* Revert "[SNMP][IPv6]: Fix to use link local IPv6 address as snmp agentAddress (#16013)"
This reverts commit ebe8c8c223.
* Revert "[SNMP][IPv6]: Fix SNMP IPv6 reachability issue in certain scenarios (#15487) (#15874)"
This reverts commit 83aa8b8180.
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#### Why I did it
fixes: https://github.com/sonic-net/sonic-buildimage/issues/16001
Caused by: https://github.com/sonic-net/sonic-buildimage/pull/15487
The above PR introduced change to use Management and Loopback Ipv4 and ipv6 addresses as snmpagent address in snmpd.conf file.
With this change, if Link local IP address is configured as management or Loopback IPv6 address, then snmpd tries to open socket on that ipv6 address and fails with the below error:
```
Error opening specified endpoint "udp6:[fe80::5054:ff:fe6f:16f0]:161"
Server Exiting with code 1
```
From RFC4007, if we need to specify non-global ipv6 address without ambiguity, we need to use zone id along with the ipv6 address: <address>%<zone_id>
Reference: https://datatracker.ietf.org/doc/html/rfc4007
##### Work item tracking
- Microsoft ADO **(number only)**:
#### How I did it
Modify snmpd.conf file to use the %zone_id representation for ipv6 address.
#### How to verify it
In VS testbed, modify config_db to use link local ipv6 address as management address:
"MGMT_INTERFACE": {
"eth0|10.250.0.101/24": {
"forced_mgmt_routes": [
"172.17.0.1/24"
],
"gwaddr": "10.250.0.1"
},
"eth0|fe80::5054:ff:fe6f:16f0/64": {
"gwaddr": "fe80::1"
}
},
Execute config_reload after the above change.
snmpd comes up and check if snmpd is listening on ipv4 and ipv6 addresses:
```
admin@vlab-01:~$ sudo netstat -tulnp | grep 161
tcp 0 0 127.0.0.1:3161 0.0.0.0:* LISTEN 274060/snmpd
udp 0 0 10.1.0.32:161 0.0.0.0:* 274060/snmpd
udp 0 0 10.250.0.101:161 0.0.0.0:* 274060/snmpd
udp6 0 0 fc00:1::32:161 :::* 274060/snmpd
udp6 0 0 fe80::5054:ff:fe6f::161 :::* 274060/snmpd -- Link local
admin@vlab-01:~$ sudo ifconfig eth0
eth0: flags=4163<UP,BROADCAST,RUNNING,MULTICAST> mtu 1500
inet 10.250.0.101 netmask 255.255.255.0 broadcast 10.250.0.255
inet6 fe80::5054:ff:fe6f:16f0 prefixlen 64 scopeid 0x20<link>
ether 52:54:00:6f:16:f0 txqueuelen 1000 (Ethernet)
RX packets 36384 bytes 22878123 (21.8 MiB)
RX errors 0 dropped 0 overruns 0 frame 0
TX packets 261265 bytes 46585948 (44.4 MiB)
TX errors 0 dropped 0 overruns 0 carrier 0 collisions 0
admin@vlab-01:~$ docker exec -it snmp snmpget -v2c -c public fe80::5054:ff:fe6f:16f0 1.3.6.1.2.1.1.1.0
iso.3.6.1.2.1.1.1.0 = STRING: "SONiC Software Version: SONiC.master.327516-04a6031b2 - HwSku: Force10-S6000 - Distribution: Debian 11.7 - Kernel: 5.10.0-18-2-amd64"
```
Logs from snmpd:
```
Turning on AgentX master support.
NET-SNMP version 5.9
Connection from UDP/IPv6: [fe80::5054:ff:fe6f:16f0%eth0]:44308
```
Ran test_snmp_loopback test to check if loopback ipv4 and ipv6 works:
```
./run_tests.sh -n vms-kvm-t0 -d vlab-01 -c snmp/test_snmp_loopback.py -f vtestbed.yaml -i ../ansible/veos_vtb -e "--skip_sanity --disable_loganalyzer" -u
=== Running tests in groups ===
Running: pytest snmp/test_snmp_loopback.py --inventory ../ansible/veos_vtb --host-pattern vlab-01 --testbed vms-kvm-t0 --testbed_file vtestbed.yaml --log-cli-level warning --log-file-level debug --kube_master unset --showlocals --assert plain --show-capture no -rav --allow_recover --ignore=ptftests --ignore=acstests --ignore=saitests --ignore=scripts --ignore=k8s --ignore=sai_qualify --junit-xml=logs/tr.xml --log-file=logs/test.log --skip_sanity --disable_loganalyzer
..
snmp/test_snmp_loopback.py::test_snmp_loopback[vlab-01] PASSED
```
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#### Description for the changelog
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**- Why I did it**
I'm updating the jinja2 template to support getting SNMP information from the redis configdb.
I'm using the format approved here:
https://github.com/Azure/SONiC/pull/718
This will pave the way for us to decrement using the snmp.yml in the future.
Right now we will still be using both the snmp.yml and configdb to get variable information in order to create the snmpd.conf via the sonic-cfggen tool.
**- How I did it**
I first updated the SNMP Schema in PR #718 to get that approved as a standardized format.
Then I verified I could add snmp configs to the configdb using this standard schema. Once the configs were added to the configdb then I updated the snmpd.conf.j2 file to support the updates via the configdb while still using the variables in the snmp.yml file in parallel. This way we will have backward compatibility until we can fully migrate to the configdb only.
By updating the snmpd.conf.j2 template and running the sonic-cfggen tool the snmpd.conf gets generated with using the values in both the configdb and snmp.yml file.
Co-authored-by: trvanduy <trvanduy@microsoft.com>
The `-sv2` suffix was used to differentiate SNMP Dockers when we transitioned from "SONiCv1" to "SONiCv2", about four years ago. The old Docker materials were removed long ago; there is no need to keep this suffix. Removing it aligns the name with all the other Dockers.
Also edit Monit configuration to detect proper snmp-subagent command line in Buster, and make snmpd command line matching more robust.
