+ u32 ecn = (iph->tos + 1) & INET_ECN_MASK;
+
+ /*
+ * After the last operation we have (in binary):
+ * INET_ECN_NOT_ECT => 01
+ * INET_ECN_ECT_1 => 10
+ * INET_ECN_ECT_0 => 11
+ * INET_ECN_CE => 00
+ */
+ if (!(ecn & 2))
+ return;
+
+ /*
+ * The following gives us:
+ * INET_ECN_ECT_1 => check += htons(0xFFFD)
+ * INET_ECN_ECT_0 => check += htons(0xFFFE)
+ */
+ check += htons(0xFFFB) + htons(ecn);
+