Networking: Update ICMPv6 logic to RFCs

11 files changed, 181 insertions, 78 deletions

diff --git a/nuttx/include/nuttx/net/icmpv6.h b/nuttx/include/nuttx/net/icmpv6.h
index ab8ed9a57..108f1c19b 100644
--- a/nuttx/include/nuttx/net/icmpv6.h
+++ b/nuttx/include/nuttx/net/icmpv6.h
@@ -94,14 +94,25 @@
 
 #define ICMPv6_FLAG_S (1 << 6)
 
-#define ICMPv6_OPTION_SOURCE_LINK_ADDRESS 1
-#define ICMPv6_OPTION_TARGET_LINK_ADDRESS 2
-
 /* Header sizes */
 
 #define ICMPv6_HDRLEN    4                             /* Size of ICMPv6 header */
 #define IPICMPv6_HDRLEN  (ICMPv6_HDRLEN + IPv6_HDRLEN) /* Size of IPv6 + ICMPv6 header */
 
+/* Option types */
+
+#define ICMPv6_OPT_SRCLLADDR  1 /* Source Link-Layer Address */
+#define ICMPv6_OPT_TGTLLADDR  2 /* Target Link-Layer Address */
+#define ICMPv6_OPT_PREFIX     3 /* Prefix Information */
+#define ICMPv6_OPT_REDIRECT   4 /* Redirected Header */
+#define ICMPv6_OPT_MTU        5 /* MTU */
+
+/* ICMPv6 Neighbor Advertisement message flags */
+
+#define ICMPv6_FLAG_R    (1 << 7) /* Router flag */
+#define ICMPv6_FLAG_S    (1 << 6) /* Solicited flag */
+#define ICMPv6_FLAG_O    (1 << 5) /* Override flag */
+
 /****************************************************************************
  * Public Type Definitions
  ****************************************************************************/
@@ -113,7 +124,7 @@ struct icmpv6_iphdr_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), bits 4-7: flow label (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) */
@@ -124,21 +135,44 @@ struct icmpv6_iphdr_s
   /* ICMPv6 header */
 
   uint8_t  type;             /* Defines the format of the ICMP message */
-  uint8_t  icode;            /* Further qualifies the ICMP messages */
-  uint16_t icmpv6chksum;     /* Checksum of ICMP header and data */
+  uint8_t  code;             /* Further qualifies the ICMP messages */
+  uint16_t chksum;           /* Checksum of ICMP header and data */
 
   /* Data following the ICMP header contains the data specific to the
    * message type indicated by the Type and Code fields.
    */
+};
 
-  /* ICMPv6_ECHO_REQUEST and ICMPv6_ECHO_REPLY data */
+/* This the message format for the ICMPv6 Neighbor Solicitation message */
 
-  uint8_t flags;
-  uint8_t reserved1;
-  uint8_t reserved2;
-  uint8_t reserved3;
-  uint8_t icmpv6data[16];
-  uint8_t options[1];
+struct icmpv6_neighbor_solicit_s
+{
+  uint8_t  type;             /* Message Type: ICMPv6_NEIGHBOR_SOLICIT */
+  uint8_t  code;             /* Further qualifies the ICMP messages */
+  uint16_t chksum;           /* Checksum of ICMP header and data */
+  uint8_t  flags[4];         /* See ICMPv6_FLAG_ definitions */
+  net_ipv6addr_t tgtaddr;    /* 128-bit Target IPv6 address */
+  uint8_t  opttype;          /* Option Type: ICMPv6_OPT_SRCLLADDR */
+  uint8_t  optlen;           /* Option length: 8 octets */
+#ifdef CONFIG_NET_ETHERNET
+  uint8_t  srclladdr[6];     /* Options: Source link layer address */
+#endif
+};
+
+/* This the message format for the ICMPv6 Neighbor Advertisement message */
+
+struct icmpv6_neighbor_advertise_s
+{
+  uint8_t  type;             /* Message Type: ICMPv6_NEIGHBOR_ADVERTISE */
+  uint8_t  code;             /* Further qualifies the ICMP messages */
+  uint16_t chksum;           /* Checksum of ICMP header and data */
+  uint8_t  flags[4];         /* See ICMPv6_FLAG_ definitions */
+  net_ipv6addr_t tgtaddr;    /* Target IPv6 address */
+  uint8_t  opttype;          /* Option Type: ICMPv6_OPT_TGTLLADDR */
+  uint8_t  optlen;           /* Option length: 8 octets */
+#ifdef CONFIG_NET_ETHERNET
+  uint8_t  tgtlladdr[6];     /* Options: Target link layer address */
+#endif
 };
 
 /* The structure holding the ICMP statistics that are gathered if
diff --git a/nuttx/net/devif/devif.h b/nuttx/net/devif/devif.h
index 270b4b0f6..06ce8cc06 100644
--- a/nuttx/net/devif/devif.h
+++ b/nuttx/net/devif/devif.h
@@ -83,7 +83,7 @@
  *   UDP_POLL           periodically from the drivers to support (1) timed
  *   PKT_POLL           operations, and (2) to check if the socket layer has
  *   ICMP_POLL          data that it wants to send
- *                 OUT: Not used
+ *   ICMPv6_POLL   OUT: Not used
  *
  *   TCP_BACKLOG    IN: There is a new connection in the backlog list set
  *                      up by the listen() command. (TCP only)
@@ -126,6 +126,7 @@
 #define UDP_POLL        TCP_POLL
 #define PKT_POLL        TCP_POLL
 #define ICMP_POLL       TCP_POLL
+#define ICMPv6_POLL     TCP_POLL
 #define TCP_BACKLOG     (1 << 5)
 #define TCP_CLOSE       (1 << 6)
 #define TCP_ABORT       (1 << 7)
@@ -178,6 +179,7 @@ struct devif_callback_s
 /****************************************************************************
  * Public Data
  ****************************************************************************/
+/* Well-known addresses */
 
 #ifdef CONFIG_NET_IPv4
 extern const in_addr_t g_ipv4_alloneaddr;
@@ -193,16 +195,22 @@ extern const net_ipv6addr_t g_ipv6_allzeroaddr;
 
 extern uint16_t g_ipid;
 
+#if defined(CONFIG_NET_TCP_REASSEMBLY) && !defined(CONFIG_NET_IPv6)
 /* Reassembly timer (units: deci-seconds) */
 
-#if defined(CONFIG_NET_TCP_REASSEMBLY) && !defined(CONFIG_NET_IPv6)
 extern uint8_t g_reassembly_timer;
 #endif
 
+#if defined(CONFIG_NET_ICMP) && defined(CONFIG_NET_ICMP_PING)
 /* List of applications waiting for ICMP ECHO REPLY */
 
-#if defined(CONFIG_NET_ICMP) && defined(CONFIG_NET_ICMP_PING)
-extern struct devif_callback_s *g_echocallback;
+extern struct devif_callback_s *g_icmp_echocallback;
+#endif
+
+#if defined(CONFIG_NET_ICMPv6) && defined(CONFIG_NET_ICMPv6_PING)
+/* List of applications waiting for ICMPv6 ECHO REPLY */
+
+extern struct devif_callback_s *g_icmpv6_echocallback;
 #endif
 
 /****************************************************************************
diff --git a/nuttx/net/icmp/icmp_input.c b/nuttx/net/icmp/icmp_input.c
index 268742120..ada65595f 100644
--- a/nuttx/net/icmp/icmp_input.c
+++ b/nuttx/net/icmp/icmp_input.c
@@ -77,7 +77,7 @@
  ****************************************************************************/
 
 #ifdef CONFIG_NET_ICMP_PING
-FAR struct devif_callback_s *g_echocallback = NULL;
+FAR struct devif_callback_s *g_icmp_echocallback = NULL;
 #endif
 
 /****************************************************************************
@@ -182,9 +182,9 @@ void icmp_input(FAR struct net_driver_s *dev)
    */
 
 #ifdef CONFIG_NET_ICMP_PING
-  else if (picmp->type == ICMP_ECHO_REPLY && g_echocallback)
+  else if (picmp->type == ICMP_ECHO_REPLY && g_icmp_echocallback)
     {
-      (void)devif_callback_execute(dev, picmp, ICMP_ECHOREPLY, g_echocallback);
+      (void)devif_callback_execute(dev, picmp, ICMP_ECHOREPLY, g_icmp_echocallback);
     }
 #endif
 
diff --git a/nuttx/net/icmp/icmp_ping.c b/nuttx/net/icmp/icmp_ping.c
index f7c84a072..2efeddab2 100644
--- a/nuttx/net/icmp/icmp_ping.c
+++ b/nuttx/net/icmp/icmp_ping.c
@@ -70,8 +70,8 @@
 
 /* Allocate a new ICMP data callback */
 
-#define icmp_callback_alloc()   devif_callback_alloc(&g_echocallback)
-#define icmp_callback_free(cb)  devif_callback_free(cb, &g_echocallback)
+#define icmp_callback_alloc()   devif_callback_alloc(&g_icmp_echocallback)
+#define icmp_callback_free(cb)  devif_callback_free(cb, &g_icmp_echocallback)
 
 /****************************************************************************
  * Private Types
diff --git a/nuttx/net/icmp/icmp_poll.c b/nuttx/net/icmp/icmp_poll.c
index 4f99464dd..067ffef68 100644
--- a/nuttx/net/icmp/icmp_poll.c
+++ b/nuttx/net/icmp/icmp_poll.c
@@ -96,7 +96,7 @@ void icmp_poll(FAR struct net_driver_s *dev)
 
   /* Perform the application callback */
 
-  (void)devif_callback_execute(dev, NULL, ICMP_POLL, g_echocallback);
+  (void)devif_callback_execute(dev, NULL, ICMP_POLL, g_icmp_echocallback);
 }
 
 #endif /* CONFIG_NET && CONFIG_NET_ICMP && CONFIG_NET_ICMP_PING */
diff --git a/nuttx/net/icmpv6/Kconfig b/nuttx/net/icmpv6/Kconfig
index bc95a6678..89c03c36c 100644
--- a/nuttx/net/icmpv6/Kconfig
+++ b/nuttx/net/icmpv6/Kconfig
@@ -16,6 +16,13 @@ config NET_ICMPv6
 
 if NET_ICMPv6
 
+config NET_ICMPv6_PING
+	bool "ICMPv6 ping interfaces"
+	default n
+	---help---
+		Provide interfaces to support application level support for
+		for sending ECHO (ping) requests and associating ECHO replies.
+
 endif # NET_ICMPv6
 endmenu # ICMPv6 Networking Support
 endif # NET_IPv6
diff --git a/nuttx/net/icmpv6/icmpv6_input.c b/nuttx/net/icmpv6/icmpv6_input.c
index df42d75e5..9cfe59c55 100644
--- a/nuttx/net/icmpv6/icmpv6_input.c
+++ b/nuttx/net/icmpv6/icmpv6_input.c
@@ -71,6 +71,11 @@
 #define ETHBUF    ((struct eth_hdr_s *)&dev->d_buf[0])
 #define ICMPv6BUF ((struct icmpv6_iphdr_s *)&dev->d_buf[NET_LL_HDRLEN(dev)])
 
+#define ICMPv6SOLICIT \
+  ((struct icmpv6_neighbor_solicit_s *)&dev->d_buf[NET_LL_HDRLEN(dev) + IPv6_HDRLEN])
+#define ICMPv6ADVERTISE \
+  ((struct icmpv6_neighbor_advertise_s *)&dev->d_buf[NET_LL_HDRLEN(dev) + IPv6_HDRLEN])
+
 /****************************************************************************
  * Public Variables
  ****************************************************************************/
@@ -79,8 +84,8 @@
  * Private Variables
  ****************************************************************************/
 
-#ifdef CONFIG_NET_ICMPv6v6_PING
-FAR struct devif_callback_s *g_echocallback = NULL;
+#ifdef CONFIG_NET_ICMPv6_PING
+FAR struct devif_callback_s *g_icmpv6_echocallback = NULL;
 #endif
 
 /****************************************************************************
@@ -127,42 +132,84 @@ void icmpv6_input(FAR struct net_driver_s *dev)
 
   if (icmp->type == ICMPv6_NEIGHBOR_SOLICIT)
     {
+      FAR struct icmpv6_neighbor_solicit_s *sol;
+      FAR struct icmpv6_neighbor_advertise_s *adv;
+
       /* If the data matches our address, add the neighbor to the list
        * of neighbors.
+       *
+       * Missing checks:
+       *  optlen = 1 (8 octets)
        */
 
-      if (net_ipv6addr_cmp(icmp->icmpv6data, dev->d_ipv6addr))
+      sol = ICMPv6SOLICIT;
+      if (net_ipv6addr_cmp(sol->tgtaddr, dev->d_ipv6addr))
         {
-          if (icmp->options[0] == ICMPv6_OPTION_SOURCE_LINK_ADDRESS)
+          if (sol->opttype == ICMPv6_OPT_SRCLLADDR)
             {
               /* Save the sender's address in our neighbor list. */
 
               net_neighbor_add(icmp->srcipaddr,
-                               (FAR struct net_neighbor_addr_s *)&(icmp->options[2]));
+                               (FAR struct net_neighbor_addr_s *)sol->srclladdr);
             }
 
           /* We should now send a neighbor advertisement back to where the
            * neighbor solicitation came from.
            */
 
-          icmp->type = ICMPv6_NEIGHBOR_ADVERTISE;
-          icmp->flags = ICMPv6_FLAG_S; /* Solicited flag. */
+          /* Set up the IPv6 header (most is probably already in place) */
+
+          icmp->vtc    = 0x60;           /* Version/traffic class (MS) */
+          icmp->tcf    = 0;              /* Traffic class (LS)/Flow label (MS) */
+          icmp->flow   = 0;              /* Flow label (LS) */
+
+          /* Length excludes the IPv6 header */
 
-          icmp->reserved1 = 0;
-          icmp->reserved2 = 0;
-          icmp->reserved3 = 0;
+          icmp->len[0] = (sizeof(struct icmpv6_neighbor_advertise_s) >> 8);
+          icmp->len[1] = (sizeof(struct icmpv6_neighbor_advertise_s) & 0xff);
+
+          icmp->proto  = IP_PROTO_ICMP6; /* Next header */
+          icmp->ttl    = IP_TTL;         /* Hop limit */
+
+          /* Swap source for destination IP address, add our source IP
+           * address
+           */
 
           net_ipv6addr_copy(icmp->destipaddr, icmp->srcipaddr);
           net_ipv6addr_copy(icmp->srcipaddr, dev->d_ipv6addr);
 
-          icmp->options[0]   = ICMPv6_OPTION_TARGET_LINK_ADDRESS;
-          icmp->options[1]   = 1;  /* Options length, 1 = 8 bytes. */
-          memcpy(&(icmp->options[2]), &dev->d_mac, IFHWADDRLEN);
+          /* Set up the ICMPv6 Neighbor Advertise response */
 
-          icmp->icmpv6chksum = 0;
-          icmp->icmpv6chksum = ~icmpv6_chksum(dev);
+          adv            = ICMPv6ADVERTISE;
+          adv->type      = ICMPv6_NEIGHBOR_ADVERTISE; /* Message type */
+          adv->code      = 0;                         /* Message qualifier */
+          adv->flags[0]  = ICMPv6_FLAG_S;             /* Solicited flag. */
+          adv->flags[1]  = 0;
+          adv->flags[2]  = 0;
+          adv->flags[3]  = 0;
+          adv->opttype   = ICMPv6_OPT_TGTLLADDR;      /* Option type */
+          adv->optlen    = 1;                         /* Option length = 1 octet */
+
+          /* Copy our link layer address into the message
+           * REVISIT:  What if the link layer is not Ethernet?
+           */
+
+          memcpy(&(adv->tgtlladdr), &dev->d_mac, IFHWADDRLEN);
+
+          /* Calculate the checksum over both the ICMP header and payload */
+
+          icmp->chksum   = 0;
+          icmp->chksum   = ~icmpv6_chksum(dev);
+
+          /* Set the size to the size of the IPv6 header and the payload size */
+
+          dev->d_len     = IPv6_HDRLEN + sizeof(struct icmpv6_neighbor_advertise_s);
 
 #ifdef CONFIG_NET_ETHERNET
+          /* Add the size of the Ethernet header */
+
+          dev->d_len    += ETH_HDRLEN;
+
           /* Move the source and to the destination addresses in the
            * Ethernet header and use our MAC as the new source address.
            */
@@ -195,8 +242,8 @@ void icmpv6_input(FAR struct net_driver_s *dev)
       net_ipv6addr_copy(icmp->destipaddr, icmp->srcipaddr);
       net_ipv6addr_copy(icmp->srcipaddr, dev->d_ipv6addr);
 
-      icmp->icmpv6chksum = 0;
-      icmp->icmpv6chksum = ~icmpv6_chksum(dev);
+      icmp->chksum = 0;
+      icmp->chksum = ~icmpv6_chksum(dev);
     }
 
   /* If an ICMPv6 echo reply is received then there should also be
@@ -204,15 +251,15 @@ void icmpv6_input(FAR struct net_driver_s *dev)
    */
 
 #ifdef CONFIG_NET_ICMPv6v6_PING
-  else if (icmp->type == ICMPv6_ECHO_REPLY && g_echocallback)
+  else if (icmp->type == ICMPv6_ECHO_REPLY && g_icmpv6_echocallback)
     {
       uint16_t flags = ICMPv6_ECHOREPLY;
 
-      if (g_echocallback)
+      if (g_icmpv6_echocallback)
         {
           /* Dispatch the ECHO reply to the waiting thread */
 
-          flags = devif_callback_execute(dev, icmp, flags, g_echocallback);
+          flags = devif_callback_execute(dev, icmp, flags, g_icmpv6_echocallback);
         }
 
       /* If the ECHO reply was not handled, then drop the packet */
diff --git a/nuttx/net/icmpv6/icmpv6_ping.c b/nuttx/net/icmpv6/icmpv6_ping.c
index bedc11567..e946860be 100644
--- a/nuttx/net/icmpv6/icmpv6_ping.c
+++ b/nuttx/net/icmpv6/icmpv6_ping.c
@@ -70,8 +70,8 @@
 
 /* Allocate a new ICMPv6 data callback */
 
-#define icmpv6_callback_alloc()   devif_callback_alloc(&g_echocallback)
-#define icmpv6_callback_free(cb)  devif_callback_free(cb, &g_echocallback)
+#define icmpv6_callback_alloc()   devif_callback_alloc(&g_icmpv6_echocallback)
+#define icmpv6_callback_free(cb)  devif_callback_free(cb, &g_icmpv6_echocallback)
 
 /****************************************************************************
  * Private Types
diff --git a/nuttx/net/icmpv6/icmpv6_poll.c b/nuttx/net/icmpv6/icmpv6_poll.c
index 20ca9210c..c8d31f937 100644
--- a/nuttx/net/icmpv6/icmpv6_poll.c
+++ b/nuttx/net/icmpv6/icmpv6_poll.c
@@ -96,7 +96,7 @@ void icmpv6_poll(FAR struct net_driver_s *dev)
 
   /* Perform the application callback */
 
-  (void)devif_callback_execute(dev, NULL, ICMPv6_POLL, g_echocallback);
+  (void)devif_callback_execute(dev, NULL, ICMPv6_POLL, g_icmpv6_echocallback);
 }
 
 #endif /* CONFIG_NET && CONFIG_NET_ICMPv6 && CONFIG_NET_ICMPv6_PING */
diff --git a/nuttx/net/icmpv6/icmpv6_send.c b/nuttx/net/icmpv6/icmpv6_send.c
index 6df8dc26b..0464aa274 100644
--- a/nuttx/net/icmpv6/icmpv6_send.c
+++ b/nuttx/net/icmpv6/icmpv6_send.c
@@ -40,6 +40,7 @@
 #include <nuttx/config.h>
 #if defined(CONFIG_NET) && defined(CONFIG_NET_ICMPv6) && defined(CONFIG_NET_ICMPv6_PING)
 
+#include <string.h>
 #include <debug.h>
 
 #include <arpa/inet.h>
@@ -48,6 +49,7 @@
 #include <nuttx/net/netdev.h>
 #include <nuttx/net/netstats.h>
 #include <nuttx/net/ip.h>
+#include <nuttx/net/icmpv6.h>
 
 #include "devif/devif.h"
 #include "utils/utils.h"
@@ -94,7 +96,7 @@
 
 void icmpv6_send(FAR struct net_driver_s *dev, FAR net_ipv6addr_t *destaddr)
 {
-  FAR struct icmpv6_iphdr_s *picmpv6 = ICMPv6BUF;
+  FAR struct icmpv6_iphdr_s *icmp = ICMPv6BUF;
 
   if (dev->d_sndlen > 0)
     {
@@ -114,28 +116,24 @@ void icmpv6_send(FAR struct net_driver_s *dev, FAR net_ipv6addr_t *destaddr)
        * does not include the IPv6 IP header length.
        */
 
-      picmpv6->vtc         = 0x60;
-      picmpv6->tcf         = 0x00;
-      picmpv6->flow        = 0x00;
-      picmpv6->len[0]      = (dev->d_sndlen >> 8);
-      picmpv6->len[1]      = (dev->d_sndlen & 0xff);
-      picmpv6->nexthdr     = IP_PROTO_ICMPv6;
-      picmpv6->hoplimit    = IP_TTL;
+      icmp->vtc         = 0x60;
+      icmp->tcf         = 0x00;
+      icmp->flow        = 0x00;
+      icmp->len[0]      = (dev->d_sndlen >> 8);
+      icmp->len[1]      = (dev->d_sndlen & 0xff);
+      icmp->proto       = IP_PROTO_ICMP6;
+      icmp->ttl         = IP_TTL;
 
-      net_ipv6addr_copy(picmpv6->srcipaddr, &dev->d_ipaddr);
-      net_ipv6addr_copy(picmpv6->destipaddr, destaddr);
+      net_ipv6addr_copy(icmp->srcipaddr, dev->d_ipv6addr);
+      net_ipv6addr_copy(icmp->destipaddr, destaddr);
 
       /* Calculate the ICMPv6 checksum. */
 
-      picmpv6->icmpv6chksum  = 0;
-      picmpv6->icmpv6chksum  = ~(icmpv6_chksum(dev, dev->d_sndlen));
-      if (picmpv6->icmpv6chksum == 0)
-        {
-          picmpv6->icmpv6chksum = 0xffff;
-        }
+      icmp->chksum  = 0;
+      icmp->chksum  = ~icmpv6_chksum(dev);
 
       nllvdbg("Outgoing ICMPv6 packet length: %d (%d)\n",
-              dev->d_len, (picmpv6->len[0] << 8) | picmpv6->len[1]);
+              dev->d_len, (icmp->len[0] << 8) | icmp->len[1]);
 
 #ifdef CONFIG_NET_STATISTICS
       g_netstats.icmpv6.sent++;
diff --git a/nuttx/net/utils/net_chksum.c b/nuttx/net/utils/net_chksum.c
index 033aa7e59..d4179470c 100644
--- a/nuttx/net/utils/net_chksum.c
+++ b/nuttx/net/utils/net_chksum.c
@@ -74,9 +74,9 @@
 #if !CONFIG_NET_ARCH_CHKSUM
 static uint16_t chksum(uint16_t sum, FAR const uint8_t *data, uint16_t len)
 {
+  FAR const uint8_t *dataptr;
+  FAR const uint8_t *last_byte;
   uint16_t t;
-  const uint8_t *dataptr;
-  const uint8_t *last_byte;
 
   dataptr = data;
   last_byte = data + len - 1;
@@ -85,7 +85,7 @@ static uint16_t chksum(uint16_t sum, FAR const uint8_t *data, uint16_t len)
     {
       /* At least two more bytes */
 
-      t = (dataptr[0] << 8) + dataptr[1];
+      t = ((uint16_t)dataptr[0] << 8) + dataptr[1];
       sum += t;
       if (sum < t)
         {
@@ -119,11 +119,16 @@ 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 ipv4_hdr_s *pbuf = IPv4BUF;
+  FAR struct ipv4_hdr_s *ipv4 = IPv4BUF;
   uint16_t upperlen;
   uint16_t sum;
 
-  upperlen = (((uint16_t)(pbuf->len[0]) << 8) + pbuf->len[1]) - IPv4_HDRLEN;
+  /* The length reported in the IPv4 header is the length of both the IPv4
+   * header and the payload that follows the header.  We need to subtract
+   * the size of the IPv4 header to get the size of the payload.
+   */
+
+  upperlen = (((uint16_t)(ipv4->len[0]) << 8) + ipv4->len[1]) - IPv4_HDRLEN;
 
   /* Verify some minimal assumptions */
 
@@ -139,12 +144,11 @@ static uint16_t ipv4_upperlayer_chksum(FAR struct net_driver_s *dev,
 
   /* Sum IP source and destination addresses. */
 
-  sum = chksum(sum, (uint8_t *)&pbuf->srcipaddr, 2 * sizeof(in_addr_t));
+  sum = chksum(sum, (FAR uint8_t *)&ipv4->srcipaddr, 2 * sizeof(in_addr_t));
 
-  /* Sum TCP header and data. */
+  /* Sum IP payload data. */
 
   sum = chksum(sum, &dev->d_buf[IPv4_HDRLEN + NET_LL_HDRLEN(dev)], upperlen);
-
   return (sum == 0) ? 0xffff : htons(sum);
 }
 #endif /* CONFIG_NET_ARCH_CHKSUM */
@@ -157,11 +161,15 @@ 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 ipv6_hdr_s *pbuf = IPv6BUF;
+  FAR struct ipv6_hdr_s *ipv6 = IPv6BUF;
   uint16_t upperlen;
   uint16_t sum;
 
-  upperlen = (((uint16_t)(pbuf->len[0]) << 8) + pbuf->len[1]);
+  /* The length reported in the IPv6 header is the length of the payload
+   * that follows the header.
+   */
+
+  upperlen = ((uint16_t)ipv6->len[0] << 8) + ipv6->len[1];
 
   /* Verify some minimal assumptions */
 
@@ -170,19 +178,20 @@ static uint16_t ipv6_upperlayer_chksum(FAR struct net_driver_s *dev,
       return 0;
     }
 
-  /* First sum pseudo-header. */
-  /* IP protocol and length fields. This addition cannot carry. */
+  /* The checksum is calculated starting with a pseudo-header of IPv6 header
+   * fields according to the IPv6 standard, which consists of the source
+   * and destination addresses, the packet length and the next header field.
+   */
 
   sum = upperlen + proto;
 
   /* Sum IP source and destination addresses. */
 
-  sum = chksum(sum, (uint8_t *)&pbuf->srcipaddr, 2 * sizeof(net_ipv6addr_t));
+  sum = chksum(sum, (FAR uint8_t *)&ipv6->srcipaddr, 2 * sizeof(net_ipv6addr_t));
 
-  /* Sum TCP header and data. */
+  /* Sum IP payload data. */
 
   sum = chksum(sum, &dev->d_buf[IPv6_HDRLEN + NET_LL_HDRLEN(dev)], upperlen);
-
   return (sum == 0) ? 0xffff : htons(sum);
 }
 #endif /* CONFIG_NET_ARCH_CHKSUM */