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Subject DO NOT REPLY [Bug 49699] New: Inconsistent Keep-alive from proxy to the origin server.
Date Wed, 04 Aug 2010 03:01:00 GMT

           Summary: Inconsistent Keep-alive from proxy to the origin
           Product: Apache httpd-2
           Version: 2.2-HEAD
          Platform: PC
        OS/Version: Linux
            Status: NEW
          Severity: normal
          Priority: P2
         Component: mod_proxy_http

Created an attachment (id=25836)
 --> (
Captured packets (can be opened by tcpdump, Wireshark, etc.)

If the (forward-)proxy receives "Connection: Keep-alive" request from client,
it sends "Connection: Keep-alive" to the origin server as well. But the proxy
closes the connection to the origin server immediately after it receives the
response (or after it sends response to the client).
[Initially found on 2.2.11 and confirmed with 2.2.16]

The possible negative impact of the symptom:
The origin server would expect the upcoming HTTP request in the persistent
connection. So the sudden close of connection may cause a confusion on the
origin server.

If the Keep-alive to the origin server is disabled ("SetEnv proxy-nokeepalive"
in httpd.conf), then there is no chance that the proxy confuses the origin
server with "Connection: Keep-alive".
However, I don't know how can we enable Keep-alive (without immediate closing
the connection) to the origin server.

How to reproduce:
1. Turn on forward proxy feature with the following httpd.conf, and run httpd.
ProxyRequests On
<Proxy *>
Allow from all

2. Run tcpdump (or anything equivalent) to monitor the packets.
# tcpdump -i any -s 0 -w 0.cap tcp port 80

3. Use telnet to send a request:
$ telnet localhost 80
Connection: Keep-Alive

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