On 5/11/20 11:59 AM, Tuong Lien wrote:
> When a service subscription is expired or canceled by user, it needs to
> be deleted from the subscription list, so that new subscriptions can be
> registered (max = 65535 per net). However, there are two issues in code
> that can cause such an unused subscription to persist:
>
> 1) The 'tipc_conn_delete_sub()' has a loop on the subscription list but
> it makes a break shortly when the 1st subscription differs from the one
> specified, so the subscription will not be deleted.
>
> 2) In case a subscription is canceled, the code to remove the
> 'TIPC_SUB_CANCEL' flag from the subscription filter does not work if it
> is a local subscription (i.e. the little endian isn't involved). So, it
> will be no matches when looking for the subscription to delete later.
>
> The subscription(s) will be removed eventually when the user terminates
> its topology connection but that could be a long time later. Meanwhile,
> the number of available subscriptions may be exhausted.
>
> This commit fixes the two issues above, so as needed a subscription can
> be deleted correctly.
>
> v2: define a new macro to write sub field value (- Jon's comment)
> v3: break if the sub to be deleted has been found
>
> Signed-off-by: Tuong Lien <tuong.t.l...@dektech.com.au>
Acked-by: Ying Xue <ying....@windriver.com>
> ---
> net/tipc/subscr.h | 10 ++++++++++
> net/tipc/topsrv.c | 9 +++++----
> 2 files changed, 15 insertions(+), 4 deletions(-)
>
> diff --git a/net/tipc/subscr.h b/net/tipc/subscr.h
> index aa015c233898..6ebbec1bedd1 100644
> --- a/net/tipc/subscr.h
> +++ b/net/tipc/subscr.h
> @@ -96,6 +96,16 @@ void tipc_sub_get(struct tipc_subscription *subscription);
> (swap_ ? swab32(val__) : val__); \
> })
>
> +/* tipc_sub_write - write val_ to field_ of struct sub_ in user endian format
> + */
> +#define tipc_sub_write(sub_, field_, val_) \
> + ({ \
> + struct tipc_subscr *sub__ = sub_; \
> + u32 val__ = val_; \
> + int swap_ = !((sub__)->filter & TIPC_FILTER_MASK); \
> + (sub__)->field_ = swap_ ? swab32(val__) : val__; \
> + })
> +
> /* tipc_evt_write - write val_ to field_ of struct evt_ in user endian format
> */
> #define tipc_evt_write(evt_, field_, val_) \
> diff --git a/net/tipc/topsrv.c b/net/tipc/topsrv.c
> index 931c426673c0..446af7bbd13e 100644
> --- a/net/tipc/topsrv.c
> +++ b/net/tipc/topsrv.c
> @@ -237,8 +237,8 @@ static void tipc_conn_delete_sub(struct tipc_conn *con,
> struct tipc_subscr *s)
> if (!s || !memcmp(s, &sub->evt.s, sizeof(*s))) {
> tipc_sub_unsubscribe(sub);
> atomic_dec(&tn->subscription_count);
> - } else if (s) {
> - break;
> + if (s)
> + break;
> }
> }
> spin_unlock_bh(&con->sub_lock);
> @@ -362,9 +362,10 @@ static int tipc_conn_rcv_sub(struct tipc_topsrv *srv,
> {
> struct tipc_net *tn = tipc_net(srv->net);
> struct tipc_subscription *sub;
> + u32 s_filter = tipc_sub_read(s, filter);
>
> - if (tipc_sub_read(s, filter) & TIPC_SUB_CANCEL) {
> - s->filter &= __constant_ntohl(~TIPC_SUB_CANCEL);
> + if (s_filter & TIPC_SUB_CANCEL) {
> + tipc_sub_write(s, filter, s_filter & ~TIPC_SUB_CANCEL);
> tipc_conn_delete_sub(con, s);
> return 0;
> }
>
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