Re: [PATCH v5 03/13] fwd: Unify guest accessibility checks with unified address array

On Sun, Feb 22, 2026 at 12:44:35PM -0500, Jon Maloy wrote:

We replace the fwd_guest_accessible4() and fwd_guest_accessible6() functions with a unified fwd_guest_accessible() function that handles both address families. With the unified address array, we can check all configured addresses in a single pass using for_each_addr() with family filter INADDR_UNSPEC (== 0).

Signed-off-by: Jon Maloy --- fwd.c | 70 +++++++++++++++-------------------------------------------- 1 file changed, 18 insertions(+), 52 deletions(-)

diff --git a/fwd.c b/fwd.c index cf13ddd..edf6a6b 100644 --- a/fwd.c +++ b/fwd.c @@ -880,19 +880,19 @@ static bool is_dns_flow(uint8_t proto, const struct flowside *ini) }

/** - * fwd_guest_accessible4() - Is IPv4 address guest-accessible + * fwd_guest_accessible() - Is address guest-accessible * @c: Execution context - * @addr: Host visible IPv4 address + * @addr: Host visible address (IPv4 or IPv6) * * Return: true if @addr on the host is accessible to the guest without * translation, false otherwise */ -static bool fwd_guest_accessible4(const struct ctx *c, - const struct in_addr *addr) +static bool fwd_guest_accessible(const struct ctx *c, + const union inany_addr *addr) { - struct inany_addr_entry *e = first_v4(c); + const struct inany_addr_entry *e;

- if (IN4_IS_ADDR_LOOPBACK(addr)) + if (inany_is_loopback(addr)) return false;

/* In socket interfaces 0.0.0.0 generally means "any" or unspecified, @@ -900,66 +900,32 @@ static bool fwd_guest_accessible4(const struct ctx *c, * that has a different meaning for host and guest, we can't let it * through untranslated. */ - if (IN4_IS_ADDR_UNSPECIFIED(addr)) - return false; - - /* For IPv4, addr_seen is initialised to addr, so is always a valid - * address - */ - if ((e && IN4_ARE_ADDR_EQUAL(addr, inany_v4(&e->addr))) || - IN4_ARE_ADDR_EQUAL(addr, &c->ip4.addr_seen)) + if (inany_is_unspecified4(addr))

You want inany_is_unspecified(), not inany_is_unspecified4().

return false;

- return true; -} - -/** - * fwd_guest_accessible6() - Is IPv6 address guest-accessible - * @c: Execution context - * @addr: Host visible IPv6 address - * - * Return: true if @addr on the host is accessible to the guest without - * translation, false otherwise - */ -static bool fwd_guest_accessible6(const struct ctx *c, - const struct in6_addr *addr) -{ - if (IN6_IS_ADDR_LOOPBACK(addr)) - return false; + /* Check against all configured guest addresses */ + for_each_addr(e, c, 0) + if (inany_equals(addr, &e->addr)) + return false;

- if (first_v6(c) && IN6_ARE_ADDR_EQUAL(addr, &first_v6(c)->addr.a6)) + /* Also check addr_seen: it tracks the address the guest is actually + * using, which may differ from configured addresses. + */ + if (inany_equals4(addr, &c->ip4.addr_seen)) return false;

/* For IPv6, addr_seen starts unspecified, because we don't know what LL * address the guest will take until we see it. Only check against it * if it has been set to a real address. */ - if (!IN6_IS_ADDR_UNSPECIFIED(&c->ip6.addr_seen) && - IN6_ARE_ADDR_EQUAL(addr, &c->ip6.addr_seen)) + if (!inany_v4(addr) &&

You don't need this test. If addr is IPv4, it necessarily won't equal ip6.addr_seen which is IPv6.

+ !IN6_IS_ADDR_UNSPECIFIED(&c->ip6.addr_seen) && + inany_equals6(addr, &c->ip6.addr_seen)) return false;

return true; }

-/** - * fwd_guest_accessible() - Is IPv[46] address guest-accessible - * @c: Execution context - * @addr: Host visible IPv[46] address - * - * Return: true if @addr on the host is accessible to the guest without - * translation, false otherwise - */ -static bool fwd_guest_accessible(const struct ctx *c, - const union inany_addr *addr) -{ - const struct in_addr *a4 = inany_v4(addr); - - if (a4) - return fwd_guest_accessible4(c, a4); - - return fwd_guest_accessible6(c, &addr->a6); -} - /** * nat_outbound() - Apply address translation for outbound (TAP to HOST) * @c: Execution context -- 2.52.0

-- David Gibson (he or they) | I'll have my music baroque, and my code david AT gibson.dropbear.id.au | minimalist, thank you, not the other way | around. http://www.ozlabs.org/~dgibson