mptcp: implement mptcp_userspace_pm_get_addr

This patch implements mptcp_userspace_pm_get_addr() to get an address
from userspace pm address list according the given 'token' and 'id'.
Use nla_get_u32() to get the u32 value of 'token', then pass it to
mptcp_token_get_sock() to get the msk. Pass 'msk' and 'id' to the helper
mptcp_userspace_pm_lookup_addr_by_id() to get the address entry. Put
this entry to userspace using mptcp_pm_nl_put_entry_info().
Signed-off-by: Geliang Tang <tanggeliang@kylinos.cn>
Reviewed-by: Matthieu Baerts (NGI0) <matttbe@kernel.org>
Reviewed-by: Mat Martineau <martineau@kernel.org>
Signed-off-by: Matthieu Baerts (NGI0) <matttbe@kernel.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/mptcp/pm_userspace.c

@@ -638,3 +638,77 @@ int mptcp_userspace_pm_dump_addr(struct sk_buff *msg,
 	sock_put(sk);
 	return ret;
 }
+
+int mptcp_userspace_pm_get_addr(struct sk_buff *skb,
+				struct genl_info *info)
+{
+	struct nlattr *attr = info->attrs[MPTCP_PM_ENDPOINT_ADDR];
+	struct nlattr *token = info->attrs[MPTCP_PM_ATTR_TOKEN];
+	struct mptcp_pm_addr_entry addr, *entry;
+	struct net *net = sock_net(skb->sk);
+	struct mptcp_sock *msk;
+	struct sk_buff *msg;
+	int ret = -EINVAL;
+	struct sock *sk;
+	void *reply;
+
+	msk = mptcp_token_get_sock(net, nla_get_u32(token));
+	if (!msk) {
+		NL_SET_ERR_MSG_ATTR(info->extack, token, "invalid token");
+		return ret;
+	}
+
+	sk = (struct sock *)msk;
+
+	if (!mptcp_pm_is_userspace(msk)) {
+		GENL_SET_ERR_MSG(info, "invalid request; userspace PM not selected");
+		goto out;
+	}
+
+	ret = mptcp_pm_parse_entry(attr, info, false, &addr);
+	if (ret < 0)
+		goto out;
+
+	msg = nlmsg_new(NLMSG_DEFAULT_SIZE, GFP_KERNEL);
+	if (!msg) {
+		ret = -ENOMEM;
+		goto out;
+	}
+
+	reply = genlmsg_put_reply(msg, info, &mptcp_genl_family, 0,
+				  info->genlhdr->cmd);
+	if (!reply) {
+		GENL_SET_ERR_MSG(info, "not enough space in Netlink message");
+		ret = -EMSGSIZE;
+		goto fail;
+	}
+
+	lock_sock(sk);
+	spin_lock_bh(&msk->pm.lock);
+	entry = mptcp_userspace_pm_lookup_addr_by_id(msk, addr.addr.id);
+	if (!entry) {
+		GENL_SET_ERR_MSG(info, "address not found");
+		ret = -EINVAL;
+		goto unlock_fail;
+	}
+
+	ret = mptcp_nl_fill_addr(msg, entry);
+	if (ret)
+		goto unlock_fail;
+
+	genlmsg_end(msg, reply);
+	ret = genlmsg_reply(msg, info);
+	spin_unlock_bh(&msk->pm.lock);
+	release_sock(sk);
+	sock_put(sk);
+	return ret;
+
+unlock_fail:
+	spin_unlock_bh(&msk->pm.lock);
+	release_sock(sk);
+fail:
+	nlmsg_free(msg);
+out:
+	sock_put(sk);
+	return ret;
+}

net/mptcp/protocol.h

@@ -1069,6 +1069,8 @@ int mptcp_pm_nl_dump_addr(struct sk_buff *msg,
 			  struct netlink_callback *cb);
 int mptcp_userspace_pm_dump_addr(struct sk_buff *msg,
 				 struct netlink_callback *cb);
+int mptcp_userspace_pm_get_addr(struct sk_buff *skb,
+				struct genl_info *info);
 
 static inline u8 subflow_get_local_id(const struct mptcp_subflow_context *subflow)
 {