Subject: Re: [patch v2 04/11] nf_conntrack_netlink: pass nf_conntrack_netlink module to netlink_dump_start

From: Gao feng <[email-masked]>
Date: Wed, 26 Sep 2012 17:42:31 +0800

Hi Pablo:

于 2012年09月26日 17:26, Pablo Neira Ayuso 写道:
> On Wed, Sep 26, 2012 at 04:41:21PM +0800, Gao feng wrote:
>> use proper netlink_dump_control.done and .module to avoid panic.
>>
>> Signed-off-by: Gao feng <[email-masked]>
>> ---
>>  net/netfilter/nf_conntrack_netlink.c |    8 ++++++++
>>  1 files changed, 8 insertions(+), 0 deletions(-)
>>
>> diff --git a/net/netfilter/nf_conntrack_netlink.c b/net/netfilter/nf_conntrack_netlink.c
>> index 9807f32..509a257 100644
>> --- a/net/netfilter/nf_conntrack_netlink.c
>> +++ b/net/netfilter/nf_conntrack_netlink.c
>> @@ -706,6 +706,7 @@ static int ctnetlink_done(struct netlink_callback *cb)
>>  		nf_ct_put((struct nf_conn *)cb->args[1]);
>>  	if (cb->data)
>>  		kfree(cb->data);
>> +	netlink_dump_done(cb);
> 
> I think you can call netlink_dump_done from af_netlink.c:
> 
> static int netlink_dump(struct sock *sk) 
>         ...
>         if (cb->done) {
>                 cb->done(cb);
>                 netlink_dump_done(...);
>         }
> 
> Thus, you don't need to change netlink_dump_control in every netlink
> subsystem.

because cb->done is called by netlink_sock_destruct too,it's very usefully
when userspace program only send dump request to kernel without reading
data from kernel.

> 
>>  	return 0;
>>  }
>>  
>> @@ -1022,6 +1023,7 @@ ctnetlink_get_conntrack(struct sock *ctnl, struct sk_buff *skb,
>>  		struct netlink_dump_control c = {
>>  			.dump = ctnetlink_dump_table,
>>  			.done = ctnetlink_done,
>> +			.module = THIS_MODULE,
> 
> You can do something similar to:
> 
> 9f00d97 netlink: hide struct module parameter in netlink_kernel_create
> 
> by definiting netlink_dump_start as static inline and using
> THIS_MODULE from there.
> 
> If I'm not missing anything, with those two changes, you will not need
> to modify any caller and it will result one single patch.
> 

You can see the patch [11/11], THIS_MODULE in infiniband/core/cma.c
means module rdma_cm,but we call netlink_dump_start in infiniband/core/netlink.c

we should make sure the cb.moudle point to the module which cb.dump belongs to.
we can call netlink_dump_start to set cb->dump everywhere, so I think we still
need to pass struct module to the netlink_callback.

thanks for your comments!