T5086: Add sFlow feature based on hsflowd

Add sFlow feature based on hsflowd
According to user reviews, it works more stable and more productive
than pmacct
I haven't deleted 'pmacct' 'system flow-accounting sflow' yet
It could be migrated or deprecated later

  set system sflow agent-address '192.0.2.14'
  set system sflow interface 'eth0'
  set system sflow interface 'eth1'
  set system sflow polling '30'
  set system sflow sampling-rate '100'
  set system sflow server 192.0.2.1 port '6343'
  set system sflow server 192.0.2.11 port '6343'

1 files changed, 118 insertions, 0 deletions

diff --git a/src/conf_mode/system_sflow.py b/src/conf_mode/system_sflow.py
new file mode 100755
index 000000000..2e19a5d76
--- /dev/null
+++ b/src/conf_mode/system_sflow.py
@@ -0,0 +1,118 @@
+#!/usr/bin/env python3
+#
+# Copyright (C) 2023 VyOS maintainers and contributors
+#
+# This program is free software; you can redistribute it and/or modify
+# it under the terms of the GNU General Public License version 2 or later as
+# published by the Free Software Foundation.
+#
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+import os
+
+from sys import exit
+
+from vyos.config import Config
+from vyos.configdict import dict_merge
+from vyos.template import render
+from vyos.util import call
+from vyos.validate import is_addr_assigned
+from vyos.xml import defaults
+from vyos import ConfigError
+from vyos import airbag
+airbag.enable()
+
+hsflowd_conf_path = '/run/sflow/hsflowd.conf'
+systemd_service = 'hsflowd.service'
+systemd_override = f'/run/systemd/system/{systemd_service}.d/override.conf'
+
+
+def get_config(config=None):
+    if config:
+        conf = config
+    else:
+        conf = Config()
+    base = ['system', 'sflow']
+    if not conf.exists(base):
+        return None
+
+    sflow = conf.get_config_dict(base,
+                                 key_mangling=('-', '_'),
+                                 get_first_key=True)
+
+    # We have gathered the dict representation of the CLI, but there are default
+    # options which we need to update into the dictionary retrived.
+    default_values = defaults(base)
+
+    sflow = dict_merge(default_values, sflow)
+
+    # Ignore default XML values if config doesn't exists
+    # Delete key from dict
+    if 'port' in sflow['server']:
+        del sflow['server']['port']
+
+    return sflow
+
+
+def verify(sflow):
+    if not sflow:
+        return None
+
+    # Check if configured sflow agent-address exist in the system
+    if 'agent_address' in sflow:
+        tmp = sflow['agent_address']
+        if not is_addr_assigned(tmp):
+            raise ConfigError(
+                f'Configured "sflow agent-address {tmp}" does not exist in the system!'
+            )
+
+    # Check if at least one interface is configured
+    if 'interface' not in sflow:
+        raise ConfigError(
+            'sFlow requires at least one interface to be configured!')
+
+    # Check if at least one server is configured
+    if 'server' not in sflow:
+        raise ConfigError('You need to configure at least one sFlow server!')
+
+    # return True if all checks were passed
+    return True
+
+
+def generate(sflow):
+    if not sflow:
+        return None
+
+    render(hsflowd_conf_path, 'sflow/hsflowd.conf.j2', sflow)
+    render(systemd_override, 'sflow/override.conf.j2', sflow)
+    # Reload systemd manager configuration
+    call('systemctl daemon-reload')
+
+
+def apply(sflow):
+    if not sflow:
+        # Stop flow-accounting daemon and remove configuration file
+        call(f'systemctl stop {systemd_service}')
+        if os.path.exists(hsflowd_conf_path):
+            os.unlink(hsflowd_conf_path)
+        return
+
+    # Start/reload flow-accounting daemon
+    call(f'systemctl restart {systemd_service}')
+
+
+if __name__ == '__main__':
+    try:
+        config = get_config()
+        verify(config)
+        generate(config)
+        apply(config)
+    except ConfigError as e:
+        print(e)
+        exit(1)