Re: [PATCH v6 02/13] ip: Introduce unified multi-address data structures

[Stefano Brivio <sbrivio@redhat.com>]

On Mon, 30 Mar 2026 23:57:10 +0200
Stefano Brivio <sbrivio@redhat.com> wrote:

> On Sat, 21 Mar 2026 20:43:22 -0400
> Jon Maloy <jmaloy@redhat.com> wrote:
> 
> [...]
>
> > +/**
> > + * fwd_get_addr() - Get guest address entry matching criteria
> > + * @c:		Execution context
> > + * @af:		Address family (AF_INET, AF_INET6, or 0 for any)
> > + * @incl:	Flags that must be present (any-match)
> > + * @excl:	Flags that must not be present
> > + *
> > + * Return: first address entry matching criteria, or NULL
> > + */
> > +const struct guest_addr *fwd_get_addr(const struct ctx *c, sa_family_t af,
> > +				      uint8_t incl, uint8_t excl)
> > +{
> > +	const struct guest_addr *a;
> > +
> > +	for_each_addr(a, c, af) {
> > +		if (incl && !(a->flags & incl))
> > +			continue;
> > +		if (a->flags & excl)
> > +			continue;  
> 
> Slightly less generic, but maybe good enough for this purpose: you
> could admit a set of flags, or a negation of a flag (for example
> ~CONF_ADDR_USER), in a single argument.
> 
> See how conn_flag_do() does that. Here it would be something like:
> 
> 		if (flags & (flags - 1)) {
> 			if (a->flags & ~flag)
> 				continue;
> 		} else {
> 			if (!(a->flags & flag))
> 				continue;
> 		}
> 
> ...it makes callers more readable in my opinion, for example:
> 
> 		a = fwd_get_addr(c, AF_INET6, ~CONF_ADDR_LINKLOCAL);
> 
> which makes it entirely clear you're selecting all addresses that are
> link-local, compared to:
> 
> 		a = fwd_get_addr(c, AF_INET6, 0, CONF_ADDR_LINKLOCAL);
> 
> which forces the reader to look up the prototype.
> 
> But again it's less generic, you can't exclude multiple flags like
> that. Unless... you define a reserved bit which is always 0 in that
> uint8_t, so that if you pass it as 1, you can conclude a negated set of
> flags was passed.

...at least until I finally reached 9/13 where you pass both matching
and non-matching flags, and my trick doesn't work anymore. Oops, sorry.

-- 
Stefano