http_host, host 和 proxy_host 的区别

参考

An unchanged “Host” request header field can be passed like this:

  proxy_set_header Host       $http_host;

However, if this field is not present in a client request header then nothing will be passed.
In such a case it is better to use the $host variable - 
its value equals the server name in the “Host” request header field 
or the primary server name if this field is not present:

  proxy_set_header Host       $host;

server {
    listen 8000;
    server_name lindyang.com;
    default_type text/html;
    location / {
        proxy_pass http://127.0.0.2:8888;  # 8888 -> 80
        proxy_set_header Host $http_host;
        proxy_set_header X-Proxy-Host $proxy_host;
    }
}

server {
    listen 8888;  # 8888 -> 80
    server_name yld.com www.yld.com;
    default_type text/html;
    location / {
        return 200 'http_host=[$http_host] host=[$host] proxy_host=[$http_x_proxy_host]\n';
    }
}

• 不携带请求头 Host

curl -H 'Host:' --http1.0 http://lindyang.com:8000

http_host=[] host=[yld.com] proxy_host=[127.0.0.2:8888]

变量	值	说明
http_host		请求无 Host, 则 http_host 为空
host	yld.com	忽略空 Host , 使用 server_name 的第一项
proxy_host	127.0.0.2:8888	取自于 proxy_pass 的参数

• 携带请求头 Host

为验证 proxy_host 不带端口的情况，需将 8888 -> 80

curl -H 'Host: Dummy:abc' http://lindyang.com:8000

http_host=[dummy:abc] host=[dummy] proxy_host=[127.0.0.2]

变量	值	说明
http_host	Dummy:abc	给啥拿啥
host	dummy	第一个:前的内容(d小写)
proxy_host	127.0.0.2	省略端口 80