netiface.cpp

#include "dpitunnel-cli.h"

#include "netiface.h"
#include "profiles.h"
#include "utils.h"

#include <atomic>
#include <cerrno>
#include <cstring>
#include <fcntl.h>
#include <sys/socket.h>
#include <iostream>
#include <net/if.h>
#include <linux/netlink.h>
#include <linux/rtnetlink.h>
#include <linux/nl80211.h>
#include <linux/wireless.h>
#include <poll.h>
#include <sys/ioctl.h>
#include <arpa/inet.h>
#include <netinet/in.h>
#include <sys/types.h>
#include <ifaddrs.h>

#include <unistd.h>

#include <netlink/netlink.h>    //lots of netlink functions
#include <netlink/genl/genl.h>  //genl_connect, genlmsg_put
#include <netlink/genl/family.h>
#include <netlink/genl/ctrl.h>

extern int Interrupt_pipe[2];
extern std::atomic<bool> stop_flag;

struct Netlink {
    int id;
    struct nl_sock *socket;
    struct nl_cb *cb;
    int result;
};

struct Wifi {
    std::string ssid;
};

void parse_rtattr(struct rtattr *tb[], int max, struct rtattr *rta, int len) {
    memset(tb, 0, sizeof(struct rtattr *) * (max + 1));

    while (RTA_OK(rta, len)) {
        if (rta->rta_type <= max)
            tb[rta->rta_type] = rta;

        rta = RTA_NEXT(rta, len);
    }
}

// Monitor when client changes interfaces. We need it to change profiles according to current net interface
void route_monitor_thread() {
    int sock;
    if ((sock = socket(AF_NETLINK, SOCK_RAW, NETLINK_ROUTE)) < 0) {
        std::cerr << "Failed to open netlink socket. Errno: " << std::strerror(errno) << std::endl;
        return;
    }

    struct sockaddr_nl addr;
    memset(&addr, 0, sizeof(addr));
    addr.nl_family = AF_NETLINK;
    addr.nl_groups = RTMGRP_IPV4_ROUTE;

    if (bind(sock, (struct sockaddr *) &addr, sizeof(addr)) == -1) {
        std::cerr << "Failed to bind netlink socket. Errno: " << std::strerror(errno) << std::endl;
        close(sock);
        return;
    }

    // Make sokcet non-blocking
    if (fcntl(sock, F_SETFL, fcntl(sock, F_GETFL, 0) | O_NONBLOCK) == -1) {
        std::cerr << "Failed to make netlink socket non-blocking. Errno: " << std::strerror(errno)
                  << std::endl;
        close(sock);
        return;
    }

    struct nlmsghdr *nlh;
    std::string buffer(8192, '\x00');
    nlh = (struct nlmsghdr *) &buffer[0];

    struct pollfd fds[2];

    // fds[0] is netlink socket
    fds[0].fd = sock;
    fds[0].events = POLLIN;

    // fds[1] is interrupt pipe
    fds[1].fd = Interrupt_pipe[0];
    fds[1].events = POLLIN;

    // Set poll() timeout
    int timeout = -1;

    int len;
    while (!stop_flag.load()) {
        int ret = poll(fds, 2, timeout);

        // Check state
        if (ret == -1) {
            std::cerr << "Poll error. Errno:" << std::strerror(errno) << std::endl;
            break;
        } else if (ret == 0)
            continue; // Timeout happened
        else {
            if (fds[0].revents & POLLERR ||
                fds[0].revents & POLLHUP ||
                fds[0].revents & POLLNVAL)
                break;

            // Process netlink socket
            if (fds[0].revents & POLLIN) {
                len = recv(sock, nlh, buffer.size(), 0);
                if (len <= 0) {
                    std::cerr << "Netlink socket receive error. Errno: " << std::strerror(errno)
                              << std::endl;
                    break;
                }
                while ((NLMSG_OK(nlh, len)) && (nlh->nlmsg_type != NLMSG_DONE)) {
                    if (nlh->nlmsg_type == RTM_NEWROUTE) {
                        // Check is it default route
                        struct rtattr *tb[RTA_MAX + 1];
                        struct rtmsg *r = (struct rtmsg *) NLMSG_DATA(nlh);
                        parse_rtattr(tb, RTA_MAX, RTM_RTA(r),
                                     nlh->nlmsg_len - NLMSG_LENGTH(sizeof(*r)));
                        if (!tb[RTA_DST] && !r->rtm_dst_len && tb[RTA_OIF]) {
                            std::cout << "Detected network changes. Changing profile..."
                                      << std::endl;

                            char iface_c_str[IF_NAMESIZE];
                            if_indextoname(*(int *) RTA_DATA(tb[RTA_OIF]), iface_c_str);
                            std::string iface = std::string(iface_c_str);

                            std::string wifi_ap = get_current_wifi_name(iface);

                            std::cout << "Netiface: " << iface;
                            if (!wifi_ap.empty())
                                std::cout << ", Wi-Fi point name: " << wifi_ap;
                            std::cout << std::endl;

                            std::string temp;
                            if (change_profile(iface, wifi_ap, &temp) == 0)
                                std::cout << "Current profile: " << temp << std::endl;
                            else
                                std::cerr << "Failed to change profile" << std::endl;
                        }
                    }
                    nlh = NLMSG_NEXT(nlh, len);
                }
            }

            fds[0].revents = 0;
            fds[1].revents = 0;
        }
    }

    close(sock);
}

std::string get_current_iface_name() {
    // "Connect" to IP from global Internet and getsockname()
    const std::string global_ip = "198.41.0.4"; // 'A' root server IP

    std::string res = "";

    int sock;
    if ((sock = socket(AF_INET, SOCK_DGRAM, 0)) < 0) {
        std::cerr << "Failed to open test socket. Errno: " << std::strerror(errno) << std::endl;
        return "";
    }
    // Add port and address
    struct sockaddr_in server_address;
    server_address.sin_family = AF_INET;
    server_address.sin_port = htons(80);
    inet_pton(AF_INET, global_ip.c_str(), &server_address.sin_addr);

    if (connect(sock, (struct sockaddr *) &server_address, sizeof(server_address)) < 0) {
        std::cerr << "Test socket can't \"connect\". Errno: " << std::strerror(errno) << std::endl;
        close(sock);
        return "";
    }

    struct sockaddr_in addr;
    struct ifaddrs *ifaddr;
    struct ifaddrs *ifa;
    socklen_t addr_len;

    addr_len = sizeof(addr);
    getsockname(sock, (struct sockaddr *) &addr, &addr_len);
    getifaddrs(&ifaddr);

    // look which interface contains the wanted IP.
    // When found, ifa->ifa_name contains the name of the interface (eth0, eth1, ppp0...)
    for (ifa = ifaddr; ifa != NULL; ifa = ifa->ifa_next) {
        if (ifa->ifa_addr) {
            if (AF_INET == ifa->ifa_addr->sa_family) {
                struct sockaddr_in *inaddr = (struct sockaddr_in *) ifa->ifa_addr;

                if (inaddr->sin_addr.s_addr == addr.sin_addr.s_addr) {
                    if (ifa->ifa_name) {
                        res = ifa->ifa_name;
                    }
                }
            }
        }
    }
    freeifaddrs(ifaddr);
    close(sock);

    if (res.empty())
        std::cerr << "Failed to find default network interface" << std::endl;
    return res;
}

std::string get_current_wifi_name_ioctl(std::string iface_name) {
    int sock;
    if ((sock = socket(AF_INET, SOCK_DGRAM, 0)) < 0) {
        std::cerr << "Failed to open socket. Errno: " << std::strerror(errno) << std::endl;
        return "";
    }

    std::string essid(IW_ESSID_MAX_SIZE, '\x00');
    struct iwreq wreq;
    strncpy(wreq.ifr_ifrn.ifrn_name, iface_name.c_str(), IFNAMSIZ);
    strncpy(wreq.ifr_name, iface_name.c_str(), iface_name.size());
    wreq.u.essid.pointer = (caddr_t *) &essid[0];
    wreq.u.data.length = IW_ESSID_MAX_SIZE;
    wreq.u.data.flags = 0;
    if (ioctl(sock, SIOCGIWESSID, &wreq) == -1) {
        std::cerr << "Get ESSID ioctl failed. Errno: " << std::strerror(errno) << std::endl;
        close(sock);
        return "";
    }

    close(sock);
    return std::string(essid.c_str());
}

// Based on NetworkManager/src/platform/wifi/wifi-utils-nl80211.c
static void find_ssid(uint8_t *ies, uint32_t ies_len, uint8_t **ssid, uint32_t *ssid_len) {
#define WLAN_EID_SSID 0
    *ssid = NULL;
    *ssid_len = 0;

    while (ies_len > 2 && ies[0] != WLAN_EID_SSID) {
        ies_len -= ies[1] + 2;
        ies += ies[1] + 2;
    }
    if (ies_len < 2)
        return;
    if (ies_len < (uint32_t) (2 + ies[1]))
        return;

    *ssid_len = ies[1];
    *ssid = ies + 2;
}

static int get_scan_callback(struct nl_msg *msg, void *arg) {
    struct nlattr *tb[NL80211_ATTR_MAX + 1];
    struct genlmsghdr *gnlh = (genlmsghdr *) nlmsg_data(nlmsg_hdr(msg));
    struct nlattr *bss[NL80211_BSS_MAX + 1];
    static struct nla_policy bss_policy[NL80211_BSS_MAX + 1];
    bss_policy[NL80211_BSS_TSF].type = NLA_U64;
    bss_policy[NL80211_BSS_FREQUENCY].type = NLA_U32;
    bss_policy[NL80211_BSS_BEACON_INTERVAL].type = NLA_U16;
    bss_policy[NL80211_BSS_CAPABILITY].type = NLA_U16;
    bss_policy[NL80211_BSS_SIGNAL_MBM].type = NLA_U32;
    bss_policy[NL80211_BSS_SIGNAL_UNSPEC].type = NLA_U8;
    bss_policy[NL80211_BSS_STATUS].type = NLA_U32;
    bss_policy[NL80211_BSS_SEEN_MS_AGO].type = NLA_U32;
    char mac_addr[18];

    nla_parse(tb,
              NL80211_ATTR_MAX,
              genlmsg_attrdata(gnlh, 0),
              genlmsg_attrlen(gnlh, 0),
              NULL);

    if (!tb[NL80211_ATTR_BSS]) {
        std::cerr << "NL80211_ATTR_BSS missing" << std::endl;
        return NL_SKIP;
    }

    if (nla_parse_nested(bss, NL80211_BSS_MAX, tb[NL80211_ATTR_BSS], bss_policy)) {
        std::cerr << "Failed to parse nested attributes" << std::endl;
        return NL_SKIP;
    }

    // Check is it associated AP
    if (bss[NL80211_BSS_STATUS] == NULL ||
        nla_get_u32(bss[NL80211_BSS_STATUS]) != NL80211_BSS_STATUS_ASSOCIATED)
        return NL_SKIP;

    if (!bss[NL80211_BSS_INFORMATION_ELEMENTS]) {
        std::cerr << "NL80211_BSS_INFORMATION_ELEMENTS missing" << std::endl;
        return NL_SKIP;
    }

    uint8_t *ssid;
    uint32_t ssid_len;

    find_ssid((uint8_t *) nla_data(bss[NL80211_BSS_INFORMATION_ELEMENTS]),
              nla_len(bss[NL80211_BSS_INFORMATION_ELEMENTS]),
              &ssid, &ssid_len);

    if (!ssid || !ssid_len) {
        std::cerr << "Failed to find SSID" << std::endl;
        return NL_SKIP;
    }

    (*(Wifi *) arg).ssid = std::string((const char *) ssid, ssid_len);

    return NL_SKIP;
}

static int finish_handler(struct nl_msg *msg, void *arg) {
    int *ret = (int *) arg;
    *ret = 0;
    return NL_SKIP;
}

static int init_nl80211(Netlink *nl, Wifi *w) {
    nl->socket = nl_socket_alloc();
    if (!nl->socket) {
        std::cerr << "Failed to open netlink socket" << std::endl;
        return -ENOMEM;
    }

    nl_socket_set_buffer_size(nl->socket, 8192, 8192);

    if (genl_connect(nl->socket)) {
        std::cerr << "Failed to connect to netlink socket" << std::endl;
        nl_close(nl->socket);
        nl_socket_free(nl->socket);
        return -ENOLINK;
    }

    nl->id = genl_ctrl_resolve(nl->socket, "nl80211");
    if (nl->id < 0) {
        std::cerr << "Nl80211 interface not found" << std::endl;
        nl_close(nl->socket);
        nl_socket_free(nl->socket);
        return -ENOENT;
    }

    nl->cb = nl_cb_alloc(NL_CB_DEFAULT);
    if (nl->cb == NULL) {
        std::cerr << "Failed to allocate netlink callback" << std::endl;
        nl_close(nl->socket);
        nl_socket_free(nl->socket);
        return -ENOMEM;
    }

    nl_cb_set(nl->cb, NL_CB_VALID, NL_CB_CUSTOM, get_scan_callback, w);
    nl_cb_set(nl->cb, NL_CB_FINISH, NL_CB_CUSTOM, finish_handler, &(nl->result));

    return 0;
}

std::string get_current_wifi_name_netlink(std::string iface_name) {
    Netlink nl;
    Wifi w;

    if (init_nl80211(&nl, &w) != 0) {
        std::cerr << "Error initializing netlink 802.11" << std::endl;
        return "";
    }

    nl.result = 1;

    // Get scan results
    struct nl_msg *msg = nlmsg_alloc();
    if (!msg) {
        std::cerr << "Failed to allocate netlink message" << std::endl;
        nl_cb_put(nl.cb);
        nl_close(nl.socket);
        nl_socket_free(nl.socket);
        return "";
    }

    genlmsg_put(msg,
                NL_AUTO_PORT,
                NL_AUTO_SEQ,
                nl.id,
                0,
                NLM_F_DUMP,
                NL80211_CMD_GET_SCAN,
                0);

    int ifindex = if_nametoindex(iface_name.c_str());
    if (ifindex == 0) {
        std::cerr << "if_nametoindex failed. Errno: " << std::strerror(errno) << std::endl;
        nl_cb_put(nl.cb);
        nl_close(nl.socket);
        nl_socket_free(nl.socket);
        nlmsg_free(msg);
        return "";
    }

    nla_put_u32(msg, NL80211_ATTR_IFINDEX, ifindex);
    nl_send_auto(nl.socket, msg);
    while (nl.result > 0) { nl_recvmsgs(nl.socket, nl.cb); }
    nlmsg_free(msg);

    return w.ssid;
}

std::string get_current_wifi_name(std::string iface_name) {
    std::string response;
    if ((response = get_current_wifi_name_ioctl(iface_name)).empty())
        response = get_current_wifi_name_netlink(iface_name);

    return response;
}