From: Álvaro Fernández Rojas <noltari@gmail.com>
Date: Sun, 14 Dec 2025 08:04:33 +0000 (+0100)
Subject: Revert "router: optimize duplicated PIO comparison"
X-Git-Url: http://git.cdn.openwrt.org/?a=commitdiff_plain;h=03c1468355c0ffb8fa965cdf57f0d3fc8f01f006;p=project%2Fodhcpd.git

Revert "router: optimize duplicated PIO comparison"

This reverts commit d354ebb66cdcccc3373156468eec1c660fb2922c.

As stated by David Härdeman at [1]:
Note that time_t will have an alignment of 4 (unlikely) or 8, meaning
that struct ra_pio will have padding. A straight memcmp() could
therefore generate the wrong result unless both struct ra_pios that are
compared are guaranteed to have been memset to zero.

Avoid the risk of something going wrong here by doing a straight
comparison of the two members of the struct that we want to compare.

[1]: https://github.com/openwrt/odhcpd/pull/348/changes/d02fce006abd4f0761bf3100c9ddd4ce70847edb

Link: https://github.com/openwrt/odhcpd/pull/354
Signed-off-by: Álvaro Fernández Rojas <noltari@gmail.com>
---

diff --git a/src/odhcpd.h b/src/odhcpd.h
index 86375ab..f005909 100644
--- a/src/odhcpd.h
+++ b/src/odhcpd.h
@@ -346,13 +346,10 @@ struct dnr_options {
 
 // RA PIO - RFC9096
 struct ra_pio {
-	struct {
-		struct in6_addr prefix;
-		uint8_t length;
-	};
+	struct in6_addr prefix;
+	uint8_t length;
 	time_t lifetime;
 };
-#define ra_pio_cmp_len offsetof(struct ra_pio, lifetime)
 
 
 struct interface {
diff --git a/src/router.c b/src/router.c
index 8334a1c..05c4fcb 100644
--- a/src/router.c
+++ b/src/router.c
@@ -539,7 +539,8 @@ static void router_clear_duplicated_ra_pio(struct interface *iface)
 		while (j < iface->pio_cnt) {
 			struct ra_pio *pio_b = &iface->pios[j];
 
-			if (!memcmp(pio_a, pio_b, ra_pio_cmp_len)) {
+			if (pio_a->length == pio_b->length &&
+			    !memcmp(&pio_a->prefix, &pio_b->prefix, sizeof(struct in6_addr))) {
 				warn("rfc9096: %s: clear duplicated %s/%u",
 				     iface->ifname,
 				     inet_ntop(AF_INET6, &pio_a->prefix, ipv6_str, sizeof(ipv6_str)),