From 670dc2833d144375eac36ad74111495a825a9288 Mon Sep 17 00:00:00 2001 From: Johannes Berg Date: Mon, 20 Jun 2011 13:40:46 +0200 Subject: 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 Acked-by: David S. Miller Signed-off-by: John W. Linville --- include/linux/netlink.h | 2 ++ 1 file changed, 2 insertions(+) (limited to 'include/linux/netlink.h') diff --git a/include/linux/netlink.h b/include/linux/netlink.h index 4c4ac3f3ce5a..8d1bcec5cc06 100644 --- a/include/linux/netlink.h +++ b/include/linux/netlink.h @@ -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]; }; -- cgit v1.2.3