os: expose broadcast address in os.networkInterfaces()

Not using the correct broadcast address in applications can cause
disasterous results. Rather than letting the programmer guess at
the broadcast address and try to derive it correctly, allow him to
query the system instead for the correctly configured state.

Fixes: #23437
Depends-on: libuv/libuv#2033

Author: pprindeville

doc/api/os.md

@@ -259,6 +259,8 @@ The properties available on the assigned network address object include:
 
 * `address` {string} The assigned IPv4 or IPv6 address
 * `netmask` {string} The IPv4 or IPv6 network mask
+* `broadcast` {string} The IPv4 or IPv6 broadcast address (not available
+  on all interface types)
 * `family` {string} Either `IPv4` or `IPv6`
 * `mac` {string} The MAC address of the network interface
 * `internal` {boolean} `true` if the network interface is a loopback or
@@ -294,6 +296,7 @@ The properties available on the assigned network address object include:
     {
       address: '192.168.1.108',
       netmask: '255.255.255.0',
+      broadcast: '192.168.1.255',
       family: 'IPv4',
       mac: '01:02:03:0a:0b:0c',
       internal: false,

src/env.h

@@ -127,6 +127,7 @@ struct PackageConfig {
   V(args_string, "args")                                                      \
   V(async, "async")                                                           \
   V(async_ids_stack_string, "async_ids_stack")                                \
+  V(broadcast_string, "broadcast")                                            \
   V(buffer_string, "buffer")                                                  \
   V(bytes_string, "bytes")                                                    \
   V(bytes_parsed_string, "bytesParsed")                                       \

src/node_os.cc

@@ -237,6 +237,7 @@ static void GetInterfaceAddresses(const FunctionCallbackInfo<Value>& args) {
   int count, i;
   char ip[INET6_ADDRSTRLEN];
   char netmask[INET6_ADDRSTRLEN];
+  char broadcast[INET6_ADDRSTRLEN];
   char mac[18];
   Local<Object> ret, o;
   Local<String> name, family;
@@ -296,11 +297,24 @@ static void GetInterfaceAddresses(const FunctionCallbackInfo<Value>& args) {
       family = env->unknown_string();
     }
 
+    if (interfaces[i].broadcast.broadcast4.sin_family == AF_INET) {
+      uv_ip4_name(&interfaces[i].broadcast.broadcast4, broadcast,
+                   sizeof(broadcast));
+    } else if (interfaces[i].broadcast.broadcast4.sin_family == AF_INET6) {
+      uv_ip6_name(&interfaces[i].broadcast.broadcast6, broadcast,
+                  sizeof(broadcast));
+    } else {
+      broadcast[0] = '\0';
+    }
+
     o = Object::New(env->isolate());
     o->Set(env->address_string(), OneByteString(env->isolate(), ip));
     o->Set(env->netmask_string(), OneByteString(env->isolate(), netmask));
     o->Set(env->family_string(), family);
     o->Set(env->mac_string(), FIXED_ONE_BYTE_STRING(env->isolate(), mac));
+    if (broadcast[0]) {
+      o->Set(env->broadcast_string(), OneByteString(env->isolate(), broadcast));
+    }
 
     if (interfaces[i].address.address4.sin_family == AF_INET6) {
       uint32_t scopeid = interfaces[i].address.address6.sin6_scope_id;
@@ -450,6 +464,11 @@ void Initialize(Local<Object> target,
                 Local<Value> unused,
                 Local<Context> context) {
   Environment* env = Environment::GetCurrent(context);
+  const struct sockaddr_in6 allhosts_in6 = {
+    AF_INET6, 0, 0, IN6ADDR_ALLHOSTS_GROUP, 0,
+  };
+  static char allhosts_str[INET6_ADDRSTRLEN];
+
   env->SetMethod(target, "getHostname", GetHostname);
   env->SetMethod(target, "getLoadAvg", GetLoadAvg);
   env->SetMethod(target, "getUptime", GetUptime);
@@ -465,6 +484,10 @@ void Initialize(Local<Object> target,
   env->SetMethod(target, "getPriority", GetPriority);
   target->Set(FIXED_ONE_BYTE_STRING(env->isolate(), "isBigEndian"),
               Boolean::New(env->isolate(), IsBigEndian()));
+
+  uv_ip6_name(&allhosts_in6, allhosts_str, sizeof(allhosts_str));
+  NODE_DEFINE_STRING_CONSTANT(target, STRINGIFY_(IN6ADDR_ALLHOSTS_GROUP),
+                              allhosts_str);
 }
 
 }  // namespace os