我在服务器上有以下 stunnel 配置：
chroot = /var/run/stunnel
setuid = nobody
setgid = nobody
pid = /stunnel.pid
cert = /etc/stunnel/stunnel.pem
key = /etc/stunnel/stunnel.pem
client = no
[https]
accept = 443
connect = 10051
客户端：
chroot = /var/run/stunnel
setuid = nobody
setgid = nobody
pid = /stunnel.pid
cert = /etc/stunnel/stunnel.pem
key = /etc/stunnel/stunnel.pem
client = yes
[https]
accept = 127.0.0.1:10051
connect = 10.0.10.116:443
当我在每台机器上运行“sudo stunnel”时，我没有收到任何错误。在客户端上运行以下命令来测试隧道，我什么也没得到？
tcpdump port 10051 -n -vvvv
其次是：
echo "blah" > nc localhost 10051
我是否滥用了“tcpdump”？还有另一种方法可以测试这个吗？我使用的是 Centos 7。服务器 IP 地址是 10.0.10.116，客户端 IP 地址是 10.0.10.27，这是一个带有自签名证书的测试实验室设置。
我应该补充一点，如果我使用 sudo 发出上面的 tcpdump 命令：
sudo tcpdump port 10051 -n -vvvv
我得到以下信息，然后什么也没有：
tcpdump: NFLOG link-layer type filtering not implemented
不确定这告诉我什么？
答案1
好吧，我已经让它和一些周一起工作了。我决定尝试使用 ssh，而不是使用 tcpdump。所以我将服务器上的连接更改为：
...
[https]
accept = 443
connect = 22
...
然后我输入
ssh localhost -p 10051
回来了
chuck@scorch:~$ ssh chuck@localhost -p 10051
The authenticity of host '[localhost]:10051 ([127.0.0.1]:10051)' can't be
established.
ECDSA key fingerprint is SHA256:DcEUrtP7I5KJqaZIfsTK+2lNB8AF00Je97z9obNneac.
Are you sure you want to continue connecting (yes/no)? y
Please type 'yes' or 'no': yes
Warning: Permanently added '[localhost]:10051' (ECDSA) to the list of known
hosts.
chuck@localhost's password:
Welcome to Ubuntu 17.04 (GNU/Linux 4.10.0-19-generic x86_64)
* Documentation: https://help.ubuntu.com
* Management: https://landscape.canonical.com
* Support: https://ubuntu.com/advantage
* What are your preferred Linux desktop apps? Help us set the default
desktop apps in Ubuntu 18.04 LTS:
- https://ubu.one/apps1804
11 packages can be updated.
8 updates are security updates.
Last login: Tue Oct 3 15:36:24 2017 from 10.0.10.60
chuck@ion:~$
请注意，登录现在显示“ion”，我通过 ssh 与 https 移植到服务器上。日志显示
2017.10.03 15:38:00 LOG7[0]: Service [https] started
2017.10.03 15:38:00 LOG7[0]: Option TCP_NODELAY set on local socket
2017.10.03 15:38:00 LOG5[0]: Service [https] accepted connection from
10.0.10.27:36976
2017.10.03 15:38:00 LOG6[0]: Peer certificate not required
2017.10.03 15:38:00 LOG7[0]: TLS state (accept): before/accept
initialization
2017.10.03 15:38:00 LOG7[0]: Get session callback
2017.10.03 15:38:00 LOG7[0]: SNI: no virtual services defined
2017.10.03 15:38:00 LOG7[0]: New session callback
2017.10.03 15:38:00 LOG7[0]: 1 server accept(s) requested
2017.10.03 15:38:00 LOG7[0]: 1 server accept(s) succeeded
2017.10.03 15:38:00 LOG7[0]: 0 server renegotiation(s) requested
2017.10.03 15:38:00 LOG7[0]: 0 session reuse(s)
2017.10.03 15:38:00 LOG7[0]: 0 internal session cache item(s)
2017.10.03 15:38:00 LOG7[0]: 0 internal session cache fill-up(s)
2017.10.03 15:38:00 LOG7[0]: 1 internal session cache miss(es)
2017.10.03 15:38:00 LOG7[0]: 0 external session cache hit(s)
2017.10.03 15:38:00 LOG7[0]: 0 expired session(s) retrieved
2017.10.03 15:38:00 LOG6[0]: TLS accepted: new session negotiated
2017.10.03 15:38:00 LOG6[0]: No peer certificate received
2017.10.03 15:38:00 LOG6[0]: Negotiated TLSv1.2 ciphersuite ECDHE-RSA-
AES256-GCM-SHA384 (256-bit encryption)
2017.10.03 15:38:00 LOG7[0]: Compression: null, expansion: null
2017.10.03 15:38:00 LOG6[0]: failover: round-robin, starting at entry #1
2017.10.03 15:38:00 LOG6[0]: s_connect: connecting 127.0.0.1:22
2017.10.03 15:38:00 LOG7[0]: s_connect: s_poll_wait 127.0.0.1:22: waiting 10
seconds
2017.10.03 15:38:00 LOG5[0]: s_connect: connected 127.0.0.1:22
2017.10.03 15:38:00 LOG6[0]: persistence: 127.0.0.1:22 cached
2017.10.03 15:38:00 LOG5[0]: Service [https] connected remote server from
127.0.0.1:54818
2017.10.03 15:38:00 LOG7[0]: Option TCP_NODELAY set on remote socket
2017.10.03 15:38:00 LOG7[0]: Remote descriptor (FD=9) initialized
所以我知道它可以在 Ubuntu 上运行。我注意到在安装 stunnel 的过程中它会自动创建一个“stunnel4”用户、组和服务。所以我想我需要在 Centos 上尝试一下，看看会发生什么。
我终于让它在 Centos 上运行了。原来我以为我已经关闭了防火墙，但实际上并没有。将适当的端口添加到防火墙解决了问题。但是我仍然无法让 tcpdump 工作......
答案2
如果尝试使用 '-i lo' 的 tcpdump 在环回接口上进行嗅探会怎样：
tcpdump -i lo -n -v port 10051