Haproxy Appending Port to `HTTP_HOST` Header in Backend Request

Question

I am using haproxy in front of my web-server for ssl termination.

I am forwarding request on port 81 if request is https and 80 if request is normal http-

backend b1_http
    mode http
    server bkend_server


backend b1_https
    mode http
    server bkend_server:81

Problem is, when haproxy sends request to back-end, it sends HTTP_HOST header as request.domain.com:81.

Is it possible in haproxy that I can send https request to back-end at specific port without appending the port in HTTP_HOST request header?

Michael - sqlbot · Accepted Answer · 2016-04-13 07:55:59Z

1

There are two issues, here.

First, there is no HTTP_HOST header. The header is Host:. It sounds like HTTP_HOST is something being generated internally by your web server or framework.

Second, HAProxy doesn't modify the Host: header just because your back-end is listening on a port other than 80. It doesn't actually modify the Host: header at all, unless explicit configured to, using a mechanism like reqirep ^Host: ... or http-request set-header host ....

You can confirm this with a packet capture. You should find that whatever HTTP_HOST is, the value is necessarily being generated internally on the back-end system itself, because it's not coming from HAProxy.

answered Apr 13, 2016 at 7:55

Michael - sqlbot

180k28 gold badges388 silver badges458 bronze badges

Sign up to request clarification or add additional context in comments.

6 Comments

Sumit Murari Over a year ago

Thanks, you were correct. There is nothing like HTTP_HOST header sent by haproxy, it was internal.

Sumit Murari Over a year ago

But when the request is sent to some backend like bkend_server:123, the http request received at backend was abc.domain.com:123, [i understand it's standard convention (host:port) to send request] which earlier with elb was abc.domain.com, if backend port was 123 or any port. I wasn't doing any explicit configuration. What else can be the cause that it behaving in that way. =====. I've logged request in IIS under cs-host was like abc.domain.com:port when request was passed via haproxy and abc.domain.com when passed via elastic loadbalancer.

Michael - sqlbot Over a year ago

The browser should append the port to the hostname, but only when it is not :80 for http or not :443 for https. I have never seen ELB nor HAProxy autonomously append a port number, regardless of the actual back-end port. Was ELB hitting 81 just like HAProxy?

Sumit Murari Over a year ago

I was also surprised to see this behavior, i wasn't expecting it either. Both elb and haproxy are hitting 81 port, but request via haproxy hits IIS as ab.domain.com:81 and via ELB as 'abc.domain.com`

Michael - sqlbot Over a year ago

What version of HAProxy? What web server is on the back-end? What port is the front-end listening on (443 I assume)?

|

Collectives™ on Stack Overflow

Haproxy Appending Port to `HTTP_HOST` Header in Backend Request

1 Answer 1

6 Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

6 Comments

Your Answer

Sign up or log in

Post as a guest

Related