Hi Bernhard, On 22 November 2016 at 15:30, Bernhard Nortmann <bernhard.nortm...@web.de> wrote: > Hi Simon! > > > Am 19.11.2016 um 14:47 schrieb Simon Glass: >> >> Hi Bernhard, >> >> On 16 November 2016 at 03:30, Bernhard Nortmann >> <bernhard.nortm...@web.de> wrote: >>> >>> This is an attempt to prevent such information from ending up >>> in exported environment data, especially when doing "saveenv". >>> (http://lists.denx.de/pipermail/u-boot/2015-September/227611.html) >>> >>> The patch makes use of the new setenv_transient() helper for >>> environment variables that get updated via network configuration: >>> BOOTP/DHCP (netboot_update_env), CDP (cdp_update_env) and >>> link-local protocol (do_link_local). >>> >>> Signed-off-by: Bernhard Nortmann <bernhard.nortm...@web.de> >>> --- >>> >>> Changes in v2: None >>> >>> cmd/net.c | 34 +++++++++++++++++----------------- >>> 1 file changed, 17 insertions(+), 17 deletions(-) >> >> Reviewed-by: Simon Glass <s...@chromium.org> >> >> How would you make these variables non-transient? Does the transient >> nature show up in 'printenv'? >> >> Regards, >> Simon > > > I think it's best to consider a practical example. I'm firing up my > sunxi-based > device with these patches applied on top of U-Boot v2016.11, and interrupt > the > autoboot. > > The standard way to examine variables that have non-default flags is the > "env > flags" command. In my case this outputs (discarding the explanations near > the > top): > > Static flags: > Variable Name Variable Type Variable Access > ------------- ------------- --------------- > eth\d?addr MAC address write-once > ipaddr IP address any > gatewayip IP address any > netmask IP address any > serverip IP address any > nvlan decimal any > vlan decimal any > dnsip IP address any > serial# string write-once > fel_booted boolean system > fel_scriptaddr hexadecimal system > > Active flags: > Variable Name Variable Type Variable Access > ------------- ------------- --------------- > serial# string write-once > ethaddr MAC address write-once > fel_booted boolean system > > As you can see, patch 5/7 has sneaked in two new "system" flags and since > I've > booted using the FEL mechanism, the "fel_booted" one is in effect > ("active"). > > Okay, now I use the command "setenv autoload no; dhcp" to auto-configure > networking. Let's check "env flags" again. The "Static flags" section is > unchanged, but at the bottom there's now: > > Active flags: > Variable Name Variable Type Variable Access > ------------- ------------- --------------- > ipaddr IP address transient > serial# string write-once > hostname string transient > ethaddr MAC address write-once > netmask IP address transient > serverip IP address transient > fel_booted boolean system > dnsip IP address transient > gatewayip IP address transient > >>Does the transient nature show up in 'printenv'? > > No, it doesn't. "printenv" will give output that looks as usual / perfectly > normal. You're also not restricted in modifying "transient" variables, for > example I can do "ipaddr 10.11.12.13" with no problems. > > But: The differences will become apparent when trying to export the > environment > with something like "saveenv" or "env export": > => env export 0x40000000 > ## Don't export "ipaddr" > ## Don't export "hostname" > ## Don't export "netmask" > ## Don't export "serverip" > ## Don't export "fel_booted" > ## Don't export "dnsip" > ## Don't export "gatewayip" > > U-Boot refuses to store the 'volatile' information for those variables that > have been flagged accordingly, and informs the user about it. This is > checked > individually per variable, i.e. the other ones will get exported normally. > > At this point I decide that I want to set up a *static* IP configuration and > make it persistent with "saveenv". Houston, we have a problem! > >>How would you make these variables non-transient? > > Well, again there's a standard U-Boot mechanism for this. The README > mentions > it in the description of CONFIG_ENV_FLAGS_LIST_STATIC: "To override a > setting > in the static list, simply add an entry for the same variable name to the > '.flags' variable.". > > So we could do "setenv .flags ipaddr:i,netmask:i,gatewayip.i" to reset the > variables to access level "any", meaning they'll get exported again. > > Admittedly, there's a slight inconsistency here. Due to the fact that > setenv_transient() only sets a temporary flag, and U-Boot will rebuild the > access flags list (from the "static" default one) when assigning ".flags", > the "transient" flags for the networking variables will get cleared anyway - > even when deleting ".flags". > > The alternative would be to mark these variables "transient" from the > beginning > (in the static flags), but I considered that more awkward - when taking into > account that users might want to setup (and "saveenv") the network manually > right from the start, and are less likely to override the values retrieved > via > auto-configuration (DHCP etc.).
Thanks for the explanation. It looks fine to me. Regards, Simon _______________________________________________ U-Boot mailing list U-Boot@lists.denx.de http://lists.denx.de/mailman/listinfo/u-boot
