[NETLINK]: Extend netlink messaging interface

Adds:
 nlmsg_get_pos()                 return current position in message
 nlmsg_trim()                    trim part of message
 nla_reserve_nohdr(skb, len)     reserve room for an attribute w/o hdr
 nla_put_nohdr(skb, len, data)   add attribute w/o hdr
 nla_find_nested()               find attribute in nested attributes

Fixes nlmsg_new() to take allocation flags and consider size.

Signed-off-by: Thomas Graf <tgraf@suug.ch>
Signed-off-by: David S. Miller <davem@davemloft.net>

2 files changed, 76 insertions, 1 deletions

diff --git a/net/netlink/attr.c b/net/netlink/attr.c
index dddbd15..136e529 100644
--- a/net/netlink/attr.c
+++ b/net/netlink/attr.c
@@ -255,6 +255,26 @@ struct nlattr *__nla_reserve(struct sk_buff *skb, int attrtype, int attrlen)
 }
 
 /**
+ * __nla_reserve_nohdr - reserve room for attribute without header
+ * @skb: socket buffer to reserve room on
+ * @attrlen: length of attribute payload
+ *
+ * Reserves room for attribute payload without a header.
+ *
+ * The caller is responsible to ensure that the skb provides enough
+ * tailroom for the payload.
+ */
+void *__nla_reserve_nohdr(struct sk_buff *skb, int attrlen)
+{
+	void *start;
+
+	start = skb_put(skb, NLA_ALIGN(attrlen));
+	memset(start, 0, NLA_ALIGN(attrlen));
+
+	return start;
+}
+
+/**
  * nla_reserve - reserve room for attribute on the skb
  * @skb: socket buffer to reserve room on
  * @attrtype: attribute type
@@ -275,6 +295,24 @@ struct nlattr *nla_reserve(struct sk_buff *skb, int attrtype, int attrlen)
 }
 
 /**
+ * nla_reserve - reserve room for attribute without header
+ * @skb: socket buffer to reserve room on
+ * @len: length of attribute payload
+ *
+ * Reserves room for attribute payload without a header.
+ *
+ * Returns NULL if the tailroom of the skb is insufficient to store
+ * the attribute payload.
+ */
+void *nla_reserve_nohdr(struct sk_buff *skb, int attrlen)
+{
+	if (unlikely(skb_tailroom(skb) < NLA_ALIGN(attrlen)))
+		return NULL;
+
+	return __nla_reserve_nohdr(skb, attrlen);
+}
+
+/**
  * __nla_put - Add a netlink attribute to a socket buffer
  * @skb: socket buffer to add attribute to
  * @attrtype: attribute type
@@ -293,6 +331,22 @@ void __nla_put(struct sk_buff *skb, int attrtype, int attrlen,
 	memcpy(nla_data(nla), data, attrlen);
 }
 
+/**
+ * __nla_put_nohdr - Add a netlink attribute without header
+ * @skb: socket buffer to add attribute to
+ * @attrlen: length of attribute payload
+ * @data: head of attribute payload
+ *
+ * The caller is responsible to ensure that the skb provides enough
+ * tailroom for the attribute payload.
+ */
+void __nla_put_nohdr(struct sk_buff *skb, int attrlen, const void *data)
+{
+	void *start;
+
+	start = __nla_reserve_nohdr(skb, attrlen);
+	memcpy(start, data, attrlen);
+}
 
 /**
  * nla_put - Add a netlink attribute to a socket buffer
@@ -313,15 +367,36 @@ int nla_put(struct sk_buff *skb, int attrtype, int attrlen, const void *data)
 	return 0;
 }
 
+/**
+ * nla_put_nohdr - Add a netlink attribute without header
+ * @skb: socket buffer to add attribute to
+ * @attrlen: length of attribute payload
+ * @data: head of attribute payload
+ *
+ * Returns -1 if the tailroom of the skb is insufficient to store
+ * the attribute payload.
+ */
+int nla_put_nohdr(struct sk_buff *skb, int attrlen, const void *data)
+{
+	if (unlikely(skb_tailroom(skb) < NLA_ALIGN(attrlen)))
+		return -1;
+
+	__nla_put_nohdr(skb, attrlen, data);
+	return 0;
+}
 
 EXPORT_SYMBOL(nla_validate);
 EXPORT_SYMBOL(nla_parse);
 EXPORT_SYMBOL(nla_find);
 EXPORT_SYMBOL(nla_strlcpy);
 EXPORT_SYMBOL(__nla_reserve);
+EXPORT_SYMBOL(__nla_reserve_nohdr);
 EXPORT_SYMBOL(nla_reserve);
+EXPORT_SYMBOL(nla_reserve_nohdr);
 EXPORT_SYMBOL(__nla_put);
+EXPORT_SYMBOL(__nla_put_nohdr);
 EXPORT_SYMBOL(nla_put);
+EXPORT_SYMBOL(nla_put_nohdr);
 EXPORT_SYMBOL(nla_memcpy);
 EXPORT_SYMBOL(nla_memcmp);
 EXPORT_SYMBOL(nla_strcmp);
diff --git a/net/netlink/genetlink.c b/net/netlink/genetlink.c
index a298f77..75bb47a 100644
--- a/net/netlink/genetlink.c
+++ b/net/netlink/genetlink.c
@@ -440,7 +440,7 @@ static struct sk_buff *ctrl_build_msg(struct genl_family *family, u32 pid,
 	struct sk_buff *skb;
 	int err;
 
-	skb = nlmsg_new(NLMSG_GOODSIZE);
+	skb = nlmsg_new(NLMSG_GOODSIZE, GFP_KERNEL);
 	if (skb == NULL)
 		return ERR_PTR(-ENOBUFS);