ethtool: netlink: handle SET intro/outro in the common code

Most ethtool SET callbacks follow the same general structure.

  ethnl_parse_header_dev_get()
  rtnl_lock()
  ethnl_ops_begin()

  ... do stuff ...

  ethtool_notify()
  ethnl_ops_complete()
  rtnl_unlock()
  ethnl_parse_header_dev_put()

This leads to a lot of copy / pasted code an bugs when people
mis-handle the error path.

Add a generic implementation of this pattern with a .set callback
in struct ethnl_request_ops called to "do stuff".

Also add an optional .set_validate which is called before
ethnl_ops_begin() -- a lot of implementations do basic request
capability / sanity checking at that point.

Because we want to avoid generating the notification when
no change happened - adopt a slightly hairy return values:
 - 0 means nothing to do (no notification)
 - 1 means done / continue
 - negative error codes on error

Reuse .hdr_attr from struct ethnl_request_ops, GET and SET
use the same attr spaces in all cases.

Convert pause as an example (and to avoid unused function warnings).

Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 48 insertions, 1 deletions

diff --git a/net/ethtool/netlink.c b/net/ethtool/netlink.c
index 6412c4dc663d..e90ac1f0a1d7 100644
--- a/net/ethtool/netlink.c
+++ b/net/ethtool/netlink.c
@@ -279,6 +279,7 @@ ethnl_default_requests[__ETHTOOL_MSG_USER_CNT] = {
 	[ETHTOOL_MSG_CHANNELS_GET]	= &ethnl_channels_request_ops,
 	[ETHTOOL_MSG_COALESCE_GET]	= &ethnl_coalesce_request_ops,
 	[ETHTOOL_MSG_PAUSE_GET]		= &ethnl_pause_request_ops,
+	[ETHTOOL_MSG_PAUSE_SET]		= &ethnl_pause_request_ops,
 	[ETHTOOL_MSG_EEE_GET]		= &ethnl_eee_request_ops,
 	[ETHTOOL_MSG_FEC_GET]		= &ethnl_fec_request_ops,
 	[ETHTOOL_MSG_TSINFO_GET]	= &ethnl_tsinfo_request_ops,
@@ -591,6 +592,52 @@ static int ethnl_default_done(struct netlink_callback *cb)
 	return 0;
 }
 
+static int ethnl_default_set_doit(struct sk_buff *skb, struct genl_info *info)
+{
+	const struct ethnl_request_ops *ops;
+	struct ethnl_req_info req_info = {};
+	const u8 cmd = info->genlhdr->cmd;
+	int ret;
+
+	ops = ethnl_default_requests[cmd];
+	if (WARN_ONCE(!ops, "cmd %u has no ethnl_request_ops\n", cmd))
+		return -EOPNOTSUPP;
+	if (GENL_REQ_ATTR_CHECK(info, ops->hdr_attr))
+		return -EINVAL;
+
+	ret = ethnl_parse_header_dev_get(&req_info, info->attrs[ops->hdr_attr],
+					 genl_info_net(info), info->extack,
+					 true);
+	if (ret < 0)
+		return ret;
+
+	if (ops->set_validate) {
+		ret = ops->set_validate(&req_info, info);
+		/* 0 means nothing to do */
+		if (ret <= 0)
+			goto out_dev;
+	}
+
+	rtnl_lock();
+	ret = ethnl_ops_begin(req_info.dev);
+	if (ret < 0)
+		goto out_rtnl;
+
+	ret = ops->set(&req_info, info);
+	if (ret <= 0)
+		goto out_ops;
+	ethtool_notify(req_info.dev, ops->set_ntf_cmd, NULL);
+
+	ret = 0;
+out_ops:
+	ethnl_ops_complete(req_info.dev);
+out_rtnl:
+	rtnl_unlock();
+out_dev:
+	ethnl_parse_header_dev_put(&req_info);
+	return ret;
+}
+
 static const struct ethnl_request_ops *
 ethnl_default_notify_ops[ETHTOOL_MSG_KERNEL_MAX + 1] = {
 	[ETHTOOL_MSG_LINKINFO_NTF]	= &ethnl_linkinfo_request_ops,
@@ -921,7 +968,7 @@ static const struct genl_ops ethtool_genl_ops[] = {
 	{
 		.cmd	= ETHTOOL_MSG_PAUSE_SET,
 		.flags	= GENL_UNS_ADMIN_PERM,
-		.doit	= ethnl_set_pause,
+		.doit	= ethnl_default_set_doit,
 		.policy = ethnl_pause_set_policy,
 		.maxattr = ARRAY_SIZE(ethnl_pause_set_policy) - 1,
 	},