diff options
author | Johannes Berg | 2011-06-20 13:40:46 +0200 |
---|---|---|
committer | John W. Linville | 2011-06-22 16:09:45 -0400 |
commit | 670dc2833d144375eac36ad74111495a825a9288 (patch) | |
tree | 12d5d3a925da562a6ba0497c47f4b55c71ff545b /include/net | |
parent | c1c3daee97498f5d74bfd23531cfe23c8e14a619 (diff) |
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>
Diffstat (limited to 'include/net')
-rw-r--r-- | include/net/genetlink.h | 32 | ||||
-rw-r--r-- | include/net/netlink.h | 24 |
2 files changed, 56 insertions, 0 deletions
diff --git a/include/net/genetlink.h b/include/net/genetlink.h index d420f28b6d60..82d8d09faa44 100644 --- a/include/net/genetlink.h +++ b/include/net/genetlink.h @@ -160,6 +160,38 @@ static inline void *genlmsg_put(struct sk_buff *skb, u32 pid, u32 seq, } /** + * 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 * @info: receiver info diff --git a/include/net/netlink.h b/include/net/netlink.h index 02740a94f108..98c185441bee 100644 --- a/include/net/netlink.h +++ b/include/net/netlink.h @@ -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 **************************************************************************/ |