[RFC PATCH net-next v3 08/21] ethtool: generic handlers for GET requests

[Michal Kubecek]

Some parts of processing GET type requests and related notifications are
independent of a command. Provide universal functions so that only four
callbacks need to be defined for each command type:

  parse_request() - parse incoming message
  prepare_data()  - retrieve data from driver or NIC
  reply_size()    - estimate reply message size
  fill_reply()    - compose reply message

These callback are defined in an instance of struct get_request_ops.

Signed-off-by: Michal Kubecek <mkubecek@xxxxxxx>
---
 net/ethtool/netlink.c | 286 ++++++++++++++++++++++++++++++++++++++++++
 net/ethtool/netlink.h |  84 +++++++++++++
 2 files changed, 370 insertions(+)

diff --git a/net/ethtool/netlink.c b/net/ethtool/netlink.c
index ee3424cd1f90..8cdb6f52cb4a 100644
--- a/net/ethtool/netlink.c
+++ b/net/ethtool/netlink.c
@@ -84,6 +84,41 @@ int ethnl_fill_dev(struct sk_buff *msg, struct net_device *dev, u16 attrtype)
 	return ret;
 }
 
+/* GET request helpers */
+
+const struct get_request_ops *get_requests[__ETHNL_CMD_CNT] = {
+};
+
+static struct common_req_info *alloc_get_data(const struct get_request_ops *ops)
+{
+	struct common_req_info *req_info = kmalloc(ops->data_size, GFP_KERNEL);
+
+	if (!req_info)
+		return NULL;
+	memset(req_info, '\0', ops->repdata_offset);
+	req_info->reply_data =
+		(struct common_reply_data *)((char *)req_info +
+					     ops->repdata_offset);
+	return req_info;
+}
+
+static void free_get_data(const struct get_request_ops *ops,
+			  struct common_req_info *req_info)
+{
+	if (ops->cleanup)
+		ops->cleanup(req_info);
+	kfree(req_info);
+}
+
+static void init_reply_data(const struct common_req_info *req_info,
+			    const struct get_request_ops *ops,
+			    struct net_device *dev)
+{
+	memset(req_info->reply_data, '\0',
+	       ops->data_size - ops->repdata_offset);
+	req_info->reply_data->dev = dev;
+}
+
 /* create skb for a reply and fill device identification
  * payload: payload length (without netlink and genetlink header)
  * dev:     device the reply is about (may be null)
@@ -124,6 +159,257 @@ struct sk_buff *ethnl_reply_init(size_t payload, struct net_device *dev, u8 cmd,
 	return NULL;
 }
 
+int ethnl_get_doit(struct sk_buff *skb, struct genl_info *info)
+{
+	const u8 cmd = info->genlhdr->cmd;
+	struct common_req_info *req_info;
+	const struct get_request_ops *ops;
+	struct sk_buff *rskb;
+	void *reply_payload;
+	int reply_len;
+	int ret;
+
+	ops = get_requests[cmd];
+	if (WARN_ONCE(!ops, "cmd %u has no get_request_ops\n", cmd))
+		return -EOPNOTSUPP;
+	req_info = alloc_get_data(ops);
+	if (!req_info)
+		return -ENOMEM;
+	ret = ops->parse_request(req_info, skb, info, info->nlhdr);
+	if (!ops->allow_nodev_do && !req_info->dev) {
+		ETHNL_SET_ERRMSG(info, "device not specified in do request");
+		ret = -EINVAL;
+	}
+	if (ret < 0)
+		goto err_dev;
+	init_reply_data(req_info, ops, req_info->dev);
+
+	rtnl_lock();
+	ret = ops->prepare_data(req_info, info);
+	if (ret < 0)
+		goto err_rtnl;
+	reply_len = ops->reply_size(req_info);
+	if (ret < 0)
+		goto err_rtnl;
+	ret = -ENOMEM;
+	rskb = ethnl_reply_init(reply_len, req_info->dev, ops->reply_cmd,
+				ops->dev_attrtype, info, &reply_payload);
+	if (!rskb)
+		goto err_rtnl;
+	ret = ops->fill_reply(rskb, req_info);
+	if (ret < 0)
+		goto err;
+	rtnl_unlock();
+
+	genlmsg_end(rskb, reply_payload);
+	if (req_info->dev)
+		dev_put(req_info->dev);
+	free_get_data(ops, req_info);
+	return genlmsg_reply(rskb, info);
+
+err:
+	WARN_ONCE(ret == -EMSGSIZE,
+		  "calculated message payload length (%d) not sufficient\n",
+		  reply_len);
+	nlmsg_free(rskb);
+	free_get_data(ops, req_info);
+err_rtnl:
+	rtnl_unlock();
+err_dev:
+	if (req_info->dev)
+		dev_put(req_info->dev);
+	return ret;
+}
+
+static int ethnl_get_dump_one(struct sk_buff *skb,
+			      struct net_device *dev,
+			      const struct get_request_ops *ops,
+			      struct common_req_info *req_info)
+{
+	int ret;
+
+	init_reply_data(req_info, ops, dev);
+	rtnl_lock();
+	ret = ops->prepare_data(req_info, NULL);
+	if (ret < 0)
+		return ret;
+	ret = ethnl_fill_dev(skb, dev, ops->dev_attrtype);
+	if (ret < 0)
+		return ret;
+	ret = ops->fill_reply(skb, req_info);
+	rtnl_unlock();
+
+	req_info->reply_data->dev = NULL;
+	return ret;
+}
+
+/* generic ->dumpit() handler; device iteration copied from rtnl_dump_ifinfo()
+ * cb->args[0]: pointer to struct get_request_ops
+ * cb->args[1]: pointer to request data
+ * cb->args[2]: iteration position - hashbucket
+ * cb->args[3]: iteration position - ifindex
+ */
+int ethnl_get_dumpit(struct sk_buff *skb, struct netlink_callback *cb)
+{
+	struct net *net = sock_net(skb->sk);
+	struct common_req_info *req_info;
+	const struct get_request_ops *ops;
+	int h, s_h, idx = 0, s_idx;
+	struct hlist_head *head;
+	struct net_device *dev;
+	int ret = 0;
+	void *ehdr;
+
+	ops = (const struct get_request_ops *)cb->args[0];
+	req_info = (struct common_req_info *)cb->args[1];
+	s_h = cb->args[2];
+	s_idx = cb->args[3];
+
+	for (h = s_h; h < NETDEV_HASHENTRIES; h++, s_idx = 0) {
+		idx = 0;
+		head = &net->dev_index_head[h];
+		hlist_for_each_entry(dev, head, index_hlist) {
+			if (idx < s_idx)
+				goto cont;
+			ehdr = genlmsg_put(skb, NETLINK_CB(cb->skb).portid,
+					   cb->nlh->nlmsg_seq,
+					   &ethtool_genl_family, 0,
+					   ops->reply_cmd);
+			ret = ethnl_get_dump_one(skb, dev, ops, req_info);
+			if (ret < 0) {
+				genlmsg_cancel(skb, ehdr);
+				if (ret == -EOPNOTSUPP)
+					goto cont;
+				if (likely(skb->len))
+					goto out;
+				goto out_err;
+			}
+			genlmsg_end(skb, ehdr);
+cont:
+			idx++;
+		}
+	}
+out:
+	ret = skb->len;
+out_err:
+	cb->args[2] = h;
+	cb->args[3] = idx;
+	cb->seq = net->dev_base_seq;
+	nl_dump_check_consistent(cb, nlmsg_hdr(skb));
+
+	return ret;
+}
+
+/* generic ->start() handler for GET requests */
+static int ethnl_get_start(struct netlink_callback *cb)
+{
+	struct common_req_info *req_info;
+	const struct get_request_ops *ops;
+	struct genlmsghdr *ghdr;
+	int ret;
+
+	ghdr = nlmsg_data(cb->nlh);
+	ops = get_requests[ghdr->cmd];
+	if (WARN_ONCE(!ops, "cmd %u has no get_request_ops\n", ghdr->cmd))
+		return -EOPNOTSUPP;
+	req_info = alloc_get_data(ops);
+	if (!req_info)
+		return -ENOMEM;
+
+	ret = ops->parse_request(req_info, cb->skb, NULL, cb->nlh);
+	if (req_info->dev) {
+		/* We ignore device specification in dump requests but as the
+		 * same parser as for non-dump (doit) requests is used, it
+		 * would take reference to the device if it finds one
+		 */
+		dev_put(req_info->dev);
+		req_info->dev = NULL;
+	}
+	if (ret < 0)
+		return ret;
+
+	cb->args[0] = (long)ops;
+	cb->args[1] = (long)req_info;
+	cb->args[2] = 0;
+	cb->args[3] = 0;
+
+	return 0;
+}
+
+/* generic ->done() handler for GET requests */
+static int ethnl_get_done(struct netlink_callback *cb)
+{
+	free_get_data((const struct get_request_ops *)cb->args[0],
+		      (struct common_req_info *)cb->args[1]);
+
+	return 0;
+}
+
+/* generic notification handler */
+static void ethnl_std_notify(struct net_device *dev,
+			     struct netlink_ext_ack *extack, unsigned int cmd,
+			     u32 req_mask, const void *data)
+{
+	struct common_req_info *req_info;
+	const struct get_request_ops *ops;
+	struct sk_buff *skb;
+	void *reply_payload;
+	int reply_len;
+	int ret;
+
+	ops = get_requests[cmd - 1];
+	if (WARN_ONCE(!ops, "cmd %u has no get_request_ops\n", cmd - 1))
+		return;
+	/* when ethnl_std_notify() is used as notify handler, command id of
+	 * corresponding GET request must be one less than cmd argument passed
+	 * to ethnl_std_notify()
+	 */
+	if (WARN_ONCE(ops->reply_cmd != cmd,
+		      "reply_cmd for %u is %u, expected %u\n", cmd - 1,
+		      ops->reply_cmd, cmd))
+		return;
+
+	req_info = alloc_get_data(ops);
+	if (!req_info)
+		return;
+	req_info->dev = dev;
+	req_info->req_mask = req_mask;
+	req_info->compact = true;
+
+	init_reply_data(req_info, ops, dev);
+	ret = ops->prepare_data(req_info, NULL);
+	if (ret < 0)
+		goto err_data;
+	reply_len = ops->reply_size(req_info);
+	if (reply_len < 0)
+		goto err_data;
+	skb = genlmsg_new(reply_len, GFP_KERNEL);
+	if (!skb)
+		goto err_data;
+	reply_payload = genlmsg_put(skb, 0, ++ethnl_bcast_seq,
+				    &ethtool_genl_family, 0, ops->reply_cmd);
+	if (!reply_payload)
+		goto err_skb;
+
+	ret = ethnl_fill_dev(skb, dev, ops->dev_attrtype);
+	if (ret < 0)
+		goto err_skb;
+	ret = ops->fill_reply(skb, req_info);
+	if (ret < 0)
+		goto err_skb;
+	free_get_data(ops, req_info);
+	genlmsg_end(skb, reply_payload);
+
+	genlmsg_multicast(&ethtool_genl_family, skb, 0, ETHNL_MCGRP_MONITOR,
+			  GFP_KERNEL);
+	return;
+
+err_skb:
+	nlmsg_free(skb);
+err_data:
+	free_get_data(ops, req_info);
+}
+
 /* notifications */
 
 typedef void (*ethnl_notify_handler_t)(struct net_device *dev,
diff --git a/net/ethtool/netlink.h b/net/ethtool/netlink.h
index 78385baeaec0..7141ec71a6d3 100644
--- a/net/ethtool/netlink.h
+++ b/net/ethtool/netlink.h
@@ -155,4 +155,88 @@ static inline unsigned int dev_ident_size(void)
 			      nla_total_size(IFNAMSIZ));
 }
 
+/* GET request handling */
+
+struct common_reply_data;
+
+/* Structure holding data for unified processing a GET request consists of two
+ * parts: request info and reply data. Request info starts at offset 0 with
+ * embedded struct common_req_info, is usually filled by ->parse_request()
+ * and is common for all reply messages to one request. Reply data start with
+ * embedded struct common_reply_data and contain data specific to a reply
+ * message (usually one per device for dump requests); this part is filled by
+ * ->prepare_data()
+ *
+ * @reply_data: pointer to corresponding struct common_reply_data
+ * @dev: requested device; may be null (dumps), if not, reference is held
+ * @req_mask: bit mask of parts of information requested
+ * @compact: use compact format for bitsets
+ */
+struct common_req_info {
+	struct common_reply_data	*reply_data;
+	struct net_device		*dev;
+	u32				req_mask;
+	bool				compact;
+};
+
+/* @dev: device for current reply message
+ * @info_mask: subset of req_mask (without information which is not available)
+ */
+struct common_reply_data {
+	struct net_device		*dev;
+	u32				info_mask;
+};
+
+static inline int ethnl_before_ops(struct net_device *dev)
+{
+	if (dev && dev->ethtool_ops->begin)
+		return dev->ethtool_ops->begin(dev);
+	else
+		return 0;
+}
+
+static inline void ethnl_after_ops(struct net_device *dev)
+{
+	if (dev && dev->ethtool_ops->complete)
+		dev->ethtool_ops->complete(dev);
+}
+
+/* parameters and callbacks for unified handling of GET requests
+ * @request_cmd: command id for request (GET)
+ * @reply_cmd: command id for reply (SET)
+ * @dev_attr: attr type for device specification
+ * @data_size: total length of data structure
+ * @repdata_offset: offset of "reply data" part (struct common_reply_data)
+ * @allow_nodev_do: do not fail if device is not specified for non-dump request
+ * @parse_request: parse request message and fill request info; request info
+ *     is zero initialized on entry except reply_data pointer (which is set)
+ * @prepare_data: retrieve data needed to compose a reply message; reply data
+ *     is zero initialized on entry except @dev
+ * @reply_size: return size of reply message payload without device
+ *     specification; reported size may be slightly bigger than actual reply
+ *     but must not be smaller
+ * @fill_reply: fill reply message payload
+ * @cleanup: (optional) called when data are no longer needed; use e.g. to free
+ *           any additional data allocated in prepare_data() which are not part
+ *           of the main structure
+ */
+struct get_request_ops {
+	u8			request_cmd;
+	u8			reply_cmd;
+	u16			dev_attrtype;
+	unsigned int		data_size;
+	unsigned int		repdata_offset;
+	bool			allow_nodev_do;
+
+	int (*parse_request)(struct common_req_info *req_info,
+			     struct sk_buff *skb, struct genl_info *info,
+			     const struct nlmsghdr *nlhdr);
+	int (*prepare_data)(struct common_req_info *req_info,
+			    struct genl_info *info);
+	int (*reply_size)(const struct common_req_info *req_info);
+	int (*fill_reply)(struct sk_buff *skb,
+			  const struct common_req_info *req_info);
+	void (*cleanup)(struct common_req_info *req_info);
+};
+
 #endif /* _NET_ETHTOOL_NETLINK_H */
-- 
2.20.1