Support podman-specific per-network mac_address specifiation

Signed-off-by: Bas Zoetekouw <bas.zoetekouw@surf.nl>

docs/Extensions.md

@@ -0,0 +1,47 @@
+# Podman specific extensions to the docker-compose format
+
+Podman-compose supports the following extension to the docker-compose format.
+
+## Per-network MAC-addresses
+
+Generic docker-compose files support specification of the MAC address on the container level. If the
+container has multiple network interfaces, the specified MAC address is applied to the first
+specified network.
+
+Podman-compose in addition supports the specification of MAC addresses on a per-network basis. This
+is done by adding a `podman.mac_address` key to the network configuration in the container. The
+value of the `podman.mac_address` key is the MAC address to be used for the network interface.
+
+Specifying a MAC address for the container and for individual networks at the same time is not
+supported.
+
+Example:
+
+```yaml
+---
+version: "3"
+
+networks:
+  net0:
+    driver: "bridge"
+    ipam:
+      config:
+        - subnet: "192.168.0.0/24"
+  net1:
+    driver: "bridge"
+    ipam:
+      config:
+        - subnet: "192.168.1.0/24"
+
+services:
+  webserver
+    image: "busybox"
+    command: ["/bin/busybox", "httpd", "-f", "-h", "/etc", "-p", "8001"]
+    networks:
+      net0:
+        ipv4_address: "192.168.0.10"
+        podman.mac_address: "02:aa:aa:aa:aa:aa"
+      net1:
+        ipv4_address: "192.168.1.10"
+        podman.mac_address: "02:bb:bb:bb:bb:bb"
+```