[PATCH 5.15.y] mptcp: fix NL PM announced address accounting

["Matthieu Baerts (NGI0)" <matttbe@kernel.org>]

From: Paolo Abeni <pabeni@redhat.com>

commit 4b317e0eb287bd30a1b329513531157c25e8b692 upstream.

Currently the per connection announced address counter is never
decreased. As a consequence, after connection establishment, if
the NL PM deletes an endpoint and adds a new/different one, no
additional subflow is created for the new endpoint even if the
current limits allow that.

Address the issue properly updating the signaled address counter
every time the NL PM removes such addresses.

Fixes: 01cacb00b35c ("mptcp: add netlink-based PM")
Cc: stable@vger.kernel.org
Signed-off-by: Paolo Abeni <pabeni@redhat.com>
Reviewed-by: Matthieu Baerts (NGI0) <matttbe@kernel.org>
Signed-off-by: Matthieu Baerts (NGI0) <matttbe@kernel.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
[ Conflicts in pm_netlink.c, because the commit 6fa0174a7c86 ("mptcp:
  more careful RM_ADDR generation") is not in this version. The
  conditions are slightly different, but the same fix can be applied:
  first checking the IDs, then removing the address. ]
Signed-off-by: Matthieu Baerts (NGI0) <matttbe@kernel.org>
---
 net/mptcp/pm_netlink.c | 12 +++++++-----
 1 file changed, 7 insertions(+), 5 deletions(-)

diff --git a/net/mptcp/pm_netlink.c b/net/mptcp/pm_netlink.c
index 7b312aa03e6b..1d64c9fed39e 100644
--- a/net/mptcp/pm_netlink.c
+++ b/net/mptcp/pm_netlink.c
@@ -1323,6 +1323,7 @@ static bool mptcp_pm_remove_anno_addr(struct mptcp_sock *msk,
 	ret = remove_anno_list_by_saddr(msk, addr);
 	if (ret || force) {
 		spin_lock_bh(&msk->pm.lock);
+		msk->pm.add_addr_signaled -= ret;
 		mptcp_pm_remove_addr(msk, &list);
 		spin_unlock_bh(&msk->pm.lock);
 	}
@@ -1462,19 +1463,20 @@ static void mptcp_pm_remove_addrs_and_subflows(struct mptcp_sock *msk,
 	struct mptcp_pm_addr_entry *entry;
 
 	list_for_each_entry(entry, rm_list, list) {
-		if (lookup_subflow_by_saddr(&msk->conn_list, &entry->addr) &&
-		    alist.nr < MPTCP_RM_IDS_MAX &&
-		    slist.nr < MPTCP_RM_IDS_MAX) {
+		if (alist.nr < MPTCP_RM_IDS_MAX &&
+		    slist.nr < MPTCP_RM_IDS_MAX &&
+		    lookup_subflow_by_saddr(&msk->conn_list, &entry->addr)) {
 			alist.ids[alist.nr++] = entry->addr.id;
 			slist.ids[slist.nr++] = entry->addr.id;
-		} else if (remove_anno_list_by_saddr(msk, &entry->addr) &&
-			 alist.nr < MPTCP_RM_IDS_MAX) {
+		} else if (alist.nr < MPTCP_RM_IDS_MAX &&
+			   remove_anno_list_by_saddr(msk, &entry->addr)) {
 			alist.ids[alist.nr++] = entry->addr.id;
 		}
 	}
 
 	if (alist.nr) {
 		spin_lock_bh(&msk->pm.lock);
+		msk->pm.add_addr_signaled -= alist.nr;
 		mptcp_pm_remove_addr(msk, &alist);
 		spin_unlock_bh(&msk->pm.lock);
 	}
-- 
2.45.2