Add DiscoveryNetworkMonitor implementation

chrome/browser/net/discovery_network_list_wifi_linux.cc

+// Copyright (c) 2017 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "chrome/browser/net/discovery_network_list_wifi.h"
+
+#include <string.h>
+#include <sys/ioctl.h>
+#include <sys/socket.h>
+#include <sys/types.h>
+
+#include <linux/wireless.h>
+
+#include "base/logging.h"
+
+bool MaybeGetWifiSSID(const char* if_name, std::string* ssid) {

[imcheng, 2017/03/14 22:45:35]

Can this be reused?
https://cs.chromium.org/chromium/src/net/base/network_interfaces_linux.cc?typ...

[btolsch, 2017/04/03 10:16:35]

Done.  Should I move it out of the internal namespace though?

+  DCHECK(if_name);
+
+  struct iwreq iwreq;
+  memset(&iwreq, 0, sizeof(iwreq));
+
+  int sock = socket(AF_INET, SOCK_DGRAM, 0);
+  if (sock == -1) {
+    return false;
+  }
+
+  strncpy(iwreq.ifr_name, if_name, IFNAMSIZ);
+  char id[IW_ESSID_MAX_SIZE];
+  iwreq.u.essid.pointer = id;
+  iwreq.u.essid.length = IW_ESSID_MAX_SIZE;
+
+  if (ioctl(sock, SIOCGIWESSID, &iwreq) == -1) {
+    return false;
+  }
+  ssid->assign(std::string(id, iwreq.u.essid.length));
+  return true;
+}