From: Paul Donald <newtwen+github@gmail.com>
Date: Wed, 12 Nov 2025 23:59:13 +0000 (+0100)
Subject: dhcpv6: set a static define for DUID max length
X-Git-Url: http://git.openwrt.org/?a=commitdiff_plain;h=cf203ceb3fc8434b1b9ab31bfc3c59ef33d1c785;p=project%2Fodhcp6c.git

dhcpv6: set a static define for DUID max length

so the number 130 isn't so mysterious at first glance.

Signed-off-by: Paul Donald <newtwen+github@gmail.com>
Link: https://github.com/openwrt/odhcp6c/pull/118
Signed-off-by: Álvaro Fernández Rojas <noltari@gmail.com>
---

diff --git a/src/dhcpv6.c b/src/dhcpv6.c
index 21fd16b..a6fe176 100644
--- a/src/dhcpv6.c
+++ b/src/dhcpv6.c
@@ -1190,7 +1190,7 @@ static int dhcpv6_handle_advert(enum dhcpv6_msg orig, const int rc,
 
 		switch (otype) {
 		case DHCPV6_OPT_SERVERID:
-			if (olen <= 130) {
+			if (olen <= DHCPV6_DUID_MAX_LEN) {
 				memcpy(cand.duid, odata, olen);
 				cand.duid_len = olen;
 			}
diff --git a/src/odhcp6c.h b/src/odhcp6c.h
index 405a2bf..6c669c0 100644
--- a/src/odhcp6c.h
+++ b/src/odhcp6c.h
@@ -272,6 +272,7 @@ struct dhcpv6_retx {
 
 #define DHCPV6_OPT_HDR_SIZE 4
 #define DHCPV6_OPT_HDR_SIZE_U 4U
+#define DHCPV6_DUID_MAX_LEN 130 // 2-byte type + 128-byte DUID, RFC8415, §11.1
 
 // DHCPv6 Protocol Headers
 struct dhcpv6_header {
@@ -364,7 +365,7 @@ struct dhcpv6_server_cand {
 	bool wants_reconfigure;
 	int16_t preference;
 	uint8_t duid_len;
-	uint8_t duid[130];
+	uint8_t duid[DHCPV6_DUID_MAX_LEN];
 	struct in6_addr server_addr;
 	uint32_t sol_max_rt;
 	uint32_t inf_max_rt;