[PATCH v2 4/6] base-files: fwtool: make compat_version backward compatible

[Paul Spooren]

On 14.07.20 04:28, Adrian Schmutzler wrote:

> So far, the compatibility mechanism only works if both device and
> image are already updated to the new routines. This patch extends
> the sysupgrade metadata and fwtool_check_image() to account for
> "older" images as well:
>
> The basic mechanism for older devices to check for image compatibility
> is the supported_devices entry. This can be exploited by putting
> a custom message into this variable of the metadata, so older FW
> will produce a mismatch and print the message as it thinks it's the
> list of supported devices. So, we have two cases:
>
> device 1.0, image 1.0:
>    The metadata will just contain supported_devices as before.
>
> device 1.0, image 1.1:
>    The metadata will contain:
>
>    "new_supported_devices":["device_string1", "device_string2", ...],
>    "supported_devices":["Upgrade incompatible. Please check Wiki ..."]

Does that mean starting from 1.1 all sysupgrade images will carry a 
informative only "supported_device" array until the end of time?

This is maybe a bit of a big request but as there will be 19.07.4 
release without DSA, couldn't some firmware migration patches be added 
there and anyone trying to upgrade from 19.07.x will receive a message 
like "Please upgrade to 19.07.4 before installing 20.x"? Maybe it's not 
feasible, but as ideally all (correct?) devices move to DSA, we will 
have compat 1.1 everywhere and `supported_devices` is useless.

>    If the device is "legacy", i.e. does not have the updated fwtool.sh,
>    it will just fail with image check and print the content of
>    supported_devices. Upgrade can still be performed with -F like when
>    SUPPORTED_DEVICES has been removed to prevent bricking.
>
>    If the device has updated fwtool.sh (but is 1.0), it will just use
>    the new_supported_devices instead, and work as intended (flashing
>    with -n will work, flashing without will print the appropriate
>    warning).
>
> This mechanism should provide a fair tradeoff between simplicity
> and functionality.
>
> Signed-off-by: Adrian Schmutzler <freifunk at adrianschmutzler.de>
>
> ---
>
> Changes in v2:
> - Add DEVICE_COMPAT_MESSAGE and reword comment for legacy warning.
> ---
>   include/image-commands.mk                      | 5 ++++-
>   package/base-files/files/lib/upgrade/fwtool.sh | 7 ++++++-
>   2 files changed, 10 insertions(+), 2 deletions(-)
>
> diff --git a/include/image-commands.mk b/include/image-commands.mk
> index 9da712e733..e21472a659 100644
> --- a/include/image-commands.mk
> +++ b/include/image-commands.mk
> @@ -393,7 +393,10 @@ metadata_json = \
>   		"metadata_version": "1.0", \
By replacing the meaning of `supported_devices` to 
`new_supported_devices` we should also modify `metadata_version`.
>   		"compat_version": "$(call json_quote,$(compat_version))", \
>   		$(if $(DEVICE_COMPAT_MESSAGE),"compat_message": "$(call json_quote,$(DEVICE_COMPAT_MESSAGE))"$(comma)) \
> -		"supported_devices":[$(call metadata_devices,$(SUPPORTED_DEVICES))], \
> +		$(if $(filter-out 1.0,$(compat_version)),"new_supported_devices":[$(call metadata_devices,$(SUPPORTED_DEVICES))]$(comma)) \
> +		$(if $(filter-out 1.0,$(compat_version)),"supported_devices": \
> +			["$(call json_quote,Image version $(compat_version) incompatible to device: $(if $(DEVICE_COMPAT_MESSAGE),$(DEVICE_COMPAT_MESSAGE),Please check documentation ...)"]$(comma)) \
> +		$(if $(filter 1.0,$(compat_version)),"supported_devices":[$(call metadata_devices,$(SUPPORTED_DEVICES))]$(comma)) \
>   		"version": { \
>   			"dist": "$(call json_quote,$(VERSION_DIST))", \
>   			"version": "$(call json_quote,$(VERSION_NUMBER))", \
> diff --git a/package/base-files/files/lib/upgrade/fwtool.sh b/package/base-files/files/lib/upgrade/fwtool.sh
> index 1807aecd6d..59f981f6c3 100644
> --- a/package/base-files/files/lib/upgrade/fwtool.sh
> +++ b/package/base-files/files/lib/upgrade/fwtool.sh
> @@ -51,7 +51,12 @@ fwtool_check_image() {
>   	json_get_var compatmessage compat_message
>   	[ -n "$imagecompat" ] || imagecompat="1.0"
>   
> -	json_select supported_devices || return 1
> +	# select correct supported list based on compat_version
> +	# (using this ensures that compatibility check works for devices
> +	#  not knowing about compat-version)
> +	local supported=supported_devices
> +	[ "$imagecompat" != "1.0" ] && supported=new_supported_devices
> +	json_select $supported || return 1
>   
>   	json_get_keys dev_keys
>   	for k in $dev_keys; do