qosmngr: move Routing doc from bbfdm to qosmngr

This file contains guidance on how to use Device.QoS.
and Policy Based Routing. So, move this to qosmngr.

docs/guide/libbbfdm_Routing.md

+# PBR (Policy based routing)
+
+Aim of this document to explain policy based routing management using TR181 Routing/QoS datamodel parameter mappings with network and qos uci.
+
+In order to enable source based routing, you must first add a new 'Device.Routing.Router.{i}.' object to redirect routes for specific interface to a separate routing table, then configure the policy by adding new instances for 'Device.QoS.Classification.{i}.' object.
+
+## How to handle 'Device.Routing.Router.{i}.' object:
+
+By default, all interfaces with all routes being available in the main routing table which is 'Device.Routing.Router.1.'.
+
+```bash
+config interface 'lan'
+    option device 'br-lan'
+    option proto 'static'
+    option ipaddr '192.168.1.1'
+    option netmask '255.255.255.0'
+    option ip6assign '60'
+    option is_lan '1'
+
+config interface 'wan'
+    option proto 'dhcp'
+    option device 'eth0'
+
+config interface 'wan6'
+    option proto 'dhcpv6'
+    option device 'eth0'
+```
+
+Its table id should be 254 according to rt_tables as defined below:
+
+```bash
+$ cat /etc/iproute2/rt_tables 
+#
+# reserved values
+#
+128 prelocal
+255 local
+254 main
+253 default
+0   unspec
+#
+# local
+#
+#1  inr.ruhep
+````
+
+To redirect routes for specific interface to a separate routing table, you need to add a new 'Device.Routing.Router.{i}.' object.
+
+1. Adding a new 'Device.Routing.Router.{i}.' object:
+
+Each new routing object must have a unique route table which is calculated as follows:
+
+route table = local route which is the highest known reserved table id + current instance number - 1 which is the instance number for the main table
+
+For example: 
+In our case, the local route is 255 as defined in '/etc/iproute2/rt_tables' file and the current instance number is 2 so the new route table will be 255+2-1 = 256
+
+```bash
+$ cat /etc/bbfdm/dmmap/dmmap
+config route
+    option router_instance '1'
+    option rt_table '254'
+
+config route
+    option router_instance '2'
+    option rt_table '256'
+```
+
+2. Setting new routing object to needed interface:
+
+```bash
+obuspa -c set Device.IP.Interface.{i}.Router=Device.Routing.Router.{i}.
+```
+
+At this stage, the network uci should add the options 'ip4table' and 'ip6table' to needed main interface and its alias sections with the new route table id which is 256.
+
+For example:
+In our case, we used wan interface to redirect routes to a separate routing table which is 'Device.Routing.Router.2.'
+
+```bash
+config interface 'lan'
+    option device 'br-lan'
+    option proto 'static'
+    option ipaddr '192.168.1.1'
+    option netmask '255.255.255.0'
+    option ip6assign '60'
+    option is_lan '1'
+
+config interface 'wan'
+    option proto 'dhcp'
+    option device 'eth0'
+    option ip4table '256'
+    option ip6table '256'
+
+config interface 'wan6'
+    option proto 'dhcpv6'
+    option device 'eth0'
+    option ip4table '256'
+    option ip6table '256'
+```
+
+> Note1: All the routes for wan interface should be visible in the 'Device.Routing.Router.2.' instead of 'Device.Routing.Router.1.'
+> Note2: The 'Device.Routing.Router.1.' should contain the contents of main table as before except all routes related to wan interface
+
+## How to handle 'Device.Routing.Router.{i}.[IPv4Forwarding.{i},IPv6Forwarding.{i}].' object:
+
+Each routing object can have ipv{4,6} static routes defined in uci network and ipv{4,6} dynamic routes defined in '/proc/net/route' and '/proc/net/ipv6_route' files.
+
+1. Dynamic routes:
+
+For each route defined in '/proc/net/route' and '/proc/net/ipv6_route' files, a new instance will be created for IPv4Forwarding.{i} and IPv6Forwarding.{i} objects under the main routing object which is Device.Routing.Router.1. or any specific routing object (Device.Routing.Router.{2,3,..}.)
+
+
+2. Static routes:
+
+When adding a new static route there are two options that need to be populated from routing object which are interface and table id.
+
+For example:
+In our case, we used wan interface to redirect routes to a separate routing table which is 'Device.Routing.Router.2.' and we created an ipv4 static route for table 256.
+
+ ```bash
+config interface 'lan'
+    option device 'br-lan'
+    option proto 'static'
+    option ipaddr '192.168.1.1'
+    option netmask '255.255.255.0'
+    option ip6assign '60'
+    option is_lan '1'
+
+config interface 'wan'
+    option proto 'dhcp'
+    option device 'eth0'
+    option ip4table '256'
+    option ip6table '256'
+
+config interface 'wan6'
+    option proto 'dhcpv6'
+    option device 'eth0'
+    option ip4table '256'
+    option ip6table '256'
+
+config route 'wan_rt'
+    option interface 'wan'
+    option target '0.0.0.0/0'
+    option table '256'
+
+config route6 'wan_rt6'
+    option interface 'wan'
+    option target '::/0'
+    option table '256'
+```
+
+> Note: The same can be done for ipv6 static route.
+
+## How to handle 'Device.QoS.Classification.{i}.' object:
+
+To configure the policy based routing we need to add new instances for 'Device.QoS.Classification.{i}.' object. Each instance should maps to qos->classify section and network->rule section, so each qos->classify section must have its network->rule section and vice versa and the syncronisation between them will be handled in dmmap_qos file.
+
+```bash
+$ cat /etc/config/qos
+
+config classify 'classify_1'
+    option enable '1'
+    option dest_ip '1.1.1.0/24'
+    option src_ip '172.16.11.1/32'
+
+$ cat /etc/config/network
+
+config rule 'rule_1'
+    option enable '1'
+    option dest '1.1.1.0/24'
+    option src '172.16.11.1/32'
+    option lookup '256'
+    option priority '100'
+
+$ cat /etc/bbfdm/dmmap/dmmap_qos
+
+config class
+    option class_instance '1'
+    option classify 'classify_1'
+    option rule 'rule_1'
+````
+
+> Note1: The same can be done for ipv6 routing as well using rule6 uci.
+
+> Note2: The priority is significant since the default rule to lookup main table is at '32766' and we need to insert the source based routing rules before this.
+
+```bash
+$ ip rule show
+0:  from all lookup local
+100:    from all lookup 256
+32766:  from all lookup main
+32767:  from all lookup default
+```
+
+### QoS Data Model parameters mapping:
+
+- Device.QoS.Classification.{i}.Enable // maps to qos->classify->enable
+- Device.QoS.Classification.{i}.Order // maps to network->rule->priority
+- Device.QoS.Classification.{i}.Interface // maps to qos->classify->ifname
+- Device.QoS.Classification.{i}.DestIP // maps to qos->classify->dest_ip and network->rule->dest
+- Device.QoS.Classification.{i}.DestMask // maps to qos->classify->dest_ip and network->rule->dest
+- Device.QoS.Classification.{i}.SourceIP // maps to qos->classify->src_ip and network->rule->src
+- Device.QoS.Classification.{i}.SourceMask // maps to qos->classify->src_ip and network->rule->src
+- Device.QoS.Classification.{i}.ForwardingPolicy // maps to network->rule->lookup
+
+# Limitations
+
+- The value of 'ForwardingPolicy' should same as the routing table that we want to lookup for the packet meeting the classification criteria.
+
+- For 'Device.QoS.Classification.{i}.ForwardingPolicy' and 'Device.Routing.Router.{i}.IPv4Forwarding.{i}.ForwardingPolicy' parameters, only values defined in the 'rt_tables' file are allowed like 254 for main table.
+
+# References
+1. [Network route uci](https://openwrt.org/docs/guide-user/network/routing/routes_configuration)
+2. [Network rule uci](https://openwrt.org/docs/guide-user/network/routing/ip_rules)
+3. [PBR with netifd](https://openwrt.org/docs/guide-user/network/routing/pbr_netifd)
+4. [Examples of PBR with netifd](https://openwrt.org/docs/guide-user/network/routing/examples/pbr_netifd)