Forum Discussion

Nimbostratus

Apr 18, 2016

iRule Redirect To Specific Pool Member Based On HTTP Header String

Greetings,

I apologize for my lack of iRule experience upfront. Our SME that normally handles the writing of specific iRules is out this week. I have been asked to write an iRule that will check incoming HTTP connections for a string named "X-SLOWROLL" = 1 condition. If the statement is true the connection should be sent to a specific pool member host and if its false it should be sent to the pool.

I don't have any iRule experience and need some help or advice with regards where to research for a base rule that would help me write one to meet the above requirement.

Any help or feedback would be greatly appreciated.

Sample iRule with Loggings:
config  tmsh list ltm rule SLOWROLL
ltm rule SLOWROLL {
    when HTTP_REQUEST {
 if { [HTTP::header exists X-SLOWROLL] and [HTTP::header X-SLOWROLL] equals "1" } {
    node 10.29.100.20 80
        set url [HTTP::header Host][HTTP::uri]
        set vip [IP::local_addr]:[TCP::local_port]
        foreach aHeader [HTTP::header names] {
      log local0. "HTTP REQUEST HEADER $aHeader: [HTTP::header value $aHeader]"
                }
        }
}
when HTTP_RESPONSE {
        set client [IP::client_addr]:[TCP::client_port]
        set node [IP::server_addr]:[TCP::server_port]
        set nodeResp [HTTP::status]
        log local0.info "SUMMARY: Client: $client -> VIP name is [virtual name] $vip and URL is $url -> Node: $node with response $nodeResp"
 }
}




Request from a client:
 curl -v -H 'X-SLOWROLL: 1' http://150.29.100.98
* About to connect() to 150.29.100.98 port 80 (0)
*   Trying 150.29.100.98... connected
* Connected to 150.29.100.98 (150.29.100.98) port 80 (0)
> GET / HTTP/1.1
> User-Agent: curl/7.19.7 (x86_64-redhat-linux-gnu) libcurl/7.19.7 OpenSSL/1.0.1l zlib/1.2.3 libidn/0.6.5
> Host: 150.29.100.98
> Accept: */*
> X-SLOWROLL: 1
>
< HTTP/1.1 200 OK
< Content-Type: text/html
< Last-Modified: Fri, 19 Sep 2014 09:29:52 GMT
< Accept-Ranges: bytes
< ETag: "7bf75a44ecd3cf1:0"
< Server: Microsoft-IIS/7.5
< Date: Tue, 19 Apr 2016 05:32:06 GMT
< Content-Length: 1162


Log output:
Apr 18 15:33:36 MAMA-ATM-SGDC info tmm1[11293]: Rule /Common/SLOWROLL : HTTP REQUEST HEADER User-Agent: curl/7.19.7 (x86_64-redhat-linux-gnu) libcurl/7.19.7 OpenSSL/1.0.1l zlib/1.2.3 libidn/0.6.5
Apr 18 15:33:36 MAMA-ATM-SGDC info tmm1[11293]: Rule /Common/SLOWROLL : HTTP REQUEST HEADER Host: 150.29.100.98
Apr 18 15:33:36 MAMA-ATM-SGDC info tmm1[11293]: Rule /Common/SLOWROLL : HTTP REQUEST HEADER Accept: */*
Apr 18 15:33:36 MAMA-ATM-SGDC info tmm1[11293]: Rule /Common/SLOWROLL : HTTP REQUEST HEADER X-SLOWROLL: 1
Apr 18 15:33:36 MAMA-ATM-SGDC info tmm1[11293]: Rule /Common/SLOWROLL : SUMMARY: Client: 150.29.100.3:49555 -> VIP name is /Common/HSL_TEST_VS 150.29.100.98:80 and URL is 150.29.100.98/ -> Node: 10.29.100.20:80 with response 200

iamczar_12961

Cirrus

Apr 18, 2016

Sample iRule with Loggings:
config  tmsh list ltm rule SLOWROLL
ltm rule SLOWROLL {
    when HTTP_REQUEST {
 if { [HTTP::header exists X-SLOWROLL] and [HTTP::header X-SLOWROLL] equals "1" } {
    node 10.29.100.20 80
        set url [HTTP::header Host][HTTP::uri]
        set vip [IP::local_addr]:[TCP::local_port]
        foreach aHeader [HTTP::header names] {
      log local0. "HTTP REQUEST HEADER $aHeader: [HTTP::header value $aHeader]"
                }
        }
}
when HTTP_RESPONSE {
        set client [IP::client_addr]:[TCP::client_port]
        set node [IP::server_addr]:[TCP::server_port]
        set nodeResp [HTTP::status]
        log local0.info "SUMMARY: Client: $client -> VIP name is [virtual name] $vip and URL is $url -> Node: $node with response $nodeResp"
 }
}




Request from a client:
 curl -v -H 'X-SLOWROLL: 1' http://150.29.100.98
* About to connect() to 150.29.100.98 port 80 (0)
*   Trying 150.29.100.98... connected
* Connected to 150.29.100.98 (150.29.100.98) port 80 (0)
> GET / HTTP/1.1
> User-Agent: curl/7.19.7 (x86_64-redhat-linux-gnu) libcurl/7.19.7 OpenSSL/1.0.1l zlib/1.2.3 libidn/0.6.5
> Host: 150.29.100.98
> Accept: */*
> X-SLOWROLL: 1
>
< HTTP/1.1 200 OK
< Content-Type: text/html
< Last-Modified: Fri, 19 Sep 2014 09:29:52 GMT
< Accept-Ranges: bytes
< ETag: "7bf75a44ecd3cf1:0"
< Server: Microsoft-IIS/7.5
< Date: Tue, 19 Apr 2016 05:32:06 GMT
< Content-Length: 1162


Log output:
Apr 18 15:33:36 MAMA-ATM-SGDC info tmm1[11293]: Rule /Common/SLOWROLL : HTTP REQUEST HEADER User-Agent: curl/7.19.7 (x86_64-redhat-linux-gnu) libcurl/7.19.7 OpenSSL/1.0.1l zlib/1.2.3 libidn/0.6.5
Apr 18 15:33:36 MAMA-ATM-SGDC info tmm1[11293]: Rule /Common/SLOWROLL : HTTP REQUEST HEADER Host: 150.29.100.98
Apr 18 15:33:36 MAMA-ATM-SGDC info tmm1[11293]: Rule /Common/SLOWROLL : HTTP REQUEST HEADER Accept: */*
Apr 18 15:33:36 MAMA-ATM-SGDC info tmm1[11293]: Rule /Common/SLOWROLL : HTTP REQUEST HEADER X-SLOWROLL: 1
Apr 18 15:33:36 MAMA-ATM-SGDC info tmm1[11293]: Rule /Common/SLOWROLL : SUMMARY: Client: 150.29.100.3:49555 -> VIP name is /Common/HSL_TEST_VS 150.29.100.98:80 and URL is 150.29.100.98/ -> Node: 10.29.100.20:80 with response 200

silvajai_01_131
Nimbostratus
Apr 19, 2016
Thanks!

David_M

Cirrostratus

Jun 24, 2019

Why do we need to do the for each here?

foreach aHeader [HTTP::header names] {
      log local0. "HTTP REQUEST HEADER $aHeader: [HTTP::header value $aHeader]"
                }

Yann_Desmarest
Cirrus
Apr 18, 2016
Hello,

You can use something similar to this :

when HTTP_REQUEST { if { [HTTP::header exists X-SLOWROLL] and [HTTP::header X-SLOWROLL] equals "1" } { node x.x.x.x 80 node ip port } }
- silvajai_01_131
  Nimbostratus
  Apr 18, 2016
  Thanks. In my desperation, I came up with the below rule, which I haven't tested yet. Just curious, but do you think the below rule would have worked as well. when HTTP_REQUEST { set tcip [HTTP::header X-SLOWROLL] if { $tcip eq 1 } { node 10.16.18.1 80 } }
- silvajai_01_131
  Nimbostratus
  Apr 18, 2016
  when HTTP_REQUEST { set tcip [HTTP::header X-SLOWROLL] if { $tcip eq 1 } { node 10.16.18.1 80 } }
Yann_Desmarest_
Nacreous
Apr 18, 2016
Hello,

You can use something similar to this :

when HTTP_REQUEST { if { [HTTP::header exists X-SLOWROLL] and [HTTP::header X-SLOWROLL] equals "1" } { node x.x.x.x 80 node ip port } }
- silvajai_01_131
  Nimbostratus
  Apr 18, 2016
  Thanks. In my desperation, I came up with the below rule, which I haven't tested yet. Just curious, but do you think the below rule would have worked as well. when HTTP_REQUEST { set tcip [HTTP::header X-SLOWROLL] if { $tcip eq 1 } { node 10.16.18.1 80 } }
- silvajai_01_131
  Nimbostratus
  Apr 18, 2016
  when HTTP_REQUEST { set tcip [HTTP::header X-SLOWROLL] if { $tcip eq 1 } { node 10.16.18.1 80 } }