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https://issues.apache.org/jira/browse/TS-3874?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Leif Hedstrom closed TS-3874.
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> Header-rewrite doesn't support multiple header values in conditionals
> ---------------------------------------------------------------------
>
> Key: TS-3874
> URL: https://issues.apache.org/jira/browse/TS-3874
> Project: Traffic Server
> Issue Type: Bug
> Components: Plugins
> Reporter: Thomas Jackson
> Assignee: Thomas Jackson
> Fix For: 6.0.0
>
>
> Lets say we have the following rule
> {code}
> cond %{HEADER:foo} /bar/
> add-header Baz1 1
> cond %{HEADER:foo} =bar
> add-header Baz2 2
> {code}
> There are some weird interactions with how this works today, so lets start
> with that:
> some request headers, and outcomes
> {code}
> # matches 1 and 2
> foo: bar
> # matches both 1 and 2
> foo: bar
> foo: baz
> # matches nothing
> foo: baz
> foo: bar
> {code}
> So the main problem we see here is that the second value is completely
> ignored all of the time-- which is bad ;)
> And when we get more complicated there are some more issues. In HTTP headers
> have to be collapsible into a single line
> (http://tools.ietf.org/html/rfc2616#section-4.2). This means that 2 headers
> with values `foo` and `bar` *must* be equivalent to a single header with
> value `foo,bar`. With that information, lets assume the downstream actually
> sent the values in the same header (which is completely valid-- and has to be
> treated the same according to the RFC).
> {code}
> # matches 1
> foo: bar,baz
> # matches 1
> foo: baz,bar
> {code}
> So this means we can boil down the problem into 2 pieces: (1) duplicate
> headers are ignored and (2) collapsed headers are treated differently than
> separate headers.
> So, I have a PR open on github
> (https://github.com/apache/trafficserver/pull/284) which combines the headers
> (according to the RFC) before passing it to the conditional's matcher. Here
> are the outcomes of the same set of headers
> {code}
> # matches 1 and 2
> foo: bar
> # matches 1
> foo: bar
> foo: baz
> # matches 1
> foo: baz
> foo: bar
> # matches 1
> foo: bar,baz
> # matches 1
> foo: baz,bar
> {code}
> And with this we have fixed both (1) taking the second header value as well
> as (2) treating collapsed and non-collapsed the same.
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