[RFC PATCH net-next 12/12] drop_monitor: Add a command to query current configuration

[Ido Schimmel <idosch@idosch.org>]

From: Ido Schimmel <idosch@mellanox.com>

Users should be able to query the current configuration of drop monitor
before they start using it. Add a command to query the existing
configuration which currently consists of alert mode and packet
truncation length.

Signed-off-by: Ido Schimmel <idosch@mellanox.com>
---
 include/uapi/linux/net_dropmon.h |  2 ++
 net/core/drop_monitor.c          | 48 ++++++++++++++++++++++++++++++++
 2 files changed, 50 insertions(+)

diff --git a/include/uapi/linux/net_dropmon.h b/include/uapi/linux/net_dropmon.h
index eb36b61485ef..cdcd23a8b72b 100644
--- a/include/uapi/linux/net_dropmon.h
+++ b/include/uapi/linux/net_dropmon.h
@@ -54,6 +54,8 @@ enum {
 	NET_DM_CMD_START,
 	NET_DM_CMD_STOP,
 	NET_DM_CMD_PACKET_ALERT,
+	NET_DM_CMD_CONFIG_GET,
+	NET_DM_CMD_CONFIG_NEW,
 	_NET_DM_CMD_MAX,
 };
 
diff --git a/net/core/drop_monitor.c b/net/core/drop_monitor.c
index 5af1e1e8d4d0..c753cd6c39ec 100644
--- a/net/core/drop_monitor.c
+++ b/net/core/drop_monitor.c
@@ -656,6 +656,50 @@ static int net_dm_cmd_trace(struct sk_buff *skb,
 	return -EOPNOTSUPP;
 }
 
+static int net_dm_config_fill(struct sk_buff *msg, struct genl_info *info)
+{
+	void *hdr;
+
+	hdr = genlmsg_put(msg, info->snd_portid, info->snd_seq,
+			  &net_drop_monitor_family, 0, NET_DM_CMD_CONFIG_NEW);
+	if (!hdr)
+		return -EMSGSIZE;
+
+	if (nla_put_u8(msg, NET_DM_ATTR_ALERT_MODE, net_dm_alert_mode))
+		goto nla_put_failure;
+
+	if (nla_put_u32(msg, NET_DM_ATTR_TRUNC_LEN, net_dm_trunc_len))
+		goto nla_put_failure;
+
+	genlmsg_end(msg, hdr);
+
+	return 0;
+
+nla_put_failure:
+	genlmsg_cancel(msg, hdr);
+	return -EMSGSIZE;
+}
+
+static int net_dm_cmd_config_get(struct sk_buff *skb, struct genl_info *info)
+{
+	struct sk_buff *msg;
+	int rc;
+
+	msg = nlmsg_new(NLMSG_DEFAULT_SIZE, GFP_KERNEL);
+	if (!msg)
+		return -ENOMEM;
+
+	rc = net_dm_config_fill(msg, info);
+	if (rc)
+		goto err_config_fill;
+
+	return genlmsg_reply(msg, info);
+
+err_config_fill:
+	nlmsg_free(msg);
+	return rc;
+}
+
 static int dropmon_net_event(struct notifier_block *ev_block,
 			     unsigned long event, void *ptr)
 {
@@ -718,6 +762,10 @@ static const struct genl_ops dropmon_ops[] = {
 		.validate = GENL_DONT_VALIDATE_STRICT | GENL_DONT_VALIDATE_DUMP,
 		.doit = net_dm_cmd_trace,
 	},
+	{
+		.cmd = NET_DM_CMD_CONFIG_GET,
+		.doit = net_dm_cmd_config_get,
+	},
 };
 
 static struct genl_family net_drop_monitor_family __ro_after_init = {
-- 
2.21.0