域名访问Nginx报400 Bad Request，IP访问正常的问题求助

访问http://exhibit.technology时Nginx返回400 Bad Request错误，但直接访问对应IP192.81.211.160站点可正常加载。Webconfs头部检测显示域名请求返回400响应头，IP请求返回200响应头。站点DNS和托管在Digital Ocean，基于Django开发，已设置Debug=False并配置ALLOWED_HOSTS。

域名访问响应头（400） #

HTTP/1.1 400 Bad Request =>
Server => nginx/1.14.0 (Ubuntu)
Date => Sun, 23 Apr 2023 20:24:50 GMT
Content-Type => text/html
Connection => close
X-Content-Type-Options => nosniff
Referrer-Policy => same-origin

IP访问响应头（200） #

HTTP/1.1 200 OK =>
Server => nginx/1.14.0 (Ubuntu)
Date => Sun, 23 Apr 2023 20:23:35 GMT
Content-Type => text/html; charset=utf-8
Content-Length => 6857
Connection => close
X-Frame-Options => DENY
Vary => Cookie
X-Content-Type-Options => nosniff
Referrer-Policy => same-origin

Nginx调试日志片段 #

2023/04/23 20:42:39 [debug] 13352#13352: *2 http upstream dummy handler
2023/04/23 20:42:39 [debug] 13352#13352: *2 http upstream request: "/?"
2023/04/23 20:42:39 [debug] 13352#13352: *2 http upstream dummy handler
2023/04/23 20:42:39 [debug] 13352#13352: *2 http upstream request: "/?"
2023/04/23 20:42:39 [debug] 13352#13352: *2 http upstream process header
2023/04/23 20:42:39 [debug] 13352#13352: *2 malloc: 000056424E53BD20:4096
2023/04/23 20:42:39 [debug] 13352#13352: *2 recv: eof:0, avail:1
2023/04/23 20:42:39 [debug] 13352#13352: *2 recv: fd:12 190 of 4096
2023/04/23 20:42:39 [debug] 13352#13352: *2 http proxy status 400 "400 Bad Request"
2023/04/23 20:42:39 [debug] 13352#13352: *2 http proxy header: "Server: gunicorn"
2023/04/23 20:42:39 [debug] 13352#13352: *2 http proxy header: "Date: Sun, 23 Apr 2023 20:42:39 GMT"
2023/04/23 20:42:39 [debug] 13352#13352: *2 http proxy header: "Connection: close"
2023/04/23 20:42:39 [debug] 13352#13352: *2 http proxy header: "Content-Type: text/html"
2023/04/23 20:42:39 [debug] 13352#13352: *2 http proxy header: "X-Content-Type-Options: nosniff"
2023/04/23 20:42:39 [debug] 13352#13352: *2 http proxy header: "Referrer-Policy: same-origin"
2023/04/23 20:42:39 [debug] 13352#13352: *2 http proxy header done
2023/04/23 20:42:39 [debug] 13352#13352: *2 xslt filter header
2023/04/23 20:42:39 [debug] 13352#13352: *2 HTTP/1.1 400 Bad Request
Server: nginx/1.14.0 (Ubuntu)
Date: Sun, 23 Apr 2023 20:42:39 GMT
Content-Type: text/html
Transfer-Encoding: chunked
Connection: keep-alive
X-Content-Type-Options: nosniff
Referrer-Policy: same-origin

2023/04/23 20:42:39 [debug] 13352#13352: *2 write new buf t:1 f:0 000056424E567A58, pos 000056424E567A58, size: 236 file: 0, size: 0
2023/04/23 20:42:39 [debug] 13352#13352: *2 http write filter: l:0 f:0 s:236
2023/04/23 20:42:39 [debug] 13352#13352: *2 http cacheable: 0
2023/04/23 20:42:39 [debug] 13352#13352: *2 posix_memalign: 000056424E53CD30:4096 @16
2023/04/23 20:42:39 [debug] 13352#13352: *2 http proxy filter init s:400 h:0 c:0 l:-1
2023/04/23 20:42:39 [debug] 13352#13352: *2 http upstream process upstream
2023/04/23 20:42:39 [debug] 13352#13352: *2 pipe read upstream: 0
2023/04/23 20:42:39 [debug] 13352#13352: *2 pipe preread: 0

问题原因分析 #

从Nginx调试日志可见，400错误实际是上游gunicorn服务返回的，而非Nginx直接拒绝请求。结合域名访问报错、IP访问正常的现象，核心原因集中在以下几点：

1. Nginx未正确传递Host头到gunicorn
   访问IP时请求的Host头是IP地址，访问域名时Host头是exhibit.technology。如果Nginx配置中缺少proxy_set_header Host $host;，gunicorn转发给Django的请求会缺失正确的Host信息，触发Django的ALLOWED_HOSTS校验失败，返回400错误。

2. Django的ALLOWED_HOSTS配置不完整
   即便已配置ALLOWED_HOSTS，可能存在拼写错误，或未包含exhibit.technology（比如仅添加了IP或子域名），导致域名请求被Django拦截。

3. DNS解析异常导致Host头格式错误
   极少数情况下，DNS解析异常会导致请求的Host头包含多余字符，触发Nginx或Django的请求校验逻辑。

解决方案 #

• 修复Nginx配置：在对应server块的proxy配置中添加Host头传递规则，示例：

location / {
    proxy_pass http://127.0.0.1:8000;
    proxy_set_header Host $host;
    proxy_set_header X-Real-IP $remote_addr;
    proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
}

修改后重启Nginx：sudo systemctl restart nginx

• 验证Django的ALLOWED_HOSTS：确保settings.py中包含目标域名，示例：

ALLOWED_HOSTS = ['192.81.211.160', 'exhibit.technology']

修改后重启gunicorn服务。

• 排查DNS解析：本地执行nslookup exhibit.technology确认解析结果为目标IP，再用curl -v http://exhibit.technology观察请求的Host头是否正确。

内容的提问来源于stack exchange，提问作者Andrew