string Dim::GetLocalIp

(

const std::string &

dns = "10.0.100.1"

)

Tries to determine the local IP address with which we will connect to the DIM dns.

The local IP address is necessary because in some circumstances Dim needs the IP address of the connecting machine (DIM_HOST_NODE) for the clients to correctly connect to them. So what we would need is the IP address over which the machine is reachable from the client. Unfortunately, we have no access to the client connection, hence, we have to find the best guess of an address which is not our own machine and hope it is routed over the standard ethernet interface over which other clients will connect.

To not send random packages over the network we use a local IP address. To make sure it is something which leaves the network card and is not just our machine, we can use a broadcast address. Consequently, the deafult has been chosen to be "192.168.0.255"

Parameters

dns	Address of the Dim-dns

Returns

The IP Address through which the connection to the DNS will take place.

Todo:

Implement a –host command line option (just in case)

Definition at line 51 of file DimSetup.cc.

Referenced by GetLocalIp(), and Setup().

{
    using namespace boost::asio;
    using namespace boost::asio::ip;

    cout << "Trying to resolve local IP address..." << endl;

    boost::system::error_code ec;

    boost::asio::io_service io_service;

    udp::socket socket(io_service);

    udp::resolver resolver(io_service);
    udp::resolver::query query(dns, "0");
    udp::resolver::iterator iterator = resolver.resolve(query, ec);
    if (ec)
    {
        //cout << "WARNING - Failure in name-resolution of '" << dns << ":0': ";
        cout << "WARNING - Could not resolve local ip address: ";
        cout << ec.message() << " (" << ec << ")" << endl;
        return dns;
    }

    for (; iterator != udp::resolver::iterator(); ++iterator)
    {
        udp::endpoint endpoint = *iterator;
        socket.connect(endpoint, ec);
        if (ec)
        {
            cout << "WARNING - Could not resolve local ip address: ";
            cout << ec.message() << " (" << ec << ")" << endl;
            continue;
        }

        const string addr = socket.local_endpoint().address().to_v4().to_string();
        return addr;
    }

    return "localhost";

/*
    struct addrinfo hints, *servinfo, *p;

    memset(&hints, 0, sizeof hints);
    hints.ai_family   = AF_INET; //AF_UNSPEC; // use AF_INET6 to force IPv6
    hints.ai_socktype = SOCK_STREAM;

    int rv;
    if ((rv = getaddrinfo(dns.c_str(), NULL, &hints, &servinfo)) != 0)
    {
        cout << "WARNING - getaddrinfo: " << gai_strerror(rv) << endl;
        return dns;
    }

    // loop through all the results and connect to the first we can
    for (p=servinfo; p; p=p->ai_next)
    {
        const int sock = socket(AF_INET, SOCK_DGRAM, 0);
        if (sock==-1)
            continue;

        if (connect(sock, p->ai_addr, p->ai_addrlen)==-1)
        {
            cout << "WARNING - connect: " << strerror(errno) << endl;
            close(sock);
            continue;
        }

        sockaddr_in name;
        socklen_t namelen = sizeof(name);
        if (getsockname(sock, (sockaddr*)&name, &namelen)==-1)
        {
            cout << "WARNING - getsockname: " << strerror(errno) << endl;
            close(sock);
            continue;
        }

        char buffer[16];
        if (!inet_ntop(AF_INET, &name.sin_addr, buffer, 16))
        {
            cout << "WARNING - inet_ntop: " << strerror(errno) << endl;
            close(sock);
            continue;
        }

        close(sock);

        freeaddrinfo(servinfo); // all done with this structure

        cout << "DIM_HOST_NODE=" << buffer << endl;
        return buffer;
    }

    freeaddrinfo(servinfo); // all done with this structure

    return dns;
*/
}

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