File "/usr/libexec/vyos/services/vyos-configd", line 157, in run_script
    script.apply(c)
  File "/usr/libexec/vyos/conf_mode/vrf.py", line 317, in apply
    vrf_if.add_addr('127.0.0.1/8')
  File "/usr/lib/python3/dist-packages/vyos/ifconfig/interface.py", line 1294, in add_addr
    elif not is_intf_addr_assigned(self.ifname, addr, netns=netns):
             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/usr/lib/python3/dist-packages/vyos/utils/network.py", line 444, in is_intf_addr_assigned
    json_out = json.loads(out)
               ^^^^^^^^^^^^^^^
  File "/usr/lib/python3.11/json/__init__.py", line 346, in loads
    return _default_decoder.decode(s)
           ^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/usr/lib/python3.11/json/decoder.py", line 337, in decode
    obj, end = self.raw_decode(s, idx=_w(s, 0).end())
               ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/usr/lib/python3.11/json/decoder.py", line 355, in raw_decode
    raise JSONDecodeError("Expecting value", s, err.value) from None
json.decoder.JSONDecodeError: Expecting value: line 1 column 1 (char 0)

[[vrf]] failed
Commit failed

1 files changed, 7 insertions, 0 deletions

diff --git a/src/validators/vrf-name b/src/validators/vrf-name
index cc4be2510..b56ebd036 100755
--- a/src/validators/vrf-name
+++ b/src/validators/vrf-name
@@ -24,15 +24,22 @@ if __name__ == '__main__':
     vrf = argv[1]
     length = len(vrf)
 
+    # must not exceed Linux Kernel IFNAMSIZ definition
     if length not in range(1, 16):
         exit(1)
 
+    # allow only alpha numerical characters, - and _
+    pattern = r'^[A-Za-z0-9_-]+$'
+    if not re.match(pattern, vrf):
+        exit(1)
+
     # Treat loopback interface "lo" explicitly. Adding "lo" explicitly to the
     # following regex pattern would deny any VRF name starting with lo - thuse
     # local-vrf would be illegal - and that we do not want.
     if vrf == "lo":
         exit(1)
 
+    # VRF name must not conflict with local interface type prefix
     pattern = r'^(?!(bond|br|dum|eth|lan|eno|ens|enp|enx|gnv|ipoe|l2tp|l2tpeth|\
        vtun|ppp|pppoe|peth|tun|vti|vxlan|wg|wlan|wwan|\d)\d*(\.\d+)?(v.+)?).*$'
     if not re.match(pattern, vrf):