各位好，我碰到了一个SSH反向隧道的问题，折腾了一阵没找到根因，想请教下大家：

我是这么建立SSH反向隧道的：

/usr/bin/ssh -vvv -o ServerAliveInterval=10 -o ServerAliveCountMax=3 -R 15000:127.0.0.1: 15000 -N mylinode.domain.com

隧道建立时的调试日志如下，看起来认证和转发设置都成功了：

debug1: Offering public key: /Users/rcook/.ssh/id_rsa RSA SHA256:8Y33c0fxIoqd3SmemVpq5jOPdaqPQ/DnadmlP6A4q14
debug1: Server accepts key: /Users/rcook/.ssh/id_rsa RSA SHA256:8Y33c0fxIoqd3SmemVpq5jOPdaqPQ/DnadmlP6A4q14
Authenticated to mylinode.domain.com ([45.79.100.248]:22) using "publickey".
debug1: Remote connections from LOCALHOST:15000 forwarded to local address localhost:15000
debug1: Requesting no-more-sessions@openssh.com
debug1: Entering interactive session.
debug1: pledge: filesystem
debug1: client_input_global_request: rtype hostkeys-00@openssh.com want_reply 0
debug1: client_input_hostkeys: searching /Users/rcook/.ssh/known_hosts for mylinode.domain.com / (none)
debug1: client_input_hostkeys: searching /Users/rcook/.ssh/known_hosts2 for mylinode.domain.com / (none)
debug1: client_input_hostkeys: hostkeys file /Users/rcook/.ssh/known_hosts2 does not exist
debug1: client_input_hostkeys: host key found matching a different name/address, skipping UserKnownHostsFile update
debug1: pledge: network
debug1: Remote: /home/rcook/.ssh/authorized_keys:2: key options: agent-forwarding port-forwarding pty user-rc x11-forwarding
debug1: Remote: /home/rcook/.ssh/authorized_keys:2: key options: agent-forwarding port-forwarding pty user-rc x11-forwarding
debug1: Remote: Forwarding listen address "localhost" overridden by server GatewayPorts
debug1: remote forward success for: listen 15000, connect localhost:15000

现在的问题是：

• 我在防火墙里已经为这台linode主机开放了22000端口的TCP和UDP访问
• 在linode机器上，用telnet localhost 22000能正常连接到隧道
• 但从其他机器尝试连接时，直接被拒绝，比如用nc测试的结果：

rcook@MacBook-Pro-2021 (obsidian-media-db-plugin (master)): nc -zv mylinode.domain.com 22000
nc: connectx to mylinode.domain.com port 22000 (tcp) failed: Connection refused

我检查了linode上的/etc/sshd/sshd_config，相关配置是这样的：

#AllowAgentForwarding yes
AllowTcpForwarding yes
GatewayPorts yes
X11Forwarding yes

有没有大佬能帮我分析下可能的原因？

备注：内容来源于stack exchange，提问作者Rich