Forum Discussion
Jamey_Price_105
Nimbostratus
NimbostratusProblem rewriting header attribute on HTTP code 302
I'm new to TCL as of yesterday, so if I'm doing something monumentally dumb, please pardon me.
Our application runs on a server on port 9080, clients access it via port 80 or 443. When the server needs to issue a 302 Found to instruct the client to go elsewhere (say to log in first) it throws in the port that the internal server is running on. We need to strip that out and return the rest to the client. My rule is below, and something is just not right. The string does not seem to be stored in variable result. Any time I try to reference it in any way I can come up with that I ought, I get the string "result" instead.
when HTTP_RESPONSE {
if { [HTTP::header Location] starts_with "http://dev.oursite.com:9080" } {
variable result
regsub :9080 [HTTP::header Location] {} result
log {Result is [set result] or $result or [result]}
[HTTP::redirect ${result}]
[HTTP::redirect [regsub :9080 [HTTP::header Location] {}]]
}
}
Also, there seems to be some difference between TCL regsub as implemented on the Big-IP and in the official documentation. According to the official documentation, the variable is optional, and if excluded the modified string will be returned. If I try that (such as in the last, commented-out line) I get an error stating that I have the wrong number of arguments for regsub.
Please, can someone help me out here?
Thanks,
Jamey
4 Replies
Jamey_Price_105Replying to my own post here...
I've modified the way it works, and like this, things are fine-ish. What I don't understand is if I try to use the commented line below to just fix the header instead of issuing my own redirect, I get the following in the logs.
TCL error: Rule redirectwrongport - Illegal argument. Illegal argument. Illegal argument. Illegal argument. Ille (line 1) invoked from within "HTTP::header Location $thingy"
when HTTP_RESPONSE {
if { [HTTP::header Location] starts_with "http://dev.oursite.com:9080" } {
regexp .+:9080/(.*) [HTTP::header Location] garbage whatiwant
variable thingy
set thingy "http://dev.oursite.com/"
append thingy $whatiwant
log "Thingy is $thingy"
HTTP::header Location $thingy
HTTP::redirect $thingy
}
}
Any ideas now?
Thanks,
Jamey- A couple of notes pertaining to our Tcl implementation.
a) You don't really need to declare local variables with the "variable" command. On first initialization, variables are automatically scoped into a per-connection, local scope.
b) As for the regexp command, you may have misinterpreted the optional nature of the matchVar and subMatchVar's. The matchVar is the complete matching string, where subMatchVar is the part within the parenthesis. In order to have a subMatchVar, you must have a matchVar (Tcl otherwise doesn't know whether you meant matchVar or subMatchVar). I often see the use of the variable '->' to make this appear more readable, however it is still just a garbage variable.
Eg: regexp .+:9080/(.*) [HTTP::header Location] -> whatiwant
c) In order to replace the header, you need to specify "replace" on the HTTP::header command. I am looking into why this ended up resulting in the bizarre error message you received, but it's probably some kind of bug.
d) Thanks for continuing to try!
Here is an updated example of your rule:when HTTP_RESPONSE { if { [HTTP::header Location] starts_with "http://dev.oursite.com:9080" } { regexp .+:9080/(.*) [HTTP::header Location] garbage whatiwant set thingy "http://dev.oursite.com/$whatiwant" log "Thingy is $thingy" HTTP::header replace Location $thingy } } - One thing I'll add to unruley's well-written response is that you may want to condition your check on the server's response actually being a 302. Otherwise you'll be needlessly scanning non-redirects for Location: headers.
- Oh, sorry, I confused myself regarding regexp and regsub.
The problem is with the Tcl syntax validator that we incorporated which is based on an earlier version of Tcl. It erroneously requires 4 arguments, not 3 arguments with an optional 4th argument. This will be fixed in an upcoming release.
![\"F5](\"https://www.f5.com/content/dam/f5/f5-logo.svg\"){kind=logo}
