mptcp: remove id 0 address

This patch added a new function mptcp_nl_remove_id_zero_address to
remove the id 0 address.

In this function, traverse all the existing msk sockets to find the
msk matched the input IP address. Then fill the removing list with
id 0, and pass it to mptcp_pm_remove_addr and mptcp_pm_remove_subflow.
Suggested-by: Paolo Abeni <pabeni@redhat.com>
Suggested-by: Matthieu Baerts <matthieu.baerts@tessares.net>
Reviewed-by: Mat Martineau <mathew.j.martineau@linux.intel.com>
Signed-off-by: Geliang Tang <geliangtang@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/mptcp/pm_netlink.c

@@ -1156,6 +1156,41 @@ static void mptcp_pm_free_addr_entry(struct mptcp_pm_addr_entry *entry)
 	}
 }
 
+static int mptcp_nl_remove_id_zero_address(struct net *net,
+					   struct mptcp_addr_info *addr)
+{
+	struct mptcp_rm_list list = { .nr = 0 };
+	long s_slot = 0, s_num = 0;
+	struct mptcp_sock *msk;
+
+	list.ids[list.nr++] = 0;
+
+	while ((msk = mptcp_token_iter_next(net, &s_slot, &s_num)) != NULL) {
+		struct sock *sk = (struct sock *)msk;
+		struct mptcp_addr_info msk_local;
+
+		if (list_empty(&msk->conn_list))
+			goto next;
+
+		local_address((struct sock_common *)msk, &msk_local);
+		if (!addresses_equal(&msk_local, addr, addr->port))
+			goto next;
+
+		lock_sock(sk);
+		spin_lock_bh(&msk->pm.lock);
+		mptcp_pm_remove_addr(msk, &list);
+		mptcp_pm_nl_rm_subflow_received(msk, &list);
+		spin_unlock_bh(&msk->pm.lock);
+		release_sock(sk);
+
+next:
+		sock_put(sk);
+		cond_resched();
+	}
+
+	return 0;
+}
+
 static int mptcp_nl_cmd_del_addr(struct sk_buff *skb, struct genl_info *info)
 {
 	struct nlattr *attr = info->attrs[MPTCP_PM_ATTR_ADDR];
@@ -1168,6 +1203,14 @@ static int mptcp_nl_cmd_del_addr(struct sk_buff *skb, struct genl_info *info)
 	if (ret < 0)
 		return ret;
 
+	/* the zero id address is special: the first address used by the msk
+	 * always gets such an id, so different subflows can have different zero
+	 * id addresses. Additionally zero id is not accounted for in id_bitmap.
+	 * Let's use an 'mptcp_rm_list' instead of the common remove code.
+	 */
+	if (addr.addr.id == 0)
+		return mptcp_nl_remove_id_zero_address(sock_net(skb->sk), &addr.addr);
+
 	spin_lock_bh(&pernet->lock);
 	entry = __lookup_addr_by_id(pernet, addr.addr.id);
 	if (!entry) {