Merge branch 'nlattr_align'

Nicolas Dichtel says:

====================
libnl: enhance API to ease 64bit alignment for attribute

Here is a proposal to add more helpers in the libnetlink to manage 64-bit
alignment issues.
Note that this series was only tested on x86 by tweeking
CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS and adding some traces.

The first patch adds helpers for 64bit alignment and other patches
use them.

We could also add helpers for nla_put_u64() and its variants if needed.

v1 -> v2:
 - remove patch #1
 - split patch #2 (now #1 and #2)
 - add nla_need_padding_for_64bit()
====================

Signed-off-by: David S. Miller <davem@davemloft.net>

include/net/netlink.h

@@ -244,13 +244,21 @@ int nla_memcpy(void *dest, const struct nlattr *src, int count);
 int nla_memcmp(const struct nlattr *nla, const void *data, size_t size);
 int nla_strcmp(const struct nlattr *nla, const char *str);
 struct nlattr *__nla_reserve(struct sk_buff *skb, int attrtype, int attrlen);
+struct nlattr *__nla_reserve_64bit(struct sk_buff *skb, int attrtype,
+				   int attrlen, int padattr);
 void *__nla_reserve_nohdr(struct sk_buff *skb, int attrlen);
 struct nlattr *nla_reserve(struct sk_buff *skb, int attrtype, int attrlen);
+struct nlattr *nla_reserve_64bit(struct sk_buff *skb, int attrtype,
+				 int attrlen, int padattr);
 void *nla_reserve_nohdr(struct sk_buff *skb, int attrlen);
 void __nla_put(struct sk_buff *skb, int attrtype, int attrlen,
 	       const void *data);
+void __nla_put_64bit(struct sk_buff *skb, int attrtype, int attrlen,
+		     const void *data, int padattr);
 void __nla_put_nohdr(struct sk_buff *skb, int attrlen, const void *data);
 int nla_put(struct sk_buff *skb, int attrtype, int attrlen, const void *data);
+int nla_put_64bit(struct sk_buff *skb, int attrtype, int attrlen,
+		  const void *data, int padattr);
 int nla_put_nohdr(struct sk_buff *skb, int attrlen, const void *data);
 int nla_append(struct sk_buff *skb, int attrlen, const void *data);
 
@@ -1230,6 +1238,27 @@ static inline int nla_validate_nested(const struct nlattr *start, int maxtype,
 	return nla_validate(nla_data(start), nla_len(start), maxtype, policy);
 }
 
+/**
+ * nla_need_padding_for_64bit - test 64-bit alignment of the next attribute
+ * @skb: socket buffer the message is stored in
+ *
+ * Return true if padding is needed to align the next attribute (nla_data()) to
+ * a 64-bit aligned area.
+ */
+static inline bool nla_need_padding_for_64bit(struct sk_buff *skb)
+{
+#ifndef CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS
+	/* The nlattr header is 4 bytes in size, that's why we test
+	 * if the skb->data _is_ aligned.  A NOP attribute, plus
+	 * nlattr header for next attribute, will make nla_data()
+	 * 8-byte aligned.
+	 */
+	if (IS_ALIGNED((unsigned long)skb_tail_pointer(skb), 8))
+		return true;
+#endif
+	return false;
+}
+
 /**
  * nla_align_64bit - 64-bit align the nla_data() of next attribute
  * @skb: socket buffer the message is stored in
@@ -1244,16 +1273,10 @@ static inline int nla_validate_nested(const struct nlattr *start, int maxtype,
  */
 static inline int nla_align_64bit(struct sk_buff *skb, int padattr)
 {
-#ifndef CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS
-	/* The nlattr header is 4 bytes in size, that's why we test
-	 * if the skb->data _is_ aligned.  This NOP attribute, plus
-	 * nlattr header for next attribute, will make nla_data()
-	 * 8-byte aligned.
-	 */
-	if (IS_ALIGNED((unsigned long)skb_tail_pointer(skb), 8) &&
+	if (nla_need_padding_for_64bit(skb) &&
 	    !nla_reserve(skb, padattr, 0))
 		return -EMSGSIZE;
-#endif
+
 	return 0;
 }
 

include/uapi/linux/rtnetlink.h

@@ -317,6 +317,7 @@ enum rtattr_type_t {
 	RTA_ENCAP_TYPE,
 	RTA_ENCAP,
 	RTA_EXPIRES,
+	RTA_PAD,
 	__RTA_MAX
 };
 

lib/nlattr.c

@@ -354,6 +354,29 @@ struct nlattr *__nla_reserve(struct sk_buff *skb, int attrtype, int attrlen)
 }
 EXPORT_SYMBOL(__nla_reserve);
 
+/**
+ * __nla_reserve_64bit - reserve room for attribute on the skb and align it
+ * @skb: socket buffer to reserve room on
+ * @attrtype: attribute type
+ * @attrlen: length of attribute payload
+ *
+ * Adds a netlink attribute header to a socket buffer and reserves
+ * room for the payload but does not copy it. It also ensure that this
+ * attribute will be 64-bit aign.
+ *
+ * The caller is responsible to ensure that the skb provides enough
+ * tailroom for the attribute header and payload.
+ */
+struct nlattr *__nla_reserve_64bit(struct sk_buff *skb, int attrtype,
+				   int attrlen, int padattr)
+{
+	if (nla_need_padding_for_64bit(skb))
+		nla_align_64bit(skb, padattr);
+
+	return __nla_reserve(skb, attrtype, attrlen);
+}
+EXPORT_SYMBOL(__nla_reserve_64bit);
+
 /**
  * __nla_reserve_nohdr - reserve room for attribute without header
  * @skb: socket buffer to reserve room on
@@ -396,6 +419,35 @@ struct nlattr *nla_reserve(struct sk_buff *skb, int attrtype, int attrlen)
 }
 EXPORT_SYMBOL(nla_reserve);
 
+/**
+ * nla_reserve_64bit - reserve room for attribute on the skb and align it
+ * @skb: socket buffer to reserve room on
+ * @attrtype: attribute type
+ * @attrlen: length of attribute payload
+ *
+ * Adds a netlink attribute header to a socket buffer and reserves
+ * room for the payload but does not copy it. It also ensure that this
+ * attribute will be 64-bit aign.
+ *
+ * Returns NULL if the tailroom of the skb is insufficient to store
+ * the attribute header and payload.
+ */
+struct nlattr *nla_reserve_64bit(struct sk_buff *skb, int attrtype, int attrlen,
+				 int padattr)
+{
+	size_t len;
+
+	if (nla_need_padding_for_64bit(skb))
+		len = nla_total_size_64bit(attrlen);
+	else
+		len = nla_total_size(attrlen);
+	if (unlikely(skb_tailroom(skb) < len))
+		return NULL;
+
+	return __nla_reserve_64bit(skb, attrtype, attrlen, padattr);
+}
+EXPORT_SYMBOL(nla_reserve_64bit);
+
 /**
  * nla_reserve_nohdr - reserve room for attribute without header
  * @skb: socket buffer to reserve room on
@@ -435,6 +487,26 @@ void __nla_put(struct sk_buff *skb, int attrtype, int attrlen,
 }
 EXPORT_SYMBOL(__nla_put);
 
+/**
+ * __nla_put_64bit - Add a netlink attribute to a socket buffer and align it
+ * @skb: socket buffer to add attribute to
+ * @attrtype: attribute type
+ * @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 header and payload.
+ */
+void __nla_put_64bit(struct sk_buff *skb, int attrtype, int attrlen,
+		     const void *data, int padattr)
+{
+	struct nlattr *nla;
+
+	nla = __nla_reserve_64bit(skb, attrtype, attrlen, padattr);
+	memcpy(nla_data(nla), data, attrlen);
+}
+EXPORT_SYMBOL(__nla_put_64bit);
+
 /**
  * __nla_put_nohdr - Add a netlink attribute without header
  * @skb: socket buffer to add attribute to
@@ -473,6 +545,33 @@ int nla_put(struct sk_buff *skb, int attrtype, int attrlen, const void *data)
 }
 EXPORT_SYMBOL(nla_put);
 
+/**
+ * nla_put_64bit - Add a netlink attribute to a socket buffer and align it
+ * @skb: socket buffer to add attribute to
+ * @attrtype: attribute type
+ * @attrlen: length of attribute payload
+ * @data: head of attribute payload
+ *
+ * Returns -EMSGSIZE if the tailroom of the skb is insufficient to store
+ * the attribute header and payload.
+ */
+int nla_put_64bit(struct sk_buff *skb, int attrtype, int attrlen,
+		  const void *data, int padattr)
+{
+	size_t len;
+
+	if (nla_need_padding_for_64bit(skb))
+		len = nla_total_size_64bit(attrlen);
+	else
+		len = nla_total_size(attrlen);
+	if (unlikely(skb_tailroom(skb) < len))
+		return -EMSGSIZE;
+
+	__nla_put_64bit(skb, attrtype, attrlen, data, padattr);
+	return 0;
+}
+EXPORT_SYMBOL(nla_put_64bit);
+
 /**
  * nla_put_nohdr - Add a netlink attribute without header
  * @skb: socket buffer to add attribute to

net/core/rtnetlink.c

@@ -1051,14 +1051,9 @@ static noinline_for_stack int rtnl_fill_stats(struct sk_buff *skb,
 {
 	struct rtnl_link_stats64 *sp;
 	struct nlattr *attr;
-	int err;
-
-	err = nla_align_64bit(skb, IFLA_PAD);
-	if (err)
-		return err;
 
-	attr = nla_reserve(skb, IFLA_STATS64,
-			   sizeof(struct rtnl_link_stats64));
+	attr = nla_reserve_64bit(skb, IFLA_STATS64,
+				 sizeof(struct rtnl_link_stats64), IFLA_PAD);
 	if (!attr)
 		return -EMSGSIZE;
 
@@ -3469,17 +3464,10 @@ static int rtnl_fill_statsinfo(struct sk_buff *skb, struct net_device *dev,
 
 	if (filter_mask & IFLA_STATS_FILTER_BIT(IFLA_STATS_LINK_64)) {
 		struct rtnl_link_stats64 *sp;
-		int err;
-
-		/* if necessary, add a zero length NOP attribute so that
-		 * IFLA_STATS_LINK_64 will be 64-bit aligned
-		 */
-		err = nla_align_64bit(skb, IFLA_STATS_UNSPEC);
-		if (err)
-			goto nla_put_failure;
 
-		attr = nla_reserve(skb, IFLA_STATS_LINK_64,
-				   sizeof(struct rtnl_link_stats64));
+		attr = nla_reserve_64bit(skb, IFLA_STATS_LINK_64,
+					 sizeof(struct rtnl_link_stats64),
+					 IFLA_STATS_UNSPEC);
 		if (!attr)
 			goto nla_put_failure;
 

net/ipv4/ipmr.c

@@ -2104,7 +2104,7 @@ static int __ipmr_fill_mroute(struct mr_table *mrt, struct sk_buff *skb,
 	mfcs.mfcs_packets = c->mfc_un.res.pkt;
 	mfcs.mfcs_bytes = c->mfc_un.res.bytes;
 	mfcs.mfcs_wrong_if = c->mfc_un.res.wrong_if;
-	if (nla_put(skb, RTA_MFC_STATS, sizeof(mfcs), &mfcs) < 0)
+	if (nla_put_64bit(skb, RTA_MFC_STATS, sizeof(mfcs), &mfcs, RTA_PAD) < 0)
 		return -EMSGSIZE;
 
 	rtm->rtm_type = RTN_MULTICAST;
@@ -2237,7 +2237,7 @@ static size_t mroute_msgsize(bool unresolved, int maxvif)
 		      + nla_total_size(0)	/* RTA_MULTIPATH */
 		      + maxvif * NLA_ALIGN(sizeof(struct rtnexthop))
 						/* RTA_MFC_STATS */
-		      + nla_total_size(sizeof(struct rta_mfc_stats))
+		      + nla_total_size_64bit(sizeof(struct rta_mfc_stats))
 		;
 
 	return len;

net/ipv6/ip6mr.c

@@ -2268,7 +2268,7 @@ static int __ip6mr_fill_mroute(struct mr6_table *mrt, struct sk_buff *skb,
 	mfcs.mfcs_packets = c->mfc_un.res.pkt;
 	mfcs.mfcs_bytes = c->mfc_un.res.bytes;
 	mfcs.mfcs_wrong_if = c->mfc_un.res.wrong_if;
-	if (nla_put(skb, RTA_MFC_STATS, sizeof(mfcs), &mfcs) < 0)
+	if (nla_put_64bit(skb, RTA_MFC_STATS, sizeof(mfcs), &mfcs, RTA_PAD) < 0)
 		return -EMSGSIZE;
 
 	rtm->rtm_type = RTN_MULTICAST;
@@ -2411,7 +2411,7 @@ static int mr6_msgsize(bool unresolved, int maxvif)
 		      + nla_total_size(0)	/* RTA_MULTIPATH */
 		      + maxvif * NLA_ALIGN(sizeof(struct rtnexthop))
 						/* RTA_MFC_STATS */
-		      + nla_total_size(sizeof(struct rta_mfc_stats))
+		      + nla_total_size_64bit(sizeof(struct rta_mfc_stats))
 		;
 
 	return len;