Re: [PATCH net-next 4/5] sctp: add SCTP_AUTH_FREE_KEY type for AUTHENTICATION_EVENT

[Marcelo Ricardo Leitner <marcelo.leitner@gmail.com>]

On Wed, Mar 14, 2018 at 07:05:33PM +0800, Xin Long wrote:
> This patch is to add SCTP_AUTH_FREE_KEY type for AUTHENTICATION_EVENT,
> as described in section 6.1.8 of RFC6458.
> 
>       SCTP_AUTH_FREE_KEY:  This report indicates that the SCTP
>          implementation will no longer use the key identifier specified
>          in auth_keynumber.
> 
> After deactivating a key, it would never be used again, which means
> it's refcnt can't be held/increased by new chunks. But there may be
> some chunks in out queue still using it. So only when refcnt is 1,
> which means no chunk in outqueue is using/holding this key either,
> this EVENT would be sent.
> 
> When users receive this notification, they could do DEL_KEY sockopt to
> remove this shkey, and also tell the peer that this key won't be used
> in any chunk thoroughly from now on, then the peer can remove it as
> well safely.
> 
> Signed-off-by: Xin Long <lucien.xin@gmail.com>

Acked-by: Marcelo Ricardo Leitner <marcelo.leitner@gmail.com>

> ---
>  include/uapi/linux/sctp.h |  6 +++++-
>  net/sctp/auth.c           | 14 ++++++++++++++
>  net/sctp/sm_make_chunk.c  | 20 +++++++++++++++++++-
>  net/sctp/sm_statefuns.c   |  2 +-
>  net/sctp/socket.c         | 19 ++++++++++++++++++-
>  5 files changed, 57 insertions(+), 4 deletions(-)
> 
> diff --git a/include/uapi/linux/sctp.h b/include/uapi/linux/sctp.h
> index 08fc313..18ebbfe 100644
> --- a/include/uapi/linux/sctp.h
> +++ b/include/uapi/linux/sctp.h
> @@ -518,7 +518,11 @@ struct sctp_authkey_event {
>  	sctp_assoc_t auth_assoc_id;
>  };
>  
> -enum { SCTP_AUTH_NEWKEY = 0, };
> +enum {
> +	SCTP_AUTH_NEW_KEY,
> +#define	SCTP_AUTH_NEWKEY	SCTP_AUTH_NEW_KEY /* compatible with before */
> +	SCTP_AUTH_FREE_KEY,
> +};
>  
>  /*
>   * 6.1.9. SCTP_SENDER_DRY_EVENT
> diff --git a/net/sctp/auth.c b/net/sctp/auth.c
> index a073123..e64630c 100644
> --- a/net/sctp/auth.c
> +++ b/net/sctp/auth.c
> @@ -992,6 +992,20 @@ int sctp_auth_deact_key_id(struct sctp_endpoint *ep,
>  	if (!found)
>  		return -EINVAL;
>  
> +	/* refcnt = 1 and !list_empty mean it's not being used anywhere
> +	 * and deactivated will be set, so it's time to notify userland
> +	 * that this shkey can be freed.
> +	 */
> +	if (asoc && !list_empty(&key->key_list) &&
> +	    refcount_read(&key->refcnt) = 1) {
> +		struct sctp_ulpevent *ev;
> +
> +		ev = sctp_ulpevent_make_authkey(asoc, key->key_id,
> +						SCTP_AUTH_FREE_KEY, GFP_KERNEL);
> +		if (ev)
> +			asoc->stream.si->enqueue_event(&asoc->ulpq, ev);
> +	}
> +
>  	key->deactivated = 1;
>  
>  	return 0;
> diff --git a/net/sctp/sm_make_chunk.c b/net/sctp/sm_make_chunk.c
> index 10f071c..cc20bc3 100644
> --- a/net/sctp/sm_make_chunk.c
> +++ b/net/sctp/sm_make_chunk.c
> @@ -89,8 +89,26 @@ static void sctp_control_release_owner(struct sk_buff *skb)
>  {
>  	struct sctp_chunk *chunk = skb_shinfo(skb)->destructor_arg;
>  
> -	if (chunk->shkey)
> +	if (chunk->shkey) {
> +		struct sctp_shared_key *shkey = chunk->shkey;
> +		struct sctp_association *asoc = chunk->asoc;
> +
> +		/* refcnt = 2 and !list_empty mean after this release, it's
> +		 * not being used anywhere, and it's time to notify userland
> +		 * that this shkey can be freed if it's been deactivated.
> +		 */
> +		if (shkey->deactivated && !list_empty(&shkey->key_list) &&
> +		    refcount_read(&shkey->refcnt) = 2) {
> +			struct sctp_ulpevent *ev;
> +
> +			ev = sctp_ulpevent_make_authkey(asoc, shkey->key_id,
> +							SCTP_AUTH_FREE_KEY,
> +							GFP_KERNEL);
> +			if (ev)
> +				asoc->stream.si->enqueue_event(&asoc->ulpq, ev);
> +		}
>  		sctp_auth_shkey_release(chunk->shkey);
> +	}
>  }
>  
>  static void sctp_control_set_owner_w(struct sctp_chunk *chunk)
> diff --git a/net/sctp/sm_statefuns.c b/net/sctp/sm_statefuns.c
> index 792e0e2..1e41dee 100644
> --- a/net/sctp/sm_statefuns.c
> +++ b/net/sctp/sm_statefuns.c
> @@ -4246,7 +4246,7 @@ enum sctp_disposition sctp_sf_eat_auth(struct net *net,
>  		struct sctp_ulpevent *ev;
>  
>  		ev = sctp_ulpevent_make_authkey(asoc, ntohs(auth_hdr->shkey_id),
> -				    SCTP_AUTH_NEWKEY, GFP_ATOMIC);
> +				    SCTP_AUTH_NEW_KEY, GFP_ATOMIC);
>  
>  		if (!ev)
>  			return -ENOMEM;
> diff --git a/net/sctp/socket.c b/net/sctp/socket.c
> index 65cc354..aeecdd6 100644
> --- a/net/sctp/socket.c
> +++ b/net/sctp/socket.c
> @@ -8166,8 +8166,25 @@ static void sctp_wfree(struct sk_buff *skb)
>  	sk->sk_wmem_queued   -= skb->truesize;
>  	sk_mem_uncharge(sk, skb->truesize);
>  
> -	if (chunk->shkey)
> +	if (chunk->shkey) {
> +		struct sctp_shared_key *shkey = chunk->shkey;
> +
> +		/* refcnt = 2 and !list_empty mean after this release, it's
> +		 * not being used anywhere, and it's time to notify userland
> +		 * that this shkey can be freed if it's been deactivated.
> +		 */
> +		if (shkey->deactivated && !list_empty(&shkey->key_list) &&
> +		    refcount_read(&shkey->refcnt) = 2) {
> +			struct sctp_ulpevent *ev;
> +
> +			ev = sctp_ulpevent_make_authkey(asoc, shkey->key_id,
> +							SCTP_AUTH_FREE_KEY,
> +							GFP_KERNEL);
> +			if (ev)
> +				asoc->stream.si->enqueue_event(&asoc->ulpq, ev);
> +		}
>  		sctp_auth_shkey_release(chunk->shkey);
> +	}
>  
>  	sock_wfree(skb);
>  	sctp_wake_up_waiters(sk, asoc);
> -- 
> 2.1.0
>