Re: [PATCH] net: ipv4: ipconfig: Support RFC 4361/3315 DHCP client ID in hex format

 		/* the minimum length of identifier is 2, include 1 byte type,
 		 * and can not be larger than the length of options
 		 */
-		if (len >= 1 && len < 312 - (e - options) - 1) {
-			*e++ = 61;
-			*e++ = len + 1;
-			memcpy(e, dhcp_client_identifier, len + 1);
-			e += len + 1;
+		if (dhcp_client_identifier_len >= 2) {
+			if (dhcp_client_identifier_len <= 312 - (e - options) - 3) {
+				pr_debug("DHCP: sending client identifier %*phC\n",
+					 dhcp_client_identifier_len,
+					 dhcp_client_identifier);
+				*e++ = 61;
+				*e++ = dhcp_client_identifier_len;
+				memcpy(e, dhcp_client_identifier,
+				       dhcp_client_identifier_len);
+				e += dhcp_client_identifier_len;
+			} else {
+				pr_warn("DHCP: client identifier doesn't fit in the packet\n");
+			}
 		}
 	}
 

@@ -1661,6 +1669,33 @@ static int __init ip_auto_config(void)
 
 late_initcall(ip_auto_config);
 
+#ifdef CONFIG_IP_PNP_DHCP
+/*
+ *  Parses DHCP Client ID in the hex form "XX:XX ... :XX" (like MAC address).
+ *  Returns the length (min 2, max 253) or -EINVAL on parsing error.
+ */
+static int __init parse_client_id(const char *s, u8 *buf)
+{
+	int slen = strlen(s);
+	int len = (slen + 1) / 3;
+	int i;
+
+	/* Format: XX:XX ... :XX */
+	if (len * 3 - 1 != slen || len < 2 || len > 253)
+		return -EINVAL;
+
+	for (i = 0; i < len; i++) {
+		if (!isxdigit(s[i * 3]) || !isxdigit(s[i * 3 + 1]))
+			return -EINVAL;
+		if (i != len - 1 && s[i * 3 + 2] != ':')
+			return -EINVAL;
+
+		buf[i] = (hex_to_bin(s[i * 3]) << 4) | hex_to_bin(s[i * 3 + 1]);
+	}
+
+	return i;
+}