Support SO_RCVBUF, SO_SNDBUF, and SO_BUSY_POLL in AsyncUdpSocket

Summary:
Add API to AsyncUdpSocket to support three options on the socket.

- SO_RCVBUF and SO_SNDBUG options are responsible for the size of the queues that contain received and sent messages, respectively.
- SO_BUSY_POLL sets the approximate time in microseconds to busy poll on a blocking receive when there is no data

Details in socket man: http://man7.org/linux/man-pages/man7/socket.7.html

Reviewed By: yfeldblum

Differential Revision: D7372123

fbshipit-source-id: 5fd92489cbe86879d63df208c3821febdadb0020

folly/io/async/AsyncUDPSocket.cpp

@@ -95,6 +95,58 @@ void AsyncUDPSocket::bind(const folly::SocketAddress& address) {
     }
   }
 
+  if (busyPollUs_ > 0) {
+#ifdef SO_BUSY_POLL
+    // Set busy_poll time in microseconds on the socket.
+    // It sets how long socket will be in busy_poll mode when no event occurs.
+    int value = busyPollUs_;
+    if (setsockopt(socket,
+                   SOL_SOCKET,
+                   SO_BUSY_POLL,
+                   &value,
+                   sizeof(value)) != 0) {
+      throw AsyncSocketException(AsyncSocketException::NOT_OPEN,
+                                "failed to set SO_BUSY_POLL on the socket",
+                                errno);
+
+    }
+#else /* SO_BUSY_POLL is not supported*/
+    throw AsyncSocketException(AsyncSocketException::NOT_OPEN,
+                              "SO_BUSY_POLL is not supported",
+                              errno);
+#endif
+  }
+
+  if (rcvBuf_ > 0) {
+    // Set the size of the buffer for the received messages in rx_queues.
+    int value = rcvBuf_;
+    if (setsockopt(socket,
+                   SOL_SOCKET,
+                   SO_RCVBUF,
+                   &value,
+                   sizeof(value)) != 0) {
+      throw AsyncSocketException(AsyncSocketException::NOT_OPEN,
+                                "failed to set SO_RCVBUF on the socket",
+                                errno);
+
+    }
+  }
+
+  if (sndBuf_ > 0) {
+    // Set the size of the buffer for the sent messages in tx_queues.
+    int value = rcvBuf_;
+    if (setsockopt(socket,
+                   SOL_SOCKET,
+                   SO_SNDBUF,
+                   &value,
+                   sizeof(value)) != 0) {
+      throw AsyncSocketException(AsyncSocketException::NOT_OPEN,
+                                "failed to set SO_SNDBUF on the socket",
+                                errno);
+
+    }
+  }
+
   // If we're using IPv6, make sure we don't accept V4-mapped connections
   if (address.getFamily() == AF_INET6) {
     int flag = 1;

folly/io/async/AsyncUDPSocket.h

@@ -158,6 +158,28 @@ class AsyncUDPSocket : public EventHandler {
     reuseAddr_ = reuseAddr;
   }
 
+  /**
+   * Set SO_RCVBUF option on the socket, if not zero. Default is zero.
+   */
+  virtual void setRcvBuf(int rcvBuf) {
+    rcvBuf_ = rcvBuf;
+  }
+
+  /**
+   * Set SO_SNDBUG option on the socket, if not zero. Default is zero.
+   */
+  virtual void setSndBuf(int sndBuf) {
+    sndBuf_ = sndBuf;
+  }
+
+  /**
+   * Set SO_BUSY_POLL option on the socket, if not zero. Default is zero.
+   * Caution! The feature is not available on Apple's systems.
+   */
+  virtual void setBusyPoll(int busyPollUs) {
+    busyPollUs_ = busyPollUs;
+  }
+
   EventBase* getEventBase() const {
     return eventBase_;
   }
@@ -203,6 +225,9 @@ class AsyncUDPSocket : public EventHandler {
 
   bool reuseAddr_{true};
   bool reusePort_{false};
+  int rcvBuf_{0};
+  int sndBuf_{0};
+  int busyPollUs_{0};
 };
 
 } // namespace folly