update checks for Server-Id

As per RFC 9915 the server MUST discard any Solicit, Confirm,
or Rebind messages that include a Server Identifier option.

Signed-off-by: ethan-thompson <ethan.thompson@networkradius.com>

Author: ethan-thompson

src/protocols/dhcpv6/base.c

@@ -453,9 +453,8 @@ static bool verify_from_client(uint8_t const *packet, size_t packet_len, fr_dhcp
 			return false;
 		}
 
-		if (!fr_dhcpv6_option_find(options, end, FR_SERVER_ID)) {
-		fail_sid:
-			fr_strerror_const("Packet does not contain a Server-Id option");
+		if (fr_dhcpv6_option_find(options, end, FR_SERVER_ID)) {
+			fr_strerror_const("Packet contains a Server-Id option");
 			return false;
 		}
 		break;
@@ -467,7 +466,10 @@ static bool verify_from_client(uint8_t const *packet, size_t packet_len, fr_dhcp
 		if (!fr_dhcpv6_option_find(options, end, FR_CLIENT_ID)) goto fail_cid;
 
 		option = fr_dhcpv6_option_find(options, end, FR_SERVER_ID);
-		if (!option) goto fail_sid;
+		if (!option) {
+			fr_strerror_const("Packet does not contain a Server-Id option");
+			return false;
+		}
 
 		if (!duid_match(option, packet_ctx)) {
 		fail_match: