feat: get_management_peer, the address the host sees the SSH connection come from

From SSH_CONNECTION's client side; None when it is empty or no address.
The caller uses it to choose the sources an SNMP agent answers.

napalm_linux/linux.py

@@ -1999,6 +1999,14 @@ class LinuxDriver(
             output = f"{output}\n{_SUDO_PASSWORD_HINT}"
         return {"ok": status == 0, "output": (output.strip()[-300:] if status != 0 else done)}
 
+    def get_management_peer(self) -> str | None:
+        """The address this host sees the SSH connection come from (``SSH_CONNECTION``)."""
+        out = self.run_command('printf "%s\\n" "$SSH_CONNECTION"', timeout=15).stdout.split()
+        try:
+            return str(ipaddress.ip_address(out[0])) if out else None
+        except ValueError:
+            return None
+
     def _install_snmp_agent(self) -> FixStepOutcomeDict:
         pm = self._pkg_manager or self._detect_pkg_manager()
         command = _SNMP_INSTALL.get(pm or "")