RFC 5531 assigns only unsigned constants to program, version, and
procedure numbers (Section 12.3) and encodes each as an unsigned
32-bit integer (Section 9), so a valid number falls within
[0, 2**32 - 1]. RFC 4506 Section 6.2 permits a signed decimal constant
for XDR constants in general and sets no ceiling on magnitude, so the
grammar accepts an out-of-range value without complaint. It reaches
generated code -- a negative procedure number emerges as an enumerator
such as "FOO = -5", valid C that compiles cleanly even though the wire
field is an unsigned 32-bit integer. Thus the xdrgen front end is the
only place that can reject the malformed value.
Extend the semantic checks to require each program, version, and
procedure number to fall within [0, 2**32 - 1].
Link: https://patch.msgid.link/20260712203451.124902-6-cel@kernel.org
Signed-off-by: Chuck Lever <cel@kernel.org>
Add a Python-based tool for translating XDR specifications into XDR
encoder and decoder functions written in the Linux kernel's C coding
style. The generator attempts to match the usual C coding style of
the Linux kernel's SunRPC consumers.
This approach is similar to the netlink code generator in
tools/net/ynl .
The maintainability benefits of machine-generated XDR code include:
- Stronger type checking
- Reduces the number of bugs introduced by human error
- Makes the XDR code easier to audit and analyze
- Enables rapid prototyping of new RPC-based protocols
- Hardens the layering between protocol logic and marshaling
- Makes it easier to add observability on demand
- Unit tests might be built for both the tool and (automatically)
for the generated code
In addition, converting the XDR layer to use memory-safe languages
such as Rust will be easier if much of the code can be converted
automatically.
Tested-by: Jeff Layton <jlayton@kernel.org>
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
