netlink: advertise incomplete dumps
Consider the following situation: * a dump that would show 8 entries, four in the first round, and four in the second * between the first and second rounds, 6 entries are removed * now the second round will not show any entry, and even if there is a sequence/generation counter the application will not know To solve this problem, add a new flag NLM_F_DUMP_INTR to the netlink header that indicates the dump wasn't consistent, this flag can also be set on the MSG_DONE message that terminates the dump, and as such above situation can be detected. To achieve this, add a sequence counter to the netlink callback struct. Of course, netlink code still needs to use this new functionality. The correct way to do that is to always set cb->seq when a dumpit callback is invoked and call nl_dump_check_consistent() for each new message. The core code will also call this function for the final MSG_DONE message. To make it usable with generic netlink, a new function genlmsg_nlhdr() is needed to obtain the netlink header from the genetlink user header. Signed-off-by: Johannes Berg <johannes.berg@intel.com> Acked-by: David S. Miller <davem@davemloft.net> Signed-off-by: John W. Linville <linville@tuxdriver.com>
This commit is contained in:
parent
c1c3daee97
commit
670dc2833d
|
@ -48,6 +48,7 @@ struct nlmsghdr {
|
|||
#define NLM_F_MULTI 2 /* Multipart message, terminated by NLMSG_DONE */
|
||||
#define NLM_F_ACK 4 /* Reply with ack, with zero or error code */
|
||||
#define NLM_F_ECHO 8 /* Echo this request */
|
||||
#define NLM_F_DUMP_INTR 16 /* Dump was inconsistent due to sequence change */
|
||||
|
||||
/* Modifiers to GET request */
|
||||
#define NLM_F_ROOT 0x100 /* specify tree root */
|
||||
|
@ -221,6 +222,7 @@ struct netlink_callback {
|
|||
struct netlink_callback *cb);
|
||||
int (*done)(struct netlink_callback *cb);
|
||||
int family;
|
||||
unsigned int prev_seq, seq;
|
||||
long args[6];
|
||||
};
|
||||
|
||||
|
|
|
@ -159,6 +159,38 @@ static inline void *genlmsg_put(struct sk_buff *skb, u32 pid, u32 seq,
|
|||
return (char *) hdr + GENL_HDRLEN;
|
||||
}
|
||||
|
||||
/**
|
||||
* genlmsg_nlhdr - Obtain netlink header from user specified header
|
||||
* @user_hdr: user header as returned from genlmsg_put()
|
||||
* @family: generic netlink family
|
||||
*
|
||||
* Returns pointer to netlink header.
|
||||
*/
|
||||
static inline struct nlmsghdr *genlmsg_nlhdr(void *user_hdr,
|
||||
struct genl_family *family)
|
||||
{
|
||||
return (struct nlmsghdr *)((char *)user_hdr -
|
||||
family->hdrsize -
|
||||
GENL_HDRLEN -
|
||||
NLMSG_HDRLEN);
|
||||
}
|
||||
|
||||
/**
|
||||
* genl_dump_check_consistent - check if sequence is consistent and advertise if not
|
||||
* @cb: netlink callback structure that stores the sequence number
|
||||
* @user_hdr: user header as returned from genlmsg_put()
|
||||
* @family: generic netlink family
|
||||
*
|
||||
* Cf. nl_dump_check_consistent(), this just provides a wrapper to make it
|
||||
* simpler to use with generic netlink.
|
||||
*/
|
||||
static inline void genl_dump_check_consistent(struct netlink_callback *cb,
|
||||
void *user_hdr,
|
||||
struct genl_family *family)
|
||||
{
|
||||
nl_dump_check_consistent(cb, genlmsg_nlhdr(user_hdr, family));
|
||||
}
|
||||
|
||||
/**
|
||||
* genlmsg_put_reply - Add generic netlink header to a reply message
|
||||
* @skb: socket buffer holding the message
|
||||
|
|
|
@ -638,6 +638,30 @@ static inline int nlmsg_unicast(struct sock *sk, struct sk_buff *skb, u32 pid)
|
|||
nlmsg_ok(pos, rem); \
|
||||
pos = nlmsg_next(pos, &(rem)))
|
||||
|
||||
/**
|
||||
* nl_dump_check_consistent - check if sequence is consistent and advertise if not
|
||||
* @cb: netlink callback structure that stores the sequence number
|
||||
* @nlh: netlink message header to write the flag to
|
||||
*
|
||||
* This function checks if the sequence (generation) number changed during dump
|
||||
* and if it did, advertises it in the netlink message header.
|
||||
*
|
||||
* The correct way to use it is to set cb->seq to the generation counter when
|
||||
* all locks for dumping have been acquired, and then call this function for
|
||||
* each message that is generated.
|
||||
*
|
||||
* Note that due to initialisation concerns, 0 is an invalid sequence number
|
||||
* and must not be used by code that uses this functionality.
|
||||
*/
|
||||
static inline void
|
||||
nl_dump_check_consistent(struct netlink_callback *cb,
|
||||
struct nlmsghdr *nlh)
|
||||
{
|
||||
if (cb->prev_seq && cb->seq != cb->prev_seq)
|
||||
nlh->nlmsg_flags |= NLM_F_DUMP_INTR;
|
||||
cb->prev_seq = cb->seq;
|
||||
}
|
||||
|
||||
/**************************************************************************
|
||||
* Netlink Attributes
|
||||
**************************************************************************/
|
||||
|
|
|
@ -1693,6 +1693,8 @@ static int netlink_dump(struct sock *sk)
|
|||
if (!nlh)
|
||||
goto errout_skb;
|
||||
|
||||
nl_dump_check_consistent(cb, nlh);
|
||||
|
||||
memcpy(nlmsg_data(nlh), &len, sizeof(len));
|
||||
|
||||
if (sk_filter(sk, skb))
|
||||
|
|
Loading…
Reference in New Issue