mptcp: create subflow or signal addr for newly added address

Currently, when a new MPTCP endpoint is added, the existing MPTCP
sockets are not affected.

This patch implements a new function mptcp_nl_add_subflow_or_signal_addr,
invoked when an address is added from PM netlink. This function traverses
the MPTCP sockets list and invokes mptcp_pm_create_subflow_or_signal_addr
to try to create a subflow or signal an address for the newly added
address, if local constraint allows that.

Closes: #19
Reviewed-by: Mat Martineau <mathew.j.martineau@linux.intel.com>
Signed-off-by: Geliang Tang <geliangtang@gmail.com>

net/mptcp/pm_netlink.c

@@ -850,6 +850,31 @@ static struct pm_nl_pernet *genl_info_pm_nl(struct genl_info *info)
  return net_generic(genl_info_net(info), pm_nl_pernet_id);
 }
 
+static int mptcp_nl_add_subflow_or_signal_addr(struct net *net)
+{
+ struct mptcp_sock *msk;
+ long s_slot = 0, s_num = 0;
+
+ while ((msk = mptcp_token_iter_next(net, &s_slot, &s_num)) != NULL) {
+ struct sock *sk = (struct sock *)msk;
+
+ if (!READ_ONCE(msk->fully_established))
+ goto next;
+
+ lock_sock(sk);
+ spin_lock_bh(&msk->pm.lock);
+ mptcp_pm_create_subflow_or_signal_addr(msk);
+ spin_unlock_bh(&msk->pm.lock);
+ release_sock(sk);
+
+next:
+ sock_put(sk);
+ cond_resched();
+ }
+
+ return 0;
+}
+
 static int mptcp_nl_cmd_add_addr(struct sk_buff *skb, struct genl_info *info)
 {
  struct nlattr *attr = info->attrs[MPTCP_PM_ATTR_ADDR];
@@ -875,6 +900,8 @@ static int mptcp_nl_cmd_add_addr(struct sk_buff *skb, struct genl_info *info)
  return ret;
  }
 
+ mptcp_nl_add_subflow_or_signal_addr(sock_net(skb->sk));
+
  return 0;
 }