Original Source

The original source http filter replicates the downstream remote address of the connection on the upstream side of Envoy. For example, if a downstream connection connects to Envoy with IP address, then Envoy will connect to the upstream with source IP The downstream remote address is determined based on the logic for the “trusted client address” outlined in XFF.

Note that the filter is intended to be used in conjunction with the Router filter. In particular, it must run prior to the router filter so that it may add the desired source IP to the state of the filter chain.

IP Version Support

The filter supports both IPv4 and IPv6 as addresses. Note that the upstream connection must support the version used.

Extra Setup

The downstream remote address used will likely be globally routable. By default, packets returning from the upstream host to that address will not route through Envoy. The network must be configured to forcefully route any traffic whose IP was replicated by Envoy back through the Envoy host.

If Envoy and the upstream are on the same host – e.g. in an sidecar deployment –, then iptables and routing rules can be used to ensure correct behaviour. The filter has an unsigned integer configuration, mark. Setting this to X causes Envoy to mark all upstream packets originating from this http with value X. Note that if mark is set to 0, Envoy will not mark upstream packets.

We can use the following set of commands to ensure that all ipv4 and ipv6 traffic marked with X (assumed to be 123 in the example) routes correctly. Note that this example assumes that eth0 is the default outbound interface.

iptables  -t mangle -I PREROUTING -m mark     --mark 123 -j CONNMARK --save-mark
iptables  -t mangle -I OUTPUT     -m connmark --mark 123 -j CONNMARK --restore-mark
ip6tables -t mangle -I PREROUTING -m mark     --mark 123 -j CONNMARK --save-mark
ip6tables -t mangle -I OUTPUT     -m connmark --mark 123 -j CONNMARK --restore-mark
ip rule add fwmark 123 lookup 100
ip route add local dev lo table 100
ip -6 rule add fwmark 123 lookup 100
ip -6 route add local ::/0 dev lo table 100
echo 1 > /proc/sys/net/ipv4/conf/eth0/route_localnet

Example HTTP configuration

The following example configures Envoy to use the original source for all connections made on port 8888. All upstream packets are marked with 123.

  - name: envoy.filters.http.original_src
      mark: 123
  - name: envoy.router
    config: {}