[ovs-dev] [PATCH v2 6/6] netdev-linux: monitor and offload LAG slaves to TC

Roi Dayan roid at mellanox.com
Wed Jun 27 05:48:41 UTC 2018



On 26/06/2018 20:43, John Hurley wrote:
> A LAG slave cannot be added directly to an OvS bridge, nor can a OvS
> bridge port be added to a LAG dev. However, LAG masters can be added to
> OvS.
> 
> Use TC blocks to indirectly offload slaves when their master is attached
> as a linux-netdev to an OvS bridge. In the kernel TC datapath, blocks link
> together netdevs in a similar way to LAG devices. For example, if a filter
> is added to a block then it is added to all block devices, or if stats are
> incremented on 1 device then the stats on the entire block are incremented.
> This mimics LAG devices in that if a rule is applied to the LAG master
> then it should be applied to all slaves etc.
> 
> Monitor LAG slaves via the netlink socket in netdev-linux and, if their
> master is attached to the OvS bridge and has a block id, add the slave's
> qdisc to the same block. Similarly, if a slave is freed from a master,
> remove the qdisc from the masters block.
> 
> Signed-off-by: John Hurley <john.hurley at netronome.com>
> Reviewed-by: Simon Horman <simon.horman at netronome.com>
> Reviewed-by: Dirk van der Merwe <dirk.vandermerwe at netronome.com>
> ---
>  lib/netdev-linux.c | 69 ++++++++++++++++++++++++++++++++++++++++++++++++++++++
>  1 file changed, 69 insertions(+)
> 
> diff --git a/lib/netdev-linux.c b/lib/netdev-linux.c
> index 81de3b1..4aec735 100644
> --- a/lib/netdev-linux.c
> +++ b/lib/netdev-linux.c
> @@ -233,6 +233,18 @@ enum {
>      VALID_FEATURES          = 1 << 7,
>  };
>  
> +struct linux_lag_slave {
> +   uint32_t block_id;
> +   struct shash_node *node;
> +};
> +
> +/* Protects 'lag_shash' and the mutable members of struct linux_lag_slave. */
> +static struct ovs_mutex lag_mutex = OVS_MUTEX_INITIALIZER;
> +
> +/* All slaves whose LAG masters are network devices in OvS. */
> +static struct shash lag_shash OVS_GUARDED_BY(lag_mutex)
> +    = SHASH_INITIALIZER(&lag_shash);
> +
>  /* Traffic control. */
>  
>  /* An instance of a traffic control class.  Always associated with a particular
> @@ -692,6 +704,57 @@ netdev_linux_kind_is_lag(const char *kind)
>  }
>  
>  static void
> +netdev_linux_update_lag(struct rtnetlink_change *change)
> +    OVS_REQUIRES(lag_mutex)
> +{
> +    struct linux_lag_slave *lag;

hi,

I reproduced today another possible segfault where change->slave is a bad pointer.
This happened using vxlan interface.

2018-06-27T05:30:15.166Z|00038|netdev_linux|ERR|netdev_linux_update_lag: name vxlan_sys_4789 slave 0x40000000000   

both rtnetlink_parse() and the caller netdev_linux_run() didn't zero the change struct.

I zero change like the following to verify the fix.

netdev_linux_run()
...
        if (!error) {
            struct rtnetlink_change change = {0};

            if (rtnetlink_parse(&buf, &change)) {
                struct netdev *netdev_ = NULL;
...

I checked the 2 other places calling rtnetlink_parse()

1. netdev_linux_update_via_netlink() 
    struct rtnetlink_change chg;
    struct rtnetlink_change *change = &chg;

There is a problem here as well as chg is not zero.

2. rtnetlink_notifier_create()->rtnetlink_parse_cb()
Uses global rtn_change so no problem first time but from a second time we could be
with incorrect data.


So i reproduced the issue only from 1 out of 3 call places but I think we should zero
change inside rtnetlink_parse().



> +
> +    if (change->slave && netdev_linux_kind_is_lag(change->slave)) {
> +        lag = shash_find_data(&lag_shash, change->ifname);
> +
> +        if (!lag) {
> +            struct netdev *master_netdev;
> +            char master_name[IFNAMSIZ];
> +            uint32_t block_id;
> +            int error = 0;
> +
> +            if_indextoname(change->master_ifindex, master_name);
> +            master_netdev = netdev_from_name(master_name);
> +
> +            if (is_netdev_linux_class(master_netdev->netdev_class)) {
> +                block_id = netdev_get_block_id(master_netdev);
> +                if (!block_id) {
> +                   return;
> +                }
> +
> +                lag = xmalloc(sizeof *lag);
> +                lag->block_id = block_id;
> +                lag->node = shash_add(&lag_shash, change->ifname, lag);
> +
> +                /* LAG master is linux netdev so add slave to same block. */
> +                error = tc_add_del_ingress_qdisc(change->if_index, true,
> +                                                 block_id);
> +                if (error) {
> +                    VLOG_WARN("failed to bind LAG slave to master's block");
> +                    shash_delete(&lag_shash, lag->node);
> +                    free(lag);
> +                }
> +            }
> +        }
> +    } else if (change->master_ifindex == 0) {
> +        /* Check if this was a lag slave that has been freed. */
> +        lag = shash_find_data(&lag_shash, change->ifname);
> +
> +        if (lag) {
> +            tc_add_del_ingress_qdisc(change->if_index, false,
> +                                     lag->block_id);
> +            shash_delete(&lag_shash, lag->node);
> +            free(lag);
> +        }
> +    }
> +}
> +
> +static void
>  netdev_linux_run(const struct netdev_class *netdev_class OVS_UNUSED)
>  {
>      struct nl_sock *sock;
> @@ -734,6 +797,12 @@ netdev_linux_run(const struct netdev_class *netdev_class OVS_UNUSED)
>                      netdev_linux_update(netdev, nsid, &change);
>                      ovs_mutex_unlock(&netdev->mutex);
>                  }
> +                else if (!netdev_ && change.ifname) {
> +                    /* Netdev is not present in OvS but its master could be. */
> +                    ovs_mutex_lock(&lag_mutex);
> +                    netdev_linux_update_lag(&change);
> +                    ovs_mutex_unlock(&lag_mutex);
> +                }
>                  netdev_close(netdev_);
>              }
>          } else if (error == ENOBUFS) {
> 


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