Network: All logic will now handle varialbe length link layer protocol headers within incoming packets. This permits use of multiple network interfaces with differing data links. For example, ETHERNET + SLIP

30 files changed, 159 insertions, 95 deletions

diff --git a/apps/include/netutils/httpd.h b/apps/include/netutils/httpd.h
index d5a9b21c4..1ae9b7c1e 100644
--- a/apps/include/netutils/httpd.h
+++ b/apps/include/netutils/httpd.h
@@ -77,9 +77,14 @@
 /* For efficiency reasons, the size of the IO buffer should be a multiple
  * of the TCP MSS value.  Also, the current design requires that the IO
  * buffer be sufficiently large to contain the entire GET request.
+ *
+ * In the case where there are multiple network devices with different
+ * link layer protocols (CONFIG_NET_MULTILINK), each network device
+ * may support a different TCP MSS value.  Here we arbitrarily select
+ * the minimum MSS for that case.
  */
 
-#define HTTPD_IOBUFFER_SIZE (3*TCP_MSS)
+#define HTTPD_IOBUFFER_SIZE (3*MIN_TCP_MSS)
 
 /* This is the maximum size of a file path */
 
diff --git a/apps/netutils/tftpc/tftpc_internal.h b/apps/netutils/tftpc/tftpc_internal.h
index 436090193..31a3faade 100644
--- a/apps/netutils/tftpc/tftpc_internal.h
+++ b/apps/netutils/tftpc/tftpc_internal.h
@@ -84,15 +84,20 @@
 #define TFTP_ERRHEADERSIZE  4
 #define TFTP_DATAHEADERSIZE 4
 
-/* The maximum size for TFTP data is determined by the configured uIP packet
- * size (but cannot exceed 512 + sizeof(TFTP_DATA header).
+/* The maximum size for TFTP data is determined by the configured UDP packet
+ * payload size (UDP_MSS), but cannot exceed 512 + sizeof(TFTP_DATA header).
+ *
+ * In the case where there are multiple network devices with different
+ * link layer protocols (CONFIG_NET_MULTILINK), each network device
+ * may support a different UDP MSS value.  Here we arbitrarily select
+ * the minimum MSS for that case.
  */
 
 #define TFTP_DATAHEADERSIZE 4
 #define TFTP_MAXPACKETSIZE  (TFTP_DATAHEADERSIZE+512)
 
-#if UDP_MSS < TFTP_MAXPACKETSIZE
-#  define TFTP_PACKETSIZE   UDP_MSS
+#if MIN_UDP_MSS < TFTP_MAXPACKETSIZE
+#  define TFTP_PACKETSIZE   MIN_UDP_MSS
 #  ifdef CONFIG_CPP_HAVE_WARNING
 #    warning "uIP MSS is too small for TFTP"
 #  endif
diff --git a/nuttx/fs/nfs/nfs_vfsops.c b/nuttx/fs/nfs/nfs_vfsops.c
index 362343d01..fe7a77f0d 100644
--- a/nuttx/fs/nfs/nfs_vfsops.c
+++ b/nuttx/fs/nfs/nfs_vfsops.c
@@ -1713,11 +1713,17 @@ static int nfs_bind(FAR struct inode *blkdriver, FAR const void *data,
       buflen = tmp;
     }
 
-  /* But don't let the buffer size exceed the MSS of the socket type */
+  /* But don't let the buffer size exceed the MSS of the socket type.
+   *
+   * In the case where there are multiple network devices with different
+   * link layer protocols (CONFIG_NET_MULTILINK), each network device
+   * may support a different UDP MSS value.  Here we arbitrarily select
+   * the minimum MSS for that case.
+   */
 
-  if (buflen > UDP_MSS)
+  if (buflen > MIN_UDP_MSS)
     {
-      buflen = UDP_MSS;
+      buflen = MIN_UDP_MSS;
     }
 
   /* Create an instance of the mountpt state structure */
diff --git a/nuttx/include/nuttx/net/netconfig.h b/nuttx/include/nuttx/net/netconfig.h
index c5c69b2c7..fef0294c3 100644
--- a/nuttx/include/nuttx/net/netconfig.h
+++ b/nuttx/include/nuttx/net/netconfig.h
@@ -86,16 +86,16 @@
  * varies and is obtained from the network device structure.
  */
 
-#ifdef CONFIG_NET_MULTILINK
-/* We are supporting multiple network devices and using different link
- * level protocols.  Get the size of the link layer header from the
- * device structure.
- */
+#if defined(CONFIG_NET_MULTILINK)
+   /* We are supporting multiple network devices using different link layer
+    * protocols.  Get the size of the link layer header from the device
+    * structure.
+    */
 
 #  define NET_LL_HDRLEN(d) ((d)->d_llhdrlen)
 
-#if defined(CONFIG_NET_SLIP)
-/* There is no link layer header with SLIP */
+#elif defined(CONFIG_NET_SLIP)
+   /* There is no link layer header with SLIP */
 
 #  ifdef CONFIG_NET_IPv6
 #    error SLIP is not available for IPv6
@@ -103,11 +103,11 @@
 #  define NET_LL_HDRLEN(d) 0
 
 #else /* if defined(CONFIG_NET_ETHERNET) */
-/* Assume standard Ethernet header */
+   /* Assume standard Ethernet link layer header */
 
 #  define NET_LL_HDRLEN(d) 14
 
-#endif
+#endif /* MULTILINK or SLIP or ETHERNET */
 
 /* Layer 3/4 Configuration Options ******************************************/
 
@@ -162,10 +162,22 @@
 #endif
 
 /* The UDP maximum packet size. This is should not be to set to more
- * than CONFIG_NET_BUFSIZE - NET_LL_HDRLEN - IPUDP_HDRLEN.
+ * than CONFIG_NET_BUFSIZE - NET_LL_HDRLEN(dev) - IPUDP_HDRLEN.
  */
 
-#define UDP_MSS(d) (CONFIG_NET_BUFSIZE - NET_LL_HDRLEN(d) - IPUDP_HDRLEN)
+#define UDP_MSS(d)    (CONFIG_NET_BUFSIZE - NET_LL_HDRLEN(d) - IPUDP_HDRLEN)
+
+#ifdef CONFIG_NET_ETHERNET
+#  define MIN_UDP_MSS (CONFIG_NET_BUFSIZE - ETH_HDRLEN - IPUDP_HDRLEN)
+#else /* if defined(CONFIG_NET_SLIP) */
+#  define MIN_UDP_MSS (CONFIG_NET_BUFSIZE - IPUDP_HDRLEN)
+#endif
+
+#ifdef CONFIG_NET_SLIP
+#  define MAX_UDP_MSS (CONFIG_NET_BUFSIZE - IPUDP_HDRLEN)
+#else /* if defined(CONFIG_NET_ETHERNET) */
+#  define MAX_UDP_MSS (CONFIG_NET_BUFSIZE - ETH_HDRLEN - IPUDP_HDRLEN)
+#endif
 
 /* TCP configuration options */
 
@@ -227,20 +239,39 @@
 #define TCP_MAXSYNRTX 5
 
 /* The TCP maximum segment size. This is should not be set to more
- * than CONFIG_NET_BUFSIZE - NET_LL_HDRLEN - IPTCP_HDRLEN.
+ * than CONFIG_NET_BUFSIZE - NET_LL_HDRLEN(dev) - IPTCP_HDRLEN.
+ *
+ * In the case where there are multiple network devices with different
+ * link layer protocols (CONFIG_NET_MULTILINK), each network device
+ * may support a different UDP MSS value.  Here we arbitrarily select
+ * the minimum MSS for that case.
  */
 
-#define TCP_MSS (CONFIG_NET_BUFSIZE - NET_LL_HDRLEN - IPTCP_HDRLEN)
+#define TCP_MSS(d)    (CONFIG_NET_BUFSIZE - NET_LL_HDRLEN(d) - IPTCP_HDRLEN)
+
+#ifdef CONFIG_NET_ETHERNET
+#  define MIN_TCP_MSS (CONFIG_NET_BUFSIZE - ETH_HDRLEN - IPTCP_HDRLEN)
+#else /* if defined(CONFIG_NET_SLIP) */
+#  define MIN_TCP_MSS (CONFIG_NET_BUFSIZE - IPTCP_HDRLEN)
+#endif
+
+#ifdef CONFIG_NET_SLIP
+#  define MAX_TCP_MSS (CONFIG_NET_BUFSIZE - IPTCP_HDRLEN)
+#else /* if defined(CONFIG_NET_ETHERNET) */
+#  define MAX_TCP_MSS (CONFIG_NET_BUFSIZE - ETH_HDRLEN - IPTCP_HDRLEN)
+#endif
 
 /* The size of the advertised receiver's window.
  *
  * Should be set low (i.e., to the size of the d_buf buffer) is the
  * application is slow to process incoming data, or high (32768 bytes)
  * if the application processes data quickly.
+ *
+ * See the note above regarding the TCP MSS and CONFIG_NET_MULTILINK.
  */
 
 #ifndef CONFIG_NET_RECEIVE_WINDOW
-#  define CONFIG_NET_RECEIVE_WINDOW TCP_MSS
+#  define CONFIG_NET_RECEIVE_WINDOW MIN_TCP_MSS
 #endif
 
 /* How long a connection should stay in the TIME_WAIT state.
diff --git a/nuttx/include/nuttx/net/netdev.h b/nuttx/include/nuttx/net/netdev.h
index 2899170a2..92146b179 100644
--- a/nuttx/include/nuttx/net/netdev.h
+++ b/nuttx/include/nuttx/net/netdev.h
@@ -119,7 +119,7 @@ struct net_driver_s
    * driver should place incoming data into this buffer. When sending data,
    * the device driver should read the link level headers and the TCP/IP
    * headers from this buffer. The size of the link level headers is
-   * configured by the NET_LL_HDRLEN define.
+   * configured by the NET_LL_HDRLEN(dev) define.
    *
    * uIP will handle only a single buffer for both incoming and outgoing
    * packets.  However, the drive design may be concurrently send and
diff --git a/nuttx/include/nuttx/net/tcp.h b/nuttx/include/nuttx/net/tcp.h
index da768bd7c..db511cee9 100644
--- a/nuttx/include/nuttx/net/tcp.h
+++ b/nuttx/include/nuttx/net/tcp.h
@@ -56,6 +56,7 @@
 #include <stdint.h>
 
 #include <nuttx/net/netconfig.h>
+#include <nuttx/net/arp.h>
 #include <nuttx/net/ip.h>
 
 /****************************************************************************
@@ -117,11 +118,10 @@
  * This is a long established rule.
  */
 
-#if TCP_MSS > 576
-#  define TCP_INITIAL_MSS 576
-#else
-#  define TCP_INITIAL_MSS TCP_MSS
-#endif
+#define TCP_INITIAL_MSS(d)  (TCP_MSS(d) > 576 ? 576 : TCP_MSS(d))
+
+#define MIN_TCP_INITIAL_MSS (MIN_TCP_MSS > 576 ? 576 : MIN_TCP_MSS)
+#define MAX_TCP_INITIAL_MSS (MAX_TCP_MSS > 576 ? 576 : MAX_TCP_MSS)
 
 /****************************************************************************
  * Public Type Definitions
diff --git a/nuttx/net/devif/devif_input.c b/nuttx/net/devif/devif_input.c
index f97911f74..03b5f64ca 100644
--- a/nuttx/net/devif/devif_input.c
+++ b/nuttx/net/devif/devif_input.c
@@ -107,13 +107,13 @@
 
 /* Macros */
 
-#define BUF                  ((FAR struct net_iphdr_s *)&dev->d_buf[NET_LL_HDRLEN])
+#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])
 
 /* IP fragment re-assembly */
 
 #define IP_MF                0x20
-#define TCP_REASS_BUFSIZE    (CONFIG_NET_BUFSIZE - NET_LL_HDRLEN)
+#define TCP_REASS_BUFSIZE    (CONFIG_NET_BUFSIZE - NET_LL_HDRLEN(dev))
 #define TCP_REASS_LASTFRAG   0x01
 
 /****************************************************************************
diff --git a/nuttx/net/icmp/icmp_input.c b/nuttx/net/icmp/icmp_input.c
index 778ce4dee..154bd384f 100644
--- a/nuttx/net/icmp/icmp_input.c
+++ b/nuttx/net/icmp/icmp_input.c
@@ -66,7 +66,7 @@
  * Pre-processor Definitions
  ****************************************************************************/
 
-#define ICMPBUF ((struct icmp_iphdr_s *)&dev->d_buf[NET_LL_HDRLEN])
+#define ICMPBUF ((struct icmp_iphdr_s *)&dev->d_buf[NET_LL_HDRLEN(dev)])
 
 /****************************************************************************
  * Public Variables
diff --git a/nuttx/net/icmp/icmp_ping.c b/nuttx/net/icmp/icmp_ping.c
index 3cd900b94..be80b1b0a 100644
--- a/nuttx/net/icmp/icmp_ping.c
+++ b/nuttx/net/icmp/icmp_ping.c
@@ -65,8 +65,8 @@
  * Pre-processor Definitions
  ****************************************************************************/
 
-#define ICMPBUF ((struct icmp_iphdr_s *)&dev->d_buf[NET_LL_HDRLEN])
-#define ICMPDAT (&dev->d_buf[NET_LL_HDRLEN + sizeof(struct icmp_iphdr_s)])
+#define ICMPBUF ((struct icmp_iphdr_s *)&dev->d_buf[NET_LL_HDRLEN(dev)])
+#define ICMPDAT (&dev->d_buf[NET_LL_HDRLEN(dev) + sizeof(struct icmp_iphdr_s)])
 
 /* Allocate a new ICMP data callback */
 
diff --git a/nuttx/net/icmp/icmp_poll.c b/nuttx/net/icmp/icmp_poll.c
index 16f4abf00..6c3f63b26 100644
--- a/nuttx/net/icmp/icmp_poll.c
+++ b/nuttx/net/icmp/icmp_poll.c
@@ -90,8 +90,8 @@ void icmp_poll(FAR struct net_driver_s *dev)
 {
   /* Setup for the application callback */
 
-  dev->d_appdata = &dev->d_buf[NET_LL_HDRLEN + IPICMP_HDRLEN];
-  dev->d_snddata = &dev->d_buf[NET_LL_HDRLEN + IPICMP_HDRLEN];
+  dev->d_appdata = &dev->d_buf[NET_LL_HDRLEN(dev) + IPICMP_HDRLEN];
+  dev->d_snddata = &dev->d_buf[NET_LL_HDRLEN(dev) + IPICMP_HDRLEN];
 
   dev->d_len     = 0;
   dev->d_sndlen  = 0;
diff --git a/nuttx/net/icmp/icmp_send.c b/nuttx/net/icmp/icmp_send.c
index 18de2c01a..be6621839 100644
--- a/nuttx/net/icmp/icmp_send.c
+++ b/nuttx/net/icmp/icmp_send.c
@@ -57,7 +57,7 @@
  * Pre-processor Definitions
  ****************************************************************************/
 
-#define ICMPBUF ((struct icmp_iphdr_s *)&dev->d_buf[NET_LL_HDRLEN])
+#define ICMPBUF ((struct icmp_iphdr_s *)&dev->d_buf[NET_LL_HDRLEN(dev)])
 
 /****************************************************************************
  * Public Variables
diff --git a/nuttx/net/igmp/igmp_input.c b/nuttx/net/igmp/igmp_input.c
index 04ec4709c..14bd531ef 100644
--- a/nuttx/net/igmp/igmp_input.c
+++ b/nuttx/net/igmp/igmp_input.c
@@ -62,7 +62,7 @@
  * Pre-processor Definitions
  ****************************************************************************/
 
-#define IGMPBUF ((struct igmp_iphdr_s *)&dev->d_buf[NET_LL_HDRLEN])
+#define IGMPBUF ((struct igmp_iphdr_s *)&dev->d_buf[NET_LL_HDRLEN(dev)])
 
 /****************************************************************************
  * Private Functions
@@ -125,7 +125,7 @@ void igmp_input(struct net_driver_s *dev)
 
   /* Verify the message length */
 
-  if (dev->d_len < NET_LL_HDRLEN+IPIGMP_HDRLEN)
+  if (dev->d_len < NET_LL_HDRLEN(dev) + IPIGMP_HDRLEN)
     {
       IGMP_STATINCR(g_netstats.igmp.length_errors);
       nlldbg("Length error\n");
diff --git a/nuttx/net/igmp/igmp_poll.c b/nuttx/net/igmp/igmp_poll.c
index 147f9f810..cb20a81c0 100644
--- a/nuttx/net/igmp/igmp_poll.c
+++ b/nuttx/net/igmp/igmp_poll.c
@@ -151,8 +151,8 @@ void igmp_poll(FAR struct net_driver_s *dev)
 
   /* Setup the poll operation */
 
-  dev->d_appdata = &dev->d_buf[NET_LL_HDRLEN + IPIGMP_HDRLEN];
-  dev->d_snddata = &dev->d_buf[NET_LL_HDRLEN + IPIGMP_HDRLEN];
+  dev->d_appdata = &dev->d_buf[NET_LL_HDRLEN(dev) + IPIGMP_HDRLEN];
+  dev->d_snddata = &dev->d_buf[NET_LL_HDRLEN(dev) + IPIGMP_HDRLEN];
 
   dev->d_len     = 0;
   dev->d_sndlen  = 0;
diff --git a/nuttx/net/igmp/igmp_send.c b/nuttx/net/igmp/igmp_send.c
index bb827029d..cc5430f90 100644
--- a/nuttx/net/igmp/igmp_send.c
+++ b/nuttx/net/igmp/igmp_send.c
@@ -76,7 +76,7 @@
 /* Buffer layout */
 
 #define RASIZE      (4)
-#define IGMPBUF     ((struct igmp_iphdr_s *)&dev->d_buf[NET_LL_HDRLEN])
+#define IGMPBUF     ((struct igmp_iphdr_s *)&dev->d_buf[NET_LL_HDRLEN(dev)])
 
 /****************************************************************************
  * Public Variables
diff --git a/nuttx/net/pkt/pkt_poll.c b/nuttx/net/pkt/pkt_poll.c
index 0b7c6f08d..7c8384268 100644
--- a/nuttx/net/pkt/pkt_poll.c
+++ b/nuttx/net/pkt/pkt_poll.c
@@ -102,8 +102,8 @@ void pkt_poll(FAR struct net_driver_s *dev, FAR struct pkt_conn_s *conn)
     {
       /* Setup for the application callback */
 
-      dev->d_appdata = &dev->d_buf[NET_LL_HDRLEN + IPUDP_HDRLEN];
-      dev->d_snddata = &dev->d_buf[NET_LL_HDRLEN + IPUDP_HDRLEN];
+      dev->d_appdata = &dev->d_buf[NET_LL_HDRLEN(dev) + IPUDP_HDRLEN];
+      dev->d_snddata = &dev->d_buf[NET_LL_HDRLEN(dev) + IPUDP_HDRLEN];
 
       dev->d_len     = 0;
       dev->d_sndlen  = 0;
diff --git a/nuttx/net/socket/connect.c b/nuttx/net/socket/connect.c
index d88961e4d..291a16008 100644
--- a/nuttx/net/socket/connect.c
+++ b/nuttx/net/socket/connect.c
@@ -169,7 +169,7 @@ static inline void psock_teardown_callbacks(FAR struct tcp_connect_s *pstate,
  *   connection operation via by the lower, device interfacing layer.
  *
  * Parameters:
- *   dev      The sructure of the network driver that caused the interrupt
+ *   dev      The structure of the network driver that caused the interrupt
  *   pvconn   The connection structure associated with the socket
  *   flags    Set of events describing why the callback was invoked
  *
@@ -250,6 +250,17 @@ static uint16_t psock_connect_interrupt(FAR struct net_driver_s *dev,
 
       psock_teardown_callbacks(pstate, pstate->tc_result);
 
+#ifdef CONFIG_NET_MULTILINK
+      /* When we set up the connection structure, we did not know the size
+       * of the initial MSS.  Now that the connection is associated with a
+       * network device, we now know the size of link layer header and can
+       * determine the correct initial MSS.
+       */
+
+      DEBUGASSERT(psock->s_conn);
+      psock->s_conn->mss = TCP_INITIAL_MSS(dev);
+#endif
+
       /* Wake up the waiting thread */
 
       sem_post(&pstate->tc_sem);
@@ -305,7 +316,7 @@ static inline int psock_tcp_connect(FAR struct socket *psock,
     }
   else
     {
-      /* Perform the uIP connection operation */
+      /* Perform the TCP connection operation */
 
       ret = tcp_connect(psock->s_conn, inaddr);
     }
diff --git a/nuttx/net/socket/net_sendfile.c b/nuttx/net/socket/net_sendfile.c
index de5a01efc..807bdcc7d 100644
--- a/nuttx/net/socket/net_sendfile.c
+++ b/nuttx/net/socket/net_sendfile.c
@@ -70,14 +70,14 @@
 #include "socket/socket.h"
 
 /****************************************************************************
- * Definitions
+ * Pre-processor Definitions
  ****************************************************************************/
 
 #if defined(CONFIG_NET_TCP_SPLIT) && !defined(CONFIG_NET_TCP_SPLIT_SIZE)
 #  define CONFIG_NET_TCP_SPLIT_SIZE 40
 #endif
 
-#define TCPBUF ((struct tcp_iphdr_s *)&dev->d_buf[NET_LL_HDRLEN])
+#define TCPBUF ((struct tcp_iphdr_s *)&dev->d_buf[NET_LL_HDRLEN(dev)])
 
 /****************************************************************************
  * Private Types
diff --git a/nuttx/net/socket/recvfrom.c b/nuttx/net/socket/recvfrom.c
index aeffcba32..992eb40b3 100644
--- a/nuttx/net/socket/recvfrom.c
+++ b/nuttx/net/socket/recvfrom.c
@@ -71,11 +71,11 @@
 #include "socket/socket.h"
 
 /****************************************************************************
- * Definitions
+ * Pre-processor Definitions
  ****************************************************************************/
 
-#define UDPBUF ((struct udp_iphdr_s *)&dev->d_buf[NET_LL_HDRLEN])
-#define TCPBUF ((struct tcp_iphdr_s *)&dev->d_buf[NET_LL_HDRLEN])
+#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)])
 
 /****************************************************************************
  * Private Types
diff --git a/nuttx/net/tcp/tcp.h b/nuttx/net/tcp/tcp.h
index 72116e523..67d902126 100644
--- a/nuttx/net/tcp/tcp.h
+++ b/nuttx/net/tcp/tcp.h
@@ -358,7 +358,8 @@ FAR struct tcp_conn_s *tcp_listener(uint16_t portno);
  *
  ****************************************************************************/
 
-FAR struct tcp_conn_s *tcp_alloc_accept(FAR struct tcp_iphdr_s *buf);
+FAR struct tcp_conn_s *tcp_alloc_accept(FAR struct net_driver_s *dev,
+                                        FAR struct tcp_iphdr_s *buf);
 
 /****************************************************************************
  * Name: tcp_bind()
diff --git a/nuttx/net/tcp/tcp_conn.c b/nuttx/net/tcp/tcp_conn.c
index a505cc221..666480012 100644
--- a/nuttx/net/tcp/tcp_conn.c
+++ b/nuttx/net/tcp/tcp_conn.c
@@ -508,7 +508,8 @@ FAR struct tcp_conn_s *tcp_listener(uint16_t portno)
  *
  ****************************************************************************/
 
-FAR struct tcp_conn_s *tcp_alloc_accept(FAR struct tcp_iphdr_s *buf)
+FAR struct tcp_conn_s *tcp_alloc_accept(FAR struct net_driver_s *dev,
+                                        FAR struct tcp_iphdr_s *buf)
 {
   FAR struct tcp_conn_s *conn = tcp_alloc();
   if (conn)
@@ -522,7 +523,7 @@ FAR struct tcp_conn_s *tcp_alloc_accept(FAR struct tcp_iphdr_s *buf)
       conn->nrtx          = 0;
       conn->lport         = buf->destport;
       conn->rport         = buf->srcport;
-      conn->mss           = TCP_INITIAL_MSS;
+      conn->mss           = TCP_INITIAL_MSS(dev);
       net_ipaddr_copy(conn->ripaddr, net_ip4addr_conv32(buf->srcipaddr));
       conn->tcpstateflags = TCP_SYN_RCVD;
 
@@ -670,12 +671,16 @@ int tcp_connect(FAR struct tcp_conn_s *conn,
       return port;
     }
 
-  /* Initialize and return the connection structure, bind it to the port number */
+  /* Initialize and return the connection structure, bind it to the port
+   * number.  At this point, we do not know the size of the initial MSS We
+   * know the total size of the packet buffer, but we don't yet know the
+   * size of link layer header.
+   */
 
   conn->tcpstateflags = TCP_SYN_SENT;
   tcp_initsequence(conn->sndseq);
 
-  conn->mss        = TCP_INITIAL_MSS;
+  conn->mss        = MIN_TCP_INITIAL_MSS;
   conn->unacked    = 1;    /* TCP length of the SYN is one. */
   conn->nrtx       = 0;
   conn->timer      = 1;    /* Send the SYN next time around. */
diff --git a/nuttx/net/tcp/tcp_input.c b/nuttx/net/tcp/tcp_input.c
index c84777c39..0106c390f 100644
--- a/nuttx/net/tcp/tcp_input.c
+++ b/nuttx/net/tcp/tcp_input.c
@@ -64,7 +64,7 @@
  * Pre-processor Definitions
  ****************************************************************************/
 
-#define BUF ((struct tcp_iphdr_s *)&dev->d_buf[NET_LL_HDRLEN])
+#define BUF ((struct tcp_iphdr_s *)&dev->d_buf[NET_LL_HDRLEN(dev)])
 
 /****************************************************************************
  * Public Variables
@@ -110,8 +110,8 @@ void tcp_input(FAR struct net_driver_s *dev)
   int      len;
   int      i;
 
-  dev->d_snddata = &dev->d_buf[IPTCP_HDRLEN + NET_LL_HDRLEN];
-  dev->d_appdata = &dev->d_buf[IPTCP_HDRLEN + NET_LL_HDRLEN];
+  dev->d_snddata = &dev->d_buf[IPTCP_HDRLEN + NET_LL_HDRLEN(dev)];
+  dev->d_appdata = &dev->d_buf[IPTCP_HDRLEN + NET_LL_HDRLEN(dev)];
 
 #ifdef CONFIG_NET_STATISTICS
   g_netstats.tcp.recv++;
@@ -177,7 +177,7 @@ void tcp_input(FAR struct net_driver_s *dev)
            * user application to accept it.
            */
 
-          conn = tcp_alloc_accept(pbuf);
+          conn = tcp_alloc_accept(dev, pbuf);
           if (conn)
             {
               /* The connection structure was successfully allocated.  Now see if
@@ -219,7 +219,7 @@ void tcp_input(FAR struct net_driver_s *dev)
             {
               for (i = 0; i < ((pbuf->tcpoffset >> 4) - 5) << 2 ;)
                 {
-                  opt = dev->d_buf[IPTCP_HDRLEN + NET_LL_HDRLEN + i];
+                  opt = dev->d_buf[IPTCP_HDRLEN + NET_LL_HDRLEN(dev) + i];
                   if (opt == TCP_OPT_END)
                     {
                       /* End of options. */
@@ -233,13 +233,13 @@ void tcp_input(FAR struct net_driver_s *dev)
                       ++i;
                     }
                   else if (opt == TCP_OPT_MSS &&
-                          dev->d_buf[IPTCP_HDRLEN + NET_LL_HDRLEN + 1 + i] == TCP_OPT_MSS_LEN)
+                          dev->d_buf[IPTCP_HDRLEN + NET_LL_HDRLEN(dev) + 1 + i] == TCP_OPT_MSS_LEN)
                     {
                       /* An MSS option with the right option length. */
 
-                      tmp16 = ((uint16_t)dev->d_buf[IPTCP_HDRLEN + NET_LL_HDRLEN + 2 + i] << 8) |
-                               (uint16_t)dev->d_buf[IPTCP_HDRLEN + NET_LL_HDRLEN + 3 + i];
-                      conn->mss = tmp16 > TCP_MSS ? TCP_MSS : tmp16;
+                      tmp16 = ((uint16_t)dev->d_buf[IPTCP_HDRLEN + NET_LL_HDRLEN(dev) + 2 + i] << 8) |
+                               (uint16_t)dev->d_buf[IPTCP_HDRLEN + NET_LL_HDRLEN(dev) + 3 + i];
+                      conn->mss = tmp16 > TCP_MSS(dev) ? TCP_MSS(dev) : tmp16;
 
                       /* And we are done processing options. */
 
@@ -251,7 +251,7 @@ void tcp_input(FAR struct net_driver_s *dev)
                        * can skip past them.
                        */
 
-                      if (dev->d_buf[IPTCP_HDRLEN + NET_LL_HDRLEN + 1 + i] == 0)
+                      if (dev->d_buf[IPTCP_HDRLEN + NET_LL_HDRLEN(dev) + 1 + i] == 0)
                         {
                           /* If the length field is zero, the options are malformed
                            * and we don't process them further.
@@ -259,7 +259,7 @@ void tcp_input(FAR struct net_driver_s *dev)
 
                           break;
                         }
-                      i += dev->d_buf[IPTCP_HDRLEN + NET_LL_HDRLEN + 1 + i];
+                      i += dev->d_buf[IPTCP_HDRLEN + NET_LL_HDRLEN(dev) + 1 + i];
                     }
                 }
             }
@@ -509,7 +509,7 @@ found:
               {
                 for (i = 0; i < ((pbuf->tcpoffset >> 4) - 5) << 2 ;)
                   {
-                    opt = dev->d_buf[IPTCP_HDRLEN + NET_LL_HDRLEN + i];
+                    opt = dev->d_buf[IPTCP_HDRLEN + NET_LL_HDRLEN(dev) + i];
                     if (opt == TCP_OPT_END)
                       {
                         /* End of options. */
@@ -523,14 +523,14 @@ found:
                         ++i;
                       }
                     else if (opt == TCP_OPT_MSS &&
-                              dev->d_buf[IPTCP_HDRLEN + NET_LL_HDRLEN + 1 + i] == TCP_OPT_MSS_LEN)
+                              dev->d_buf[IPTCP_HDRLEN + NET_LL_HDRLEN(dev) + 1 + i] == TCP_OPT_MSS_LEN)
                       {
                         /* An MSS option with the right option length. */
 
                         tmp16 =
-                          (dev->d_buf[IPTCP_HDRLEN + NET_LL_HDRLEN + 2 + i] << 8) |
-                          dev->d_buf[IPTCP_HDRLEN + NET_LL_HDRLEN + 3 + i];
-                        conn->mss = tmp16 > TCP_MSS ? TCP_MSS : tmp16;
+                          (dev->d_buf[IPTCP_HDRLEN + NET_LL_HDRLEN(dev) + 2 + i] << 8) |
+                          dev->d_buf[IPTCP_HDRLEN + NET_LL_HDRLEN(dev) + 3 + i];
+                        conn->mss = tmp16 > TCP_MSS(dev) ? TCP_MSS(dev) : tmp16;
 
                         /* And we are done processing options. */
 
@@ -542,7 +542,7 @@ found:
                          * easily can skip past them.
                          */
 
-                        if (dev->d_buf[IPTCP_HDRLEN + NET_LL_HDRLEN + 1 + i] == 0)
+                        if (dev->d_buf[IPTCP_HDRLEN + NET_LL_HDRLEN(dev) + 1 + i] == 0)
                           {
                             /* If the length field is zero, the options are
                              * malformed and we don't process them further.
@@ -550,7 +550,7 @@ found:
 
                             break;
                           }
-                        i += dev->d_buf[IPTCP_HDRLEN + NET_LL_HDRLEN + 1 + i];
+                        i += dev->d_buf[IPTCP_HDRLEN + NET_LL_HDRLEN(dev) + 1 + i];
                       }
                   }
               }
@@ -692,8 +692,8 @@ found:
          * When the application is called, the d_len field
          * contains the length of the incoming data. The application can
          * access the incoming data through the global pointer
-         * d_appdata, which usually points IPTCP_HDRLEN + NET_LL_HDRLEN
-         *  bytes into the d_buf array.
+         * d_appdata, which usually points IPTCP_HDRLEN + NET_LL_HDRLEN(dev)
+         * bytes into the d_buf array.
          *
          * If the application wishes to send any data, this data should be
          * put into the d_appdata and the length of the data should be
diff --git a/nuttx/net/tcp/tcp_poll.c b/nuttx/net/tcp/tcp_poll.c
index ad1012970..0c2ea66f5 100644
--- a/nuttx/net/tcp/tcp_poll.c
+++ b/nuttx/net/tcp/tcp_poll.c
@@ -103,8 +103,8 @@ void tcp_poll(FAR struct net_driver_s *dev, FAR struct tcp_conn_s *conn)
     {
       /* Set up for the callback */
 
-      dev->d_snddata = &dev->d_buf[IPTCP_HDRLEN + NET_LL_HDRLEN];
-      dev->d_appdata = &dev->d_buf[IPTCP_HDRLEN + NET_LL_HDRLEN];
+      dev->d_snddata = &dev->d_buf[IPTCP_HDRLEN + NET_LL_HDRLEN(dev)];
+      dev->d_appdata = &dev->d_buf[IPTCP_HDRLEN + NET_LL_HDRLEN(dev)];
 
       dev->d_len     = 0;
       dev->d_sndlen  = 0;
diff --git a/nuttx/net/tcp/tcp_send.c b/nuttx/net/tcp/tcp_send.c
index 4f615721e..d68855511 100644
--- a/nuttx/net/tcp/tcp_send.c
+++ b/nuttx/net/tcp/tcp_send.c
@@ -62,7 +62,7 @@
  * Pre-processor Definitions
  ****************************************************************************/
 
-#define BUF ((struct tcp_iphdr_s *)&dev->d_buf[NET_LL_HDRLEN])
+#define BUF ((struct tcp_iphdr_s *)&dev->d_buf[NET_LL_HDRLEN(dev)])
 
 /****************************************************************************
  * Public Variables
@@ -360,8 +360,8 @@ void tcp_ack(FAR struct net_driver_s *dev, FAR struct tcp_conn_s *conn,
 
   pbuf->optdata[0] = TCP_OPT_MSS;
   pbuf->optdata[1] = TCP_OPT_MSS_LEN;
-  pbuf->optdata[2] = (TCP_MSS) / 256;
-  pbuf->optdata[3] = (TCP_MSS) & 255;
+  pbuf->optdata[2] = TCP_MSS(dev) / 256;
+  pbuf->optdata[3] = TCP_MSS(dev) & 255;
   dev->d_len       = IPTCP_HDRLEN + TCP_OPT_MSS_LEN;
   pbuf->tcpoffset  = ((TCP_HDRLEN + TCP_OPT_MSS_LEN) / 4) << 4;
 
diff --git a/nuttx/net/tcp/tcp_send_buffered.c b/nuttx/net/tcp/tcp_send_buffered.c
index 231eeebe7..d516262fa 100644
--- a/nuttx/net/tcp/tcp_send_buffered.c
+++ b/nuttx/net/tcp/tcp_send_buffered.c
@@ -79,7 +79,7 @@
  * Pre-processor Definitions
  ****************************************************************************/
 
-#define TCPBUF ((struct tcp_iphdr_s *)&dev->d_buf[NET_LL_HDRLEN])
+#define TCPBUF ((struct tcp_iphdr_s *)&dev->d_buf[NET_LL_HDRLEN(dev)])
 
 /* Debug */
 
diff --git a/nuttx/net/tcp/tcp_send_unbuffered.c b/nuttx/net/tcp/tcp_send_unbuffered.c
index 22f686082..3590024ec 100644
--- a/nuttx/net/tcp/tcp_send_unbuffered.c
+++ b/nuttx/net/tcp/tcp_send_unbuffered.c
@@ -71,7 +71,7 @@
 #  define CONFIG_NET_TCP_SPLIT_SIZE 40
 #endif
 
-#define TCPBUF ((struct tcp_iphdr_s *)&dev->d_buf[NET_LL_HDRLEN])
+#define TCPBUF ((struct tcp_iphdr_s *)&dev->d_buf[NET_LL_HDRLEN(dev)])
 
 /****************************************************************************
  * Private Types
diff --git a/nuttx/net/tcp/tcp_timer.c b/nuttx/net/tcp/tcp_timer.c
index 0a10fffbf..c0482380c 100644
--- a/nuttx/net/tcp/tcp_timer.c
+++ b/nuttx/net/tcp/tcp_timer.c
@@ -100,8 +100,8 @@ void tcp_timer(FAR struct net_driver_s *dev, FAR struct tcp_conn_s *conn,
 {
   uint8_t result;
 
-  dev->d_snddata = &dev->d_buf[IPTCP_HDRLEN + NET_LL_HDRLEN];
-  dev->d_appdata = &dev->d_buf[IPTCP_HDRLEN + NET_LL_HDRLEN];
+  dev->d_snddata = &dev->d_buf[IPTCP_HDRLEN + NET_LL_HDRLEN(dev)];
+  dev->d_appdata = &dev->d_buf[IPTCP_HDRLEN + NET_LL_HDRLEN(dev)];
 
   /* Increase the TCP sequence number */
 
diff --git a/nuttx/net/udp/udp_input.c b/nuttx/net/udp/udp_input.c
index 07699c8f6..5a78baa1f 100644
--- a/nuttx/net/udp/udp_input.c
+++ b/nuttx/net/udp/udp_input.c
@@ -60,7 +60,7 @@
  * Pre-processor Definitions
  ****************************************************************************/
 
-#define UDPBUF ((struct udp_iphdr_s *)&dev->d_buf[NET_LL_HDRLEN])
+#define UDPBUF ((struct udp_iphdr_s *)&dev->d_buf[NET_LL_HDRLEN(dev)])
 
 /****************************************************************************
  * Public Variables
@@ -114,7 +114,7 @@ int udp_input(FAR struct net_driver_s *dev)
 
   dev->d_len    -= IPUDP_HDRLEN;
 #ifdef CONFIG_NET_UDP_CHECKSUMS
-  dev->d_appdata = &dev->d_buf[NET_LL_HDRLEN + IPUDP_HDRLEN];
+  dev->d_appdata = &dev->d_buf[NET_LL_HDRLEN(dev) + IPUDP_HDRLEN];
   if (pbuf->udpchksum != 0 && udp_chksum(dev) != 0xffff)
     {
 #ifdef CONFIG_NET_STATISTICS
@@ -136,8 +136,8 @@ int udp_input(FAR struct net_driver_s *dev)
 
           /* Set-up for the application callback */
 
-          dev->d_appdata = &dev->d_buf[NET_LL_HDRLEN + IPUDP_HDRLEN];
-          dev->d_snddata = &dev->d_buf[NET_LL_HDRLEN + IPUDP_HDRLEN];
+          dev->d_appdata = &dev->d_buf[NET_LL_HDRLEN(dev) + IPUDP_HDRLEN];
+          dev->d_snddata = &dev->d_buf[NET_LL_HDRLEN(dev) + IPUDP_HDRLEN];
           dev->d_sndlen  = 0;
 
           /* Perform the application callback */
diff --git a/nuttx/net/udp/udp_poll.c b/nuttx/net/udp/udp_poll.c
index 1007adff0..e490b88ab 100644
--- a/nuttx/net/udp/udp_poll.c
+++ b/nuttx/net/udp/udp_poll.c
@@ -100,8 +100,8 @@ void udp_poll(FAR struct net_driver_s *dev, FAR struct udp_conn_s *conn)
     {
       /* Set-up for the application callback */
 
-      dev->d_appdata = &dev->d_buf[NET_LL_HDRLEN + IPUDP_HDRLEN];
-      dev->d_snddata = &dev->d_buf[NET_LL_HDRLEN + IPUDP_HDRLEN];
+      dev->d_appdata = &dev->d_buf[NET_LL_HDRLEN(dev) + IPUDP_HDRLEN];
+      dev->d_snddata = &dev->d_buf[NET_LL_HDRLEN(dev) + IPUDP_HDRLEN];
 
       dev->d_len     = 0;
       dev->d_sndlen  = 0;
diff --git a/nuttx/net/udp/udp_send.c b/nuttx/net/udp/udp_send.c
index 4b5e81ab5..52951d536 100644
--- a/nuttx/net/udp/udp_send.c
+++ b/nuttx/net/udp/udp_send.c
@@ -62,7 +62,7 @@
  * Pre-processor Definitions
  ****************************************************************************/
 
-#define UDPBUF ((struct udp_iphdr_s *)&dev->d_buf[NET_LL_HDRLEN])
+#define UDPBUF ((struct udp_iphdr_s *)&dev->d_buf[NET_LL_HDRLEN(dev)])
 
 /****************************************************************************
  * Public Variables
diff --git a/nuttx/net/utils/net_chksum.c b/nuttx/net/utils/net_chksum.c
index a2eadf1bc..1fc85a7c2 100644
--- a/nuttx/net/utils/net_chksum.c
+++ b/nuttx/net/utils/net_chksum.c
@@ -54,8 +54,8 @@
  * Pre-processor Definitions
  ****************************************************************************/
 
-#define BUF ((struct net_iphdr_s *)&dev->d_buf[NET_LL_HDRLEN])
-#define ICMPBUF ((struct icmp_iphdr_s *)&dev->d_buf[NET_LL_HDRLEN])
+#define BUF ((struct net_iphdr_s *)&dev->d_buf[NET_LL_HDRLEN(dev)])
+#define ICMPBUF ((struct icmp_iphdr_s *)&dev->d_buf[NET_LL_HDRLEN(dev)])
 
 /****************************************************************************
  * Private Data
@@ -145,7 +145,7 @@ static uint16_t upper_layer_chksum(FAR struct net_driver_s *dev, uint8_t proto)
 
   /* Sum TCP header and data. */
 
-  sum = chksum(sum, &dev->d_buf[IP_HDRLEN + NET_LL_HDRLEN], upper_layer_len);
+  sum = chksum(sum, &dev->d_buf[IP_HDRLEN + NET_LL_HDRLEN(dev)], upper_layer_len);
 
   return (sum == 0) ? 0xffff : htons(sum);
 }
@@ -285,7 +285,7 @@ uint16_t ip_chksum(FAR struct net_driver_s *dev)
 {
   uint16_t sum;
 
-  sum = chksum(0, &dev->d_buf[NET_LL_HDRLEN], IP_HDRLEN);
+  sum = chksum(0, &dev->d_buf[NET_LL_HDRLEN(dev)], IP_HDRLEN);
   return (sum == 0) ? 0xffff : htons(sum);
 }
 #endif /* CONFIG_NET_ARCH_CHKSUM */