Add DiscoveryNetworkMonitor implementation

chrome/browser/net/discovery_network_list_posix.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.h"
+
+#include <ifaddrs.h>
+#include <linux/if_packet.h>
+#include <net/if.h>
+#include <netinet/in.h>
+#include <string.h>
+#include <sys/ioctl.h>
+#include <sys/socket.h>
+#include <sys/types.h>
+
+#include "base/logging.h"
+#include "chrome/browser/net/discovery_network_list_wifi.h"
+
+namespace {
+
+char ConvertNumberToAsciiHex(unsigned char value) {
+  if (value < 10) {
+    return '0' + value;
+  }
+  return 'A' + (value - 10);
+}
+
+std::string GetMacAddressAsString(unsigned char* addr, unsigned char length) {
+  std::string address_string(length * 4 - 2, ':');
+
+  for (unsigned char i = 0; i < length; ++i) {
+    address_string[i * 4 + 0] = ConvertNumberToAsciiHex(addr[i] >> 4);
+    address_string[i * 4 + 1] = ConvertNumberToAsciiHex(addr[i] & 0xf);
+  }
+
+  return address_string;
+}
+
+void GetDiscoveryNetworkIdListImpl(
+    struct ifaddrs* if_list,

[mark a. foltz, 2017/03/18 19:58:21]

const

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

Done.

+    std::vector<DiscoveryNetworkId>* network_ids) {
+  std::string ssid;
+  for (; if_list != NULL; if_list = if_list->ifa_next) {

[mark a. foltz, 2017/03/18 19:58:21]

IF these are guaranteed to be returned in the same order, then we may not have
to worry about sorting the id components by name.

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

Acknowledged.  I don't know whether that's guaranteed.

+    struct sockaddr* addr = if_list->ifa_addr;

[mark a. foltz, 2017/03/18 19:58:21]

const

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

Done.

+    std::string name(if_list->ifa_name);
+    if (name.size() == 0 || addr->sa_family != AF_PACKET) {
+      continue;
+    }
+
+    if (MaybeGetWifiSSID(name.data(), &ssid)) {

[mark a. foltz, 2017/03/18 19:58:21]

Is there any way to further filter on the interface type before trying to get
its WiFi address?

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

We can also check the hardware address to see if it's ethernet.  Done.

+      network_ids->push_back({name, ssid});
+      continue;
+    }
+
+    struct sockaddr_ll* ll_addr = reinterpret_cast<struct sockaddr_ll*>(addr);

[mark a. foltz, 2017/03/18 19:58:21]

const

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

Done.

+    if (ll_addr->sll_halen == 0) {
+      continue;
+    }
+
+    network_ids->push_back(
+        {name, GetMacAddressAsString(ll_addr->sll_addr, ll_addr->sll_halen)});

[imcheng, 2017/03/14 22:45:34]

Can this be done with a combination of base::ToLowerASCII and base::HexEncode?
See example:
https://cs.chromium.org/chromium/src/chrome/browser/extensions/api/music_mana...

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

Done.

+  }
+}
+
+}  // namespace
+
+std::vector<DiscoveryNetworkId> GetDiscoveryNetworkIdList() {
+  std::vector<DiscoveryNetworkId> network_ids;
+
+  struct ifaddrs* if_list;
+  if (getifaddrs(&if_list)) {

[mark a. foltz, 2017/03/18 19:58:21]

If non-zero, DVLOG(2) the result (possibly using net_error_list to translate).

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

Done.

+    return network_ids;
+  }
+
+  GetDiscoveryNetworkIdListImpl(if_list, &network_ids);
+
+  freeifaddrs(if_list);
+
+  return network_ids;
+}