[PATCH] Add proxy_protocol option to mail listener

Wayde Nie niew at mcmaster.ca
Mon Aug 7 11:49:52 UTC 2017

On 08/07/2017 03:44 AM, Kees Bos wrote:, and when I do set
>> proxy_protocol
>> on the listen directive I see the correct ip and port picked up and
>> logged in the error.log, however, then nginx stops sending the smtp
>> greeting... My mail client connects to my loadbalancer, the lb
>> connects
>> to nginx:587 sending the PROXY line, nginx parses and logs the PROXY
>> fields,  then the client times out waiting for any return traffic
>> from
>> nginx... I know it's something I'm doing :-)
>> I'm happy to keep poking away at it, but curious mostly, if you think
>> the approach is sound? (ie. use $proxy_protocol_addr, set by
>> proxy_protocol directive and pass in to auth_http script in auth url
>> as
>> a get param?) and if an initial patch that starts by just setting
>> $proxy_protocol_* variables would be a useful first step in this type
>> of
>> functionality?
>>> Just to get the picture right (it looks to me that your downstream smtp
>>> server expects the proxy protocol), what's the exact flow you're trying
>>> to accomplish?

 Hi Kees,

Thanks for looking!

In my use case I have an external hardware loadbalancer that is
receiving end user connections on a VIP, pre-pending proxy_protocol
header and loadbalancing them to small pool of nginx servers running as
the mail proxies. Nginx is parsing the proxy_protocol header and (I
hope) proxying to my upstream smtp server without passing the
proxy_protocol header, which my upstream smtp server doesn't support (as
currently implemented).

Flow like:

    1) Client makes connection to [external-LB-VIP:587] for email submission
    2) [external-LB-VIP:587] --> injects proxy_protocol header --> load
    balances to set of nginx services via TCP service pool (ie: lb
    straight tcp, no application level inspection by loadbalancer, other
    than prepending proxy_protocol header)
    3) Nginx parses proxy_protocol header, logs client ip and passes
    client IP into auth_http script, along with username and password
    for authn/authz
    4) on successful return response from auth_http; nginx proxies mail
    submission to upstream smtp server without proxy_protocol header.

So, if possible, I'd like nginx to get the client ip passed to it from
the external hardware load balancer, log it and then use it in the
auth_http script, but otherwise not pass it on to the upstream smtp

Is this doable?

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