diff --git a/include/nuttx/net/ip.h b/include/nuttx/net/ip.h
index e6a9f9c9d1..a5d3df5494 100644
--- a/include/nuttx/net/ip.h
+++ b/include/nuttx/net/ip.h
@@ -143,7 +143,7 @@ union ip_binding_u
 #ifdef CONFIG_NET_IPv4
 /* The IPv4 header */
 
-struct net_iphdr_s
+struct ipv4_hdr_s
 {
   uint8_t  vhl;              /*  8-bit Version (4) and header length (5 or 6) */
   uint8_t  tos;              /*  8-bit Type of service (e.g., 6=TCP) */
@@ -161,7 +161,7 @@ struct net_iphdr_s
 #ifdef CONFIG_NET_IPv6
 /* The IPv6 header */
 
-struct net_ipv6hdr_s
+struct ipv6_hdr_s
 {
   uint8_t  vtc;              /* Bits 0-3: version, bits 4-7: traffic class (MS) */
   uint8_t  tcf;              /* Bits 0-3: traffic class (LS), 4-bits: flow label (MS) */
diff --git a/include/nuttx/net/tcp.h b/include/nuttx/net/tcp.h
index c6b9ddf17c..02dfa885cd 100644
--- a/include/nuttx/net/tcp.h
+++ b/include/nuttx/net/tcp.h
@@ -156,68 +156,6 @@ struct tcp_hdr_s
   uint8_t  optdata[4];
 };
 
-/* The TCP and IP headers */
-
-#ifdef CONFIG_NET_IPv4
-struct tcp_iphdr_s
-{
-  /* IPv4 IP header */
-
-  uint8_t  vhl;              /*  8-bit Version (4) and header length (5 or 6) */
-  uint8_t  tos;              /*  8-bit Type of service (e.g., 6=TCP) */
-  uint8_t  len[2];           /* 16-bit Total length */
-  uint8_t  ipid[2];          /* 16-bit Identification */
-  uint8_t  ipoffset[2];      /* 16-bit IP flags + fragment offset */
-  uint8_t  ttl;              /*  8-bit Time to Live */
-  uint8_t  proto;            /*  8-bit Protocol */
-  uint16_t ipchksum;         /* 16-bit Header checksum */
-  uint16_t srcipaddr[2];     /* 32-bit Source IP address */
-  uint16_t destipaddr[2];    /* 32-bit Destination IP address */
-
-  /* TCP header */
-
-  uint16_t srcport;
-  uint16_t destport;
-  uint8_t  seqno[4];
-  uint8_t  ackno[4];
-  uint8_t  tcpoffset;
-  uint8_t  flags;
-  uint8_t  wnd[2];
-  uint16_t tcpchksum;
-  uint8_t  urgp[2];
-  uint8_t  optdata[4];
-};
-#endif
-
-#ifdef CONFIG_NET_IPv6
-struct tcp_ipv6hdr_s
-{
-  /* IPv6 IP header */
-
-  uint8_t  vtc;              /* Bits 0-3: version, bits 4-7: traffic class (MS) */
-  uint8_t  tcf;              /* Bits 0-3: traffic class (LS), 4-bits: flow label (MS) */
-  uint16_t flow;             /* 16-bit flow label (LS) */
-  uint8_t  len[2];           /* 16-bit Payload length */
-  uint8_t  proto;            /*  8-bit Next header (same as IPv4 protocol field) */
-  uint8_t  ttl;              /*  8-bit Hop limit (like IPv4 TTL field) */
-  net_ipv6addr_t srcipaddr;  /* 128-bit Source address */
-  net_ipv6addr_t destipaddr; /* 128-bit Destination address */
-
-  /* TCP header */
-
-  uint16_t srcport;
-  uint16_t destport;
-  uint8_t  seqno[4];
-  uint8_t  ackno[4];
-  uint8_t  tcpoffset;
-  uint8_t  flags;
-  uint8_t  wnd[2];
-  uint16_t tcpchksum;
-  uint8_t  urgp[2];
-  uint8_t  optdata[4];
-};
-#endif
-
 /* The structure holding the TCP/IP statistics that are gathered if
  * CONFIG_NET_STATISTICS is defined.
  */
diff --git a/include/nuttx/net/udp.h b/include/nuttx/net/udp.h
index 4b2d305d68..24b47452f5 100644
--- a/include/nuttx/net/udp.h
+++ b/include/nuttx/net/udp.h
@@ -86,56 +86,6 @@ struct udp_hdr_s
   uint16_t udpchksum;
 };
 
-/* The UDP and IP headers */
-
-#ifdef CONFIG_NET_IPv4
-struct udp_iphdr_s
-{
-  /* IPv4 header */
-
-  uint8_t  vhl;              /*  8-bit Version (4) and header length (5 or 6) */
-  uint8_t  tos;              /*  8-bit Type of service (e.g., 6=TCP) */
-  uint8_t  len[2];           /* 16-bit Total length */
-  uint8_t  ipid[2];          /* 16-bit Identification */
-  uint8_t  ipoffset[2];      /* 16-bit IP flags + fragment offset */
-  uint8_t  ttl;              /*  8-bit Time to Live */
-  uint8_t  proto;            /*  8-bit Protocol */
-  uint16_t ipchksum;         /* 16-bit Header checksum */
-  uint16_t srcipaddr[2];     /* 32-bit Source IP address */
-  uint16_t destipaddr[2];    /* 32-bit Destination IP address */
-
-  /* UDP header */
-
-  uint16_t srcport;
-  uint16_t destport;
-  uint16_t udplen;
-  uint16_t udpchksum;
-};
-#endif
-
-#ifdef CONFIG_NET_IPv6
-struct udp_ipv6hdr_s
-{
-  /* IPv6 Ip header */
-
-  uint8_t  vtc;              /* Bits 0-3: version, bits 4-7: traffic class (MS) */
-  uint8_t  tcf;              /* Bits 0-3: traffic class (LS), 4-bits: flow label (MS) */
-  uint16_t flow;             /* 16-bit flow label (LS) */
-  uint8_t  len[2];           /* 16-bit Payload length */
-  uint8_t  proto;            /*  8-bit Next header (same as IPv4 protocol field) */
-  uint8_t  ttl;              /*  8-bit Hop limit (like IPv4 TTL field) */
-  net_ipv6addr_t srcipaddr;  /* 128-bit Source address */
-  net_ipv6addr_t destipaddr; /* 128-bit Destination address */
-
-  /* UDP header */
-
-  uint16_t srcport;
-  uint16_t destport;
-  uint16_t udplen;
-  uint16_t udpchksum;
-};
-#endif
-
 /* The structure holding the UDP statistics that are gathered if
  * CONFIG_NET_STATISTICS is defined.
  */
diff --git a/net/devif/ipv4_input.c b/net/devif/ipv4_input.c
index 589e685ba1..394b220a79 100644
--- a/net/devif/ipv4_input.c
+++ b/net/devif/ipv4_input.c
@@ -104,8 +104,8 @@
 
 /* Macros */
 
-#define BUF                  ((FAR struct net_iphdr_s *)&dev->d_buf[NET_LL_HDRLEN(dev)])
-#define FBUF                 ((FAR struct net_iphdr_s *)&g_reassembly_buffer[0])
+#define BUF                  ((FAR struct ipv4_hdr_s *)&dev->d_buf[NET_LL_HDRLEN(dev)])
+#define FBUF                 ((FAR struct ipv4_hdr_s *)&g_reassembly_buffer[0])
 
 /* IP fragment re-assembly */
 
@@ -151,8 +151,8 @@ static uint8_t g_reassembly_flags;
 #if defined(CONFIG_NET_TCP_REASSEMBLY) && !defined(CONFIG_NET_IPv6)
 static uint8_t devif_reassembly(void)
 {
-  FAR struct net_iphdr_s *pbuf  = BUF;
-  FAR struct net_iphdr_s *pfbuf = FBUF;
+  FAR struct ipv4_hdr_s *pbuf  = BUF;
+  FAR struct ipv4_hdr_s *pfbuf = FBUF;
   uint16_t offset;
   uint16_t len;
   uint16_t i;
@@ -311,7 +311,7 @@ nullreturn:
 
 int ipv4_input(FAR struct net_driver_s *dev)
 {
-  FAR struct net_iphdr_s *pbuf = BUF;
+  FAR struct ipv4_hdr_s *pbuf = BUF;
   uint16_t iplen;
 
   /* This is where the input processing starts. */
diff --git a/net/devif/ipv6_input.c b/net/devif/ipv6_input.c
index e190e19118..3616b04f43 100644
--- a/net/devif/ipv6_input.c
+++ b/net/devif/ipv6_input.c
@@ -104,7 +104,7 @@
 
 /* Macros */
 
-#define BUF  ((FAR struct net_ipv6hdr_s *)&dev->d_buf[NET_LL_HDRLEN(dev)])
+#define BUF  ((FAR struct ipv6_hdr_s *)&dev->d_buf[NET_LL_HDRLEN(dev)])
 
 /****************************************************************************
  * Public Data
@@ -139,7 +139,7 @@
 
 int ipv6_input(FAR struct net_driver_s *dev)
 {
-  FAR struct net_ipv6hdr_s *pbuf = BUF;
+  FAR struct ipv6_hdr_s *pbuf = BUF;
   uint16_t iplen;
 
   /* This is where the input processing starts. */
diff --git a/net/socket/net_sendfile.c b/net/socket/net_sendfile.c
index 0432626c5a..b64d3d1c96 100644
--- a/net/socket/net_sendfile.c
+++ b/net/socket/net_sendfile.c
@@ -2,7 +2,7 @@
  * net/socket/net_sendfile.c
  *
  *   Copyright (C) 2013 UVC Ingenieure. All rights reserved.
- *   Copyright (C) 2007-2014 Gregory Nutt. All rights reserved.
+ *   Copyright (C) 2007-2015 Gregory Nutt. All rights reserved.
  *   Authors: Gregory Nutt <gnutt@nuttx.org>
  *            Max Holtzberg <mh@uvc.de>
  *
@@ -77,7 +77,8 @@
 #  define CONFIG_NET_TCP_SPLIT_SIZE 40
 #endif
 
-#define TCPBUF ((struct tcp_iphdr_s *)&dev->d_buf[NET_LL_HDRLEN(dev)])
+#define TCPIPv4BUF ((struct tcp_hdr_s *)&dev->d_buf[NET_LL_HDRLEN(dev) + IPv4_HDRLEN])
+#define TCPIPv6BUF ((struct tcp_hdr_s *)&dev->d_buf[NET_LL_HDRLEN(dev) + IPv6_HDRLEN])
 
 /****************************************************************************
  * Private Types
@@ -157,12 +158,36 @@ static uint16_t ack_interrupt(FAR struct net_driver_s *dev, FAR void *pvconn,
 
   if ((flags & TCP_ACKDATA) != 0)
     {
+      FAR struct tcp_hdr_s *tcp;
+
 #ifdef CONFIG_NET_SOCKOPTS
       /* Update the timeout */
 
       pstate->snd_time = clock_systimer();
 #endif
 
+      /* Get the offset address of the TCP header */
+
+#ifdef CONFIG_NET_IPv6
+#ifdef CONFIG_NET_IPv4
+      if (IFF_IS_IPv6(dev->d_flags))
+#endif
+        {
+          DEBUGASSERT(pstate->snd_sock == PF_INET6);
+          tcp = TCPIPv6BUF;
+        }
+#endif /* CONFIG_NET_IPv6 */
+
+#ifdef CONFIG_NET_IPv4
+#ifdef CONFIG_NET_IPv6
+      else
+#endif
+        {
+          DEBUGASSERT(pstate->snd_sock == PF_INET);
+          tcp = TCPIPv4BUF;
+        }
+#endif /* CONFIG_NET_IPv4 */
+
       /* The current acknowledgement number number is the (relative) offset
        * of the of the next byte needed by the receiver.  The snd_isn is the
        * offset of the first byte to send to the receiver.  The difference
diff --git a/net/socket/recvfrom.c b/net/socket/recvfrom.c
index 6bbe9deeac..9421539d47 100644
--- a/net/socket/recvfrom.c
+++ b/net/socket/recvfrom.c
@@ -1,7 +1,7 @@
 /****************************************************************************
  * net/socket/recvfrom.c
  *
- *   Copyright (C) 2007-2009, 2011-2014 Gregory Nutt. All rights reserved.
+ *   Copyright (C) 2007-2009, 2011-2015 Gregory Nutt. All rights reserved.
  *   Author: Gregory Nutt <gnutt@nuttx.org>
  *
  * Redistribution and use in source and binary forms, with or without
@@ -74,13 +74,14 @@
  * Pre-processor Definitions
  ****************************************************************************/
 
-#if defined(CONFIG_NET_IPv4)
-#  define UDPBUF ((struct udp_iphdr_s *)&dev->d_buf[NET_LL_HDRLEN(dev)])
-#  define TCPBUF ((struct tcp_iphdr_s *)&dev->d_buf[NET_LL_HDRLEN(dev)])
-#elif defined(CONFIG_NET_IPv6)
-#  define UDPBUF ((struct udp_ipv6hdr_s *)&dev->d_buf[NET_LL_HDRLEN(dev)])
-#  define TCPBUF ((struct tcp_ipv6hdr_s *)&dev->d_buf[NET_LL_HDRLEN(dev)])
-#endif
+#define IPv4BUF    ((struct ipv4_hdr_s *)&dev->d_buf[NET_LL_HDRLEN(dev)])
+#define IPv6BUF    ((struct ipv6_hdr_s *)&dev->d_buf[NET_LL_HDRLEN(dev)])
+
+#define UDPIPv4BUF ((struct udp_hdr_s *)&dev->d_buf[NET_LL_HDRLEN(dev) + IPv4_HDRLEN])
+#define UDPIPv6BUF ((struct udp_hdr_s *)&dev->d_buf[NET_LL_HDRLEN(dev) + IPv6_HDRLEN])
+
+#define TCPIPv4BUF ((struct tcp_hdr_s *)&dev->d_buf[NET_LL_HDRLEN(dev) + IPv4_HDRLEN])
+#define TCPIPv6BUF ((struct tcp_hdr_s *)&dev->d_buf[NET_LL_HDRLEN(dev) + IPv6_HDRLEN])
 
 /****************************************************************************
  * Private Types
@@ -572,26 +573,52 @@ static uint16_t recvfrom_pktinterrupt(FAR struct net_driver_s *dev,
 static inline void recvfrom_tcpsender(FAR struct net_driver_s *dev,
                                       FAR struct recvfrom_s *pstate)
 {
-#ifdef CONFIG_NET_IPv6
-  FAR struct sockaddr_in6 *infrom = pstate->rf_from;
-#else
-  FAR struct sockaddr_in *infrom  = pstate->rf_from;
-#endif
+  /* Get the family from the packet type, IP address from the IP header, and
+   * the port number from the TCP header.
+   */
 
-  if (infrom)
+#ifdef CONFIG_NET_IPv6
+#ifdef CONFIG_NET_IPv4
+  if (IFF_IS_IPv6(dev->d_flags))
+#endif
     {
-      infrom->sin_family = AF_INET;
-      infrom->sin_port   = TCPBUF->srcport;
+      FAR struct sockaddr_in6 *infrom = pstate->rf_from;
 
-#ifdef CONFIG_NET_IPv6
-      net_ipv6addr_copy(infrom->sin6_addr.s6_addr, TCPBUF->srcipaddr);
-#else
-      net_ipv4addr_copy(infrom->sin_addr.s_addr,
-                        net_ip4addr_conv32(TCPBUF->srcipaddr));
-#endif
+      if (infrom)
+        {
+          FAR struct tcp_hdr_s *tcp   = TCPIPv6BUF;
+          FAR struct ipv6_hdr_s *ipv6 = IPv6BUF;
+
+          infrom->sin_family = AF_INET6;
+          infrom->sin_port   = tcp->srcport;
+
+          net_ipv6addr_copy(infrom->sin6_addr.s6_addr, ipv6->srcipaddr);
+        }
     }
-}
+#endif /* CONFIG_NET_IPv6 */
+
+#ifdef CONFIG_NET_IPv4
+#ifdef CONFIG_NET_IPv6
+  else
 #endif
+    {
+      FAR struct sockaddr_in *infrom  = pstate->rf_from;
+
+      if (infrom)
+        {
+          FAR struct tcp_hdr_s *tcp   = TCPIPv4BUF;
+          FAR struct ipv4_hdr_s *ipv4 = IPv4BUF;
+
+          infrom->sin_family = AF_INET;
+          infrom->sin_port   = tcp->srcport;
+
+          net_ipv4addr_copy(infrom->sin_addr.s_addr,
+                            net_ip4addr_conv32(ipv4->srcipaddr));
+        }
+    }
+#endif /* CONFIG_NET_IPv4 */
+}
+#endif /* CONFIG_NET_TCP */
 
 /****************************************************************************
  * Function: recvfrom_tcpinterrupt
@@ -819,26 +846,52 @@ static uint16_t recvfrom_tcpinterrupt(FAR struct net_driver_s *dev,
 #ifdef CONFIG_NET_UDP
 static inline void recvfrom_udpsender(struct net_driver_s *dev, struct recvfrom_s *pstate)
 {
-#ifdef CONFIG_NET_IPv6
-  FAR struct sockaddr_in6 *infrom = pstate->rf_from;
-#else
-  FAR struct sockaddr_in *infrom  = pstate->rf_from;
-#endif
+  /* Get the family from the packet type, IP address from the IP header, and
+   * the port number from the UDP header.
+   */
 
-  if (infrom)
+#ifdef CONFIG_NET_IPv6
+#ifdef CONFIG_NET_IPv4
+  if (IFF_IS_IPv6(dev->d_flags))
+#endif
     {
-      infrom->sin_family = AF_INET;
-      infrom->sin_port   = UDPBUF->srcport;
+      FAR struct sockaddr_in6 *infrom = pstate->rf_from;
 
-#ifdef CONFIG_NET_IPv6
-      net_ipv6addr_copy(infrom->sin6_addr.s6_addr, UDPBUF->srcipaddr);
-#else
-      net_ipv4addr_copy(infrom->sin_addr.s_addr,
-                        net_ip4addr_conv32(UDPBUF->srcipaddr));
-#endif
+      if (infrom)
+        {
+          FAR struct udp_hdr_s *udp   = UDPIPv6BUF;
+          FAR struct ipv6_hdr_s *ipv6 = IPv6BUF;
+
+          infrom->sin_family = AF_INET6;
+          infrom->sin_port   = udp->srcport;
+
+          net_ipv6addr_copy(infrom->sin6_addr.s6_addr, ipv6->srcipaddr);
+        }
     }
-}
+#endif /* CONFIG_NET_IPv6 */
+
+#ifdef CONFIG_NET_IPv4
+#ifdef CONFIG_NET_IPv6
+  else
 #endif
+    {
+      FAR struct sockaddr_in *infrom  = pstate->rf_from;
+
+      if (infrom)
+        {
+          FAR struct udp_hdr_s *udp   = UDPIPv4BUF;
+          FAR struct ipv4_hdr_s *ipv4 = IPv4BUF;
+
+          infrom->sin_family = AF_INET;
+          infrom->sin_port   = udp->srcport;
+
+          net_ipv4addr_copy(infrom->sin_addr.s_addr,
+                            net_ip4addr_conv32(ipv4->srcipaddr));
+        }
+    }
+#endif /* CONFIG_NET_IPv4 */
+}
+#endif /* CONFIG_NET_UDP */
 
 /****************************************************************************
  * Function: recvfrom_udpinterrupt
diff --git a/net/tcp/tcp.h b/net/tcp/tcp.h
index 16a5bbce80..1d6e78e8c6 100644
--- a/net/tcp/tcp.h
+++ b/net/tcp/tcp.h
@@ -270,7 +270,6 @@ extern "C"
 /* Defined in tcp_conn.c ****************************************************/
 
 struct sockaddr;    /* Forward reference */
-struct tcp_iphdr_s; /* Forward reference */
 
 /****************************************************************************
  * Name: tcp_initialize
diff --git a/net/tcp/tcp_conn.c b/net/tcp/tcp_conn.c
index b364e74ee3..4c531dfa13 100644
--- a/net/tcp/tcp_conn.c
+++ b/net/tcp/tcp_conn.c
@@ -64,8 +64,8 @@
  * Pre-processor Definitions
  ****************************************************************************/
 
-#define IPv4BUF ((struct net_iphdr_s *)&dev->d_buf[NET_LL_HDRLEN(dev)])
-#define IPv6BUF ((struct net_ipv6hdr_s *)&dev->d_buf[NET_LL_HDRLEN(dev)])
+#define IPv4BUF ((struct ipv4_hdr_s *)&dev->d_buf[NET_LL_HDRLEN(dev)])
+#define IPv6BUF ((struct ipv6_hdr_s *)&dev->d_buf[NET_LL_HDRLEN(dev)])
 
 /****************************************************************************
  * Private Data
@@ -357,7 +357,7 @@ static int tcp_selectport(uint16_t portno)
 static inline FAR struct tcp_conn_s *
   tcp_ipv4_active(FAR struct net_driver_s *dev, FAR struct tcp_hdr_s *tcp)
 {
-  FAR struct net_iphdr_s *ip = IPv4BUF;
+  FAR struct ipv4_hdr_s *ip = IPv4BUF;
   FAR struct tcp_conn_s *conn;
   in_addr_t srcipaddr;
 #ifdef CONFIG_NETDEV_MULTINIC
@@ -432,7 +432,7 @@ static inline FAR struct tcp_conn_s *
 static inline FAR struct tcp_conn_s *
   tcp_ipv6_active(FAR struct net_driver_s *dev, FAR struct tcp_hdr_s *tcp)
 {
-  FAR struct net_ipv6hdr_s *ip = IPv6BUF;
+  FAR struct ipv6_hdr_s *ip = IPv6BUF;
   FAR struct tcp_conn_s *conn;
   net_ipv6addr_t *srcipaddr;
 #ifdef CONFIG_NETDEV_MULTINIC
@@ -952,7 +952,7 @@ FAR struct tcp_conn_s *tcp_alloc_accept(FAR struct net_driver_s *dev,
       if (ipv6)
 #endif
         {
-          FAR struct net_ipv6hdr_s *ip = IPv6BUF;
+          FAR struct ipv6_hdr_s *ip = IPv6BUF;
 
           conn->mss = TCP_IPv6_INITIAL_MSS(dev);
           net_ipv6addr_copy(conn->u.ipv6.raddr, ip->srcipaddr);
@@ -967,7 +967,7 @@ FAR struct tcp_conn_s *tcp_alloc_accept(FAR struct net_driver_s *dev,
       else
 #endif
         {
-          FAR struct net_iphdr_s *ip = IPv4BUF;
+          FAR struct ipv4_hdr_s *ip = IPv4BUF;
 
           conn->mss = TCP_IPv4_INITIAL_MSS(dev);
           net_ipv4addr_copy(conn->u.ipv4.raddr,
diff --git a/net/tcp/tcp_send.c b/net/tcp/tcp_send.c
index 5c23b657fe..d63c595b0e 100644
--- a/net/tcp/tcp_send.c
+++ b/net/tcp/tcp_send.c
@@ -1,7 +1,7 @@
 /****************************************************************************
  * net/tcp/tcp_send.c
  *
- *   Copyright (C) 2007-2010, 2012 Gregory Nutt. All rights reserved.
+ *   Copyright (C) 2007-2010, 2012, 2015 Gregory Nutt. All rights reserved.
  *   Author: Gregory Nutt <gnutt@nuttx.org>
  *
  * Adapted for NuttX from logic in uIP which also has a BSD-like license:
@@ -62,7 +62,11 @@
  * Pre-processor Definitions
  ****************************************************************************/
 
-#define BUF ((struct tcp_iphdr_s *)&dev->d_buf[NET_LL_HDRLEN(dev)])
+#define IPv4BUF    ((struct ipv4_hdr_s *)&dev->d_buf[NET_LL_HDRLEN(dev)])
+#define IPv6BUF    ((struct ipv6_hdr_s *)&dev->d_buf[NET_LL_HDRLEN(dev)])
+
+#define TCPIPv4BUF ((struct tcp_hdr_s *)&dev->d_buf[NET_LL_HDRLEN(dev) + IPv4_HDRLEN])
+#define TCPIPv6BUF ((struct tcp_hdr_s *)&dev->d_buf[NET_LL_HDRLEN(dev) + IPv6_HDRLEN])
 
 /****************************************************************************
  * Public Variables
@@ -76,6 +80,155 @@
  * Private Functions
  ****************************************************************************/
 
+/****************************************************************************
+ * Name: tcp_header
+ *
+ * Description:
+ *   Get the length of the IP header
+ *
+ * Parameters:
+ *   dev - The device driver structure to use in the send operation
+ *
+ * Return:
+ *   The length of the IP header (IPv4_HDRLEN or IPv6_HDRLEN)
+ *
+ ****************************************************************************/
+
+static inline FAR struct tcp_hdr_s *tcp_header(FAR struct net_driver_s *dev)
+{
+#ifdef CONFIG_NET_IPv6
+#ifdef CONFIG_NET_IPv4
+  if (IFF_IS_IPv6(dev->d_flags))
+#endif
+    {
+      return TCPIPv6BUF;
+    }
+#endif /* CONFIG_NET_IPv6 */
+
+#ifdef CONFIG_NET_IPv4
+#ifdef CONFIG_NET_IPv6
+  else
+#endif
+    {
+      return TCPIPv4BUF;
+    }
+#endif /* CONFIG_NET_IPv4 */
+}
+
+/****************************************************************************
+ * Name: tcp_sendcomplete, tcp_ipv4_sendcomplete, and tcp_ipv6_sendcomplete
+ *
+ * Description:
+ *   Complete the final portions of the send operation.  This function sets
+ *   up IP header and computes the TCP checksum
+ *
+ * Parameters:
+ *   dev - The device driver structure to use in the send operation
+ *
+ * Return:
+ *   None
+ *
+ * Assumptions:
+ *   Called from the interrupt level or with interrupts disabled.
+ *
+ ****************************************************************************/
+
+#ifdef CONFIG_NET_IPv4
+static inline void tcp_ipv4_sendcomplete(FAR struct net_driver_s *dev,
+                                         FAR struct tcp_hdr_s *tcp,
+                                         FAR struct ipv4_hdr_s *ipv4)
+{
+  /* Set up some IP header fields that are needed for TCP checksum
+   * calculation.
+   */
+
+  ipv4->proto       = IP_PROTO_TCP;
+  ipv4->ttl         = IP_TTL;
+
+  ipv4->len[0]      = (dev->d_len >> 8);
+  ipv4->len[1]      = (dev->d_len & 0xff);
+
+  /* Calculate TCP checksum. */
+
+  tcp->urgp[0]      = 0;
+  tcp->urgp[1]      = 0;
+
+  tcp->tcpchksum    = 0;
+  tcp->tcpchksum    = ~tcp_ipv4_chksum(dev);
+
+  /* Finish initializing the IP header and calculate the IP checksum */
+
+  ipv4->vhl         = 0x45;
+  ipv4->tos         = 0;
+  ipv4->ipoffset[0] = 0;
+  ipv4->ipoffset[1] = 0;
+  ++g_ipid;
+  ipv4->ipid[0]     = g_ipid >> 8;
+  ipv4->ipid[1]     = g_ipid & 0xff;
+
+  /* Calculate IP checksum. */
+
+  ipv4->ipchksum    = 0;
+  ipv4->ipchksum    = ~ipv4_chksum(dev);
+}
+#endif /* CONFIG_NET_IPv4 */
+
+/****************************************************************************
+ * Name: tcp_pv6_sendcomplete
+ *
+ * Description:
+ *   Complete the final portions of the send operation.  This function sets
+ *   up IP header and computes the TCP checksum
+ *
+ * Parameters:
+ *   dev - The device driver structure to use in the send operation
+ *
+ * Return:
+ *   None
+ *
+ * Assumptions:
+ *   Called from the interrupt level or with interrupts disabled.
+ *
+ ****************************************************************************/
+
+#ifdef CONFIG_NET_IPv6
+static inline void tcp_ipv6_sendcomplete(FAR struct net_driver_s *dev,
+                                         FAR struct tcp_hdr_s *tcp,
+                                         FAR struct ipv6_hdr_s *ipv6)
+{
+  uint16_t iplen;
+
+  /* Set up some IP header fields that are needed for TCP checksum
+   * calculation.
+   */
+
+  ipv6->proto     = IP_PROTO_TCP;
+  ipv6->ttl       = IP_TTL;
+
+  /* For IPv6, the IP length field does not include the IPv6 IP header
+   * length.
+   */
+
+  iplen           = dev->d_len - IPv6_HDRLEN;
+  ipv6->len[0]    = (iplen >> 8);
+  ipv6->len[1]    = (iplen & 0xff);
+
+  /* Calculate TCP checksum. */
+
+  tcp->urgp[0]     = 0;
+  tcp->urgp[1]     = 0;
+
+  tcp->tcpchksum   = 0;
+  tcp->tcpchksum   = ~tcp_ipv6_chksum(dev);
+
+  /* Finish initializing the IP header (no IPv6 checksum) */
+
+  ipv6->vtc    = 0x60;
+  ipv6->tcf    = 0x00;
+  ipv6->flow   = 0x00;
+}
+#endif /* CONFIG_NET_IPv6 */
+
 /****************************************************************************
  * Name: tcp_sendcomplete
  *
@@ -94,60 +247,29 @@
  *
  ****************************************************************************/
 
-static void tcp_sendcomplete(FAR struct net_driver_s *dev)
+static void tcp_sendcomplete(FAR struct net_driver_s *dev,
+                             FAR struct tcp_hdr_s *tcp)
 {
-  FAR struct tcp_iphdr_s *pbuf = BUF;
-
-  pbuf->ttl         = IP_TTL;
-
 #ifdef CONFIG_NET_IPv6
-
-  /* For IPv6, the IP length field does not include the IPv6 IP header
-   * length.
-   */
-
-  pbuf->len[0]      = ((dev->d_len - IPv6_HDRLEN) >> 8);
-  pbuf->len[1]      = ((dev->d_len - IPv6_HDRLEN) & 0xff);
-
-#else /* CONFIG_NET_IPv6 */
-
-  pbuf->len[0]      = (dev->d_len >> 8);
-  pbuf->len[1]      = (dev->d_len & 0xff);
-
+#ifdef CONFIG_NET_IPv4
+  if (IFF_IS_IPv6(dev->d_flags))
+#endif
+    {
+      tcp_ipv6_sendcomplete(dev, tcp, IPv6BUF);
+    }
 #endif /* CONFIG_NET_IPv6 */
 
-  pbuf->urgp[0]     = pbuf->urgp[1] = 0;
-
-  /* Calculate TCP checksum. */
-
-  pbuf->tcpchksum   = 0;
-  pbuf->tcpchksum   = ~(tcp_chksum(dev));
-
+#ifdef CONFIG_NET_IPv4
 #ifdef CONFIG_NET_IPv6
-
-  pbuf->vtc         = 0x60;
-  pbuf->tcf         = 0x00;
-  pbuf->flow        = 0x00;
-
-#else /* CONFIG_NET_IPv6 */
-
-  pbuf->vhl         = 0x45;
-  pbuf->tos         = 0;
-  pbuf->ipoffset[0] = 0;
-  pbuf->ipoffset[1] = 0;
-  ++g_ipid;
-  pbuf->ipid[0]     = g_ipid >> 8;
-  pbuf->ipid[1]     = g_ipid & 0xff;
-
-  /* Calculate IP checksum. */
-
-  pbuf->ipchksum    = 0;
-  pbuf->ipchksum    = ~(ipv4_chksum(dev));
-
-#endif /* CONFIG_NET_IPv6 */
+  else
+#endif
+    {
+      tcp_ipv4_sendcomplete(dev, tcp, IPv4BUF);
+    }
+#endif /* CONFIG_NET_IPv4 */
 
   nllvdbg("Outgoing TCP packet length: %d (%d)\n",
-          dev->d_len, (pbuf->len[0] << 8) | pbuf->len[1]);
+          dev->d_len, (tcp->len[0] << 8) | tcp->len[1]);
 
 #ifdef CONFIG_NET_STATISTICS
   g_netstats.tcp.sent++;
@@ -176,19 +298,42 @@ static void tcp_sendcomplete(FAR struct net_driver_s *dev)
  ****************************************************************************/
 
 static void tcp_sendcommon(FAR struct net_driver_s *dev,
-                           FAR struct tcp_conn_s *conn)
+                           FAR struct tcp_conn_s *conn,
+                           FAR struct tcp_hdr_s *tcp)
 {
-  FAR struct tcp_iphdr_s *pbuf = BUF;
+      /* Copy the IP address into the IPv6 header */
 
-  memcpy(pbuf->ackno, conn->rcvseq, 4);
-  memcpy(pbuf->seqno, conn->sndseq, 4);
+#ifdef CONFIG_NET_IPv6
+#ifdef CONFIG_NET_IPv4
+  if (IFF_IS_IPv6(dev->d_flags))
+#endif
+    {
+      FAR struct ipv6_hdr_s *ipv6 = IPv6BUF;
+      net_ipv6addr_hdrcopy(ipv6->srcipaddr, dev->d_ipv6addr);
+      net_ipv6addr_hdrcopy(ipv6->destipaddr, conn->u.ipv6.raddr);
+    }
+#endif /* CONFIG_NET_IPv6 */
 
-  pbuf->proto    = IP_PROTO_TCP;
-  pbuf->srcport  = conn->lport;
-  pbuf->destport = conn->rport;
+#ifdef CONFIG_NET_IPv4
+#ifdef CONFIG_NET_IPv6
+  else
+#endif
+    {
+      FAR struct ipv4_hdr_s *ipv4 = IPv4BUF;
+      net_ipv4addr_hdrcopy(ipv4->srcipaddr, &dev->d_ipaddr);
+      net_ipv4addr_hdrcopy(ipv4->destipaddr, &conn->u.ipv4.raddr);
+    }
+#endif /* CONFIG_NET_IPv4 */
 
-  net_ipv4addr_hdrcopy(pbuf->srcipaddr, &dev->d_ipaddr);
-  net_ipv4addr_hdrcopy(pbuf->destipaddr, &conn->u.ipv4.raddr);
+  /* Set TCP sequence numbers and port numbers */
+
+  memcpy(tcp->ackno, conn->rcvseq, 4);
+  memcpy(tcp->seqno, conn->sndseq, 4);
+
+  tcp->srcport  = conn->lport;
+  tcp->destport = conn->rport;
+
+  /* Set the TCP window */
 
   if (conn->tcpstateflags & TCP_STOPPED)
     {
@@ -196,20 +341,18 @@ static void tcp_sendcommon(FAR struct net_driver_s *dev,
        * window so that the remote host will stop sending data.
        */
 
-      pbuf->wnd[0] = 0;
-      pbuf->wnd[1] = 0;
+      tcp->wnd[0] = 0;
+      tcp->wnd[1] = 0;
     }
   else
     {
-      pbuf->wnd[0] = ((NET_DEV_RCVWNDO(dev)) >> 8);
-      pbuf->wnd[1] = ((NET_DEV_RCVWNDO(dev)) & 0xff);
+      tcp->wnd[0] = ((NET_DEV_RCVWNDO(dev)) >> 8);
+      tcp->wnd[1] = ((NET_DEV_RCVWNDO(dev)) & 0xff);
     }
 
-  /* Finish the IP portion of the message, calculate checksums and send
-   * the message.
-   */
+  /* Finish the IP portion of the message and calculate checksums */
 
-  tcp_sendcomplete(dev);
+  tcp_sendcomplete(dev, tcp);
 }
 
 /****************************************************************************
@@ -239,12 +382,12 @@ static void tcp_sendcommon(FAR struct net_driver_s *dev,
 void tcp_send(FAR struct net_driver_s *dev, FAR struct tcp_conn_s *conn,
               uint16_t flags, uint16_t len)
 {
-  FAR struct tcp_iphdr_s *pbuf = BUF;
+  FAR struct tcp_hdr_s *tcp = tcp_header(dev);
 
-  pbuf->flags     = flags;
+  tcp->flags     = flags;
   dev->d_len     = len;
-  pbuf->tcpoffset = (TCP_HDRLEN / 4) << 4;
-  tcp_sendcommon(dev, conn);
+  tcp->tcpoffset = (TCP_HDRLEN / 4) << 4;
+  tcp_sendcommon(dev, conn, tcp);
 }
 
 /****************************************************************************
@@ -266,7 +409,7 @@ void tcp_send(FAR struct net_driver_s *dev, FAR struct tcp_conn_s *conn,
 
 void tcp_reset(FAR struct net_driver_s *dev)
 {
-  FAR struct tcp_iphdr_s *pbuf = BUF;
+  FAR struct tcp_hdr_s *tcp = tcp_header(dev);
   uint16_t tmp16;
   uint8_t seqbyte;
 
@@ -274,58 +417,92 @@ void tcp_reset(FAR struct net_driver_s *dev)
   g_netstats.tcp.rst++;
 #endif
 
-  pbuf->flags     = TCP_RST | TCP_ACK;
-  dev->d_len      = IPv4TCP_HDRLEN;
-  pbuf->tcpoffset = 5 << 4;
+  /* TCP setup */
+
+  tcp->flags     = TCP_RST | TCP_ACK;
+  tcp->tcpoffset = 5 << 4;
 
   /* Flip the seqno and ackno fields in the TCP header. */
 
-  seqbyte         = pbuf->seqno[3];
-  pbuf->seqno[3]  = pbuf->ackno[3];
-  pbuf->ackno[3]  = seqbyte;
+  seqbyte        = tcp->seqno[3];
+  tcp->seqno[3]  = tcp->ackno[3];
+  tcp->ackno[3]  = seqbyte;
 
-  seqbyte         = pbuf->seqno[2];
-  pbuf->seqno[2]  = pbuf->ackno[2];
-  pbuf->ackno[2]  = seqbyte;
+  seqbyte        = tcp->seqno[2];
+  tcp->seqno[2]  = tcp->ackno[2];
+  tcp->ackno[2]  = seqbyte;
 
-  seqbyte         = pbuf->seqno[1];
-  pbuf->seqno[1]  = pbuf->ackno[1];
-  pbuf->ackno[1]  = seqbyte;
+  seqbyte        = tcp->seqno[1];
+  tcp->seqno[1]  = tcp->ackno[1];
+  tcp->ackno[1]  = seqbyte;
 
-  seqbyte         = pbuf->seqno[0];
-  pbuf->seqno[0]  = pbuf->ackno[0];
-  pbuf->ackno[0]  = seqbyte;
+  seqbyte        = tcp->seqno[0];
+  tcp->seqno[0]  = tcp->ackno[0];
+  tcp->ackno[0]  = seqbyte;
 
   /* We also have to increase the sequence number we are
    * acknowledging. If the least significant byte overflowed, we need
    * to propagate the carry to the other bytes as well.
    */
 
-  if (++(pbuf->ackno[3]) == 0)
+  if (++(tcp->ackno[3]) == 0)
     {
-      if (++(pbuf->ackno[2]) == 0)
+      if (++(tcp->ackno[2]) == 0)
         {
-          if (++(pbuf->ackno[1]) == 0)
+          if (++(tcp->ackno[1]) == 0)
             {
-              ++(pbuf->ackno[0]);
+              ++(tcp->ackno[0]);
             }
         }
     }
 
   /* Swap port numbers. */
 
-  tmp16          = pbuf->srcport;
-  pbuf->srcport  = pbuf->destport;
-  pbuf->destport = tmp16;
+  tmp16         = tcp->srcport;
+  tcp->srcport  = tcp->destport;
+  tcp->destport = tmp16;
 
-  /* Swap IP addresses. */
+  /* Set the packet length and swap IP addresses. */
 
-  net_ipv4addr_hdrcopy(pbuf->destipaddr, pbuf->srcipaddr);
-  net_ipv4addr_hdrcopy(pbuf->srcipaddr, &dev->d_ipaddr);
+#ifdef CONFIG_NET_IPv6
+#ifdef CONFIG_NET_IPv4
+  if (IFF_IS_IPv6(dev->d_flags))
+#endif
+    {
+      FAR struct ipv6_hdr_s *ipv6 = IPv6BUF;
+
+      /* Set the packet length to the size of the IPv6 + TCP headers */
+
+      dev->d_len = IPv6TCP_HDRLEN;
+
+      /* Swap IPv6 addresses */
+
+      net_ipv6addr_hdrcopy(ipv6->destipaddr, ipv6->srcipaddr);
+      net_ipv6addr_hdrcopy(ipv6->srcipaddr, dev->d_ipv6addr);
+    }
+#endif /* CONFIG_NET_IPv6 */
+
+#ifdef CONFIG_NET_IPv4
+#ifdef CONFIG_NET_IPv6
+  else
+#endif
+    {
+      FAR struct ipv4_hdr_s *ipv4 = IPv4BUF;
+
+      /* Set the packet length to the size of the IPv4 + TCP headers */
+
+      dev->d_len = IPv4TCP_HDRLEN;
+
+      /* Swap IPv4 addresses */
+
+      net_ipv4addr_hdrcopy(ipv4->destipaddr, ipv4->srcipaddr);
+      net_ipv4addr_hdrcopy(ipv4->srcipaddr, &dev->d_ipaddr);
+    }
+#endif /* CONFIG_NET_IPv4 */
 
   /* And send out the RST packet */
 
-  tcp_sendcomplete(dev);
+  tcp_sendcomplete(dev, tcp);
 }
 
 /****************************************************************************
@@ -350,25 +527,58 @@ void tcp_reset(FAR struct net_driver_s *dev)
 void tcp_ack(FAR struct net_driver_s *dev, FAR struct tcp_conn_s *conn,
              uint8_t ack)
 {
-  struct tcp_iphdr_s *pbuf = BUF;
-  uint16_t tcp_mss = TCP_IPv4_MSS(dev);
+  struct tcp_hdr_s *tcp;
+  uint16_t tcp_mss;
+
+  /* Get values that vary with the underlying IP domain */
+
+#ifdef CONFIG_NET_IPv6
+#ifdef CONFIG_NET_IPv4
+  if (IFF_IS_IPv6(dev->d_flags))
+#endif
+    {
+      /* Get the MSS value and offset TCP header address for this packet */
+
+      tcp     = TCPIPv6BUF;
+      tcp_mss = TCP_IPv6_MSS(dev);
+
+      /* Set the the packet length for the TCP Maximum Segment Size */
+
+      dev->d_len  = IPv6TCP_HDRLEN + TCP_OPT_MSS_LEN;
+    }
+#endif /* CONFIG_NET_IPv6 */
+
+#ifdef CONFIG_NET_IPv4
+#ifdef CONFIG_NET_IPv6
+  else
+#endif
+    {
+      /* Get the MSS value and offset TCP header address for this packet */
+
+      tcp     = TCPIPv4BUF;
+      tcp_mss = TCP_IPv4_MSS(dev);
+
+      /* Set the the packet length for the TCP Maximum Segment Size */
+
+      dev->d_len  = IPv4TCP_HDRLEN + TCP_OPT_MSS_LEN;
+    }
+#endif /* CONFIG_NET_IPv4 */
 
   /* Save the ACK bits */
 
-  pbuf->flags      = ack;
+  tcp->flags      = ack;
 
   /* We send out the TCP Maximum Segment Size option with our ack. */
 
-  pbuf->optdata[0] = TCP_OPT_MSS;
-  pbuf->optdata[1] = TCP_OPT_MSS_LEN;
-  pbuf->optdata[2] = tcp_mss >> 8;
-  pbuf->optdata[3] = tcp_mss & 0xff;
-  dev->d_len       = IPv4TCP_HDRLEN + TCP_OPT_MSS_LEN;
-  pbuf->tcpoffset  = ((TCP_HDRLEN + TCP_OPT_MSS_LEN) / 4) << 4;
+  tcp->optdata[0] = TCP_OPT_MSS;
+  tcp->optdata[1] = TCP_OPT_MSS_LEN;
+  tcp->optdata[2] = tcp_mss >> 8;
+  tcp->optdata[3] = tcp_mss & 0xff;
+  tcp->tcpoffset  = ((TCP_HDRLEN + TCP_OPT_MSS_LEN) / 4) << 4;
 
   /* Complete the common portions of the TCP message */
 
-  tcp_sendcommon(dev, conn);
+  tcp_sendcommon(dev, conn, tcp);
 }
 
 #endif /* CONFIG_NET && CONFIG_NET_TCP */
diff --git a/net/tcp/tcp_send_buffered.c b/net/tcp/tcp_send_buffered.c
index 3b53db91b2..d7d495e7b8 100644
--- a/net/tcp/tcp_send_buffered.c
+++ b/net/tcp/tcp_send_buffered.c
@@ -86,11 +86,8 @@
 #  define NEED_IPDOMAIN_SUPPORT 1
 #endif
 
-#if defined(CONFIG_NET_IPv4)
-#  define TCPBUF ((struct tcp_iphdr_s *)&dev->d_buf[NET_LL_HDRLEN(dev)])
-#elif defined(CONFIG_NET_IPv6)
-#  define TCPBUF ((struct tcp_ipv6hdr_s *)&dev->d_buf[NET_LL_HDRLEN(dev)])
-#endif
+#define TCPIPv4BUF ((struct tcp_hdr_s *)&dev->d_buf[NET_LL_HDRLEN(dev) + IPv4_HDRLEN])
+#define TCPIPv6BUF ((struct tcp_hdr_s *)&dev->d_buf[NET_LL_HDRLEN(dev) + IPv6_HDRLEN])
 
 /* Debug */
 
@@ -285,11 +282,36 @@ static uint16_t psock_send_interrupt(FAR struct net_driver_s *dev,
   if ((flags & TCP_ACKDATA) != 0)
     {
       FAR struct tcp_wrbuffer_s *wrb;
+      FAR struct tcp_hdr_s *tcp;
       FAR sq_entry_t *entry;
       FAR sq_entry_t *next;
       uint32_t ackno;
 
-      ackno = tcp_getsequence(TCPBUF->ackno);
+      /* Get the offset address of the TCP header */
+
+#ifdef CONFIG_NET_IPv4
+#ifdef CONFIG_NET_IPv6
+      if (conn->domain == PF_INET))
+#endif
+        {
+          DEBUGASSERT(IFF_IS_IPv4(dev->d_flags));
+          tcp = TCPIPv4BUF;
+        }
+#endif /* CONFIG_NET_IPv4 */
+
+#ifdef CONFIG_NET_IPv6
+#ifdef CONFIG_NET_IPv4
+      else
+#endif
+        {
+          DEBUGASSERT(IFF_IS_IPv6(dev->d_flags));
+          tcp = TCPIPv6BUF;
+        }
+#endif /* CONFIG_NET_IPv6 */
+
+      /* Get the ACK number from the TCP header */
+
+      ackno = tcp_getsequence(tcp->ackno);
       nllvdbg("ACK: ackno=%u flags=%04x\n", ackno, flags);
 
       /* Look at every write buffer in the unacked_q.  The unacked_q
diff --git a/net/tcp/tcp_send_unbuffered.c b/net/tcp/tcp_send_unbuffered.c
index f0156c85ba..6e7fe32315 100644
--- a/net/tcp/tcp_send_unbuffered.c
+++ b/net/tcp/tcp_send_unbuffered.c
@@ -78,7 +78,8 @@
 #  define CONFIG_NET_TCP_SPLIT_SIZE 40
 #endif
 
-#define TCPBUF ((struct tcp_iphdr_s *)&dev->d_buf[NET_LL_HDRLEN(dev)])
+#define TCPIPv4BUF ((struct tcp_hdr_s *)&dev->d_buf[NET_LL_HDRLEN(dev) + IPv4_HDRLEN])
+#define TCPIPv6BUF ((struct tcp_hdr_s *)&dev->d_buf[NET_LL_HDRLEN(dev) + IPv6_HDRLEN])
 
 /****************************************************************************
  * Private Types
@@ -232,19 +233,43 @@ static uint16_t tcpsend_interrupt(FAR struct net_driver_s *dev,
 
   if ((flags & TCP_ACKDATA) != 0)
     {
+      FAR struct tcp_hdr_s *tcp;
+
       /* Update the timeout */
 
 #ifdef CONFIG_NET_SOCKOPTS
       pstate->snd_time = clock_systimer();
 #endif
 
+      /* Get the offset address of the TCP header */
+
+#ifdef CONFIG_NET_IPv4
+#ifdef CONFIG_NET_IPv6
+      if (conn->domain == PF_INET))
+#endif
+        {
+          DEBUGASSERT(IFF_IS_IPv4(dev->d_flags));
+          tcp = TCPIPv4BUF;
+        }
+#endif /* CONFIG_NET_IPv4 */
+
+#ifdef CONFIG_NET_IPv6
+#ifdef CONFIG_NET_IPv4
+      else
+#endif
+        {
+          DEBUGASSERT(IFF_IS_IPv6(dev->d_flags));
+          tcp = TCPIPv6BUF;
+        }
+#endif /* CONFIG_NET_IPv6 */
+
       /* The current acknowledgement number number is the (relative) offset
        * of the of the next byte needed by the receiver.  The snd_isn is the
        * offset of the first byte to send to the receiver.  The difference
        * is the number of bytes to be acknowledged.
        */
 
-      pstate->snd_acked = tcp_getsequence(TCPBUF->ackno) - pstate->snd_isn;
+      pstate->snd_acked = tcp_getsequence(tcp->ackno) - pstate->snd_isn;
       nllvdbg("ACK: acked=%d sent=%d buflen=%d\n",
               pstate->snd_acked, pstate->snd_sent, pstate->snd_buflen);
 
diff --git a/net/udp/udp.h b/net/udp/udp.h
index 2b5c0dba1e..f20ebf377d 100644
--- a/net/udp/udp.h
+++ b/net/udp/udp.h
@@ -96,7 +96,6 @@ extern "C"
  ****************************************************************************/
 
 struct net_driver_s;  /* Forward reference */
-struct udp_iphdr_s;   /* Forward reference */
 
 /* Defined in udp_conn.c ****************************************************/
 /****************************************************************************
diff --git a/net/udp/udp_conn.c b/net/udp/udp_conn.c
index 5895b98ed7..acce00d244 100644
--- a/net/udp/udp_conn.c
+++ b/net/udp/udp_conn.c
@@ -66,8 +66,8 @@
  * Pre-processor Definitions
  ****************************************************************************/
 
-#define IPv4BUF ((struct net_iphdr_s *)&dev->d_buf[NET_LL_HDRLEN(dev)])
-#define IPv6BUF ((struct net_ipv6hdr_s *)&dev->d_buf[NET_LL_HDRLEN(dev)])
+#define IPv4BUF ((struct ipv4_hdr_s *)&dev->d_buf[NET_LL_HDRLEN(dev)])
+#define IPv6BUF ((struct ipv6_hdr_s *)&dev->d_buf[NET_LL_HDRLEN(dev)])
 
 /****************************************************************************
  * Private Data
@@ -274,7 +274,7 @@ static uint16_t udp_select_port(void)
 static inline FAR struct udp_conn_s *
   udp_ipv4_active(FAR struct net_driver_s *dev, FAR struct udp_hdr_s *udp)
 {
-  FAR struct net_iphdr_s *ip = IPv4BUF;
+  FAR struct ipv4_hdr_s *ip = IPv4BUF;
   FAR struct udp_conn_s *conn;
 
   conn = (FAR struct udp_conn_s *)g_active_udp_connections.head;
@@ -342,7 +342,7 @@ static inline FAR struct udp_conn_s *
 static inline FAR struct udp_conn_s *
   udp_ipv6_active(FAR struct net_driver_s *dev, FAR struct udp_hdr_s *udp)
 {
-  FAR struct net_ipv6hdr_s *ip = IPv6BUF;
+  FAR struct ipv6_hdr_s *ip = IPv6BUF;
   FAR struct udp_conn_s *conn;
 
   conn = (FAR struct udp_conn_s *)g_active_udp_connections.head;
diff --git a/net/udp/udp_send.c b/net/udp/udp_send.c
index 8ceff0710c..7a640888c9 100644
--- a/net/udp/udp_send.c
+++ b/net/udp/udp_send.c
@@ -1,7 +1,7 @@
 /****************************************************************************
  * net/udp/udp_send.c
  *
- *   Copyright (C) 2007-2009, 2011 Gregory Nutt. All rights reserved.
+ *   Copyright (C) 2007-2009, 2011, 2015 Gregory Nutt. All rights reserved.
  *   Author: Gregory Nutt <gnutt@nuttx.org>
  *
  * Adapted for NuttX from logic in uIP which also has a BSD-like license:
@@ -63,7 +63,11 @@
  * Pre-processor Definitions
  ****************************************************************************/
 
-#define UDPBUF ((struct udp_iphdr_s *)&dev->d_buf[NET_LL_HDRLEN(dev)])
+#define IPv4BUF    ((struct ipv4_hdr_s *)&dev->d_buf[NET_LL_HDRLEN(dev)])
+#define IPv6BUF    ((struct ipv6_hdr_s *)&dev->d_buf[NET_LL_HDRLEN(dev)])
+
+#define UDPIPv4BUF ((struct udp_hdr_s *)&dev->d_buf[NET_LL_HDRLEN(dev) + IPv4_HDRLEN])
+#define UDPIPv6BUF ((struct udp_hdr_s *)&dev->d_buf[NET_LL_HDRLEN(dev) + IPv6_HDRLEN])
 
 /****************************************************************************
  * Public Variables
@@ -99,80 +103,114 @@
  *
  ****************************************************************************/
 
-void udp_send(struct net_driver_s *dev, struct udp_conn_s *conn)
+void udp_send(FAR struct net_driver_s *dev, FAR struct udp_conn_s *conn)
 {
-  FAR struct udp_iphdr_s *pudpbuf = UDPBUF;
+  FAR struct udp_hdr_s *udp;
 
   if (dev->d_sndlen > 0)
     {
-      /* The total length to send is the size of the application data plus
-       * the IP and UDP headers (and, eventually, the Ethernet header)
-       */
+      /* Initialize the IP header. */
 
-      dev->d_len = dev->d_sndlen + IPv4UDP_HDRLEN;
+#ifdef CONFIG_NET_IPv4
+#ifdef CONFIG_NET_IPv6
+      if (conn->domain == PF_INET)
+#endif
+        {
+          /* Get pointers to the IPv4 header and the offset TCP header */
 
-      /* Initialize the IP header.  Note that for IPv6, the IP length field
-       * does not include the IPv6 IP header length.
-       */
+          FAR struct ipv4_hdr_s *ipv4 = IPv4BUF;
+
+          DEBUGASSERT(IFF_IS_IPv4(dev->d_flags));
+          udp = UDPIPv4BUF;
+
+          /* Initialize the IPv4 header. */
+
+          ipv4->vhl         = 0x45;
+          ipv4->tos         = 0;
+          ipv4->len[0]      = (dev->d_len >> 8);
+          ipv4->len[1]      = (dev->d_len & 0xff);
+          ++g_ipid;
+          ipv4->ipid[0]     = g_ipid >> 8;
+          ipv4->ipid[1]     = g_ipid & 0xff;
+          ipv4->ipoffset[0] = 0;
+          ipv4->ipoffset[1] = 0;
+          ipv4->ttl         = conn->ttl;
+          ipv4->proto       = IP_PROTO_UDP;
+
+          net_ipv4addr_hdrcopy(ipv4->srcipaddr, &dev->d_ipaddr);
+          net_ipv4addr_hdrcopy(ipv4->destipaddr, &conn->u.ipv4.raddr);
+
+          /* Calculate IP checksum. */
+
+          ipv4->ipchksum    = 0;
+          ipv4->ipchksum    = ~ipv4_chksum(dev);
+
+          /* The total length to send is the size of the application data
+           * plus the IPv4 and UDP headers (and, eventually, the link layer
+           * header)
+           */
+
+          dev->d_len = dev->d_sndlen + IPv4UDP_HDRLEN;
+        }
+#endif /* CONFIG_NET_IPv4 */
 
 #ifdef CONFIG_NET_IPv6
+#ifdef CONFIG_NET_IPv4
+      else
+#endif
+        {
+          /* Get pointers to the IPv6 header and the offset TCP header */
 
-      pudpbuf->vtc         = 0x60;
-      pudpbuf->tcf         = 0x00;
-      pudpbuf->flow        = 0x00;
-      pudpbuf->len[0]      = (dev->d_sndlen >> 8);
-      pudpbuf->len[1]      = (dev->d_sndlen & 0xff);
-      pudpbuf->proto       = IP_PROTO_UDP;
-      pudpbuf->ttl         = conn->ttl;
+          FAR struct ipv6_hdr_s *ipv6 = IPv6BUF;
 
-      net_ipv6addr_copy(pudpbuf->srcipaddr, &dev->d_ipaddr);
-      net_ipav6ddr_copy(pudpbuf->destipaddr, &conn->u.ipv4.raddr);
+          DEBUGASSERT(IFF_IS_IPv6(dev->d_flags));
+          udp = UDPIPv6BUF;
 
-#else /* CONFIG_NET_IPv6 */
+          /* Initialize the IPv6 header.  Note that the IP length field
+           * does not include the IPv6 IP header length.
+           */
 
-      pudpbuf->vhl         = 0x45;
-      pudpbuf->tos         = 0;
-      pudpbuf->len[0]      = (dev->d_len >> 8);
-      pudpbuf->len[1]      = (dev->d_len & 0xff);
-      ++g_ipid;
-      pudpbuf->ipid[0]     = g_ipid >> 8;
-      pudpbuf->ipid[1]     = g_ipid & 0xff;
-      pudpbuf->ipoffset[0] = 0;
-      pudpbuf->ipoffset[1] = 0;
-      pudpbuf->ttl         = conn->ttl;
-      pudpbuf->proto       = IP_PROTO_UDP;
+          ipv6->vtc         = 0x60;
+          ipv6->tcf         = 0x00;
+          ipv6->flow        = 0x00;
+          ipv6->len[0]      = (dev->d_sndlen >> 8);
+          ipv6->len[1]      = (dev->d_sndlen & 0xff);
+          ipv6->proto       = IP_PROTO_UDP;
+          ipv6->ttl         = conn->ttl;
 
-      net_ipv4addr_hdrcopy(pudpbuf->srcipaddr, &dev->d_ipaddr);
-      net_ipv4addr_hdrcopy(pudpbuf->destipaddr, &conn->u.ipv4.raddr);
+          net_ipv6addr_copy(ipv6->srcipaddr, dev->d_ipv6addr);
+          net_ipv6addr_copy(ipv6->destipaddr, conn->u.ipv6.raddr);
 
-      /* Calculate IP checksum. */
-
-      pudpbuf->ipchksum    = 0;
-      pudpbuf->ipchksum    = ~(ipv4_chksum(dev));
+          /* The total length to send is the size of the application data
+           * plus the IPv4 and UDP headers (and, eventually, the link layer
+           * header)
+           */
 
+          dev->d_len = dev->d_sndlen + IPv6UDP_HDRLEN;
+        }
 #endif /* CONFIG_NET_IPv6 */
 
       /* Initialize the UDP header */
 
-      pudpbuf->srcport     = conn->lport;
-      pudpbuf->destport    = conn->rport;
-      pudpbuf->udplen      = HTONS(dev->d_sndlen + UDP_HDRLEN);
+      udp->srcport     = conn->lport;
+      udp->destport    = conn->rport;
+      udp->udplen      = HTONS(dev->d_sndlen + UDP_HDRLEN);
 
 #ifdef CONFIG_NET_UDP_CHECKSUMS
       /* Calculate UDP checksum. */
 
-      pudpbuf->udpchksum   = 0;
-      pudpbuf->udpchksum   = ~(udp_chksum(dev));
-      if (pudpbuf->udpchksum == 0)
+      udp->udpchksum   = 0;
+      udp->udpchksum   = ~(udp_chksum(dev));
+      if (udp->udpchksum == 0)
         {
-          pudpbuf->udpchksum = 0xffff;
+          udp->udpchksum = 0xffff;
         }
 #else
-      pudpbuf->udpchksum   = 0;
+      udp->udpchksum   = 0;
 #endif
 
       nllvdbg("Outgoing UDP packet length: %d (%d)\n",
-              dev->d_len, (pudpbuf->len[0] << 8) | pudpbuf->len[1]);
+              dev->d_len, (udp->len[0] << 8) | udp->len[1]);
 
 #ifdef CONFIG_NET_STATISTICS
       g_netstats.udp.sent++;
@@ -180,5 +218,4 @@ void udp_send(struct net_driver_s *dev, struct udp_conn_s *conn)
 #endif
     }
 }
-
 #endif /* CONFIG_NET && CONFIG_NET_UDP */
diff --git a/net/utils/Kconfig b/net/utils/Kconfig
index 112b257e24..5ba6ffe3e6 100644
--- a/net/utils/Kconfig
+++ b/net/utils/Kconfig
@@ -21,6 +21,6 @@ config NET_ARCH_CHKSUM
 
 			uint16_t net_chksum(FAR uint16_t *data, uint16_t len)
 			uint16_t ipv4_chksum(FAR struct net_driver_s *dev)
-			uint16_t ipv6_chksum(FAR struct net_driver_s *dev)
-			uint16_t tcp_chksum(FAR struct net_driver_s *dev);
+			uint16_t tcp_ipv4_chksum(FAR struct net_driver_s *dev);
+			uint16_t tcp_ipv6_chksum(FAR struct net_driver_s *dev);
 			uint16_t udp_chksum(FAR struct net_driver_s *dev);
diff --git a/net/utils/net_chksum.c b/net/utils/net_chksum.c
index 03e07fb47c..033aa7e59c 100644
--- a/net/utils/net_chksum.c
+++ b/net/utils/net_chksum.c
@@ -54,8 +54,8 @@
  * Pre-processor Definitions
  ****************************************************************************/
 
-#define IPv4BUF   ((struct net_iphdr_s *)&dev->d_buf[NET_LL_HDRLEN(dev)])
-#define IPv6BUF   ((struct net_ipv6hdr_s *)&dev->d_buf[NET_LL_HDRLEN(dev)])
+#define IPv4BUF   ((struct ipv4_hdr_s *)&dev->d_buf[NET_LL_HDRLEN(dev)])
+#define IPv6BUF   ((struct ipv6_hdr_s *)&dev->d_buf[NET_LL_HDRLEN(dev)])
 #define ICMPBUF   ((struct icmp_iphdr_s *)&dev->d_buf[NET_LL_HDRLEN(dev)])
 #define ICMPv6BUF ((struct icmp_ipv6hdr_s *)&dev->d_buf[NET_LL_HDRLEN(dev)])
 
@@ -119,7 +119,7 @@ static uint16_t chksum(uint16_t sum, FAR const uint8_t *data, uint16_t len)
 static uint16_t ipv4_upperlayer_chksum(FAR struct net_driver_s *dev,
                                        uint8_t proto)
 {
-  FAR struct net_iphdr_s *pbuf = IPv4BUF;
+  FAR struct ipv4_hdr_s *pbuf = IPv4BUF;
   uint16_t upperlen;
   uint16_t sum;
 
@@ -157,7 +157,7 @@ static uint16_t ipv4_upperlayer_chksum(FAR struct net_driver_s *dev,
 static uint16_t ipv6_upperlayer_chksum(FAR struct net_driver_s *dev,
                                        uint8_t proto)
 {
-  FAR struct net_ipv6hdr_s *pbuf = IPv6BUF;
+  FAR struct ipv6_hdr_s *pbuf = IPv6BUF;
   uint16_t upperlen;
   uint16_t sum;
 
@@ -314,34 +314,7 @@ uint16_t ipv4_chksum(FAR struct net_driver_s *dev)
 #endif /* CONFIG_NET_ARCH_CHKSUM */
 
 /****************************************************************************
- * Name: ipv6_chksum
- *
- * Description:
- *   Calculate the IPv6 header checksum of the packet header in d_buf.
- *
- *   The IPv6 header checksum is the Internet checksum of the 40 bytes of
- *   the IPv6 header.
- *
- *   If CONFIG_NET_ARCH_CHKSUM is defined, then this function must be
- *   provided by architecture-specific logic.
- *
- * Returned Value:
- *   The IPv6 header checksum of the IPv6 header in the d_buf buffer.
- *
- ****************************************************************************/
-
-#if defined(CONFIG_NET_IPv6) && !defined(CONFIG_NET_ARCH_CHKSUM)
-uint16_t ipv6_chksum(FAR struct net_driver_s *dev)
-{
-  uint16_t sum;
-
-  sum = chksum(0, &dev->d_buf[NET_LL_HDRLEN(dev)], IPv6_HDRLEN);
-  return (sum == 0) ? 0xffff : htons(sum);
-}
-#endif /* CONFIG_NET_ARCH_CHKSUM */
-
-/****************************************************************************
- * Name: tcp_chksum
+ * Name: tcp_chksum, tcp_ipv4_chksum, and tcp_ipv6_chksum
  *
  * Description:
  *   Calculate the TCP checksum of the packet in d_buf and d_appdata.
@@ -360,26 +333,34 @@ uint16_t ipv6_chksum(FAR struct net_driver_s *dev)
  ****************************************************************************/
 
 #if !CONFIG_NET_ARCH_CHKSUM
+#ifdef CONFIG_NET_IPv4
+uint16_t tcp_ipv4_chksum(FAR struct net_driver_s *dev)
+{
+  return ipv4_upperlayer_chksum(dev, IP_PROTO_TCP);
+}
+#endif /* CONFIG_NET_IPv4 */
+
+#ifdef CONFIG_NET_IPv6
+uint16_t tcp_ipv6_chksum(FAR struct net_driver_s *dev)
+{
+  return ipv6_upperlayer_chksum(dev, IP_PROTO_TCP);
+}
+#endif /* CONFIG_NET_IPv6 */
+#endif /* !CONFIG_NET_ARCH_CHKSUM */
+
+#if defined(CONFIG_NET_IPv4) && defined(CONFIG_NET_IPv6)
 uint16_t tcp_chksum(FAR struct net_driver_s *dev)
 {
-#if defined(CONFIG_NET_IPv4) && defined(CONFIG_NET_IPv6)
   if (IFF_IS_IPv6(dev->d_flags))
     {
-      return ipv6_upperlayer_chksum(dev, IP_PROTO_TCP);
+      return tcp_ipv6_chksum(dev);
     }
   else
     {
-      return ipv4_upperlayer_chksum(dev, IP_PROTO_TCP);
+      return tcp_ipv4_chksum(dev);
     }
-
-#elif defined(CONFIG_NET_IPv4)
-  return ipv4_upperlayer_chksum(dev, IP_PROTO_TCP);
-
-#else /* if defined(CONFIG_NET_IPv6) */
-  return ipv6_upperlayer_chksum(dev, IP_PROTO_TCP);
-#endif
 }
-#endif /* CONFIG_NET_ARCH_CHKSUM */
+#endif
 
 /****************************************************************************
  * Name: udp_chksum
diff --git a/net/utils/utils.h b/net/utils/utils.h
index 76401a27ab..6eabf097ee 100644
--- a/net/utils/utils.h
+++ b/net/utils/utils.h
@@ -139,7 +139,7 @@ unsigned int net_dsec2tick(int dsec);
 unsigned int net_timeval2dsec(FAR struct timeval *tv);
 
 /****************************************************************************
- * Name: tcp_chksum
+ * Name: tcp_chksum, tcp_ipv4_chksum, and tcp_ipv6_chksum
  *
  * Description:
  *   Calculate the TCP checksum of the packet in d_buf and d_appdata.
@@ -157,7 +157,23 @@ unsigned int net_timeval2dsec(FAR struct timeval *tv);
  *
  ****************************************************************************/
 
+#ifdef CONFIG_NET_IPv4
+uint16_t tcp_ipv4_chksum(FAR struct net_driver_s *dev);
+#endif
+
+#ifdef CONFIG_NET_IPv6
+/* REVIST: Is this used? */
+uint16_t tcp_ipv6_chksum(FAR struct net_driver_s *dev);
+#endif
+
+#if defined(CONFIG_NET_IPv4) && defined(CONFIG_NET_IPv6)
 uint16_t tcp_chksum(FAR struct net_driver_s *dev);
+#elif defined(CONFIG_NET_IPv4)
+#  define tcp_chksum(d) tcp_ipv4_chksum(d)
+#else /* if defined(CONFIG_NET_IPv6) */
+#  define tcp_chksum(d) tcp_ipv6_chksum(d)
+#endif
+
 
 /****************************************************************************
  * Name: udp_chksum