Increase pm subflows counter on both server side and client side when
userspace pm creates a new subflow, and decrease the counter when it
closes a subflow.

Signed-off-by: Geliang Tang <geliang.tang@suse.com>
---
 net/mptcp/pm.c           | 21 +++++++++++++++++----
 net/mptcp/pm_userspace.c |  1 +
 2 files changed, 18 insertions(+), 4 deletions(-)

diff --git a/net/mptcp/pm.c b/net/mptcp/pm.c
index 4ed4d29d9c11..bb01f15d8e0a 100644
--- a/net/mptcp/pm.c
+++ b/net/mptcp/pm.c
@@ -87,8 +87,15 @@ bool mptcp_pm_allow_new_subflow(struct mptcp_sock *msk)
 	unsigned int subflows_max;
 	int ret = 0;
 
-	if (mptcp_pm_is_userspace(msk))
-		return mptcp_userspace_pm_active(msk);
+	if (mptcp_pm_is_userspace(msk)) {
+		if (mptcp_userspace_pm_active(msk)) {
+			spin_lock_bh(&pm->lock);
+			pm->subflows++;
+			spin_unlock_bh(&pm->lock);
+			return true;
+		}
+		return false;
+	}
 
 	subflows_max = mptcp_pm_get_subflows_max(msk);
 
@@ -181,8 +188,14 @@ void mptcp_pm_subflow_check_next(struct mptcp_sock *msk, const struct sock *ssk,
 	struct mptcp_pm_data *pm = &msk->pm;
 	bool update_subflows;
 
-	update_subflows = (subflow->request_join || subflow->mp_join) &&
-			  mptcp_pm_is_kernel(msk);
+	if (mptcp_pm_is_userspace(msk)) {
+		spin_lock_bh(&pm->lock);
+		pm->subflows--;
+		spin_unlock_bh(&pm->lock);
+		return;
+	}
+
+	update_subflows = (subflow->request_join || subflow->mp_join);
 	if (!READ_ONCE(pm->work_pending) && !update_subflows)
 		return;
 
diff --git a/net/mptcp/pm_userspace.c b/net/mptcp/pm_userspace.c
index e5b250d39e57..4da7f0ac7d8d 100644
--- a/net/mptcp/pm_userspace.c
+++ b/net/mptcp/pm_userspace.c
@@ -311,6 +311,7 @@ int mptcp_nl_cmd_sf_create(struct sk_buff *skb, struct genl_info *info)
 	spin_lock_bh(&msk->pm.lock);
 	mptcp_pm_alloc_anno_list(msk, &addr_l);
 	msk->pm.local_addr_used++;
+	msk->pm.subflows++;
 	spin_unlock_bh(&msk->pm.lock);
 
 	lock_sock(sk);
-- 
2.35.3

Hi Geliang,


On 14/04/2023 11:11, Geliang Tang wrote:
> Increase pm subflows counter on both server side and client side when
> userspace pm creates a new subflow, and decrease the counter when it
> closes a subflow.

Do you mind adding:

  Fixes: 702c2f646d42 ("mptcp: netlink: allow userspace-driven subflow
establishment")
  Closes: https://github.com/multipath-tcp/mptcp_net-next/issues/329

Same here, it looks like a bug: we forgot to update existing counters in
this new mode.

Also, may you also add that this modification is similar to how the
in-kernel PM is updating the counter: when additional subflows are
created/removed?

> Signed-off-by: Geliang Tang <geliang.tang@suse.com>
> ---
>  net/mptcp/pm.c           | 21 +++++++++++++++++----
>  net/mptcp/pm_userspace.c |  1 +
>  2 files changed, 18 insertions(+), 4 deletions(-)
> 
> diff --git a/net/mptcp/pm.c b/net/mptcp/pm.c
> index 4ed4d29d9c11..bb01f15d8e0a 100644
> --- a/net/mptcp/pm.c
> +++ b/net/mptcp/pm.c
> @@ -87,8 +87,15 @@ bool mptcp_pm_allow_new_subflow(struct mptcp_sock *msk)
>  	unsigned int subflows_max;
>  	int ret = 0;
>  
> -	if (mptcp_pm_is_userspace(msk))
> -		return mptcp_userspace_pm_active(msk);
> +	if (mptcp_pm_is_userspace(msk)) {
> +		if (mptcp_userspace_pm_active(msk)) {
> +			spin_lock_bh(&pm->lock);
> +			pm->subflows++;
> +			spin_unlock_bh(&pm->lock);
> +			return true;
> +		}
> +		return false;
> +	}
>  
>  	subflows_max = mptcp_pm_get_subflows_max(msk);
>  
> @@ -181,8 +188,14 @@ void mptcp_pm_subflow_check_next(struct mptcp_sock *msk, const struct sock *ssk,
>  	struct mptcp_pm_data *pm = &msk->pm;
>  	bool update_subflows;
>  
> -	update_subflows = (subflow->request_join || subflow->mp_join) &&
> -			  mptcp_pm_is_kernel(msk);
> +	if (mptcp_pm_is_userspace(msk)) {
> +		spin_lock_bh(&pm->lock);
> +		pm->subflows--;
> +		spin_unlock_bh(&pm->lock);
> +		return;
> +	}
> +
> +	update_subflows = (subflow->request_join || subflow->mp_join);

Should you not also decrement the counter only if one of these
conditions is met to keep the same behaviour as what is done with the
in-kernel PM: 'subflows' counter only look at the additional subflows?

Cheers,
Matt
-- 
Tessares | Belgium | Hybrid Access Solutions
www.tessares.net