confd: add support for custom container ENTRYPOINT

This was a tough nut to crack.  Turns out the trick to changing the
ENTRYPOINT is to set --entrypoint=command and then call 'podman create
... command args'.  Not entirely obvious since the documented approach
is to use a JSON array as the argument: podman create
--entrypoint='["command", "args" ]'.

Admittedly, encoding this in C to transfer it via a POSIX shell script
to the command line, is not the easiest task I've undertaken.  So I gave
up and found this workaround.

Worth noting, however, is that one *must* set `--entrypoint`, it is not
enough to just append the command to the 'podman create' command line.
Due to differences in docker and podman, we cannot supply the full args
to an alternate entrypoint command.  But for the command to actually run
we need to override the image's ENTRYPOINT and send the command and args
as the last arguments on the command line to podman create.

Signed-off-by: Joachim Wiberg <troglobit@gmail.com>

board/common/rootfs/usr/sbin/container

@@ -43,9 +43,10 @@ create()
     fi
 
     #  --syslog --log-level info
-    log "Calling \"podman create --name $name --conmon-pidfile=$pidfn $hostname $env $network $port $args $image\""
+    log "Calling \"podman create --name $name --conmon-pidfile=$pidfn $hostname $entrypoint $env $network $port $args $image $*\""
     set -x
-    if podman create --name "$name" --conmon-pidfile="$pidfn" $hostname $env $network $port $args "$image"; then
+    # shellcheck disable=SC2048
+    if podman create --name "$name" --conmon-pidfile="$pidfn" $hostname $entrypoint $env $network $port $args "$image" $*; then
 	log "Successfully created container $name from $image"
 	rm -f "/run/containers/env/${name}.env"
 	initctl show "container:$name" |grep -q manual:yes || initctl -bq start "container:$name"
@@ -83,6 +84,7 @@ options:
       --dns NAMESERVER    Set nameserver(s) when creating a container
       --dns-search LIST   Set host lookup search list when creating container
   -e, --env FILE          Environment variables when creating container
+      --entrypoint        Disable container image's ENTRYPOINT, run cmd + arg
   -f, --force             Force operation, e.g. remove
   -h, --help              Show this help text
       --hostname NAME     Set hostname when creating container
@@ -122,6 +124,9 @@ while [ "$1" != "" ]; do
 	    shift
 	    env="$env --env-file=$1"
 	    ;;
+	--entrypoint)
+	    entrypoint="--entrypoint=\"\""
+	    ;;
 	-f | --force)
 	    force="-f"
 	    ;;

src/confd/src/infix-containers.c

@@ -86,8 +86,14 @@ static int add(const char *name, struct lyd_node *cif)
 	if (lydx_is_enabled(cif, "host-network"))
 		fprintf(fp, " --net host");
 
+	if ((string = lydx_get_cattr(cif, "entrypoint")))
+		fprintf(fp, " --entrypoint");
+
 	fprintf(fp, " create %s %s", name, image);
 
+ 	if ((string = lydx_get_cattr(cif, "entrypoint")))
+		fprintf(fp, " %s", string);
+
 	fprintf(fp, "\n");
 	fchmod(fileno(fp), 0700);
 	fclose(fp);

src/confd/yang/infix-containers@2023-12-14.yang

@@ -83,6 +83,11 @@ module infix-containers {
 	}
       }
 
+      leaf entrypoint {
+	description "Override the default ENTRYPOINT from the image.";
+	type string;
+      }
+
       leaf hostname {
 	description "Sets the container host name that is available inside the container.";
 	type inet:domain-name;