From 29075b832d1ac5709ead061292f2fe0dc92bd2fd Mon Sep 17 00:00:00 2001
From: Louis <lspgn@users.noreply.github.com>
Date: Tue, 2 Aug 2022 22:28:47 -0700
Subject: [PATCH] docs: add information about mapping (#108)

---
 README.md | 19 +++++++++++++++++++
 1 file changed, 19 insertions(+)

diff --git a/README.md b/README.md
index 474c12a..e25c894 100644
--- a/README.md
+++ b/README.md
@@ -157,6 +157,25 @@ You can also run directly with a container:
 $ sudo docker run -p 6343:6343/udp -p 2055:2055/udp -ti netsampler/goflow2:latest
 ```
 
+### Mapping extra fields
+
+In the case of exotic template fields or extra payload not supported by GoFlow2
+of out the box, it is possible to pass a mapping file using `-mapping mapping.yaml`.
+A [sample file](cmd/goflow2/mapping.yaml) is available in the `cmd/goflow2` directory.
+
+For instance, certain devices producing IPFIX use `ingressPhysicalInterface` (id: 252)
+and do not use `ingressInterface` (id: 10). Using the following you can have the interface mapped
+in the InIf protobuf field without changing the code.
+
+```yaml
+ipfix:
+  mapping:
+    - field: 252
+      destination: InIf
+    - field: 253
+      destination: OutIf
+```
+
 ### Output format considerations
 
 The JSON format is advised only when consuming a small amount of data directly.