helpers: fix maximum interface name length check

Update helpers to enforce a maximum interface name length of 15
characters, matching the actual limit. In Linux, the last byte of the
16-byte array is reserved for the null terminator.

Signed-off-by: Tomas Novotny <tomas@novotny.cz>

Author: stoupa-cz

helpers/labgrid-bound-connect

@@ -15,7 +15,7 @@ def main(ifname, address, port):
         raise ValueError("Empty interface name.")
     if any((c == "/" or c.isspace()) for c in ifname):
         raise ValueError(f"Interface name '{ifname}' contains invalid characters.")
-    if len(ifname) > 16:
+    if len(ifname) > 15:
         raise ValueError(f"Interface name '{ifname}' is too long.")
 
     address = ipaddress.ip_address(address)

helpers/labgrid-raw-interface

@@ -38,7 +38,7 @@ def main(program, options):
         raise ValueError("Empty interface name.")
     if any((c == "/" or c.isspace()) for c in options.ifname):
         raise ValueError(f"Interface name '{options.ifname}' contains invalid characters.")
-    if len(options.ifname) > 16:
+    if len(options.ifname) > 15:
         raise ValueError(f"Interface name '{options.ifname}' is too long.")
 
     denylist = get_denylist()