EventService : Support async_resolve for subscribers

The http client at bmcweb does not resolve the client's
hostname asynchronously

This commit implements the async_resolve by using systemd resolved.
The async dbus message to resolvd.service is sent when a subscriber
successfully subscribes for events. The method ResolveHostname is
used to resolve the subscriber's hostname

Tested by:
  Subscribe for the events at BMC using DMTF event listener
  Generate an event and see the same is received at the listener's console

Signed-off-by: Sunitha Harish <sunithaharish04@gmail.com>
Change-Id: I3ab8206ac4764cfa025e94c06407524d6ba220e0

1 files changed, 99 insertions, 0 deletions

diff --git a/include/async_resolve.hpp b/include/async_resolve.hpp
new file mode 100644
index 0000000000..306a49972a
--- /dev/null
+++ b/include/async_resolve.hpp
@@ -0,0 +1,99 @@
+#pragma once
+#include <boost/asio/ip/address.hpp>
+#include <boost/asio/ip/basic_endpoint.hpp>
+#include <sdbusplus/message.hpp>
+
+#include <charconv>
+#include <iostream>
+#include <memory>
+
+namespace crow
+{
+
+namespace async_resolve
+{
+
+class Resolver
+{
+  public:
+    Resolver() = default;
+
+    ~Resolver() = default;
+
+    template <typename ResolveHandler>
+    void asyncResolve(const std::string& host, const std::string& port,
+                      ResolveHandler&& handler)
+    {
+        BMCWEB_LOG_DEBUG << "Trying to resolve: " << host << ":" << port;
+        uint64_t flag = 0;
+        crow::connections::systemBus->async_method_call(
+            [host, port, handler{std::move(handler)}](
+                const boost::system::error_code ec,
+                const std::vector<
+                    std::tuple<int32_t, int32_t, std::vector<uint8_t>>>& resp,
+                const std::string& hostName, const uint64_t flagNum) {
+                std::vector<boost::asio::ip::tcp::endpoint> endpointList;
+                if (ec)
+                {
+                    BMCWEB_LOG_ERROR << "Resolve failed: " << ec.message();
+                    handler(ec, endpointList);
+                    return;
+                }
+                BMCWEB_LOG_DEBUG << "ResolveHostname returned: " << hostName
+                                 << ":" << flagNum;
+                // Extract the IP address from the response
+                for (auto resolveList : resp)
+                {
+                    std::vector<uint8_t> ipAddress = std::get<2>(resolveList);
+                    boost::asio::ip::tcp::endpoint endpoint;
+                    if (ipAddress.size() == 4) // ipv4 address
+                    {
+                        BMCWEB_LOG_DEBUG << "ipv4 address";
+                        boost::asio::ip::address_v4 ipv4Addr(
+                            {ipAddress[0], ipAddress[1], ipAddress[2],
+                             ipAddress[3]});
+                        endpoint.address(ipv4Addr);
+                    }
+                    else if (ipAddress.size() == 16) // ipv6 address
+                    {
+                        BMCWEB_LOG_DEBUG << "ipv6 address";
+                        boost::asio::ip::address_v6 ipv6Addr(
+                            {ipAddress[0], ipAddress[1], ipAddress[2],
+                             ipAddress[3], ipAddress[4], ipAddress[5],
+                             ipAddress[6], ipAddress[7], ipAddress[8],
+                             ipAddress[9], ipAddress[10], ipAddress[11],
+                             ipAddress[12], ipAddress[13], ipAddress[14],
+                             ipAddress[15]});
+                        endpoint.address(ipv6Addr);
+                    }
+                    else
+                    {
+                        BMCWEB_LOG_ERROR
+                            << "Resolve failed to fetch the IP address";
+                        handler(ec, endpointList);
+                        return;
+                    }
+                    uint16_t portNum;
+                    auto it = std::from_chars(
+                        port.data(), port.data() + port.size(), portNum);
+                    if (it.ec != std::errc())
+                    {
+                        BMCWEB_LOG_ERROR << "Failed to get the Port";
+                        handler(ec, endpointList);
+                        return;
+                    }
+                    endpoint.port(portNum);
+                    BMCWEB_LOG_DEBUG << "resolved endpoint is : " << endpoint;
+                    endpointList.push_back(endpoint);
+                }
+                // All the resolved data is filled in the endpointList
+                handler(ec, endpointList);
+            },
+            "org.freedesktop.resolve1", "/org/freedesktop/resolve1",
+            "org.freedesktop.resolve1.Manager", "ResolveHostname", 0, host,
+            AF_UNSPEC, flag);
+    }
+};
+
+} // namespace async_resolve
+} // namespace crow