Unify socket message generation, sendSocketMessage

Summary: Both `AsyncSocket` and `AsyncSSLSocket` currently have code to generate a socket message and control messages with ancillary data. Merge this code into a new function in `AsyncSocket`.

Differential Revision: D24096351

fbshipit-source-id: 87d90648c10c87832f868e322acf59c97b8ac8b7

folly/io/async/AsyncSSLSocket.cpp

@@ -1756,27 +1756,10 @@ int AsyncSSLSocket::bioWrite(BIO* b, const char* in, int inl) {
     flags = unSet(flags, folly::WriteFlags::EOR);
   }
 
-  struct msghdr msg;
-  struct iovec iov;
-  iov.iov_base = const_cast<char*>(in);
-  iov.iov_len = size_t(inl);
-  memset(&msg, 0, sizeof(msg));
-  msg.msg_iov = &iov;
-  msg.msg_iovlen = 1;
-  int msg_flags =
-      sslSock->getSendMsgParamsCB()->getFlags(flags, false /*zeroCopyEnabled*/);
-  msg.msg_controllen =
-      sslSock->getSendMsgParamsCB()->getAncillaryDataSize(flags);
-  CHECK_GE(
-      AsyncSocket::SendMsgParamsCallback::maxAncillaryDataSize,
-      msg.msg_controllen);
-  if (msg.msg_controllen != 0) {
-    msg.msg_control = reinterpret_cast<char*>(alloca(msg.msg_controllen));
-    sslSock->getSendMsgParamsCB()->getAncillaryData(flags, msg.msg_control);
-  }
-
-  auto result =
-      sslSock->sendSocketMessage(OpenSSLUtils::getBioFd(b), &msg, msg_flags);
+  struct iovec vec;
+  vec.iov_base = const_cast<char*>(in);
+  vec.iov_len = size_t(inl);
+  auto result = sslSock->sendSocketMessage(&vec, 1, flags);
   BIO_clear_retry_flags(b);
   if (!result.exception && result.writeReturn <= 0) {
     if (OpenSSLUtils::getBioShouldRetryWrite(int(result.writeReturn))) {

folly/io/async/AsyncSocket.cpp

@@ -2542,6 +2542,40 @@ ssize_t AsyncSocket::tfoSendMsg(
   return detail::tfo_sendmsg(fd, msg, msg_flags);
 }
 
+AsyncSocket::WriteResult AsyncSocket::sendSocketMessage(
+    const iovec* vec, size_t count, WriteFlags flags) {
+  struct msghdr msg = {};
+  msg.msg_name = nullptr;
+  msg.msg_namelen = 0;
+  msg.msg_iov = const_cast<struct iovec*>(vec);
+  msg.msg_iovlen = std::min<size_t>(count, kIovMax);
+  msg.msg_flags = 0; // ignored, must forward flags via sendmsg parameter
+  msg.msg_control = nullptr;
+  msg.msg_controllen = sendMsgParamCallback_->getAncillaryDataSize(flags);
+  CHECK_GE(
+      AsyncSocket::SendMsgParamsCallback::maxAncillaryDataSize,
+      msg.msg_controllen);
+
+  if (msg.msg_controllen != 0) {
+    msg.msg_control = reinterpret_cast<char*>(alloca(msg.msg_controllen));
+    sendMsgParamCallback_->getAncillaryData(flags, msg.msg_control);
+  }
+  int msg_flags = sendMsgParamCallback_->getFlags(flags, zeroCopyEnabled_);
+
+  auto writeResult = sendSocketMessage(fd_, &msg, msg_flags);
+
+  if (writeResult.writeReturn < 0 && zeroCopyEnabled_ && errno == ENOBUFS) {
+    // workaround for running with zerocopy enabled but without a big enough
+    // memlock value - see ulimit -l
+    zeroCopyEnabled_ = false;
+    zeroCopyReenableCounter_ = zeroCopyReenableThreshold_;
+    msg_flags = sendMsgParamCallback_->getFlags(flags, zeroCopyEnabled_);
+    writeResult = sendSocketMessage(fd_, &msg, msg_flags);
+  }
+
+  return writeResult;
+}
+
 AsyncSocket::WriteResult AsyncSocket::sendSocketMessage(
     NetworkSocket fd, struct msghdr* msg, int msg_flags) {
   ssize_t totalWritten = 0;
@@ -2615,40 +2649,8 @@ AsyncSocket::WriteResult AsyncSocket::performWrite(
     WriteFlags flags,
     uint32_t* countWritten,
     uint32_t* partialWritten) {
-  // We use sendmsg() instead of writev() so that we can pass in MSG_NOSIGNAL
-  // We correctly handle EPIPE errors, so we never want to receive SIGPIPE
-  // (since it may terminate the program if the main program doesn't explicitly
-  // ignore it).
-  struct msghdr msg;
-  msg.msg_name = nullptr;
-  msg.msg_namelen = 0;
-  msg.msg_iov = const_cast<iovec*>(vec);
-  msg.msg_iovlen = std::min<size_t>(count, kIovMax);
-  msg.msg_flags = 0;
-  msg.msg_controllen = sendMsgParamCallback_->getAncillaryDataSize(flags);
-  CHECK_GE(
-      AsyncSocket::SendMsgParamsCallback::maxAncillaryDataSize,
-      msg.msg_controllen);
-
-  if (msg.msg_controllen != 0) {
-    msg.msg_control = reinterpret_cast<char*>(alloca(msg.msg_controllen));
-    sendMsgParamCallback_->getAncillaryData(flags, msg.msg_control);
-  } else {
-    msg.msg_control = nullptr;
-  }
-  int msg_flags = sendMsgParamCallback_->getFlags(flags, zeroCopyEnabled_);
-
-  auto writeResult = sendSocketMessage(fd_, &msg, msg_flags);
+  auto writeResult = sendSocketMessage(vec, count, flags);
   auto totalWritten = writeResult.writeReturn;
-  if (totalWritten < 0 && zeroCopyEnabled_ && errno == ENOBUFS) {
-    // workaround for running with zerocopy enabled but without a big enough
-    // memlock value - see ulimit -l
-    zeroCopyEnabled_ = false;
-    zeroCopyReenableCounter_ = zeroCopyReenableThreshold_;
-    msg_flags = sendMsgParamCallback_->getFlags(flags, zeroCopyEnabled_);
-    writeResult = sendSocketMessage(fd_, &msg, msg_flags);
-    totalWritten = writeResult.writeReturn;
-  }
   if (totalWritten < 0) {
     bool tryAgain = (errno == EAGAIN);
 #ifdef __APPLE__

folly/io/async/AsyncSocket.h

@@ -1282,6 +1282,16 @@ class AsyncSocket : public AsyncTransport {
       uint32_t* countWritten,
       uint32_t* partialWritten);
 
+  /**
+   * Prepares a msghdr and sends the message over the socket using sendmsg
+   *
+   * @param vec             The iovec array pointing to the buffers to write.
+   * @param count           The length of the iovec array.
+   * @param flags           Set of write flags.
+   */
+  virtual AsyncSocket::WriteResult sendSocketMessage(
+      const iovec* vec, size_t count, WriteFlags flags);
+
   /**
    * Sends the message over the socket using sendmsg
    *