Added broadcasting feature to UDP server sockets.

net/udp/udp_socket_libevent.cc

Index: net/udp/udp_socket_libevent.cc
diff --git a/net/udp/udp_socket_libevent.cc b/net/udp/udp_socket_libevent.cc
index bb1cf91ede1fac18c855dca63eb4b12d701a9244..d4c61281bbe89ba4ffce125b7d8d5dd9b176add2 100644
--- a/net/udp/udp_socket_libevent.cc
+++ b/net/udp/udp_socket_libevent.cc
@@ -41,6 +41,7 @@ UDPSocketLibevent::UDPSocketLibevent(
     net::NetLog* net_log,
     const net::NetLog::Source& source)
         : socket_(kInvalidSocket),
+          allow_broadcast_(false),
           bind_type_(bind_type),
           rand_int_cb_(rand_int_cb),
           read_watcher_(this),
@@ -251,6 +252,11 @@ int UDPSocketLibevent::Bind(const IPEndPoint& address) {
   int rv = CreateSocket(address);
   if (rv < 0)
     return rv;
+  if (allow_broadcast_) {
+    rv = DoBroadcast();
+    if (rv < 0)
+      return rv;
+  }
   rv = DoBind(address);
   if (rv < 0)
     return rv;
@@ -274,6 +280,13 @@ bool UDPSocketLibevent::SetSendBufferSize(int32 size) {
   return rv == 0;
 }
 
+void UDPSocketLibevent::AllowBroadcast() {
+  DCHECK(CalledOnValidThread());
+  DCHECK(!is_connected());
+
+  allow_broadcast_ = true;
+}
+
 void UDPSocketLibevent::DoReadCallback(int rv) {
   DCHECK_NE(rv, ERR_IO_PENDING);
   DCHECK(!read_callback_.is_null());
@@ -430,6 +443,28 @@ int UDPSocketLibevent::InternalSendTo(IOBuffer* buf, int buf_len,
   return result;
 }
 
+int UDPSocketLibevent::DoBroadcast() {
+  int true_value = 1;
+  int rv = setsockopt(socket_, SOL_SOCKET, SO_REUSEADDR,
+                      reinterpret_cast<const char*>(&true_value),

[wtc, 2012/07/11 18:26:37]

Since the fourth argument to setsockopt is a const void* on Unix
(http://pubs.opengroup.org/onlinepubs/009695399/functions/setsockopt.html),
we should not need to cast &true_value to const char* here
and on lines 455 and 461.

[ygorshenin1, 2012/07/12 09:28:08]

Done.

+                      sizeof(true_value));
+  if (rv < 0)
+    return MapSystemError(errno);
+#if defined(OS_MACOSX)

[wtc, 2012/07/11 18:26:37]

If SO_REUSEPORT is defined as a macro (rather than an enum
constant) on Mac OS X, you can also test

    #if defined(SO_REUSEPORT)

here.  Then the code will automatically work on other platforms
that define the SO_REUSEPORT macro.

[ygorshenin1, 2012/07/12 09:28:08]

Done.

+  rv = setsockopt(socket_, SOL_SOCKET, SO_REUSEPORT,
+                  reinterpret_cast<const char*>(&true_value),
+                  sizeof(true_value));
+  if (rv < 0)
+    return MapSystemError(errno);
+#endif
+  rv = setsockopt(socket_, SOL_SOCKET, SO_BROADCAST,
+                  reinterpret_cast<const char*>(&true_value),
+                  sizeof(true_value));
+  if (rv < 0)
+    return MapSystemError(errno);
+  return OK;
+}
+
 int UDPSocketLibevent::DoBind(const IPEndPoint& address) {
   SockaddrStorage storage;
   if (!address.ToSockAddr(storage.addr, &storage.addr_len))