Fix: handle backward compatibility with lttng-modules 2.7

There is no major version bump between lttng-module 2.7 and 2.8 ABI.
Even though we do not guarantee compatibility, do a best effort to
maintain it when possible.

Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Signed-off-by: Jérémie Galarneau <jeremie.galarneau@efficios.com>

diff --git a/src/common/kernel-consumer/kernel-consumer.c b/src/common/kernel-consumer/kernel-consumer.c
index 68dcc02309a452c756838c6947ecdf0e6a76957b..f89ab1a6e29adf8803c9e6158cd359fab72eb4f5 100644 (file)
--- a/src/common/kernel-consumer/kernel-consumer.c
+++ b/src/common/kernel-consumer/kernel-consumer.c
@@ -1095,15 +1095,27 @@ static int get_index_values(struct ctf_packet_index *index, int infd)
 
        ret = kernctl_get_instance_id(infd, &index->stream_instance_id);
        if (ret < 0) {
-               PERROR("kernctl_get_instance_id");
-               goto error;
+               if (ret == -ENOTTY) {
+                       /* Command not implemented by lttng-modules. */
+                       index->stream_instance_id = -1ULL;
+                       ret = 0;
+               } else {
+                       PERROR("kernctl_get_instance_id");
+                       goto error;
+               }
        }
        index->stream_instance_id = htobe64(index->stream_instance_id);
 
        ret = kernctl_get_sequence_number(infd, &index->packet_seq_num);
        if (ret < 0) {
-               PERROR("kernctl_get_sequence_number");
-               goto error;
+               if (ret == -ENOTTY) {
+                       /* Command not implemented by lttng-modules. */
+                       index->packet_seq_num = -1ULL;
+                       ret = 0;
+               } else {
+                       PERROR("kernctl_get_sequence_number");
+                       goto error;
+               }
        }
        index->packet_seq_num = htobe64(index->packet_seq_num);
 
@@ -1155,8 +1167,14 @@ int update_stream_stats(struct lttng_consumer_stream *stream)
 
        ret = kernctl_get_sequence_number(stream->wait_fd, &seq);
        if (ret < 0) {
-               PERROR("kernctl_get_sequence_number");
-               goto end;
+               if (ret == -ENOTTY) {
+                       /* Command not implemented by lttng-modules. */
+                       seq = -1ULL;
+                       ret = 0;
+               } else {
+                       PERROR("kernctl_get_sequence_number");
+                       goto end;
+               }
        }
 
        /*
@@ -1215,6 +1233,14 @@ int metadata_stream_check_version(int infd, struct lttng_consumer_stream *stream
 
        ret = kernctl_get_metadata_version(infd, &cur_version);
        if (ret < 0) {
+               if (ret == -ENOTTY) {
+                       /*
+                        * LTTng-modules does not implement this
+                        * command.
+                        */
+                       ret = 0;
+                       goto end;
+               }
                ERR("Failed to get the metadata version");
                goto end;
        }