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

Suggested-by: Eric Dumazet <eric.dumazet@gmail.com>
Suggested-by: Nicolas Dichtel <nicolas.dichtel@6wind.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
David S. Miller 2016-04-19 19:49:29 -04:00
parent 18402843bf
commit 35c5845957
2 changed files with 42 additions and 19 deletions
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37
include/net/netlink.h
View File

@ -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

24
net/core/rtnetlink.c
View File

@ -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));