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Commit 35c58459 authored by David S. Miller's avatar David S. Miller
Browse files

net: Add helpers for 64-bit aligning netlink attributes. 



Suggested-by: default avatarEric Dumazet <eric.dumazet@gmail.com>
Suggested-by: default avatarNicolas Dichtel <nicolas.dichtel@6wind.com>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent 18402843

include/net/netlink.h

+37 −0
Original line number Diff line number Diff line
@@ -1230,6 +1230,43 @@ static inline int nla_validate_nested(const struct nlattr *start, int maxtype, 
	return nla_validate(nla_data(start), nla_len(start), maxtype, policy);

}



/**

 * nla_align_64bit - 64-bit align the nla_data() of next attribute

 * @skb: socket buffer the message is stored in

 * @padattr: attribute type for the padding

 *

 * Conditionally emit a padding netlink attribute in order to make

 * the next attribute we emit have a 64-bit aligned nla_data() area.

 * This will only be done in architectures which do not have

 * HAVE_EFFICIENT_UNALIGNED_ACCESS defined.

 *

 * Returns zero on success or a negative error code.

 */

static inline int nla_align_64bit(struct sk_buff *skb, int padattr)

{

#ifndef HAVE_EFFICIENT_UNALIGNED_ACCESS

	if (IS_ALIGNED((unsigned long)skb->data, 8)) {

		struct nlattr *attr = nla_reserve(skb, padattr, 0);

		if (!attr)

			return -EMSGSIZE;

	}

#endif

	return 0;

}



/**

 * nla_total_size_64bit - total length of attribute including padding

 * @payload: length of payload

 */

static inline int nla_total_size_64bit(int payload)

{

	return NLA_ALIGN(nla_attr_size(payload))

#ifndef HAVE_EFFICIENT_UNALIGNED_ACCESS

		+ NLA_ALIGN(nla_attr_size(0))

#endif

		;

}



/**

 * nla_for_each_attr - iterate over a stream of attributes

 * @pos: loop counter, set to current attribute

net/core/rtnetlink.c

+5 −19
Original line number Diff line number Diff line
@@ -878,10 +878,7 @@ static noinline size_t if_nlmsg_size(const struct net_device *dev, 
	       + nla_total_size(IFNAMSIZ) /* IFLA_QDISC */

	       + nla_total_size(sizeof(struct rtnl_link_ifmap))

	       + nla_total_size(sizeof(struct rtnl_link_stats))

#ifndef HAVE_EFFICIENT_UNALIGNED_ACCESS

	       + nla_total_size(0) /* IFLA_PAD */

#endif

	       + nla_total_size(sizeof(struct rtnl_link_stats64))

	       + nla_total_size_64bit(sizeof(struct rtnl_link_stats64))

	       + nla_total_size(MAX_ADDR_LEN) /* IFLA_ADDRESS */

	       + nla_total_size(MAX_ADDR_LEN) /* IFLA_BROADCAST */

	       + nla_total_size(4) /* IFLA_TXQLEN */
@@ -1054,22 +1051,11 @@ static noinline_for_stack int rtnl_fill_stats(struct sk_buff *skb, 
{

	struct rtnl_link_stats64 *sp;

	struct nlattr *attr;

	int err;



#ifndef HAVE_EFFICIENT_UNALIGNED_ACCESS

	/* IF necessary, add a zero length NOP attribute so that the

	 * nla_data() of the IFLA_STATS64 will be 64-bit aligned.

	 *

	 * 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 IFLA_STATS64, will make nla_data() 8-byte

	 * aligned.

	 */

	if (IS_ALIGNED((unsigned long)skb->data, 8)) {

		attr = nla_reserve(skb, IFLA_PAD, 0);

		if (!attr)

			return -EMSGSIZE;

	}

#endif

	err = nla_align_64bit(skb, IFLA_PAD);

	if (err)

		return err;



	attr = nla_reserve(skb, IFLA_STATS64,

			   sizeof(struct rtnl_link_stats64));