Use single last queue of the device and probe it dynamically.

Reviewed-by: Mina Almasry <almasrymina@google.com>
Signed-off-by: Stanislav Fomichev <sdf@fomichev.me>
---
 tools/testing/selftests/net/ncdevmem.c | 40 ++++++++++++++++++++++++--
 1 file changed, 38 insertions(+), 2 deletions(-)

diff --git a/tools/testing/selftests/net/ncdevmem.c b/tools/testing/selftests/net/ncdevmem.c
index e1faad46548b..fe4d81ef1ca5 100644
--- a/tools/testing/selftests/net/ncdevmem.c
+++ b/tools/testing/selftests/net/ncdevmem.c
@@ -75,8 +75,8 @@ static char *server_ip;
 static char *client_ip;
 static char *port;
 static size_t do_validation;
-static int start_queue = 8;
-static int num_queues = 8;
+static int start_queue = -1;
+static int num_queues = 1;
 static char *ifname;
 static unsigned int ifindex;
 static unsigned int dmabuf_id;
@@ -208,6 +208,33 @@ void validate_buffer(void *line, size_t size)
 	fprintf(stdout, "Validated buffer\n");
 }
 
+static int rxq_num(int ifindex)
+{
+	struct ethtool_channels_get_req *req;
+	struct ethtool_channels_get_rsp *rsp;
+	struct ynl_error yerr;
+	struct ynl_sock *ys;
+	int num = -1;
+
+	ys = ynl_sock_create(&ynl_ethtool_family, &yerr);
+	if (!ys) {
+		fprintf(stderr, "YNL: %s\n", yerr.msg);
+		return -1;
+	}
+
+	req = ethtool_channels_get_req_alloc();
+	ethtool_channels_get_req_set_header_dev_index(req, ifindex);
+	rsp = ethtool_channels_get(ys, req);
+	if (rsp)
+		num = rsp->rx_count + rsp->combined_count;
+	ethtool_channels_get_req_free(req);
+	ethtool_channels_get_rsp_free(rsp);
+
+	ynl_sock_destroy(ys);
+
+	return num;
+}
+
 #define run_command(cmd, ...)                                           \
 	({                                                              \
 		char command[256];                                      \
@@ -702,6 +729,15 @@ int main(int argc, char *argv[])
 
 	ifindex = if_nametoindex(ifname);
 
+	if (start_queue < 0) {
+		start_queue = rxq_num(ifindex) - 1;
+
+		if (start_queue < 0)
+			error(1, 0, "couldn't detect number of queues\n");
+
+		fprintf(stderr, "using queues %d..%d\n", start_queue, start_queue + num_queues);
+	}
+
 	for (; optind < argc; optind++)
 		fprintf(stderr, "extra arguments: %s\n", argv[optind]);
 
-- 
2.47.0