Get Local IP-Address using Boost.Asio

Question

I\'m currently searching for a portable way of getting the local IP-addresses. Because I\'m using Boost anyway I thought it would be a good idea to use Boost.Asio for this t

Answer 1

Cross platform, but only because of the #ifdef _WIN32 … #else:

boost::asio::ip::address_v6 sinaddr_to_asio(sockaddr_in6 *addr) {
    boost::asio::ip::address_v6::bytes_type buf;
    memcpy(buf.data(), addr->sin6_addr.s6_addr, sizeof(addr->sin6_addr));
    return boost::asio::ip::make_address_v6(buf, addr->sin6_scope_id);
}

#if defined(_WIN32)
#undef UNICODE
#include 
// Headers that need to be included after winsock2.h:
#include 
#include 

typedef IP_ADAPTER_UNICAST_ADDRESS_LH Addr;
typedef IP_ADAPTER_ADDRESSES *AddrList;

std::vector get_local_interfaces() {
    // It's a windows machine, we assume it has 512KB free memory
    DWORD outBufLen = 1 << 19;
    AddrList ifaddrs = (AddrList) new char[outBufLen];

    std::vector res;

    ULONG err = GetAdaptersAddresses(AF_UNSPEC,
        GAA_FLAG_INCLUDE_PREFIX | GAA_FLAG_SKIP_ANYCAST | GAA_FLAG_SKIP_DNS_SERVER, NULL, ifaddrs,
        &outBufLen);

    if (err == NO_ERROR) {
        for (AddrList addr = ifaddrs; addr != 0; addr = addr->Next) {
            if (addr->OperStatus != IfOperStatusUp) continue;
            // if (addr->NoMulticast) continue;

            // Find the first IPv4 address
            if (addr->Ipv4Enabled) {
                for (Addr *uaddr = addr->FirstUnicastAddress; uaddr != 0; uaddr = uaddr->Next) {
                    if (uaddr->Address.lpSockaddr->sa_family != AF_INET) continue;
                    res.push_back(boost::asio::ip::make_address_v4(ntohl(reinterpret_cast(addr->ifa_addr)->sin_addr.s_addr)));
                }
            }

            if (addr->Ipv6Enabled) {
                for (Addr *uaddr = addr->FirstUnicastAddress; uaddr != 0; uaddr = uaddr->Next) {
                    if (uaddr->Address.lpSockaddr->sa_family != AF_INET6) continue;
                    res.push_back(sinaddr_to_asio(reinterpret_cast(addr->ifa_addr)));
                }
            }
        }
    } else {

    }
    delete[]((char *)ifaddrs);
    return res;
}
#elif defined(__APPLE__) || defined(__linux__)
#include 
#include 
#include 
#include 

std::vector get_local_interfaces() {
    std::vector res;
    ifaddrs *ifs;
    if (getifaddrs(&ifs)) {
        return res;
    }
    for (auto addr = ifs; addr != nullptr; addr = addr->ifa_next) {
        // No address? Skip.
        if (addr->ifa_addr == nullptr) continue;

        // Interface isn't active? Skip.
        if (!(addr->ifa_flags & IFF_UP)) continue;

        if(addr->ifa_addr->sa_family == AF_INET) {
            res.push_back(boost::asio::ip::make_address_v4(ntohl(
                reinterpret_cast(addr->ifa_addr)->sin_addr.s_addr)));
        } else if(addr->ifa_addr->sa_family == AF_INET6) {
            res.push_back(sinaddr_to_asio(reinterpret_cast(addr->ifa_addr)));
        } else continue;
    }
    freeifaddrs(ifs);
    return res;
}
#else
#error "..."
#endif