The netlink dump functionality transfers a large number of entries from the kernel to userspace. It is rather likely that the transfer has to interrupted and later continued. During that time, it can happen that either new entries are added or removed. The userspace could than either receive some entries multiple times or miss entries.
Commit 670dc2833d14 ("netlink: advertise incomplete dumps") introduced a mechanism to inform userspace about this problem. Userspace can then decide whether it is necessary or not to retry dumping the information again.
The netlink dump functions have to be switched to exclusive locks to avoid changes while the current message is prepared. And an external generation sequence counter is introduced which tracks all modifications of the list/hash.
There some netlink dump commands which were not yet modified. These datastructures use subentries (or entries for multiple main object) which makes mapping to a generation sequence counter more problematic:
* originator * neighbor list (multiple interfaces make it harder) * global translation table
Also the batadv_algo stuff was ignored because it doesn't even have locks and is not supposed to be modified at runtime.
Kind regards, Sven
Sven Eckelmann (9): batman-adv: Add compat for genl_dump_check_consistent batman-adv: Add inconsistent gateway netlink dump detection batman-adv: Add inconsistent hardif netlink dump detection batman-adv: Store modification counter via hash helpers batman-adv: Add inconsistent backbone netlink dump detection batman-adv: Add inconsistent claim netlink dump detection batman-adv: Add inconsistent dat netlink dump detection batman-adv: Add inconsistent local TT netlink dump detection batman-adv: Add inconsistent multicast netlink dump detection
compat-include/net/genetlink.h | 45 ++++++++++++++ net/batman-adv/bat_iv_ogm.c | 24 +++++--- net/batman-adv/bat_v.c | 26 +++++--- net/batman-adv/bridge_loop_avoidance.c | 82 +++++++++++++++----------- net/batman-adv/distributed-arp-table.c | 42 +++++++------ net/batman-adv/gateway_client.c | 3 + net/batman-adv/hard-interface.c | 3 + net/batman-adv/hash.c | 2 + net/batman-adv/hash.h | 6 ++ net/batman-adv/main.c | 3 + net/batman-adv/main.h | 1 + net/batman-adv/multicast.c | 51 ++++++++-------- net/batman-adv/netlink.c | 24 ++++---- net/batman-adv/translation-table.c | 41 +++++++------ net/batman-adv/types.h | 5 +- 15 files changed, 233 insertions(+), 125 deletions(-) create mode 100644 compat-include/net/genetlink.h