Network interface to ip addr

network_iface_to_addr.cpp

#include <arpa/inet.h>
#include <ifaddrs.h>
#include <ifaddrs.h>

//
// network_iface_to_addr()
//

/**
 * @brief For a given network interface finds an ipv4 inet address.
 *
 * @return  A ipv4 address of the network interface if found,
 *          otherwise return empty optional.
 */
[[nodiscard]] std::optional< asio_ns::ip::address >
network_iface_to_addr( std::string_view iface_name )
{
    try
    {
        ifaddrs * ifap;

        if( -1 == getifaddrs( &ifap ) )
        {
            return std::nullopt;
        }

        std::unique_ptr< ifaddrs, decltype( &freeifaddrs ) > ifap_ptr{
            ifap, &freeifaddrs
        };

        for( auto * iface = ifap; iface != nullptr; iface = iface->ifa_next )
        {
            if( iface->ifa_addr && iface->ifa_addr->sa_family == AF_INET
                && iface->ifa_name == iface_name )
            {
                auto * sa = reinterpret_cast< sockaddr_in * >( iface->ifa_addr );
                return asio_ns::ip::address_v4{ ntohl(sa->sin_addr.s_addr) };
            }
        }
    }
    catch( ... )
    {
    }

    return std::nullopt;
}