Back out "Remove setZeroCopy() override"

Summary:
Original commit changeset: ec402ad2badb

reverting D27044720 (https://github.com/facebook/folly/commit/bda140dc1f4be1846a19e708b7c2a0aa6215c730) to S225748

This check was added in D22272411 (https://github.com/facebook/folly/commit/0ff36eaf684ee7c1eeac0e4592e47c92f2440323) as a fix for S204433. This is very likely the cause for S225748 since the behavior is very similar to the original sev

Reviewed By: clrfb

Differential Revision: D27166845

fbshipit-source-id: c0a3f44690cd7c0df5d2a67f433419b961922dec

folly/io/async/AsyncSSLSocket.h

@@ -832,6 +832,9 @@ class AsyncSSLSocket : public AsyncSocket {
     asyncOperationFinishCallback_ = std::move(cb);
   }
 
+  // zero copy is not supported by openssl.
+  bool setZeroCopy(bool /*enable*/) override { return false; }
+
  private:
   /**
    * Handle the return from invoking SSL_accept

folly/io/async/test/AsyncSSLSocketTest.cpp

@@ -206,6 +206,20 @@ TEST(AsyncSSLSocketTest, ConnectWriteReadClose) {
   EXPECT_EQ(socket->getSSLSocket()->getTotalConnectTimeout().count(), 10000);
 }
 
+/**
+ * Check that zero copy options are a noop under AsyncSSLSocket since they
+ * aren't supported.
+ */
+TEST(AsyncSSLSocketTest, ZeroCopy) {
+  // Set up SSL context.
+  std::shared_ptr<SSLContext> sslContext(new SSLContext());
+  sslContext->ciphers("ALL:!ADH:!LOW:!EXP:!MD5:@STRENGTH");
+
+  auto socket = AsyncSSLSocket::newSocket(sslContext, /*evb=*/nullptr);
+  EXPECT_FALSE(socket->setZeroCopy(true));
+  EXPECT_FALSE(socket->getZeroCopy());
+}
+
 /**
  * Same as above simple test, but with a large read len to test
  * clamping behavior.