[SOLVED] Apache Reverse Proxy show "Service Unavailable" error.

n00b_noob · 03-06-2021, 12:53 PM

Hello,
I created two VMs in the VirtualBox. One of them is Reverse Proxy server and another one is Apache Web Server.
The specifications of VM1 (Reverse Proxy) are as follows:
NIC 1 is NAT and Its IP address is "10.0.3.15".
NIC 2 is Internal Network and its IP address is "192.168.1.3".

The specifications of VM2 (Apache Web Server) are as follows:
It has one NIC and its IP address is "192.168.1.4".

Both VMs can see each other. I installed Apache Web Server on the both machines and opened ports 80 and 443 via Firewalld on them:

Code:

# firewall-cmd --list-all
FedoraServer (active)
  target: default
  icmp-block-inversion: no
  interfaces: enp0s3
  sources: 
  services: cockpit dhcpv6-client ssh
  ports: 80/tcp 443/tcp
  protocols: 
  masquerade: no
  forward-ports: 
  source-ports: 
  icmp-blocks: 
  rich rules:

My goal is:

Code:

The Internet --> Reverse Proxy (VM1) --> Apache Web Server (VM2)

On the VM1, I did:

Code:

# curl http://192.168.1.4
<html>
	<head>
		<title> This my server. </title>
	</head>
	<body>
		<p> Hello Server. </p>
	</body>
</html>

And as you see, it can see VM2 Apache Web Server.
On the VM1, I created a Virtual Host configuration file as below:

Code:

# touch /etc/httpd/conf.d/reverse.conf
# nano /etc/httpd/conf.d/reverse.conf

And filled it with below lines:

Code:

<VirtualHost *:80>

        ProxyPreserveHost On
        ProxyPass / http://192.168.1.4/
        ProxyPassReverse / http://192.168.1.4/

</VirtualHost>

Then restarted the Apache Web Server.
When I entered VM1 IP address, then I must see the VM2 "index.html" file, but I see below error:

Code:

Service Unavailable
The server is temporarily unable to service your request due to maintenance downtime or capacity problems. Please try again later.

On VM1, I used VirtualBox Port Forwarding:

Code:

Protocol        Host IP        Host Port        Guest IP        Guest Port    
TCP             127.0.0.1      2080             10.0.3.15       80

When I enter "127.0.0.1:2080" in my browser, then logs on VM1 are:

Code:

# cat access_log 
10.0.3.2 - - [06/Mar/2021:22:03:01 +0330] "GET / HTTP/1.1" 503 299 "-" "Mozilla/5.0 (X11; Linux x86_64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/88.0.4324.182 Safari/537.36"
10.0.3.2 - - [06/Mar/2021:22:03:01 +0330] "GET /favicon.ico HTTP/1.1" 503 299 "http://127.0.0.1:2080/" "Mozilla/5.0 (X11; Linux x86_64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/88.0.4324.182 Safari/537.36"

And:

Code:

# cat error_log 
[Sat Mar 06 22:03:01.275035 2021] [proxy:error] [pid 851:tid 1036] (13)Permission denied: AH00957: HTTP: attempt to connect to 192.168.1.4:80 (192.168.1.4) failed
[Sat Mar 06 22:03:01.275093 2021] [proxy_http:error] [pid 851:tid 1036] [client 10.0.3.2:33820] AH01114: HTTP: failed to make connection to backend: 192.168.1.4
[Sat Mar 06 22:03:01.320469 2021] [proxy:error] [pid 850:tid 990] (13)Permission denied: AH00957: HTTP: attempt to connect to 192.168.1.4:80 (192.168.1.4) failed
[Sat Mar 06 22:03:01.320528 2021] [proxy_http:error] [pid 850:tid 990] [client 10.0.3.2:33822] AH01114: HTTP: failed to make connection to backend: 192.168.1.4, referer: http://127.0.0.1:2080/

On VM2:

Code:

# cat access_log 
#
# cat error_log 
#

Why?

Thanks.

n00b_noob · 03-07-2021, 05:12 AM

Problem solved.
It was because of SELinux:

Code:

# setsebool -P httpd_can_network_connect on