Re: [PATCH net-next v3 0/5] Rework ip_ra_chain protection

[Kirill Tkhai <ktkhai@virtuozzo.com>]

On 22.03.2018 12:44, Kirill Tkhai wrote:
> Commit 1215e51edad1 "ipv4: fix a deadlock in ip_ra_control"
> made rtnl_lock() be used in raw_close(). This function is called
> on every RAW socket destruction, so that rtnl_mutex is taken
> every time. This scales very sadly. I observe cleanup_net()
> spending a lot of time in rtnl_lock() and raw_close() is one
> of the biggest rtnl user (since we have percpu net->ipv4.icmp_sk).
> 
> This patchset reworks the locking: reverts the problem commit
> and its descendant, and introduces rtnl-independent locking.
> This may have a continuation, and someone may work on killing
> rtnl_lock() in mrtsock_destruct() in the future.
> 
> Thanks,
> Kirill
> 
> ---
> v3: Change patches order: [2/5] and [3/5].
> v2: Fix sparse warning [4/5], as reported by kbuild test robot.
> 
> ---
> 
> Kirill Tkhai (5):
>       net: Revert "ipv4: get rid of ip_ra_lock"
>       net: Move IP_ROUTER_ALERT out of lock_sock(sk)
>       net: Revert "ipv4: fix a deadlock in ip_ra_control"
>       net: Make ip_ra_chain per struct net
>       net: Replace ip_ra_lock with per-net mutex
> 
> 
>  include/net/ip.h         |   13 +++++++++++--
>  include/net/netns/ipv4.h |    2 ++
>  net/core/net_namespace.c |    1 +
>  net/ipv4/ip_input.c      |    5 ++---
>  net/ipv4/ip_sockglue.c   |   34 +++++++++++++---------------------
>  net/ipv4/ipmr.c          |   11 +++++++++--
>  net/ipv4/raw.c           |    2 --
>  7 files changed, 38 insertions(+), 30 deletions(-)
> 
> --
> Signed-off-by: Kirill Tkhai <ktkhai@virtuozzo.com>

JFI: I used the below program to test:

#define _GNU_SOURCE
#include <sys/socket.h>
#include <netinet/in.h>
#include <sys/types.h>
#include <linux/mroute.h>
#include <sched.h>

int main()
{
        int sk, v, i = 0;

        if (unshare(CLONE_NEWNET)) {
                perror("unshare");
                return 1;
        }
        sk = socket(AF_INET, SOCK_RAW, IPPROTO_IGMP);
        if (sk < 0) {
                perror("socket");
                return 1;
        }
        for (i = 0; i < 3; i++)
                fork();

        while (1) {
                setsockopt(sk, IPPROTO_IP, MRT_INIT, (void *)&v, sizeof(v));
                setsockopt(sk, IPPROTO_IP, MRT_DONE, (void *)&v, sizeof(v));
                v = (i++)%2;
                setsockopt(sk, IPPROTO_IP, IP_ROUTER_ALERT, (void *)&v, sizeof(v));
        }

        return 0;
}