Added IP pdu class. It's compiling so far.

src/utils.cpp

@@ -0,0 +1,38 @@
+#include <stdexcept>
+#include <sstream>
+#include "utils.h"
+
+using namespace std;
+
+uint32_t Tins::Utils::ip_to_int(const string &ip) {
+    uint32_t result(0), i(0), end, bytes_found(0);
+    while(i < ip.size() && bytes_found < 4) {
+        uint8_t this_byte(0);
+        end = i + 3;
+        while(i < ip.size() && i < end && ip[i] != '.') {
+            if(ip[i] < '0' || ip[i] > '9')
+                throw std::runtime_error("Non-digit character found in ip");
+            this_byte = (this_byte * 10)  + (ip[i] - '0');
+            i++;
+        }
+        result = (result << 8) | this_byte;
+        bytes_found++;
+        if(bytes_found < 4 && i < ip.size() && ip[i] == '.')
+            i++;
+    }
+    if(bytes_found < 4 || (i < ip.size() && bytes_found == 4))
+        throw std::runtime_error("Invalid ip address");
+    return result;
+}
+
+string Tins::Utils::ip_to_string(uint32_t ip) {
+    ostringstream oss;
+    int mask(24);
+    while(mask >=0) {
+        oss << ((ip >> mask) & 0xff);
+        if(mask)
+            oss << '.';
+        mask -= 8;
+    }
+    return oss.str();
+}