dokodemo-door 无法 TPROXY 透明代理 IPv6 TCP

[LGA1150]

1. 你正在使用哪个版本的 V2Ray？（如果服务器和客户端使用了不同版本，请注明）
   4.31.0

2. 你的使用场景是什么？比如使用 Chrome 通过 Socks/VMess 代理观看 YouTube 视频。
   路由器上使用 TPROXY 透明代理访问 IPv6 网站

3. 你看到的不正常的现象是什么？（请描述具体现象，比如访问超时，TLS 证书错误等）
   任何 IPv6 TCP 均无法连接

> dig @2001:4860:4860::8888 +short +tcp
;; communications error to 2001:4860:4860::8888#53: end of file

;; communications error to 2001:4860:4860::8888#53: end of file

UDP 正常

> dig @2001:4860:4860::8888 +short
b.root-servers.net.
j.root-servers.net.
f.root-servers.net.
i.root-servers.net.
c.root-servers.net.
e.root-servers.net.
l.root-servers.net.
d.root-servers.net.
g.root-servers.net.
a.root-servers.net.
k.root-servers.net.
m.root-servers.net.
h.root-servers.net.

4. 你期待看到的正确表现是怎样的？
   可以建立 TCP 连接

5. 请附上你的配置（提交 Issue 前请隐藏服务器端IP地址）。

服务器端配置:

{
        "inbounds": [
                {
                        "port": 443,
                        "address": "0.0.0.0",
                        "protocol": "vless",
                        "settings": {
                                "clients": [
                                        {
                                                "id": "REDACTED",
                                                "flow": "xtls-rprx-direct",
                                                "level": 0
                                        }
                                ],
                                "decryption": "none",
                                "fallbacks": [
                                        {
                                                "dest": 80
                                        }
                                ]
                        },
                        "sniffing": {
                                "enabled": true,
                                "destOverride": ["http", "tls"]
                        },
                        "streamSettings": {
                                "network": "tcp",
                                "security": "xtls",
                                "xtlsSettings": {
                                        "alpn": [
                                                "http/1.1"
                                        ],
                                        "certificates": [
                                                {
                                                        "certificateFile": "/etc/ssl/ssl.crt",
                                                        "keyFile": "/etc/ssl/ssl.key"
                                                }
                                        ]
                                }
                        }
                }
        ]
}
{
        "outbounds": [
                {
                        "protocol": "freedom",
                        "settings": {}
                }
        ]
}

客户端配置:

{
  "outbound": {
    "settings": {
      "vnext": [
        {
          "port": 443,
          "users": [
            {
              "id": "REDACTED",
              "flow": "xtls-rprx-direct",
              "encryption": "none"
            }
          ],
          "address": "REDACTED"
        }
      ]
    },
    "mux": {
      "enabled": false
    },
    "protocol": "vless",
    "streamSettings": {
      "network": "tcp",
      "xtlsSettings": {
        "serverName": "REDACTED",
        "allowInsecure": true
      },
      "security": "xtls"
    }
  },
  "log": {
    "loglevel": "debug"
  },
  "outboundDetour": [
    {
      "settings": {
        "timeout": 60
      },
      "protocol": "freedom"
    }
  ],
  "inbound": {
    "listen": "::",
    "sniffing": {
      "enabled": false
    },
    "port": "1234",
    "protocol": "dokodemo-door",
    "settings": {
      "network": "tcp,udp",
      "followRedirect": true
    },
    "sockopt": {
      "tproxy": "tproxy"
    }
  }
}

6. 请附上出错时软件输出的错误日志。在 Linux 中，日志通常在 /var/log/v2ray/error.log 文件中。

服务器端错误日志:

无

客户端错误日志:

2020/10/14 16:48:38 [Debug] [25048068] v2ray.com/core/proxy/dokodemo: processing connection from: [REDACTED]:47575
2020/10/14 16:48:38 [Info] [25048068] v2ray.com/core/app/proxyman/inbound: connection ends > v2ray.com/core/proxy/dokodemo: unable to get destination
2020/10/14 16:48:38 [Info] v2ray.com/core/transport/internet/tcp: failed to call getsockopt > no such file or directory
2020/10/14 16:48:38 [Info] [1664145164] v2ray.com/core/app/proxyman/inbound: failed to get original destination > v2ray.com/core/transport/internet/tcp: failed to call getsockopt

8. 其它相关的配置文件（如 Nginx）和相关日志。
   ip6tables 规则

ip6tables -t mangle -N V2_FW
ip6tables -t mangle -A V2_FW -p tcp -j TPROXY --on-port 1234 --tproxy-mark 0x1
ip6tables -t mangle -A V2_FW -p udp -j TPROXY --on-port 1234 --tproxy-mark 0x1
ip6tables -t mangle -A PREROUTING -d 2001:4860::/32 -j V2_FW
ip6tables -t mangle -A OUTPUT -d 2001:4860::/32 -j MARK --set-mark 0x1

ip -6 rule

0:      from all lookup local
1:      from all fwmark 0x1 lookup 100
32766:  from all lookup main

ip -6 route show table 100

local default dev lo proto static metric 1024 pref medium

[LGA1150]

新讨论见 XTLS/Xray-core#48 (comment)