Re: [PATCH net] tools: ynl: preserve non-ASCII string attribute bytes

[Hangbin Liu <hangbin.liu@linux.dev>]

On Tue, Nov 10, 2026 at 03:39:22AM +0000, Jingjing Xu wrote:
> Netlink strings are not restricted to ASCII. A valid non-ASCII interface
> name makes a getlink dump fail with UnicodeDecodeError, and encoding
> such a name for a rename request raises UnicodeEncodeError.
> 
> Use UTF-8 with surrogateescape for both directions. This preserves ASCII
> behavior, handles UTF-8 names and round-trips raw non-UTF-8 bytes that
> Linux also permits in interface names. Do not replace invalid bytes and
> lose the original name.
> 
> Discovered by Codex-assisted code inspection and reproduced using real
> rtnetlink operations in a temporary network namespace. Tested ASCII
> names, a UTF-8 name and a name containing byte 0xff in link dumps, plus
> UTF-8 and non-UTF-8 rename requests. The original library fails on the
> non-ASCII inputs; the fixed library reads and writes the names without
> losing bytes. Python byte compilation passes. No kernel instrumentation
> or hardware was needed.
> 
> Fixes: e4b48ed460d3 ("tools: ynl: add a completely generic client")
> Signed-off-by: Jingjing Xu <xujingjing@cmss.chinamobile.com>
> ---
>  tools/net/ynl/pyynl/lib/ynl.py | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/tools/net/ynl/pyynl/lib/ynl.py b/tools/net/ynl/pyynl/lib/ynl.py
> index fb5acb8acded..2402d7c383e7 100644
> --- a/tools/net/ynl/pyynl/lib/ynl.py
> +++ b/tools/net/ynl/pyynl/lib/ynl.py
> @@ -301,7 +301,7 @@ class NlAttr:
>          return format_.unpack(self.raw)[0]
>  
>      def as_strz(self):
> -        return self.raw.decode('ascii')[:-1]
> +        return self.raw.decode('utf-8', 'surrogateescape')[:-1]
>  
>      def as_bin(self):
>          return self.raw
> @@ -852,7 +852,7 @@ class YnlFamily(SpecFamily):
>                  return b''
>              attr_payload = b''
>          elif attr["type"] == 'string':
> -            attr_payload = str(value).encode('ascii') + b'\x00'
> +            attr_payload = str(value).encode('utf-8', 'surrogateescape') + b'\x00'
>          elif attr["type"] == 'binary':
>              if value is None:
>                  attr_payload = b''
> base-commit: 1d5e2c57e9ffc134e14b3f837c8d7c53b508bd22
> -- 
> 2.53.0
> 

Reviewed-by: Hangbin Liu <liuhangbin@kylinos.cn>