Initial commit: Cisco Switch MCP with fixes C3, C4, C5, C6, S2

src/cisco_switch_mcp/client.py

@@ -0,0 +1,131 @@
+"""SSH client for Cisco IOS-XE switches via Netmiko."""
+
+from __future__ import annotations
+
+import json
+from contextlib import contextmanager
+from typing import Iterator
+
+from netmiko import ConnectHandler
+from netmiko.exceptions import NetmikoAuthenticationException, NetmikoTimeoutException
+
+from cisco_switch_mcp.config import settings
+from cisco_switch_mcp.guards import GuardError, require_credentials
+
+
+class CiscoSwitchError(Exception):
+    def __init__(self, message: str, *, cause: Exception | None = None):
+        super().__init__(message)
+        self.cause = cause
+
+
+def _device_params() -> dict:
+    require_credentials()
+    secret = settings.enable_password or settings.secret or settings.password
+    params = {
+        "device_type": settings.device_type,
+        "host": settings.host,
+        "port": settings.port,
+        "username": settings.username,
+        "password": settings.password,
+        "secret": secret,
+        "timeout": settings.timeout,
+        "conn_timeout": settings.timeout,
+        "fast_cli": False,
+    }
+    if settings.session_log_path:
+        params["session_log"] = settings.session_log_path
+    return params
+
+
+@contextmanager
+def connect() -> Iterator:
+    conn = None
+    try:
+        conn = ConnectHandler(**_device_params())
+        try:
+            conn.enable()
+        except Exception:
+            pass
+        yield conn
+    except NetmikoAuthenticationException as exc:
+        raise CiscoSwitchError("SSH authentication failed", cause=exc) from exc
+    except NetmikoTimeoutException as exc:
+        raise CiscoSwitchError(
+            f"SSH connection timed out to {settings.host}:{settings.port}", cause=exc
+        ) from exc
+    except Exception as exc:
+        raise CiscoSwitchError(f"SSH connection failed: {exc}", cause=exc) from exc
+    finally:
+        if conn is not None:
+            try:
+                conn.disconnect()
+            except Exception:
+                pass
+
+
+def run_command(command: str, *, use_textfsm: bool = False) -> str:
+    """Execute a privileged exec-mode show command."""
+    cmd = command.strip()
+    if not cmd:
+        raise GuardError("command is empty")
+    with connect() as conn:
+        if use_textfsm:
+            try:
+                result = conn.send_command(cmd, use_textfsm=True)
+                if isinstance(result, list):
+                    import json
+
+                    return json.dumps(result, indent=2, default=str)
+            except Exception:
+                pass
+        output = conn.send_command(cmd, read_timeout=settings.timeout)
+    lines = output.splitlines()
+    if len(lines) > settings.max_output_lines:
+        trimmed = lines[: settings.max_output_lines]
+        trimmed.append(
+            f"... truncated ({len(lines) - settings.max_output_lines} more lines)"
+        )
+        return "\n".join(trimmed)
+    return output
+
+
+def run_show_command(command: str) -> str:
+    """Execute a show command with error wrapping.
+
+    Wraps run_command in a try/except and returns a JSON error
+    payload on failure instead of raising an exception, so that
+    MCP tools always return a string even when the switch is
+    unreachable or authentication fails.
+    """
+    try:
+        return run_command(command)
+    except Exception as exc:
+        return json.dumps({"error": str(exc)}, indent=2)
+
+
+def run_config_commands(commands: list[str]) -> str:
+    """Apply configuration commands in config mode."""
+    from cisco_switch_mcp.guards import validate_config_commands
+
+    validate_config_commands(commands)
+    cleaned = [c.strip() for c in commands if c.strip()]
+    if not cleaned:
+        raise GuardError("no configuration commands provided")
+    with connect() as conn:
+        output = conn.send_config_set(cleaned)
+    return output
+
+
+def test_connection() -> dict:
+    require_credentials()
+    with connect() as conn:
+        hostname = conn.find_prompt()
+        version = conn.send_command("show version | include Cisco IOS XE|Model Number|System serial|uptime")
+    return {
+        "status": "ok",
+        "host": settings.host,
+        "prompt": hostname,
+        "version_summary": version.strip(),
+        "device_type": settings.device_type,
+    }