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

2 Apr 2026


      On Mon, 30 Mar 2026 23:57:10 +0200
Stefano Brivio  wrote:
...
On Sat, 21 Mar 2026 20:43:22 -0400
Jon Maloy  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