Johannes Berg wrote:
> Allow changing the number of groups for a netlink family
> after it has been created, use RCU to protect the listeners
> bitmap keeping netlink_has_listeners() lock-free.
>
> Signed-off-by: Johannes Berg <[EMAIL PROTECTED]>
>
> ---
> include/linux/netlink.h | 1
> net/netlink/af_netlink.c | 86
> +++++++++++++++++++++++++++++++++++------------
> 2 files changed, 66 insertions(+), 21 deletions(-)
>
> --- wireless-dev.orig/net/netlink/af_netlink.c 2007-07-17
> 14:05:30.210964463 +0200
> +++ wireless-dev/net/netlink/af_netlink.c 2007-07-17 14:05:30.720964463
> +0200
> -static int netlink_alloc_groups(struct sock *sk)
> +static int netlink_realloc_groups(struct sock *sk)
> {
> struct netlink_sock *nlk = nlk_sk(sk);
> unsigned int groups;
> + unsigned long *new_groups;
> int err = 0;
>
> netlink_lock_table();
This is actually a bug in the current code I think, netlink_lock_table
is a reader lock.
> groups = nl_table[sk->sk_protocol].groups;
> if (!nl_table[sk->sk_protocol].registered)
> err = -ENOENT;
> - netlink_unlock_table();
>
> if (err)
> - return err;
> + goto out_unlock;
>
> - nlk->groups = kzalloc(NLGRPSZ(groups), GFP_KERNEL);
> - if (nlk->groups == NULL)
> - return -ENOMEM;
> + if (nlk->ngroups >= groups)
> + goto out_unlock;
> +
> + new_groups = krealloc(nlk->groups, NLGRPSZ(groups), GFP_KERNEL);
> + if (new_groups == NULL) {
> + err = -ENOMEM;
> + goto out_unlock;
> + }
> + memset((char*)new_groups + NLGRPSZ(nlk->ngroups), 0,
> + NLGRPSZ(groups) - NLGRPSZ(nlk->ngroups));
> +
> + nlk->groups = new_groups;
> nlk->ngroups = groups;
> - return 0;
> + out_unlock:
> + netlink_unlock_table();
> + return err;
> }
> +int netlink_change_ngroups(int unit, unsigned int groups)
I think it would be more consistent to pass the kernel socket
instead of the unit.
> +{
> + unsigned long *listeners, old = NULL;
> + int err = 0;
> +
> + netlink_table_grab();
> + if (NLGRPSZ(nl_table[unit].groups) < NLGRPSZ(groups)) {
> + listeners = kzalloc(NLGRPSZ(groups), GFP_ATOMIC);
> + if (!listeners) {
> + err = -ENOMEM;
> + goto out_ungrab;
> + }
> + old = nl_table[unit].listeners;
> + memcpy(listeners, old, NLGRPSZ(nl_table[unit].groups));
> + rcu_assign_pointer(nl_table[unit].listeners, listeners);
> + }
> + nl_table[unit].groups = groups;
This might set the group to a value < 32. I don't expect it matters,
but when I changed to old code to support > 32 groups I enforced
a minimum of 32 so anything outside the kernel multicasting on them
would still work (even though its a really stupid idea). So for
consistency this should probably also use a minimum of 32.
-
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