Add DiscoveryNetworkMonitor implementation

chrome/browser/media/router/discovery/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/media/router/discovery/discovery_network_list.h"
+
+#include <ifaddrs.h>
+#include <net/if.h>
+#include <net/if_arp.h>
+#include <netinet/in.h>
+#include <netpacket/packet.h>
+#include <sys/socket.h>
+#include <sys/types.h>
+
+#include "base/logging.h"
+#include "base/strings/string_number_conversions.h"
+#include "chrome/browser/media/router/discovery/discovery_network_list_wifi.h"
+#include "net/base/net_errors.h"
+
+namespace {
+
+void GetDiscoveryNetworkIdListImpl(
+    const struct ifaddrs* if_list,
+    std::vector<DiscoveryNetworkId>* network_ids) {
+  std::string ssid;
+  for (; if_list != NULL; if_list = if_list->ifa_next) {
+    const struct sockaddr* addr = if_list->ifa_addr;
+    std::string name(if_list->ifa_name);
+    if (name.size() == 0 || addr->sa_family != AF_PACKET) {

[mark a. foltz, 2017/05/04 23:16:39]

As a future improvement, we could interrogate the interface to see if it
supports multicast (ifa_flags contains IFF_MULTICAST) and use this API to return
a list of addresses to use for local discovery.  However we'd have to plumb that
down into the implementations of DIAL and mDNS.

No changes requested for now :)

[btolsch, 2017/05/23 08:55:02]

Acknowledged.

+      continue;
+    }
+
+    // |addr| will always be sockaddr_ll when |sa_family| == AF_PACKET.
+    const struct sockaddr_ll* ll_addr =
+        reinterpret_cast<const struct sockaddr_ll*>(addr);
+    if (ll_addr->sll_hatype != ARPHRD_ETHER) {

[mark a. foltz, 2017/05/04 23:16:39]

It would be interesting to see if we could detect WiFi vs. wired ethernet from
|if_list|, versus trying to extract SSID for all interfaces.

[btolsch, 2017/05/23 08:55:02]

AFAIK, another ioctl is required either way.  We could do an SIOCGIWNAME to
check for the existence of the wireless extension on the interface, but I think
we might as well just do SIOCGIWESSID (network name) in that case.

+      continue;
+    }
+
+    if (MaybeGetWifiSSID(name.data(), &ssid)) {

[mark a. foltz, 2017/05/04 23:16:38]

Just pass |name|.

[btolsch, 2017/05/23 08:55:02]

Done.

+      network_ids->push_back({name, ssid});
+      continue;
+    }
+
+    if (ll_addr->sll_halen == 0) {
+      continue;
+    }
+
+    network_ids->push_back(
+        {name, base::HexEncode(ll_addr->sll_addr, ll_addr->sll_halen)});
+  }
+}
+
+}  // namespace
+
+std::vector<DiscoveryNetworkId> GetDiscoveryNetworkIdList() {
+  std::vector<DiscoveryNetworkId> network_ids;
+
+  struct ifaddrs* if_list;
+  if (getifaddrs(&if_list)) {
+    DVLOG(2) << "getifaddrs() error: " << net::ErrorToString(errno);
+    return network_ids;
+  }
+
+  GetDiscoveryNetworkIdListImpl(if_list, &network_ids);
+  freeifaddrs(if_list);
+  return network_ids;
+}