https://bugzilla.samba.org/show_bug.cgi?id=12776

diff --git a/source3/include/client.h b/source3/include/client.h
index db8260d..becdf77 100644
--- a/source3/include/client.h
+++ b/source3/include/client.h
@@ -61,6 +61,9 @@ struct cli_state {
 	char *server_os;
 	char *server_domain;
 
+	/* is server_os spinstream2? true/false/not-yet-checked(-1) */
+	int is_spinstream2;
+
 	char *share;
 	char *dev;
 
diff --git a/source3/libsmb/clientgen.c b/source3/libsmb/clientgen.c
index bc5c1b1..6d6b725 100644
--- a/source3/libsmb/clientgen.c
+++ b/source3/libsmb/clientgen.c
@@ -112,6 +112,7 @@ struct cli_state *cli_state_create(TALLOC_CTX *mem_ctx,
 	if (!cli->server_os) {
 		goto error;
 	}
+	cli->is_spinstream2 = -1;
 	cli->server_type = talloc_strdup(cli, "");
 	if (!cli->server_type) {
 		goto error;
@@ -430,6 +431,24 @@ time_t cli_state_server_time(struct cli_state *cli)
 	return t;
 }
 
+bool cli_state_server_is_spinstream2(struct cli_state *cli)
+{
+	int *ret = &cli->is_spinstream2;
+	if (*ret == -1) {
+		if (*cli->server_os == '\0') {
+			DEBUG(1, ("when checking if server is SpinStream2:"
+				  " server_os field is empty (should have"
+				  " been sent in Session Setup protocol"
+				  " response), so ... presuming not"));
+			*ret = 0;
+		}
+		else {
+			*ret = strequal(cli->server_os, "SpinStream2") ? 1 : 0;
+		}
+	}
+	return *ret == 1;
+}
+
 struct cli_echo_state {
 	bool is_smb2;
 };
diff --git a/source3/libsmb/clireadwrite.c b/source3/libsmb/clireadwrite.c
index 3987477..6371bc2 100644
--- a/source3/libsmb/clireadwrite.c
+++ b/source3/libsmb/clireadwrite.c
@@ -89,6 +89,13 @@ static size_t cli_write_max_bufsize(struct cli_state *cli,
 		useable_space = 0xFFFFFF - data_offset;
 	} else if (smb1cli_conn_capabilities(cli->conn) & CAP_LARGE_WRITEX) {
 		useable_space = 0x1FFFF - data_offset;
+		if (cli_state_server_is_spinstream2(cli))
+			/*
+			 * SpinStream2 (NetApp OnTAP, up to 8.3.2, at least;
+			 * XXX may need to be more discerning than this)
+			 * can't handle writes > 64k
+			 */
+			useable_space = MIN(useable_space, 64 * 1024);
 	} else {
 		return min_space;
 	}
diff --git a/source3/libsmb/proto.h b/source3/libsmb/proto.h
index b453733..e334cc6 100644
--- a/source3/libsmb/proto.h
+++ b/source3/libsmb/proto.h
@@ -203,6 +203,7 @@ uint16_t cli_state_set_uid(struct cli_state *cli, uint16_t uid);
 bool cli_set_case_sensitive(struct cli_state *cli, bool case_sensitive);
 uint32_t cli_state_available_size(struct cli_state *cli, uint32_t ofs);
 time_t cli_state_server_time(struct cli_state *cli);
+bool cli_state_server_is_spinstream2(struct cli_state *cli);
 struct tevent_req *cli_echo_send(TALLOC_CTX *mem_ctx, struct tevent_context *ev,
 				 struct cli_state *cli, uint16_t num_echos,
 				 DATA_BLOB data);