Add the network utility file

Moving utility functions from network manager to
util.cpp.

Added few more utility functions.

Change-Id: I2e73c873e9a3bea543d6979463b2181e8374e12e
Signed-off-by: Ratan Gupta <ratagupt@in.ibm.com>
diff --git a/util.cpp b/util.cpp
new file mode 100644
index 0000000..740d4a7
--- /dev/null
+++ b/util.cpp
@@ -0,0 +1,144 @@
+#include <arpa/inet.h>
+#include <dirent.h>
+#include <net/if.h>
+
+#include <iostream>
+#include <list>
+#include <string>
+#include <algorithm>
+#include <phosphor-logging/log.hpp>
+
+namespace phosphor
+{
+namespace network
+{
+namespace
+{
+
+using namespace phosphor::logging;
+
+uint8_t toV6Cidr(const std::string& subnetMask)
+{
+    uint8_t pos = 0;
+    uint8_t prevPos = 0;
+    uint8_t cidr = 0;
+    uint16_t buff {};
+    do
+    {
+        //subnet mask look like ffff:ffff::
+        // or ffff:c000::
+        pos =  subnetMask.find(":", prevPos);
+        if (pos == std::string::npos)
+        {
+            break;
+        }
+
+        auto str = subnetMask.substr(prevPos, (pos - prevPos));
+        prevPos = pos + 1;
+
+        // String length is 0
+        if (!str.length())
+        {
+            return cidr;
+        }
+        //converts it into number.
+        if (sscanf(str.c_str(), "%hx", &buff) <= 0)
+        {
+            log<level::ERR>("Invalid Mask",
+                             entry("SUBNETMASK=%s", subnetMask));
+
+            return 0;
+        }
+
+        // convert the number into bitset
+        // and check for how many ones are there.
+        // if we don't have all the ones then make
+        // sure that all the ones should be left justify.
+
+        if (__builtin_popcount(buff) != 16)
+        {
+            if (((sizeof(buff) * 8) - (__builtin_ctz(buff))) != __builtin_popcount(buff))
+            {
+                log<level::ERR>("Invalid Mask",
+                                entry("SUBNETMASK=%s", subnetMask));
+
+                return 0;
+            }
+            cidr += __builtin_popcount(buff);
+            return cidr;
+        }
+
+        cidr += 16;
+    }
+    while (1);
+
+    return cidr;
+}
+}// anonymous namespace
+
+uint8_t toCidr(int addressFamily, const std::string& subnetMask)
+{
+    if (addressFamily == AF_INET6)
+    {
+        return toV6Cidr(subnetMask);
+    }
+
+    uint32_t buff;
+
+    auto rc = inet_pton(addressFamily, subnetMask.c_str(), &buff);
+    if (rc <= 0)
+    {
+        log<level::ERR>("inet_pton failed:",
+                         entry("SUBNETMASK=%s", subnetMask));
+        return 0;
+    }
+
+    buff = be32toh(buff);
+    // total no of bits - total no of leading zero == total no of ones
+    if (((sizeof(buff) * 8) - (__builtin_ctz(buff))) == __builtin_popcount(buff))
+    {
+        return __builtin_popcount(buff);
+    }
+    else
+    {
+        log<level::ERR>("Invalid Mask",
+                         entry("SUBNETMASK=%s", subnetMask));
+        return 0;
+    }
+}
+
+std::string toMask(int addressFamily, uint8_t prefix)
+{
+    if (addressFamily == AF_INET6)
+    {
+        //TODO:- conversion for v6
+        return "";
+    }
+
+    if (prefix < 1 || prefix > 30)
+    {
+        log<level::ERR>("Invalid Prefix",
+                        entry("PREFIX=%d", prefix));
+        return "";
+    }
+    /* Create the netmask from the number of bits */
+    unsigned long mask = 0;
+    for (auto i = 0 ; i < prefix ; i++)
+    {
+        mask |= 1 << (31 - i);
+    }
+    struct in_addr netmask;
+    netmask.s_addr = htonl(mask);
+    return inet_ntoa(netmask);
+}
+
+bool isLinkLocal(const std::string& address)
+{
+    std::string linklocal = "fe80";
+    return std::mismatch(linklocal.begin(), linklocal.end(),
+                         address.begin()).first == linklocal.end() ?
+                            true : false;
+}
+
+}//namespace network
+}//namespace phosphor