feat(net): Add nl80211 support (#1009)

This patch enables support for nl80211. In case the libnl-genl-3.0
library isn't found, it will fall back to Wext instead.
The library to use can also be manually set with the CMake option
WITH_LIBNL.

The Wireless-Extensions (WE or Wext) are deprecated and long replaced
by cfg80211.

Although Wext isn't used by WiFi drivers anymore, CFG80211_WEXT allows
old tools to communicate with modern drivers by providing a wrapper
API.

README.md

@@ -106,7 +106,7 @@ A compiler with C++14 support ([clang-3.4+](http://llvm.org/releases/download.ht
 - jsoncpp *required by `internal/i3`*
 - libmpdclient *required by `internal/mpd`*
 - libcurl *required by `internal/github`*
-- wireless_tools *required by `internal/network`*
+- libnl-genl or wireless_tools *required by `internal/network`*
 
 Find a more complete list on the [dedicated wiki page](https://github.com/jaagr/polybar/wiki/Compiling).
 

build.sh

@@ -38,21 +38,21 @@ function main
 
   msg "Setting build options"
 
-  read -r -p "$(msg "Use GCC even if Clang is installed -------------------------------- [y/N]: ")" -n 1 p && echo
+  read -r -p "$(msg "Use GCC even if Clang is installed ----------------------------- [y/N]: ")" -n 1 p && echo
   [[ "${p^^}" != "Y" ]] && try_to_use_clang="ON"
-  read -r -p "$(msg "Include support for \"internal/i3\" (requires i3) ------------------- [y/N]: ")" -n 1 p && echo
+  read -r -p "$(msg "Include support for \"internal/i3\" (requires i3) ---------------- [y/N]: ")" -n 1 p && echo
   [[ "${p^^}" != "Y" ]] && enable_i3="OFF"
-  read -r -p "$(msg "Include support for \"internal/alsa\" (requires alsalib) ------------ [y/N]: ")" -n 1 p && echo
+  read -r -p "$(msg "Include support for \"internal/alsa\" (requires alsalib) --------- [y/N]: ")" -n 1 p && echo
   [[ "${p^^}" != "Y" ]] && enable_alsa="OFF"
-  read -r -p "$(msg "Include support for \"internal/pulseaudio\" (requires libpulse) ----- [y/N]: ")" -n 1 p && echo
+  read -r -p "$(msg "Include support for \"internal/pulseaudio\" (requires libpulse) -- [y/N]: ")" -n 1 p && echo
   [[ "${p^^}" != "Y" ]] && enable_pulseaudio="OFF"
-  read -r -p "$(msg "Include support for \"internal/network\" (requires wireless_tools) -- [y/N]: ")" -n 1 p && echo
+  read -r -p "$(msg "Include support for \"internal/network\" (requires libnl/libiw) -- [y/N]: ")" -n 1 p && echo
   [[ "${p^^}" != "Y" ]] && enable_network="OFF"
-  read -r -p "$(msg "Include support for \"internal/mpd\" (requires libmpdclient) -------- [y/N]: ")" -n 1 p && echo
+  read -r -p "$(msg "Include support for \"internal/mpd\" (requires libmpdclient) ----- [y/N]: ")" -n 1 p && echo
   [[ "${p^^}" != "Y" ]] && enable_mpd="OFF"
-  read -r -p "$(msg "Include support for \"internal/github\" (requires libcurl) ---------- [y/N]: ")" -n 1 p && echo
+  read -r -p "$(msg "Include support for \"internal/github\" (requires libcurl) ------- [y/N]: ")" -n 1 p && echo
   [[ "${p^^}" != "Y" ]] && enable_curl="OFF"
-  read -r -p "$(msg "Build \"polybar-msg\" used to send ipc messages --------------------- [y/N]: ")" -n 1 p && echo
+  read -r -p "$(msg "Build \"polybar-msg\" used to send ipc messages ------------------ [y/N]: ")" -n 1 p && echo
   [[ "${p^^}" != "Y" ]] && build_ipc_msg="OFF"
 
   local cxx="c++"

cmake/02-opts.cmake

@@ -6,7 +6,12 @@ checklib(ENABLE_ALSA "pkg-config" alsa)
 checklib(ENABLE_CURL "pkg-config" libcurl)
 checklib(ENABLE_I3 "binary" i3)
 checklib(ENABLE_MPD "pkg-config" libmpdclient)
-checklib(ENABLE_NETWORK "cmake" Libiw)
+checklib(WITH_LIBNL "pkg-config" libnl-genl-3.0)
+if(WITH_LIBNL)
+  checklib(ENABLE_NETWORK "pkg-config" libnl-genl-3.0)
+else()
+  checklib(ENABLE_NETWORK "cmake" Libiw)
+endif()
 checklib(ENABLE_PULSEAUDIO "pkg-config" libpulse)
 checklib(ENABLE_PULSEAUDIO "binary" pulseaudio)
 checklib(WITH_XKB "pkg-config" xcb-xkb)
@@ -28,6 +33,7 @@ option(ENABLE_ALSA "Enable alsa support" ON)
 option(ENABLE_CURL "Enable curl support" ON)
 option(ENABLE_I3 "Enable i3 support" ON)
 option(ENABLE_MPD "Enable mpd support" ON)
+option(WITH_LIBNL "Use netlink interface for wireless" ON)
 option(ENABLE_NETWORK "Enable network support" ON)
 option(ENABLE_XKEYBOARD "Enable xkeyboard support" ON)
 option(ENABLE_PULSEAUDIO "Enable PulseAudio support" ON)

cmake/03-libs.cmake

@@ -10,7 +10,11 @@ querylib(TRUE "pkg-config" cairo-fc libs dirs)
 querylib(ENABLE_ALSA "pkg-config" alsa libs dirs)
 querylib(ENABLE_CURL "pkg-config" libcurl libs dirs)
 querylib(ENABLE_MPD "pkg-config" libmpdclient libs dirs)
-querylib(ENABLE_NETWORK "cmake" Libiw libs dirs)
+if(WITH_LIBNL)
+  querylib(ENABLE_NETWORK "pkg-config" libnl-genl-3.0 libs dirs)
+else()
+  querylib(ENABLE_NETWORK "cmake" Libiw libs dirs)
+endif()
 querylib(ENABLE_PULSEAUDIO "pkg-config" libpulse libs dirs)
 
 querylib(WITH_XCOMPOSITE "pkg-config" xcb-composite libs dirs)

include/adapters/net.hpp

@@ -5,7 +5,6 @@
 
 #include <arpa/inet.h>
 #include <ifaddrs.h>
-#include <iwlib.h>
 
 #ifdef inline
 #undef inline
@@ -17,6 +16,15 @@
 #include "components/logger.hpp"
 #include "utils/math.hpp"
 
+#if WITH_LIBNL
+#include <net/if.h>
+
+struct nl_msg;
+struct nlattr;
+#else
+#include <iwlib.h>
+#endif
+
 POLYBAR_NS
 
 class file_descriptor;
@@ -103,6 +111,39 @@ namespace net {
   };
 
   // }}}
+
+#if WITH_LIBNL
+  // class : wireless_network {{{
+
+  class wireless_network : public network {
+   public:
+    wireless_network(string interface) : network(interface), m_ifid(if_nametoindex(interface.c_str())){};
+
+    bool query(bool accumulate = false) override;
+    bool connected() const override;
+    string essid() const;
+    int signal() const;
+    int quality() const;
+
+   protected:
+    static int scan_cb(struct nl_msg* msg, void* instance);
+
+    bool associated_or_joined(struct nlattr** bss);
+    void parse_essid(struct nlattr** bss);
+    void parse_frequency(struct nlattr** bss);
+    void parse_quality(struct nlattr** bss);
+    void parse_signal(struct nlattr** bss);
+
+   private:
+    unsigned int m_ifid{};
+    string m_essid{};
+    int m_frequency{};
+    quality_range m_signalstrength{};
+    quality_range m_linkquality{};
+  };
+
+  // }}}
+#else
   // class : wireless_network {{{
 
   class wireless_network : public network {
@@ -128,9 +169,10 @@ namespace net {
   };
 
   // }}}
+#endif
 
   using wireless_t = unique_ptr<wireless_network>;
   using wired_t = unique_ptr<wired_network>;
-}
+}  // namespace net
 
 POLYBAR_NS_END

include/settings.hpp.cmake

@@ -20,6 +20,7 @@
 #cmakedefine01 ENABLE_ALSA
 #cmakedefine01 ENABLE_MPD
 #cmakedefine01 ENABLE_NETWORK
+#cmakedefine01 WITH_LIBNL
 #cmakedefine01 ENABLE_I3
 #cmakedefine01 ENABLE_CURL
 #cmakedefine01 ENABLE_PULSEAUDIO

src/CMakeLists.txt

@@ -23,6 +23,13 @@ endif()
 if(NOT ENABLE_NETWORK)
   list(REMOVE_ITEM files modules/network.cpp)
   list(REMOVE_ITEM files adapters/net.cpp)
+  list(REMOVE_ITEM files adapters/net_iw.cpp)
+  list(REMOVE_ITEM files adapters/net_nl.cpp)
+endif()
+if(WITH_LIBNL)
+  list(REMOVE_ITEM files adapters/net_iw.cpp)
+else()
+  list(REMOVE_ITEM files adapters/net_nl.cpp)
 endif()
 if(NOT ENABLE_I3)
   list(REMOVE_ITEM files modules/i3.cpp)

src/adapters/net.cpp

@@ -1,21 +1,16 @@
 #include "adapters/net.hpp"
 
-#include <cerrno>
-#include <cstdio>
-#include <fstream>
 #include <iomanip>
-#include <sstream>
-#include <utility>
 
 #include <arpa/inet.h>
 #include <linux/ethtool.h>
 #include <linux/if_link.h>
 #include <linux/sockios.h>
 #include <net/if.h>
+#include <netdb.h>
 #include <netinet/in.h>
+#include <sys/ioctl.h>
 #include <sys/socket.h>
-#include <climits>
-#include <csignal>
 
 #ifdef inline
 #undef inline
@@ -306,133 +301,7 @@ namespace net {
   }
 
   // }}}
-  // class : wireless_network {{{
 
-  /**
+}  // namespace net
-   * Query the wireless device for information
-   * about the current connection
-   */
-  bool wireless_network::query(bool accumulate) {
-    if (!network::query(accumulate)) {
-      return false;
-    }
-
-    auto socket_fd = file_util::make_file_descriptor(iw_sockets_open());
-    if (!*socket_fd) {
-      return false;
-    }
-
-    struct iwreq req {};
-
-    if (iw_get_ext(*socket_fd, m_interface.c_str(), SIOCGIWMODE, &req) == -1) {
-      return false;
-    }
-
-    // Ignore interfaces in ad-hoc mode
-    if (req.u.mode == IW_MODE_ADHOC) {
-      return false;
-    }
-
-    query_essid(*socket_fd);
-    query_quality(*socket_fd);
-
-    return true;
-  }
-
-  /**
-   * Check current connection state
-   */
-  bool wireless_network::connected() const {
-    if (!network::test_interface()) {
-      return false;
-    }
-    return !m_essid.empty();
-  }
-
-  /**
-   * ESSID reported by last query
-   */
-  string wireless_network::essid() const {
-    return m_essid;
-  }
-
-  /**
-   * Signal strength percentage reported by last query
-   */
-  int wireless_network::signal() const {
-    return m_signalstrength.percentage();
-  }
-
-  /**
-   * Link quality percentage reported by last query
-   */
-  int wireless_network::quality() const {
-    return m_linkquality.percentage();
-  }
-
-  /**
-   * Query for ESSID
-   */
-  void wireless_network::query_essid(const int& socket_fd) {
-    char essid[IW_ESSID_MAX_SIZE + 1];
-
-    struct iwreq req {};
-    req.u.essid.pointer = &essid;
-    req.u.essid.length = sizeof(essid);
-    req.u.essid.flags = 0;
-
-    if (iw_get_ext(socket_fd, m_interface.c_str(), SIOCGIWESSID, &req) != -1) {
-      m_essid = string{essid};
-    } else {
-      m_essid.clear();
-    }
-  }
-
-  /**
-   * Query for device driver quality values
-   */
-  void wireless_network::query_quality(const int& socket_fd) {
-    iwrange range{};
-    iwstats stats{};
-
-    // Fill range
-    if (iw_get_range_info(socket_fd, m_interface.c_str(), &range) == -1) {
-      return;
-    }
-    // Fill stats
-    if (iw_get_stats(socket_fd, m_interface.c_str(), &stats, &range, 1) == -1) {
-      return;
-    }
-
-    // Check if the driver supplies the quality value
-    if (stats.qual.updated & IW_QUAL_QUAL_INVALID) {
-      return;
-    }
-    // Check if the driver supplies the quality level value
-    if (stats.qual.updated & IW_QUAL_LEVEL_INVALID) {
-      return;
-    }
-
-    // Check if the link quality has been uodated
-    if (stats.qual.updated & IW_QUAL_QUAL_UPDATED) {
-      m_linkquality.val = stats.qual.qual;
-      m_linkquality.max = range.max_qual.qual;
-    }
-
-    // Check if the signal strength has been uodated
-    if (stats.qual.updated & IW_QUAL_LEVEL_UPDATED) {
-      m_signalstrength.val = stats.qual.level;
-      m_signalstrength.max = range.max_qual.level;
-
-      // Check if the values are defined in dBm
-      if (stats.qual.level > range.max_qual.level) {
-        m_signalstrength.val -= 0x100;
-        m_signalstrength.max = (stats.qual.level - range.max_qual.level) - 0x100;
-      }
-    }
-  }
-
-  // }}}
-}
 
 POLYBAR_NS_END

src/adapters/net_iw.cpp

@@ -0,0 +1,137 @@
+#include "adapters/net.hpp"
+
+#include "utils/file.hpp"
+
+POLYBAR_NS
+
+namespace net {
+  // class : wireless_network {{{
+
+  /**
+   * Query the wireless device for information
+   * about the current connection
+   */
+  bool wireless_network::query(bool accumulate) {
+    if (!network::query(accumulate)) {
+      return false;
+    }
+
+    auto socket_fd = file_util::make_file_descriptor(iw_sockets_open());
+    if (!*socket_fd) {
+      return false;
+    }
+
+    struct iwreq req {};
+
+    if (iw_get_ext(*socket_fd, m_interface.c_str(), SIOCGIWMODE, &req) == -1) {
+      return false;
+    }
+
+    // Ignore interfaces in ad-hoc mode
+    if (req.u.mode == IW_MODE_ADHOC) {
+      return false;
+    }
+
+    query_essid(*socket_fd);
+    query_quality(*socket_fd);
+
+    return true;
+  }
+
+  /**
+   * Check current connection state
+   */
+  bool wireless_network::connected() const {
+    if (!network::test_interface()) {
+      return false;
+    }
+    return !m_essid.empty();
+  }
+
+  /**
+   * ESSID reported by last query
+   */
+  string wireless_network::essid() const {
+    return m_essid;
+  }
+
+  /**
+   * Signal strength percentage reported by last query
+   */
+  int wireless_network::signal() const {
+    return m_signalstrength.percentage();
+  }
+
+  /**
+   * Link quality percentage reported by last query
+   */
+  int wireless_network::quality() const {
+    return m_linkquality.percentage();
+  }
+
+  /**
+   * Query for ESSID
+   */
+  void wireless_network::query_essid(const int& socket_fd) {
+    char essid[IW_ESSID_MAX_SIZE + 1];
+
+    struct iwreq req {};
+    req.u.essid.pointer = &essid;
+    req.u.essid.length = sizeof(essid);
+    req.u.essid.flags = 0;
+
+    if (iw_get_ext(socket_fd, m_interface.c_str(), SIOCGIWESSID, &req) != -1) {
+      m_essid = string{essid};
+    } else {
+      m_essid.clear();
+    }
+  }
+
+  /**
+   * Query for device driver quality values
+   */
+  void wireless_network::query_quality(const int& socket_fd) {
+    iwrange range{};
+    iwstats stats{};
+
+    // Fill range
+    if (iw_get_range_info(socket_fd, m_interface.c_str(), &range) == -1) {
+      return;
+    }
+    // Fill stats
+    if (iw_get_stats(socket_fd, m_interface.c_str(), &stats, &range, 1) == -1) {
+      return;
+    }
+
+    // Check if the driver supplies the quality value
+    if (stats.qual.updated & IW_QUAL_QUAL_INVALID) {
+      return;
+    }
+    // Check if the driver supplies the quality level value
+    if (stats.qual.updated & IW_QUAL_LEVEL_INVALID) {
+      return;
+    }
+
+    // Check if the link quality has been uodated
+    if (stats.qual.updated & IW_QUAL_QUAL_UPDATED) {
+      m_linkquality.val = stats.qual.qual;
+      m_linkquality.max = range.max_qual.qual;
+    }
+
+    // Check if the signal strength has been uodated
+    if (stats.qual.updated & IW_QUAL_LEVEL_UPDATED) {
+      m_signalstrength.val = stats.qual.level;
+      m_signalstrength.max = range.max_qual.level;
+
+      // Check if the values are defined in dBm
+      if (stats.qual.level > range.max_qual.level) {
+        m_signalstrength.val -= 0x100;
+        m_signalstrength.max = (stats.qual.level - range.max_qual.level) - 0x100;
+      }
+    }
+  }
+
+  // }}}
+}  // namespace net
+
+POLYBAR_NS_END

src/adapters/net_nl.cpp

@@ -0,0 +1,233 @@
+#include "adapters/net.hpp"
+
+#include <linux/nl80211.h>
+#include <netlink/genl/ctrl.h>
+#include <netlink/genl/genl.h>
+
+#include "utils/file.hpp"
+
+POLYBAR_NS
+
+namespace net {
+  // class : wireless_network {{{
+
+  /**
+   * Query the wireless device for information
+   * about the current connection
+   */
+  bool wireless_network::query(bool accumulate) {
+    if (!network::query(accumulate)) {
+      return false;
+    }
+
+    struct nl_sock* sk = nl_socket_alloc();
+    if (sk == nullptr) {
+      return false;
+    }
+
+    if (genl_connect(sk) < 0) {
+      return false;
+    }
+
+    int driver_id = genl_ctrl_resolve(sk, "nl80211");
+    if (driver_id < 0) {
+      nl_socket_free(sk);
+      return false;
+    }
+
+    if (nl_socket_modify_cb(sk, NL_CB_VALID, NL_CB_CUSTOM, scan_cb, this) != 0) {
+      nl_socket_free(sk);
+      return false;
+    }
+
+    struct nl_msg* msg = nlmsg_alloc();
+    if (msg == nullptr) {
+      nl_socket_free(sk);
+      return false;
+    }
+
+    if ((genlmsg_put(msg, NL_AUTO_PORT, NL_AUTO_SEQ, driver_id, 0, NLM_F_DUMP, NL80211_CMD_GET_SCAN, 0) == nullptr) ||
+        nla_put_u32(msg, NL80211_ATTR_IFINDEX, m_ifid) < 0) {
+      nlmsg_free(msg);
+      nl_socket_free(sk);
+      return false;
+    }
+
+    // nl_send_sync always frees msg
+    if (nl_send_sync(sk, msg) < 0) {
+      nl_socket_free(sk);
+      return false;
+    }
+
+    nl_socket_free(sk);
+
+    return true;
+  }
+
+  /**
+   * Check current connection state
+   */
+  bool wireless_network::connected() const {
+    if (!network::test_interface()) {
+      return false;
+    }
+    return !m_essid.empty();
+  }
+
+  /**
+   * ESSID reported by last query
+   */
+  string wireless_network::essid() const {
+    return m_essid;
+  }
+
+  /**
+   * Signal strength percentage reported by last query
+   */
+  int wireless_network::signal() const {
+    return m_signalstrength.percentage();
+  }
+
+  /**
+   * Link quality percentage reported by last query
+   */
+  int wireless_network::quality() const {
+    return m_linkquality.percentage();
+  }
+
+  /**
+   * Callback to parse scan results
+   */
+  int wireless_network::scan_cb(struct nl_msg* msg, void* instance) {
+    auto wn = static_cast<wireless_network*>(instance);
+    auto gnlh = static_cast<genlmsghdr*>(nlmsg_data(nlmsg_hdr(msg)));
+    struct nlattr* tb[NL80211_ATTR_MAX + 1];
+    struct nlattr* bss[NL80211_BSS_MAX + 1];
+
+    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_BSSID].type = NLA_UNSPEC;
+    bss_policy[NL80211_BSS_BEACON_INTERVAL].type = NLA_U16;
+    bss_policy[NL80211_BSS_CAPABILITY].type = NLA_U16;
+    bss_policy[NL80211_BSS_INFORMATION_ELEMENTS].type = NLA_UNSPEC;
+    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;
+
+    if (nla_parse(tb, NL80211_ATTR_MAX, genlmsg_attrdata(gnlh, 0), genlmsg_attrlen(gnlh, 0), nullptr) < 0) {
+      return NL_SKIP;
+    }
+
+    if (tb[NL80211_ATTR_BSS] == nullptr) {
+      return NL_SKIP;
+    }
+
+    if (nla_parse_nested(bss, NL80211_BSS_MAX, tb[NL80211_ATTR_BSS], bss_policy) != 0) {
+      return NL_SKIP;
+    }
+
+    if (!wn->associated_or_joined(bss)) {
+      return NL_SKIP;
+    }
+
+    wn->parse_essid(bss);
+    wn->parse_frequency(bss);
+    wn->parse_signal(bss);
+    wn->parse_quality(bss);
+
+    return NL_SKIP;
+  }
+
+  /**
+   * Check for a connection to a AP
+   */
+  bool wireless_network::associated_or_joined(struct nlattr** bss) {
+    if (bss[NL80211_BSS_STATUS] == nullptr) {
+      return false;
+    }
+
+    auto status = nla_get_u32(bss[NL80211_BSS_STATUS]);
+
+    switch (status) {
+      case NL80211_BSS_STATUS_ASSOCIATED:
+      case NL80211_BSS_STATUS_IBSS_JOINED:
+      case NL80211_BSS_STATUS_AUTHENTICATED:
+        return true;
+      default:
+        return false;
+    }
+  }
+
+  /**
+   * Set the ESSID
+   */
+  void wireless_network::parse_essid(struct nlattr** bss) {
+    m_essid.clear();
+
+    if (bss[NL80211_BSS_INFORMATION_ELEMENTS] != nullptr) {
+      // Information Element ID from ieee80211.h
+      #define WLAN_EID_SSID 0
+
+      auto ies = static_cast<char*>(nla_data(bss[NL80211_BSS_INFORMATION_ELEMENTS]));
+      auto ies_len = nla_len(bss[NL80211_BSS_INFORMATION_ELEMENTS]);
+      const auto hdr_len = 2;
+
+      while (ies_len > hdr_len && ies[0] != WLAN_EID_SSID) {
+        ies_len -= ies[1] + hdr_len;
+        ies += ies[1] + hdr_len;
+      }
+
+      if (ies_len > hdr_len && ies_len > ies[1] + hdr_len) {
+        auto essid_begin = ies + hdr_len;
+        auto essid_end = essid_begin + ies[1];
+
+        // Only use printable characters of the current locale
+        std::copy_if(essid_begin, essid_end, std::back_inserter(m_essid),
+            [](char c) { return isprint(static_cast<unsigned char>(c)); });
+      }
+    }
+  }
+
+  /**
+   * Set frequency
+   */
+  void wireless_network::parse_frequency(struct nlattr** bss) {
+    if (bss[NL80211_BSS_FREQUENCY] != nullptr) {
+      // in MHz
+      m_frequency = static_cast<int>(nla_get_u32(bss[NL80211_BSS_FREQUENCY]));
+    }
+  }
+
+  /**
+   * Set device driver quality values
+   */
+  void wireless_network::parse_quality(struct nlattr** bss) {
+    if (bss[NL80211_BSS_SIGNAL_UNSPEC] != nullptr) {
+      // Signal strength in unspecified units, scaled to 0..100 (u8)
+      m_linkquality.val = nla_get_u8(bss[NL80211_BSS_SIGNAL_UNSPEC]);
+      m_linkquality.max = 100;
+    }
+  }
+
+  /**
+   * Set the signalstrength
+   */
+  void wireless_network::parse_signal(struct nlattr** bss) {
+    if (bss[NL80211_BSS_SIGNAL_MBM] != nullptr) {
+      // signalstrength in dBm
+      int signalstrength = static_cast<int>(nla_get_u32(bss[NL80211_BSS_SIGNAL_MBM])) / 100;
+
+      // WiFi-hardware usually operates in the range -90 to -20dBm.
+      const int hardware_max = -20;
+      const int hardware_min = -90;
+      signalstrength = std::max(hardware_min, std::min(signalstrength, hardware_max));
+
+      // Shift for positive values
+      m_signalstrength.val = signalstrength - hardware_min;
+      m_signalstrength.max = hardware_max - hardware_min;
+    }
+  }
+}  // namespace net
+
+POLYBAR_NS_END