Varnish: How to use `std.ip()` to set a header value - http-headers

Question

I am trying to use std.ip which is a part of varnish 4.0 to to return the client IP which should be the first valid IP address in the X-Forwarded-For header, if the example in the documentation is correct.
varnishtest "Test v4 vcl X-Forwarded-For Header logic"
server s1 {
rxreq
expect req.http.X-Real-IP == "2.1.1.1"
expect req.http.X-Forwarded-For == "2.1.1.1, 3.3.3.3, 3.3.3.3, 127.0.0.1"
txresp
} -start
varnish v1 -vcl+backend {
sub vcl_recv {
set req.http.X-Real-IP = std.ip(req.http.X-Forwarded-For, "0.0.0.0");
}
} -start
client c1 {
txreq -url "/" -hdr "X-Forwarded-For: 2.1.1.1, 3.3.3.3, 3.3.3.3"
rxresp
}
client c1 -run
The above dies an ugly death:
...
*** v1 0.9 debug| Assert error in vwk_thread(), waiter/cache_waiter_kqueue.c line 115:\n
*** v1 0.9 debug| Condition(read(vwk->pipe[0], &c, 1) == 1) not true.\n
...
And does not behave as I would want by returning the first IP address.
Updated
Alternatively I have found that the following does work for the same purposes, But still could not get std.ip to work:
varnish v1 -vcl+backend {
sub vcl_recv {
set req.http.X-Real-IP = regsub(req.http.X-Forwarded-For, "\s*,.*$", "");
}
} -start
As a follow up question. This vcl_recv{...} logic actually lives in my default.vcl file, where all my backends, probes are defined. But when I try to test that code by including into a varnishtest file as follows:
varnish v1 -vcl+backend {
include "/path/to/file.vcl";
} -start
The test does not get the expect statements in the server s1. If someone could give some clarity on the following I'd be much ablighed:
Why does std.ip(req.http.X-Forwarded-For, "0.0.0.0") not behave as expected?
How can I test an included default.vcl with expect statements in the set server s1?
Thank you.

Answer 1

You need to add the line
import std;
at the top of your vcl file