How can I return info from a callback?

[Avery Rozar]

I wrote a class to get all the available bands for a given wireless
interface. I add a callback function to the socket and send it.
Inside my callback function I parse for the available bands and print
them to the console.

How would I return a vector or something else to be used in the class
that is calling the class to get the bands? Am I looking at this
wrong? I can't get this info in nl_recvmsgs_default can I?


Channel Selection Class:

int fs_channelSelection::selectChannels(unsigned int *networkDeviceId) {
    fs_nl80211 *nl80211 = new fs_nl80211;
    vector<uint32_t> band_list;
    band_list = nl80211->getBands(networkDeviceId);
}


fs_nls80211 Class:

vector<uint32_t> fs_nl80211::getBands(unsigned int *networkDeviceId) {
    // omit code for brevity

    // add callback info to the netlink socket
    nl_socket_modify_cb((nl_sock *) netlink_sk, NL_CB_VALID,
NL_CB_CUSTOM, getBandsCallback, NULL);

    // construct the message to nlcore
    genlmsg_put((nl_msg *) netlink_msg, 0, NL_AUTO_SEQ, nl80211_id, 0,
0, NL80211_CMD_GET_WIPHY, 0);
    NLA_PUT_U32((nl_msg *) netlink_msg, NL80211_ATTR_IFINDEX, *networkDeviceId);

    // send the message to netlink socket
    nl_send_auto((nl_sock *) netlink_sk, (nl_msg *) netlink_msg);

    // receive the message
    nl_recvmsgs_default((nl_sock *) netlink_sk);
    nl_wait_for_ack((nl_sock *) netlink_sk);
}


getBandsCallback function:

static int getBandsCallback(struct nl_msg *msg, void *args) {
    // omit code for brevity

    struct nlattr *tb_band[NL80211_BAND_ATTR_MAX + 1];
    vector<uint32_t> band_list;

    // omit code for brevity
    // omit code for brevity

                    if (!tb_freq[NL80211_FREQUENCY_ATTR_FREQ])
                        continue;
                    freq = nla_get_u32(tb_freq[NL80211_FREQUENCY_ATTR_FREQ]);
                    band_list.push_back(freq);

    // omit code for brevity

    // I'd like to be able to do this in the Channel Selection Class:
    for(auto const& value: band_list) {
        cout << value << endl;

    }
}


Thank you,
Avery Rozar