eCAP

Sharing info from eCAP adapter with other adapters

Asked by Moti Berger

Hi

I have an env with Squid 4 with several ICAPs.
In this env, I set in squid.conf the following:

adaptation_masterx_shared_names X-My-Header

and I add an ICAP header X-My-Header with some data in one ICAP and next ICAPs can use it (I also see it in tcpdump output).

Now I'm writing an eCAP and I did the following (for testing):

static const libecap::Name myHeader("X-My-Header", libecap::Name::NextId());
const libecap::Area Adapter::Xaction::option(const libecap::Name &name) const
{
    if (name == myHeader) {
        std::string t = "popo";
        return libecap::Area(t.data(), t.size());
    }
    return libecap::Area();
}

void Adapter::Xaction::visitEachOption(libecap::NamedValueVisitor &visitor) const
{
    std::string t = "popo";
    visitor.visit(myHeader, libecap::Area(t.data(), t.size()));
}

It is much like the clamAV eCAP example.
What I see in tcpdump output is the following:

X.....qZREQMOD icap://my.proxy:1234/request ICAP/1.0
Host: my.proxy:1234
Date: Wed, 14 Jul 2021 20:37:33 GMT
X-My-Header: .
Encapsulated: req-hdr=0, null-body=427
Preview: 0
Allow: 204

Meaning, it indeed added the X-My-Header as ICAP header for the benefit of the ICAP server on the chain but it seems the value is just a dot. When I had to pass the data in X-My-Header from an ICAP server with ICAP header everything worked fine.
What am I doing wrong?

Thanks,
Moti

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Alex Rousskov (rousskov) said : 		#1

> if (name == myHeader) {
> std::string t = "popo";
> return libecap::Area(t.data(), t.size());

Would not t.data() lifetime _end_ before the caller can use the area object that this method creates and returns?

When created with just two parameters, Area relies on its creator/owner to keep memory around, similar to std::stringview. In the above code, that memory will be gone by the time the method returns because the "t" variable will be destroyed upon exit.

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