来自请求Python库的HTTP请求中缺少主机标头

问题描述：

HTTP请求中的 HTTP/1.1强制性主机标头字段在哪里由 requests Python库生成的消息?

Where is the HTTP/1.1 mandatory Host header field in HTTP request messages generated by the requests Python library?

import requests

response = requests.get("https://www.google.com/")
print(response.request.headers)

输出以下内容:

{'User-Agent':'python-requests/2.22.0'，'Accept-Encoding':'gzip，deflate'，'Accept':'*/*'，'Connection':'保持活跃'}

{'User-Agent': 'python-requests/2.22.0', 'Accept-Encoding': 'gzip, deflate', 'Accept': '*/*', 'Connection': 'keep-alive'}

答

默认情况下， requests 不会将 HOST 标头添加到请求中.如果未明确添加，则将决策委派给基础 http 模块.

The HOST header is not being added to the request by requests by default. If it is not explicitly added then the decision is delegated to the underlying http module.

请参见 http/client.py :

(如果在 requests.get 中显式提供了'Host'标头，则 skip_host 为 True )

(if 'Host' header is explicitly provided in requests.get then skip_host is True)

    if self._http_vsn == 11:
        # Issue some standard headers for better HTTP/1.1 compliance

        if not skip_host:
            # this header is issued *only* for HTTP/1.1
            # connections. more specifically, this means it is
            # only issued when the client uses the new
            # HTTPConnection() class. backwards-compat clients
            # will be using HTTP/1.0 and those clients may be
            # issuing this header themselves. we should NOT issue
            # it twice; some web servers (such as Apache) barf
            # when they see two Host: headers

            # If we need a non-standard port,include it in the
            # header.  If the request is going through a proxy,
            # but the host of the actual URL, not the host of the
            # proxy.

            netloc = ''
            if url.startswith('http'):
                nil, netloc, nil, nil, nil = urlsplit(url)

            if netloc:
                try:
                    netloc_enc = netloc.encode("ascii")
                except UnicodeEncodeError:
                    netloc_enc = netloc.encode("idna")
                self.putheader('Host', netloc_enc)
            else:
                if self._tunnel_host:
                    host = self._tunnel_host
                    port = self._tunnel_port
                else:
                    host = self.host
                    port = self.port

                try:
                    host_enc = host.encode("ascii")
                except UnicodeEncodeError:
                    host_enc = host.encode("idna")

                # As per RFC 273, IPv6 address should be wrapped with []
                # when used as Host header

                if host.find(':') >= 0:
                    host_enc = b'[' + host_enc + b']'

                if port == self.default_port:
                    self.putheader('Host', host_enc)
                else:
                    host_enc = host_enc.decode("ascii")
                    self.putheader('Host', "%s:%s" % (host_enc, port))

因此，在检查请求发送到服务器的标头时，我们看不到'Host'标头.

As a result we do not see the 'Host' header when inspecting the headers that requests sent to the server.

如果我们向 http://httpbin/get 发送请求并打印响应，则可以看到主机标头确实已发送.

If we send a request to http://httpbin/get and print the response we can see the Host header was indeed sent.

import requests

response = requests.get("http://httpbin.org/get")
print('Response from httpbin/get')
print(response.json())
print()
print('response.request.headers')
print(response.request.headers)

输出

Response from httpbin/get
{'args': {}, 'headers': {'Accept': '*/*', 'Accept-Encoding': 'gzip, deflate', 
 'Host': 'httpbin.org', 'User-Agent': 'python-requests/2.20.0'},
 'origin': 'XXXXXX', 'url': 'https://httpbin.org/get'}

response.request.headers
{'User-Agent': 'python-requests/2.20.0', 'Accept-Encoding': 'gzip, deflate', 
 'Accept': '*/*', 'Connection': 'keep-alive'}

来自请求Python库的HTTP请求中缺少主机标头

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