basics of ND with RADV

neighbor discovery protocol basics, just for fun and for radv slaac
this is a working version, but code is not perfect,
just commit to save the checkpoint -- this isn't the master, is it?

ipv6.h

@@ -6,10 +6,13 @@ namespace ipv6 {
   const uint8_t LEN = 128;
   const uint8_t ICMP_ECHO_REQUEST_TYPE = 128;
   const uint8_t ICMP_ECHO_REPLY_TYPE   = 129;
+  const uint8_t ICMP_RADV_TYPE         = 134;
 
   const uint8_t NH_ICMP = 58;
   const uint8_t NH_UDP  = 17;
 
+  extern uint8_t HOP_LIMIT;
+
   class IPv6Addr {
     private:
       char address[16];
@@ -18,6 +21,7 @@ namespace ipv6 {
       IPv6Addr(const char* address);
   };
 
+  extern const IPv6Addr LINK_LOCAL_ADDRESS;
   extern const IPv6Addr ALL_NODES_ADDRESS;
 
   struct ipv6_packet_header {
@@ -64,6 +68,33 @@ namespace ipv6 {
     const char* payload,      /* IPv6 payload */
     int len                   /* IPv6 payload length */
    );
+
+  struct ICMPv6_RADV {
+    uint8_t type;
+    uint8_t code;
+    char checksum[2];
+    uint8_t cur_hop_limit;
+    uint8_t mo_flags;
+    uint16_t router_lifetime;
+    uint32_t reachable_time;
+    uint32_t retrans_time;
+  };
+
+  struct ICMPv6_RADV_Option {
+    uint8_t type;
+    uint8_t len;
+  };
+
+  struct ICMPv6_RADV_PrefixInformation {
+    uint8_t type;
+    uint8_t len;
+    uint8_t prefix_length;
+    uint8_t la_flags;
+    uint32_t valid_lifetime;
+    uint32_t preferred_lifetime;
+    uint32_t reserved2;
+    char prefix[16];
+  };
 }
 
 #endif

ipv6.ino

@@ -3,7 +3,11 @@
 
 namespace ipv6 {
 /******** costants ********/
-const IPv6Addr ALL_NODES_ADDRESS("\xff\x02\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x01"); /* ff02::1 */
+const IPv6Addr  ALL_NODES_ADDRESS("\xff\x02\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x01");  /* ff02::1 */
+const IPv6Addr LINK_LOCAL_ADDRESS("\xfe\x80\x00\x00\x00\x00\x00\x00\xde\xad\xbe\xef\x12\x34\x56\x78");  /* fe80::dead:beef:1234:5678 */ /* TODO */
+
+/******** variables ********/
+uint8_t HOP_LIMIT = 64;
 
 /******** buffer ********/
 IPv6Packet packetin;
@@ -60,7 +64,7 @@ IPv6Addr::IPv6Addr(const char* address) {
 IPv6Packet::IPv6Packet() {
   memset(packet, 0, LEN);
   *(packet) = 0x60;               /* IP version 6 */
-  *(packet + 7) = 64;             /* hop limit / ttl */
+  *(packet + 7) = HOP_LIMIT;      /* hop limit / ttl */
 }
 
 IPv6Packet::IPv6Packet(const char* buffer, int len) {
@@ -112,8 +116,11 @@ void IPv6Packet::send() {
 }
 
 void IPv6Packet::doAction() {
-  /* if destination is my address, or destination is "all nodes" address, then... */
+  /* if destination is my address (global or link-local), or destination is "all nodes" address, then... */
-  if ((memcmp(&(ALL_NODES_ADDRESS), packet + 24, 16) == 0) || (memcmp(&(coppino::address), packet + 24, 16) == 0)) {
+  if (
+    (memcmp(&(ALL_NODES_ADDRESS), packet + 24, 16) == 0) ||
+    (memcmp(&(LINK_LOCAL_ADDRESS), packet + 24, 16) == 0) ||
+    (memcmp(&(coppino::address), packet + 24, 16) == 0)) {
     int ilen = this->getLen();  /* input payload length */
     int olen;                   /* output payload length */
     
@@ -148,7 +155,6 @@ void IPv6Packet::doAction() {
 int handleICMP(char* output_buffer, const char* input_buffer, int len) {
   uint8_t type = *(input_buffer);
 
-  if (type == ICMP_ECHO_REQUEST_TYPE) {  /* if it is ICMPv6 Echo Request, then... */
   /* compute checksum, and assert validity of incoming message */
   char received_checksum[2];
   memcpy(received_checksum, input_buffer + 2, 2);
@@ -163,7 +169,11 @@ int handleICMP(char* output_buffer, const char* input_buffer, int len) {
     output_buffer,
     len);
 
-      if (memcmp(&computed_checksum, received_checksum, 2) == 0) {  /* if checksum is valid, then... */
+  if (memcmp(&computed_checksum, received_checksum, 2) != 0) { /* if checksum is not valid, return */
+    return -1;
+  }
+
+  if (type == ICMP_ECHO_REQUEST_TYPE) { /* if it is ICMPv6 Echo Request, then... */
     /*  Build an echo reply:
      *  the reply has the same exact format of the request,
      *  except for Type and Checksum */
@@ -178,12 +188,30 @@ int handleICMP(char* output_buffer, const char* input_buffer, int len) {
       output_buffer,
       len);
     memcpy(output_buffer + 2, &checksum, 2);
-
     return len;
+    
+  } else if (type == ICMP_RADV_TYPE) {  /* if it is IVMPc6 Router Advertisement, then... */
+    ICMPv6_RADV* radv = (ICMPv6_RADV*)input_buffer;
+    HOP_LIMIT = (radv->cur_hop_limit != 0) ? radv->cur_hop_limit : 64;
+    
+    for (
+      ICMPv6_RADV_Option* option = (ICMPv6_RADV_Option*) (radv + 1);
+      option != input_buffer + len;
+      option = (ICMPv6_RADV_Option*) ( ((char*)(option)) + option->len )) {
+        digitalWrite(13, !digitalRead(13));
+        if (option->type == 3 && option->len == 4) {  /* if it is a ICMPv6 Prefix Information, then... */
+          ICMPv6_RADV_PrefixInformation* p = (ICMPv6_RADV_PrefixInformation*) option;
+          
+          if (p->prefix_length != 64) continue; /* only /64 prefix is supported */
+          if (! (p->la_flags & 0x40)) continue; /* only SLAAC is supported */
+          memcpy(&coppino::address, p->prefix, 8); /* set prefix -- leave host bits unchanged */
+          break;
         }
     }
     
     return -1;
   }
+  return -1;
+}
 
 }