diff --git a/[refs] b/[refs]
index 505e4b300391..fbeaf0858f71 100644
--- a/[refs]
+++ b/[refs]
@@ -1,2 +1,2 @@
 ---
-refs/heads/master: 2c67e9acb65da96ae1b0ba93ec04af7142533bef
+refs/heads/master: b5d9c9c281395f0967c8d93f42e8b0b8175b5180
diff --git a/trunk/include/net/inet_ecn.h b/trunk/include/net/inet_ecn.h
index 2fa8d1341a0a..2fa14691869c 100644
--- a/trunk/include/net/inet_ecn.h
+++ b/trunk/include/net/inet_ecn.h
@@ -30,6 +30,14 @@ static inline int INET_ECN_is_capable(__u8 dsfield)
 	return dsfield & INET_ECN_ECT_0;
 }
 
+/*
+ * RFC 3168 9.1.1
+ *  The full-functionality option for ECN encapsulation is to copy the
+ *  ECN codepoint of the inside header to the outside header on
+ *  encapsulation if the inside header is not-ECT or ECT, and to set the
+ *  ECN codepoint of the outside header to ECT(0) if the ECN codepoint of
+ *  the inside header is CE.
+ */
 static inline __u8 INET_ECN_encapsulate(__u8 outer, __u8 inner)
 {
 	outer &= ~INET_ECN_MASK;