ethtool: helper functions for netlink interface

Add common request/reply header definition and helpers to parse request
header and fill reply header. Provide ethnl_update_* helpers to update
structure members from request attributes (to be used for *_SET requests).

Signed-off-by: Michal Kubecek <mkubecek@suse.cz>
Reviewed-by: Florian Fainelli <f.fainelli@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

include/uapi/linux/ethtool_netlink.h

@@ -29,6 +29,27 @@ enum {
 	ETHTOOL_MSG_KERNEL_MAX = __ETHTOOL_MSG_KERNEL_CNT - 1
 };
 
+/* request header */
+
+/* use compact bitsets in reply */
+#define ETHTOOL_FLAG_COMPACT_BITSETS	(1 << 0)
+/* provide optional reply for SET or ACT requests */
+#define ETHTOOL_FLAG_OMIT_REPLY	(1 << 1)
+
+#define ETHTOOL_FLAG_ALL (ETHTOOL_FLAG_COMPACT_BITSETS | \
+			  ETHTOOL_FLAG_OMIT_REPLY)
+
+enum {
+	ETHTOOL_A_HEADER_UNSPEC,
+	ETHTOOL_A_HEADER_DEV_INDEX,		/* u32 */
+	ETHTOOL_A_HEADER_DEV_NAME,		/* string */
+	ETHTOOL_A_HEADER_FLAGS,			/* u32 - ETHTOOL_FLAG_* */
+
+	/* add new constants above here */
+	__ETHTOOL_A_HEADER_CNT,
+	ETHTOOL_A_HEADER_MAX = __ETHTOOL_A_HEADER_CNT - 1
+};
+
 /* generic netlink info */
 #define ETHTOOL_GENL_NAME "ethtool"
 #define ETHTOOL_GENL_VERSION 1

net/ethtool/netlink.c

@@ -1,8 +1,174 @@
 // SPDX-License-Identifier: GPL-2.0-only
 
+#include <net/sock.h>
 #include <linux/ethtool_netlink.h>
 #include "netlink.h"
 
+static struct genl_family ethtool_genl_family;
+
+static const struct nla_policy ethnl_header_policy[ETHTOOL_A_HEADER_MAX + 1] = {
+	[ETHTOOL_A_HEADER_UNSPEC]	= { .type = NLA_REJECT },
+	[ETHTOOL_A_HEADER_DEV_INDEX]	= { .type = NLA_U32 },
+	[ETHTOOL_A_HEADER_DEV_NAME]	= { .type = NLA_NUL_STRING,
+					    .len = ALTIFNAMSIZ - 1 },
+	[ETHTOOL_A_HEADER_FLAGS]	= { .type = NLA_U32 },
+};
+
+/**
+ * ethnl_parse_header() - parse request header
+ * @req_info:    structure to put results into
+ * @header:      nest attribute with request header
+ * @net:         request netns
+ * @extack:      netlink extack for error reporting
+ * @require_dev: fail if no device identified in header
+ *
+ * Parse request header in nested attribute @nest and puts results into
+ * the structure pointed to by @req_info. Extack from @info is used for error
+ * reporting. If req_info->dev is not null on return, reference to it has
+ * been taken. If error is returned, *req_info is null initialized and no
+ * reference is held.
+ *
+ * Return: 0 on success or negative error code
+ */
+int ethnl_parse_header(struct ethnl_req_info *req_info,
+		       const struct nlattr *header, struct net *net,
+		       struct netlink_ext_ack *extack, bool require_dev)
+{
+	struct nlattr *tb[ETHTOOL_A_HEADER_MAX + 1];
+	const struct nlattr *devname_attr;
+	struct net_device *dev = NULL;
+	int ret;
+
+	if (!header) {
+		NL_SET_ERR_MSG(extack, "request header missing");
+		return -EINVAL;
+	}
+	ret = nla_parse_nested(tb, ETHTOOL_A_HEADER_MAX, header,
+			       ethnl_header_policy, extack);
+	if (ret < 0)
+		return ret;
+	devname_attr = tb[ETHTOOL_A_HEADER_DEV_NAME];
+
+	if (tb[ETHTOOL_A_HEADER_DEV_INDEX]) {
+		u32 ifindex = nla_get_u32(tb[ETHTOOL_A_HEADER_DEV_INDEX]);
+
+		dev = dev_get_by_index(net, ifindex);
+		if (!dev) {
+			NL_SET_ERR_MSG_ATTR(extack,
+					    tb[ETHTOOL_A_HEADER_DEV_INDEX],
+					    "no device matches ifindex");
+			return -ENODEV;
+		}
+		/* if both ifindex and ifname are passed, they must match */
+		if (devname_attr &&
+		    strncmp(dev->name, nla_data(devname_attr), IFNAMSIZ)) {
+			dev_put(dev);
+			NL_SET_ERR_MSG_ATTR(extack, header,
+					    "ifindex and name do not match");
+			return -ENODEV;
+		}
+	} else if (devname_attr) {
+		dev = dev_get_by_name(net, nla_data(devname_attr));
+		if (!dev) {
+			NL_SET_ERR_MSG_ATTR(extack, devname_attr,
+					    "no device matches name");
+			return -ENODEV;
+		}
+	} else if (require_dev) {
+		NL_SET_ERR_MSG_ATTR(extack, header,
+				    "neither ifindex nor name specified");
+		return -EINVAL;
+	}
+
+	if (dev && !netif_device_present(dev)) {
+		dev_put(dev);
+		NL_SET_ERR_MSG(extack, "device not present");
+		return -ENODEV;
+	}
+
+	req_info->dev = dev;
+	if (tb[ETHTOOL_A_HEADER_FLAGS])
+		req_info->flags = nla_get_u32(tb[ETHTOOL_A_HEADER_FLAGS]);
+
+	return 0;
+}
+
+/**
+ * ethnl_fill_reply_header() - Put common header into a reply message
+ * @skb:      skb with the message
+ * @dev:      network device to describe in header
+ * @attrtype: attribute type to use for the nest
+ *
+ * Create a nested attribute with attributes describing given network device.
+ *
+ * Return: 0 on success, error value (-EMSGSIZE only) on error
+ */
+int ethnl_fill_reply_header(struct sk_buff *skb, struct net_device *dev,
+			    u16 attrtype)
+{
+	struct nlattr *nest;
+
+	if (!dev)
+		return 0;
+	nest = nla_nest_start(skb, attrtype);
+	if (!nest)
+		return -EMSGSIZE;
+
+	if (nla_put_u32(skb, ETHTOOL_A_HEADER_DEV_INDEX, (u32)dev->ifindex) ||
+	    nla_put_string(skb, ETHTOOL_A_HEADER_DEV_NAME, dev->name))
+		goto nla_put_failure;
+	/* If more attributes are put into reply header, ethnl_header_size()
+	 * must be updated to account for them.
+	 */
+
+	nla_nest_end(skb, nest);
+	return 0;
+
+nla_put_failure:
+	nla_nest_cancel(skb, nest);
+	return -EMSGSIZE;
+}
+
+/**
+ * ethnl_reply_init() - 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)
+ * @cmd:     ETHTOOL_MSG_* message type for reply
+ * @info:    genetlink info of the received packet we respond to
+ * @ehdrp:   place to store payload pointer returned by genlmsg_new()
+ *
+ * Return: pointer to allocated skb on success, NULL on error
+ */
+struct sk_buff *ethnl_reply_init(size_t payload, struct net_device *dev, u8 cmd,
+				 u16 hdr_attrtype, struct genl_info *info,
+				 void **ehdrp)
+{
+	struct sk_buff *skb;
+
+	skb = genlmsg_new(payload, GFP_KERNEL);
+	if (!skb)
+		goto err;
+	*ehdrp = genlmsg_put_reply(skb, info, &ethtool_genl_family, 0, cmd);
+	if (!*ehdrp)
+		goto err_free;
+
+	if (dev) {
+		int ret;
+
+		ret = ethnl_fill_reply_header(skb, dev, hdr_attrtype);
+		if (ret < 0)
+			goto err_free;
+	}
+	return skb;
+
+err_free:
+	nlmsg_free(skb);
+err:
+	if (info)
+		GENL_SET_ERR_MSG(info, "failed to setup reply message");
+	return NULL;
+}
+
 /* genetlink setup */
 
 static const struct genl_ops ethtool_genl_ops[] = {