Tiphares is an effort to implement transparent proxy capabilities in Traffic Server. This is the ability of a proxy (such as ATS) to intercept connections between clients and servers without being visible.

The general network structure that will be used in this documentation looks like this --

There must be a gateway device through which passes all network traffic from the client to the Internet (or external cloud). The gateway is responsible for effectively splicing ATS in to selected streams of that traffic. Each traffic stream is split in to two, with ATS terminating both sides. That is, stream green-1, red-2, is split in to the green connection and the red connection. Note that ATS may or may not be on the gateway system, the redirected traffic can flow over other network infrastructure.

Because ATS uses two connections transparency can be set independently on the client and origin server (Internet / external cloud) side. We will define what is generally called "transparent proxy" as two aspects, inbound transparency and outbound transparency.

Inbound transparency is a proxy that is transparent to connections that are inbound to the proxy, i.e. a connection initiated by a client which connects to the proxy (green-1). Similarly, outbound transparency is a proxy that is transparent to connections that are outbound from the proxy, i.e. a connection initiated by the proxy to an origin server (red-2).

In most treatments these two types of transparency are treated as unitarily but that is not required. This implementation supports transparency independently on the two (client, origin server) sides (use cases).

It is critical to note that any transparency requires specialized routing and cannot be done solely by configuring ATS. ATS transparency also requires support from the Linux kernel and therefore currently only works on sufficiently recent Linux kernels that support the following features --

In addition the specialized routing will require using iptables and in some cases ebtables.

Standard build procedures should work for transparency support but if not consult these more detailed instructions

Transparency is configured per server port not globally. This is done via the configuration values proxy.config.http.server_port_attr and proxy.config.http.server_other_ports. In addition, proxy.config.reverse_proxy_enabled must be enabled if the client side is transparent. That should be fixed in a future patch.

In the first case use the attribute character (replacing the default 'X')

AttributeTransparency StyleReverse Proxy
'='Full transparencyeither
'>'Inbound (client) transparencyenabled
'<'Outbound (origin server) transparencyeither

In the outbound transparent case clients must connect directly to ATS either through an explicit proxy mechanism or by advertising the IP address of the ATS server via DNS as the origin server address.

For .server_other_ports use the same characters after the port and colon, e.g. if port 8088 is to be configured for client side transparency use '8088:>'.

Some tested scenarios --