PSM 

Overview

• PSM (Persistent Storage Manager) component is responsible for the storage of default/system configurations.
• Provides software interfaces and abstractions to read/write variables stored in persistent storage and read factory config variables.
• PSM holds mainly parameters related to hardware configuration.
• In dual processor architecture a process running in peer processor can access PSM DB over DBUS.
• All defaults/system configuration which are not modified during runtime are part of PSM.
• PSM should be up and running for normal configuration of RDKB unit.
• For WiFi initialization, PSM holds all default values of OEM specific custom parameters which is fetched through PSM HAL.

Architecture

Figure 1 - Architectural view of PSM sub-system

Initialization

Figure 2 - Initialization of PSM sub-system

Current and default configuration files

PSM properties files

Configuration files are saved as below on the device:

/fss/gw/usr/ccsp/config/bbhm_def_cfg.xml

/nvram/bbhm_bak_cfg.xml

/nvram/bbhm_cur_cfg.xml

Factory reset removes the configuration files from nvram and copies default file to nvram.

 To prevent system configuration file from becoming corrupted or lost when the device is suddenly rebooted or power loss conditions, following counter-measures are in place:

• First copy the current system file into the backup file
• Then flush the configuration into the current file

Reading configuration

Figure 3 - Reading Configuration

PsmSysroCfmReadCurConfig/PsmSysroCfmReadDefConfig - This function is called to read the current or default Psm configuration into the memory. AnscReadFile - performs a sequential read

Restore configuration is tried first from the current system file. If it passes the verification, read is done otherwise restore configuration is tried from the backup system file. If it passes the verification, read is done otherwise restores the factory default configuration. This step has to succeed since there is no any other plan to back it up.

Get values from PSM

Figure 4 - Retrieving Parameter

Using CLI utility:
psmcli get <parameter name as in bbhm file>
Eg: psmcli get eRT.com.cisco.spvtg.ccsp.Device.WiFi.NotifyWiFiChanges

Set values for PSM

Figure 5 - Setting Parameter

Using CLI utility:
psmcli set <parameter name as in bbhm file>
Eg: psmcli set eRT.com.cisco.spvtg.ccsp.Device.WiFi.NotifyWiFiChanges true

User and default configuration initialization

Syscfg_create.exe executable creates shared memory with user configuration data (/nvram/syscfg.db). This is present in the code base at the location /ccsp/utopia/source/syscfg

Apply_system_defaults.exe executable reads the data from system_defaults file (path: /etc/utopia/system_defaults) and compares with syscfg.db, in case of any data is missing in syscfg, those defaults are written in to shared memory. On start of any module, data is read from the shared memory during initialization.

If syscgf.db does not exists (e.g in case of factory reset) apply_system_defaults.exe writes all default data on to shared memory and syscfg_commit() gets called which in turn creates syscgf.db.

Example Firewall Initialization

Gw_prov_utopia exe calls Init script. Init script executes all executables present in /etc/utopia/registration.d/ directory. 10_firewall exe is responsible for firewall events and it registers for sysevent callback with service name as firewall. Handler script is firewall_log_handle.sh. If any firewall event occurs sysevent is triggered with firewall-restart event name.

Firewall Initialization Process

On firewall-restart event service_start() method gets called. Ip4table and Ip6table rules are prepared by reading data from shared memory, written into /tmp/.ipt and /tmp/.ipt_v6 files respectively. Iptable rules are restored using these files.

Example Set flow

Following sequence explains flow when a SET from SNMP, TR69 or CLI is done:

• When commit needs to be done xml mapped API PCBlkURL_Commit() api gets called.
• If object is new CosaDmlBlkURL_AddEntry() is called ,else CosaDmlBlkURL_SetConf() api is called.
• Utopia_SetBlkURLByIndex() prepares the syscfg data by appending proper index to be added to the cfg file.

Eg. Second row entry details are saved as shown below in xml.

pcms_2::method=URL
pcms_2::always=1
pcms_2::end_time=
ManagedSiteBlock_2=pcms_2
pcms_2::alias=cpe-BlockedURL-2
pcms_2::days=
pcms_2::site=https://www.wellsfargo.com
pcms_2::ins_num=2
pcms_2::start_time=

• syscfg_set() checks if the syscfg value exists, if not allocates memory and add it to the end of the linked list and sets the value.
• SysCfg_Commit() – calls syscfg_commit().
• syscfg_commit API updates the persistent memory with the shared memory details.

Example set flow for PC URL