xdrgen: Reject out-of-range program, version, and procedure numbers

RFC 5531 assigns only unsigned constants to program, version, and
procedure numbers (Section 12.3) and encodes each as an unsigned

xdrgen: Reject out-of-range program, version, and procedure numbers

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>

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