Use existing read buffer in security handshaker if present
diff --git a/Makefile b/Makefile
index 325c912..7c0ee0d 100644
--- a/Makefile
+++ b/Makefile
@@ -1023,6 +1023,7 @@
 grpc_verify_jwt: $(BINDIR)/$(CONFIG)/grpc_verify_jwt
 handshake_client: $(BINDIR)/$(CONFIG)/handshake_client
 handshake_server: $(BINDIR)/$(CONFIG)/handshake_server
+handshake_server_with_readahead_handshaker: $(BINDIR)/$(CONFIG)/handshake_server_with_readahead_handshaker
 hpack_parser_fuzzer_test: $(BINDIR)/$(CONFIG)/hpack_parser_fuzzer_test
 hpack_parser_test: $(BINDIR)/$(CONFIG)/hpack_parser_test
 hpack_table_test: $(BINDIR)/$(CONFIG)/hpack_table_test
@@ -1417,6 +1418,7 @@
   $(BINDIR)/$(CONFIG)/grpc_ssl_credentials_test \
   $(BINDIR)/$(CONFIG)/handshake_client \
   $(BINDIR)/$(CONFIG)/handshake_server \
+  $(BINDIR)/$(CONFIG)/handshake_server_with_readahead_handshaker \
   $(BINDIR)/$(CONFIG)/hpack_parser_test \
   $(BINDIR)/$(CONFIG)/hpack_table_test \
   $(BINDIR)/$(CONFIG)/http_parser_test \
@@ -1894,6 +1896,8 @@
 	$(Q) $(BINDIR)/$(CONFIG)/handshake_client || ( echo test handshake_client failed ; exit 1 )
 	$(E) "[RUN]     Testing handshake_server"
 	$(Q) $(BINDIR)/$(CONFIG)/handshake_server || ( echo test handshake_server failed ; exit 1 )
+	$(E) "[RUN]     Testing handshake_server_with_readahead_handshaker"
+	$(Q) $(BINDIR)/$(CONFIG)/handshake_server_with_readahead_handshaker || ( echo test handshake_server_with_readahead_handshaker failed ; exit 1 )
 	$(E) "[RUN]     Testing hpack_parser_test"
 	$(Q) $(BINDIR)/$(CONFIG)/hpack_parser_test || ( echo test hpack_parser_test failed ; exit 1 )
 	$(E) "[RUN]     Testing hpack_table_test"
@@ -11221,6 +11225,7 @@
 
 HANDSHAKE_SERVER_SRC = \
     test/core/handshake/server_ssl.c \
+    test/core/handshake/server_ssl_common.c \
 
 HANDSHAKE_SERVER_OBJS = $(addprefix $(OBJDIR)/$(CONFIG)/, $(addsuffix .o, $(basename $(HANDSHAKE_SERVER_SRC))))
 ifeq ($(NO_SECURE),true)
@@ -11242,6 +11247,8 @@
 
 $(OBJDIR)/$(CONFIG)/test/core/handshake/server_ssl.o:  $(LIBDIR)/$(CONFIG)/libgrpc_test_util.a $(LIBDIR)/$(CONFIG)/libgrpc.a $(LIBDIR)/$(CONFIG)/libgpr_test_util.a $(LIBDIR)/$(CONFIG)/libgpr.a
 
+$(OBJDIR)/$(CONFIG)/test/core/handshake/server_ssl_common.o:  $(LIBDIR)/$(CONFIG)/libgrpc_test_util.a $(LIBDIR)/$(CONFIG)/libgrpc.a $(LIBDIR)/$(CONFIG)/libgpr_test_util.a $(LIBDIR)/$(CONFIG)/libgpr.a
+
 deps_handshake_server: $(HANDSHAKE_SERVER_OBJS:.o=.dep)
 
 ifneq ($(NO_SECURE),true)
@@ -11251,6 +11258,41 @@
 endif
 
 
+HANDSHAKE_SERVER_WITH_READAHEAD_HANDSHAKER_SRC = \
+    test/core/handshake/readahead_handshaker_server_ssl.c \
+    test/core/handshake/server_ssl_common.c \
+
+HANDSHAKE_SERVER_WITH_READAHEAD_HANDSHAKER_OBJS = $(addprefix $(OBJDIR)/$(CONFIG)/, $(addsuffix .o, $(basename $(HANDSHAKE_SERVER_WITH_READAHEAD_HANDSHAKER_SRC))))
+ifeq ($(NO_SECURE),true)
+
+# You can't build secure targets if you don't have OpenSSL.
+
+$(BINDIR)/$(CONFIG)/handshake_server_with_readahead_handshaker: openssl_dep_error
+
+else
+
+
+
+$(BINDIR)/$(CONFIG)/handshake_server_with_readahead_handshaker: $(HANDSHAKE_SERVER_WITH_READAHEAD_HANDSHAKER_OBJS) $(LIBDIR)/$(CONFIG)/libgrpc_test_util.a $(LIBDIR)/$(CONFIG)/libgrpc.a $(LIBDIR)/$(CONFIG)/libgpr_test_util.a $(LIBDIR)/$(CONFIG)/libgpr.a
+	$(E) "[LD]      Linking $@"
+	$(Q) mkdir -p `dirname $@`
+	$(Q) $(LD) $(LDFLAGS) $(HANDSHAKE_SERVER_WITH_READAHEAD_HANDSHAKER_OBJS) $(LIBDIR)/$(CONFIG)/libgrpc_test_util.a $(LIBDIR)/$(CONFIG)/libgrpc.a $(LIBDIR)/$(CONFIG)/libgpr_test_util.a $(LIBDIR)/$(CONFIG)/libgpr.a $(LDLIBS) $(LDLIBS_SECURE) -o $(BINDIR)/$(CONFIG)/handshake_server_with_readahead_handshaker
+
+endif
+
+$(OBJDIR)/$(CONFIG)/test/core/handshake/readahead_handshaker_server_ssl.o:  $(LIBDIR)/$(CONFIG)/libgrpc_test_util.a $(LIBDIR)/$(CONFIG)/libgrpc.a $(LIBDIR)/$(CONFIG)/libgpr_test_util.a $(LIBDIR)/$(CONFIG)/libgpr.a
+
+$(OBJDIR)/$(CONFIG)/test/core/handshake/server_ssl_common.o:  $(LIBDIR)/$(CONFIG)/libgrpc_test_util.a $(LIBDIR)/$(CONFIG)/libgrpc.a $(LIBDIR)/$(CONFIG)/libgpr_test_util.a $(LIBDIR)/$(CONFIG)/libgpr.a
+
+deps_handshake_server_with_readahead_handshaker: $(HANDSHAKE_SERVER_WITH_READAHEAD_HANDSHAKER_OBJS:.o=.dep)
+
+ifneq ($(NO_SECURE),true)
+ifneq ($(NO_DEPS),true)
+-include $(HANDSHAKE_SERVER_WITH_READAHEAD_HANDSHAKER_OBJS:.o=.dep)
+endif
+endif
+
+
 HPACK_PARSER_FUZZER_TEST_SRC = \
     test/core/transport/chttp2/hpack_parser_fuzzer_test.c \