[RFC PATCH net-next v3 04/21] ethtool: helper functions for netlink interface

[Michal Kubecek]

Various helpers used by ethtool netlink code.

Signed-off-by: Michal Kubecek <mkubecek@xxxxxxx>
---
 include/uapi/linux/ethtool_netlink.h |  11 +++
 net/ethtool/netlink.c                | 119 +++++++++++++++++++++++
 net/ethtool/netlink.h                | 135 +++++++++++++++++++++++++++
 3 files changed, 265 insertions(+)

diff --git a/include/uapi/linux/ethtool_netlink.h b/include/uapi/linux/ethtool_netlink.h
index d8a8d3c72c2f..01896a1ee21a 100644
--- a/include/uapi/linux/ethtool_netlink.h
+++ b/include/uapi/linux/ethtool_netlink.h
@@ -12,6 +12,17 @@ enum {
 	ETHNL_CMD_MAX = (__ETHNL_CMD_CNT - 1)
 };
 
+/* device specification */
+
+enum {
+	ETHA_DEV_UNSPEC,
+	ETHA_DEV_INDEX,				/* u32 */
+	ETHA_DEV_NAME,				/* string */
+
+	__ETHA_DEV_CNT,
+	ETHA_DEV_MAX = (__ETHA_DEV_CNT - 1)
+};
+
 /* generic netlink info */
 #define ETHTOOL_GENL_NAME "ethtool"
 #define ETHTOOL_GENL_VERSION 1
diff --git a/net/ethtool/netlink.c b/net/ethtool/netlink.c
index 5fe3e5b68e81..ffdcc7c9d4bc 100644
--- a/net/ethtool/netlink.c
+++ b/net/ethtool/netlink.c
@@ -1,8 +1,127 @@
 // SPDX-License-Identifier: GPL-2.0 WITH Linux-syscall-note
 
+#include <net/sock.h>
 #include <linux/ethtool_netlink.h>
 #include "netlink.h"
 
+static const struct nla_policy dev_policy[ETHA_DEV_MAX + 1] = {
+	[ETHA_DEV_UNSPEC]	= { .type = NLA_REJECT },
+	[ETHA_DEV_INDEX]	= { .type = NLA_U32 },
+	[ETHA_DEV_NAME]		= { .type = NLA_NUL_STRING,
+				    .len = IFNAMSIZ - 1 },
+};
+
+struct net_device *ethnl_dev_get(struct genl_info *info, struct nlattr *nest)
+{
+	struct net *net = genl_info_net(info);
+	struct nlattr *tb[ETHA_DEV_MAX + 1];
+	struct net_device *dev;
+	int ret;
+
+	if (!nest) {
+		ETHNL_SET_ERRMSG(info,
+				 "mandatory device identification missing");
+		return ERR_PTR(-EINVAL);
+	}
+	ret = nla_parse_nested(tb, ETHA_DEV_MAX, nest, dev_policy,
+			       info->extack);
+	if (ret < 0)
+		return ERR_PTR(ret);
+
+	if (tb[ETHA_DEV_INDEX]) {
+		dev = dev_get_by_index(net, nla_get_u32(tb[ETHA_DEV_INDEX]));
+		if (!dev)
+			return ERR_PTR(-ENODEV);
+		/* if both ifindex and ifname are passed, they must match */
+		if (tb[ETHA_DEV_NAME]) {
+			const char *nl_name = nla_data(tb[ETHA_DEV_NAME]);
+
+			if (strncmp(dev->name, nl_name, IFNAMSIZ)) {
+				dev_put(dev);
+				ETHNL_SET_ERRMSG(info,
+						 "ifindex and ifname do not match");
+				return ERR_PTR(-ENODEV);
+			}
+		}
+		return dev;
+	} else if (tb[ETHA_DEV_NAME]) {
+		dev = dev_get_by_name(net, nla_data(tb[ETHA_DEV_NAME]));
+		if (!dev)
+			return ERR_PTR(-ENODEV);
+	} else {
+		ETHNL_SET_ERRMSG(info, "either ifindex or ifname required");
+		return ERR_PTR(-EINVAL);
+	}
+
+	if (!netif_device_present(dev)) {
+		dev_put(dev);
+		ETHNL_SET_ERRMSG(info, "device not present");
+		return ERR_PTR(-ENODEV);
+	}
+	return dev;
+}
+
+int ethnl_fill_dev(struct sk_buff *msg, struct net_device *dev, u16 attrtype)
+{
+	struct nlattr *nest;
+	int ret = -EMSGSIZE;
+
+	nest = ethnl_nest_start(msg, attrtype);
+	if (!nest)
+		return -EMSGSIZE;
+
+	if (nla_put_u32(msg, ETHA_DEV_INDEX, (u32)dev->ifindex))
+		goto err;
+	if (nla_put_string(msg, ETHA_DEV_NAME, dev->name))
+		goto err;
+
+	nla_nest_end(msg, nest);
+	return 0;
+err:
+	nla_nest_cancel(msg, nest);
+	return ret;
+}
+
+/* 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:     ETHNL_CMD_* command for reply
+ * info:    info for the received packet we respond to
+ * ehdrp:   place to store payload pointer returned by genlmsg_new()
+ * returns: skb or null on error
+ */
+struct sk_buff *ethnl_reply_init(size_t payload, struct net_device *dev, u8 cmd,
+				 u16 dev_attrtype, struct genl_info *info,
+				 void **ehdrp)
+{
+	void *ehdr;
+	struct sk_buff *rskb;
+
+	rskb = genlmsg_new(payload, GFP_KERNEL);
+	if (!rskb) {
+		ETHNL_SET_ERRMSG(info,
+				 "failed to allocate reply message");
+		return NULL;
+	}
+
+	ehdr = genlmsg_put_reply(rskb, info, &ethtool_genl_family, 0, cmd);
+	if (!ehdr)
+		goto err;
+	if (ehdrp)
+		*ehdrp = ehdr;
+	if (dev) {
+		int ret = ethnl_fill_dev(rskb, dev, dev_attrtype);
+
+		if (ret < 0)
+			goto err;
+	}
+
+	return rskb;
+err:
+	nlmsg_free(rskb);
+	return NULL;
+}
+
 /* genetlink setup */
 
 static const struct genl_ops ethtool_genl_ops[] = {
diff --git a/net/ethtool/netlink.h b/net/ethtool/netlink.h
index 63063b582ca2..36a397656127 100644
--- a/net/ethtool/netlink.h
+++ b/net/ethtool/netlink.h
@@ -6,7 +6,142 @@
 #include <linux/ethtool_netlink.h>
 #include <linux/netdevice.h>
 #include <net/genetlink.h>
+#include <net/sock.h>
+
+#define ETHNL_SET_ERRMSG(info, msg) \
+	do { if (info) GENL_SET_ERR_MSG(info, msg); } while (0)
 
 extern struct genl_family ethtool_genl_family;
 
+struct net_device *ethnl_dev_get(struct genl_info *info, struct nlattr *nest);
+int ethnl_fill_dev(struct sk_buff *msg, struct net_device *dev, u16 attrtype);
+
+struct sk_buff *ethnl_reply_init(size_t payload, struct net_device *dev, u8 cmd,
+				 u16 dev_attrtype, struct genl_info *info,
+				 void **ehdrp);
+
+static inline int ethnl_str_size(const char *s)
+{
+	return nla_total_size(strlen(s) + 1);
+}
+
+static inline int ethnl_str_ifne_size(const char *s)
+{
+	return s[0] ? ethnl_str_size(s) : 0;
+}
+
+static inline int ethnl_put_str_ifne(struct sk_buff *skb, int attrtype,
+				     const char *s)
+{
+	if (!s[0])
+		return 0;
+	return nla_put_string(skb, attrtype, s);
+}
+
+static inline struct nlattr *ethnl_nest_start(struct sk_buff *skb,
+					      int attrtype)
+{
+	return nla_nest_start(skb, attrtype | NLA_F_NESTED);
+}
+
+/* ethnl_update_* return true if the value is changed */
+static inline bool ethnl_update_u32(u32 *dst, struct nlattr *attr)
+{
+	u32 val;
+
+	if (!attr)
+		return false;
+	val = nla_get_u32(attr);
+	if (*dst == val)
+		return false;
+
+	*dst = val;
+	return true;
+}
+
+static inline bool ethnl_update_u8(u8 *dst, struct nlattr *attr)
+{
+	u8 val;
+
+	if (!attr)
+		return false;
+	val = nla_get_u8(attr);
+	if (*dst == val)
+		return false;
+
+	*dst = val;
+	return true;
+}
+
+/* update u32 value used as bool from NLA_U8 */
+static inline bool ethnl_update_bool32(u32 *dst, struct nlattr *attr)
+{
+	u8 val;
+
+	if (!attr)
+		return false;
+	val = !!nla_get_u8(attr);
+	if (!!*dst == val)
+		return false;
+
+	*dst = val;
+	return true;
+}
+
+static inline bool ethnl_update_binary(u8 *dst, unsigned int len,
+				       struct nlattr *attr)
+{
+	if (!attr)
+		return false;
+	if (nla_len(attr) < len)
+		len = nla_len(attr);
+	if (!memcmp(dst, nla_data(attr), len))
+		return false;
+
+	memcpy(dst, nla_data(attr), len);
+	return true;
+}
+
+static inline bool ethnl_update_bitfield32(u32 *dst, struct nlattr *attr)
+{
+	struct nla_bitfield32 change;
+	u32 newval;
+
+	if (!attr)
+		return false;
+	change = nla_get_bitfield32(attr);
+	newval = (*dst & ~change.selector) | (change.value & change.selector);
+	if (*dst == newval)
+		return false;
+
+	*dst = newval;
+	return true;
+}
+
+static inline void warn_partial_info(struct genl_info *info)
+{
+	ETHNL_SET_ERRMSG(info, "not all requested data could be retrieved");
+}
+
+/* Check user privileges explicitly to allow finer access control based on
+ * context of the request or hiding part of the information from unprivileged
+ * users
+ */
+static inline bool ethnl_is_privileged(struct sk_buff *skb)
+{
+	struct net *net = sock_net(skb->sk);
+
+	return netlink_ns_capable(skb, net->user_ns, CAP_NET_ADMIN);
+}
+
+/* total size of ETHA_*_DEV nested attribute; this is an upper estimate so that
+ * we do not need to hold RTNL longer than necessary to prevent rename between
+ * estimating the size and composing the message
+ */
+static inline unsigned int dev_ident_size(void)
+{
+	return nla_total_size(nla_total_size(sizeof(u32)) +
+			      nla_total_size(IFNAMSIZ));
+}
+
 #endif /* _NET_ETHTOOL_NETLINK_H */
-- 
2.20.1