diff --git a/sys/sys/mbuf.h b/sys/sys/mbuf.h
index 8243e6cd1295..612e84908e52 100644
--- a/sys/sys/mbuf.h
+++ b/sys/sys/mbuf.h
@@ -171,7 +171,10 @@ struct pkthdr {
 			uint8_t		 l3hlen;	/* layer 3 hdr len */
 			uint8_t		 l4hlen;	/* layer 4 hdr len */
 			uint8_t		 l5hlen;	/* layer 5 hdr len */
-			uint32_t	 spare;
+			uint8_t		 inner_l2hlen;
+			uint8_t		 inner_l3hlen;
+			uint8_t		 inner_l4hlen;
+			uint8_t		 inner_l5hlen;
 		};
 	};
 	union {
@@ -616,7 +619,13 @@ m_epg_pagelen(const struct mbuf *m, int pidx, int pgoff)
  * Outbound flags that are set by upper protocol layers requesting lower
  * layers, or ideally the hardware, to perform these offloading tasks.
  * For outbound packets this field and its flags can be directly tested
- * against ifnet if_hwassist.
+ * against ifnet if_hwassist.  Note that the outbound and the inbound flags do
+ * not collide right now but they could be allowed to (as long as the flags are
+ * scrubbed appropriately when the direction of an mbuf changes).  CSUM_BITS
+ * would also have to split into CSUM_BITS_TX and CSUM_BITS_RX.
+ *
+ * CSUM_INNER_<x> is the same as CSUM_<x> but it applies to the inner frame.
+ * The CSUM_ENCAP_<x> bits identify the outer encapsulation.
  */
 #define	CSUM_IP			0x00000001	/* IP header checksum offload */
 #define	CSUM_IP_UDP		0x00000002	/* UDP checksum offload */
@@ -625,13 +634,28 @@ m_epg_pagelen(const struct mbuf *m, int pidx, int pgoff)
 #define	CSUM_IP_TSO		0x00000010	/* TCP segmentation offload */
 #define	CSUM_IP_ISCSI		0x00000020	/* iSCSI checksum offload */
 
+#define	CSUM_INNER_IP6_UDP	0x00000040
+#define	CSUM_INNER_IP6_TCP	0x00000080
+#define	CSUM_INNER_IP6_TSO	0x00000100
 #define	CSUM_IP6_UDP		0x00000200	/* UDP checksum offload */
 #define	CSUM_IP6_TCP		0x00000400	/* TCP checksum offload */
 #define	CSUM_IP6_SCTP		0x00000800	/* SCTP checksum offload */
 #define	CSUM_IP6_TSO		0x00001000	/* TCP segmentation offload */
 #define	CSUM_IP6_ISCSI		0x00002000	/* iSCSI checksum offload */
 
+#define	CSUM_INNER_IP		0x00004000
+#define	CSUM_INNER_IP_UDP	0x00008000
+#define	CSUM_INNER_IP_TCP	0x00010000
+#define	CSUM_INNER_IP_TSO	0x00020000
+
+#define	CSUM_ENCAP_VXLAN	0x00040000	/* VXLAN outer encapsulation */
+#define	CSUM_ENCAP_RSVD1	0x00080000
+
 /* Inbound checksum support where the checksum was verified by hardware. */
+#define	CSUM_INNER_L3_CALC	0x00100000
+#define	CSUM_INNER_L3_VALID	0x00200000
+#define	CSUM_INNER_L4_CALC	0x00400000
+#define	CSUM_INNER_L4_VALID	0x00800000
 #define	CSUM_L3_CALC		0x01000000	/* calculated layer 3 csum */
 #define	CSUM_L3_VALID		0x02000000	/* checksum is correct */
 #define	CSUM_L4_CALC		0x04000000	/* calculated layer 4 csum */
@@ -642,16 +666,31 @@ m_epg_pagelen(const struct mbuf *m, int pidx, int pgoff)
 
 #define	CSUM_SND_TAG		0x80000000	/* Packet header has send tag */
 
+#define CSUM_FLAGS_TX (CSUM_IP | CSUM_IP_UDP | CSUM_IP_TCP | CSUM_IP_SCTP | \
+    CSUM_IP_TSO | CSUM_IP_ISCSI | CSUM_INNER_IP6_UDP | CSUM_INNER_IP6_TCP | \
+    CSUM_INNER_IP6_TSO | CSUM_IP6_UDP | CSUM_IP6_TCP | CSUM_IP6_SCTP | \
+    CSUM_IP6_TSO | CSUM_IP6_ISCSI | CSUM_INNER_IP | CSUM_INNER_IP_UDP | \
+    CSUM_INNER_IP_TCP | CSUM_INNER_IP_TSO | CSUM_ENCAP_VXLAN | \
+    CSUM_ENCAP_RSVD1 | CSUM_SND_TAG)
+
+#define CSUM_FLAGS_RX (CSUM_INNER_L3_CALC | CSUM_INNER_L3_VALID | \
+    CSUM_INNER_L4_CALC | CSUM_INNER_L4_VALID | CSUM_L3_CALC | CSUM_L3_VALID | \
+    CSUM_L4_CALC | CSUM_L4_VALID | CSUM_L5_CALC | CSUM_L5_VALID | \
+    CSUM_COALESCED)
+
 /*
  * CSUM flag description for use with printf(9) %b identifier.
  */
 #define	CSUM_BITS \
     "\20\1CSUM_IP\2CSUM_IP_UDP\3CSUM_IP_TCP\4CSUM_IP_SCTP\5CSUM_IP_TSO" \
-    "\6CSUM_IP_ISCSI" \
-    "\12CSUM_IP6_UDP\13CSUM_IP6_TCP\14CSUM_IP6_SCTP\15CSUM_IP6_TSO" \
-    "\16CSUM_IP6_ISCSI" \
-    "\31CSUM_L3_CALC\32CSUM_L3_VALID\33CSUM_L4_CALC\34CSUM_L4_VALID" \
-    "\35CSUM_L5_CALC\36CSUM_L5_VALID\37CSUM_COALESCED\40CSUM_SND_TAG"
+    "\6CSUM_IP_ISCSI\7CSUM_INNER_IP6_UDP\10CSUM_INNER_IP6_TCP" \
+    "\11CSUM_INNER_IP6_TSO\12CSUM_IP6_UDP\13CSUM_IP6_TCP\14CSUM_IP6_SCTP" \
+    "\15CSUM_IP6_TSO\16CSUM_IP6_ISCSI\17CSUM_INNER_IP\20CSUM_INNER_IP_UDP" \
+    "\21CSUM_INNER_IP_TCP\22CSUM_INNER_IP_TSO\23CSUM_ENCAP_VXLAN" \
+    "\24CSUM_ENCAP_RSVD1\25CSUM_INNER_L3_CALC\26CSUM_INNER_L3_VALID" \
+    "\27CSUM_INNER_L4_CALC\30CSUM_INNER_L4_VALID\31CSUM_L3_CALC" \
+    "\32CSUM_L3_VALID\33CSUM_L4_CALC\34CSUM_L4_VALID\35CSUM_L5_CALC" \
+    "\36CSUM_L5_VALID\37CSUM_COALESCED\40CSUM_SND_TAG"
 
 /* CSUM flags compatibility mappings. */
 #define	CSUM_IP_CHECKED		CSUM_L3_CALC
@@ -667,6 +706,7 @@ m_epg_pagelen(const struct mbuf *m, int pidx, int pgoff)
 #define	CSUM_UDP		CSUM_IP_UDP
 #define	CSUM_SCTP		CSUM_IP_SCTP
 #define	CSUM_TSO		(CSUM_IP_TSO|CSUM_IP6_TSO)
+#define	CSUM_INNER_TSO		(CSUM_INNER_IP_TSO|CSUM_INNER_IP6_TSO)
 #define	CSUM_UDP_IPV6		CSUM_IP6_UDP
 #define	CSUM_TCP_IPV6		CSUM_IP6_TCP
 #define	CSUM_SCTP_IPV6		CSUM_IP6_SCTP