/*
    This file is part of Kismet

    Kismet is free software; you can redistribute it and/or modify
    it under the terms of the GNU General Public License as published by
    the Free Software Foundation; either version 2 of the License, or
    (at your option) any later version.

    Kismet 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 Kismet; if not, write to the Free Software
    Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
*/

/*
 * IPC remote
 *
 * Handles commands that can't/won't/shouldn't be handled by the main
 * Kismet process.  The primary example of this is the root-level 
 * control process used by the unprivileged Kismet to drive channel set
 * events.
 *
 * All commands and pointers MUST be set up BEFORE the IPC fork.
 *
 * An alternate child command can be specified.  It MUST take as the first argument
 * an integer indicating the file descriptor number of the IPC pipe, and it MUST 
 * understand the IPC protocol over this descriptor.
 *
 * The child binary must call SetChildExecMode(argc, argv) prior to filling in the
 * registered protocols, then call SpawnIPC() to kickstart processing.
 *
 * On some platforms (linux) a framework for passing file descriptors is available
 * as well via named unix sockets.  Caller must send IPC to open early in the
 * initialization process and then try to open the socket locally.
 *
 */

#ifndef __IPC_REMOTE_H__
#define __IPC_REMOTE_H__

#include "config.h"

#include <stdio.h>
#include <time.h>
#include <list>
#include <map>
#include <vector>
#include <algorithm>
#include <string>

#ifdef SYS_LINUX
#include <stdio.h>
#include <stdlib.h>
#include <errno.h>
#include <string.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <sys/un.h>
#endif


#include <sys/types.h>
#include <unistd.h>

#include "globalregistry.h"
#include "pollable.h"
#include "messagebus.h"

#define IPC_CMD_PARMS GlobalRegistry *globalreg, const void *data, int len, \
	const void *auxptr, int parent
typedef int (*IPCmdCallback)(IPC_CMD_PARMS);

// Builtin command IDs we force (added before assign, so start at 1)
#define DIE_CMD_ID			1
#define MSG_CMD_ID			2
#define SYNC_CMD_ID			3
#define LAST_BUILTIN_CMD_ID	4

// Message client to redirect messages over the IPC link
class IPC_MessageClient : public MessageClient {
public:
    IPC_MessageClient(GlobalRegistry *in_globalreg, void *in_aux) :
		MessageClient(in_globalreg, in_aux) { };
	virtual ~IPC_MessageClient() { }
	void ProcessMessage(string in_msg, int in_flags);
};

// Message frame to go over IPC
struct ipc_msgbus_pass {
	uint32_t msg_flags;
	uint32_t msg_len; // Redundant but simpler to read
	char msg[0];
};

// Super-generic IPC packet.  This never sees outside of a unix dgram
// frame, so we don't have to armor or protect it.  Just a handy method for
// tossing simple chunks of data.  Commands are responsible for filling in
// reasonable structs for *data
struct ipc_packet {
	uint32_t sentinel;
	uint32_t ipc_cmdnum;
	uint32_t data_len;
	uint8_t ipc_ack;
	uint8_t data[0];
};

// Sync frame the link names and numbers with spawned ipc children
struct ipc_sync {
	uint32_t ipc_cmdnum;
	uint8_t name[32];
};

// IPC sentinel
const uint32_t IPCRemoteSentinel = 0xDECAFBAD;

class IPCRemote : public Pollable {
public:
	IPCRemote();
	IPCRemote(GlobalRegistry *in_globalreg, string procname);
	virtual ~IPCRemote();

	virtual void SetChildCmd(string in_cmd) {
		child_cmd = in_cmd;
	}

	// Start execution as the child and get the IPC descriptor from the 
	// command line options passed from the IPC spawn
	virtual int SetChildExecMode(int argc, char *argv[]); 

	virtual int SpawnIPC();

	// Call after registering all services in a childexec, which don't have
	// to be registered before spawn
	virtual int SyncIPC();

	// Get a shutdown
	virtual void CatchSigChild(int status) {
		exit_errno = WEXITSTATUS(status);

		ShutdownIPC(NULL);
	}

	// Shutdown takes an optional final packet to send before sending the
	// death packet
	virtual int ShutdownIPC(ipc_packet *pack);

	// IPC commands are integers, which means we get away without having to care
	// at all if they duplicate commands or whatever, so we don't even really
	// care about unique callbacks.  Makes life easy for us.
	virtual int RegisterIPCCmd(IPCmdCallback in_callback, 
							   IPCmdCallback discard_ackback,
							   void *in_aux,
							   string name);

	virtual int SyncIPCCmd(ipc_sync *data);

	// Kick a command across (either direction)
	virtual int SendIPC(ipc_packet *pack);

	// Is the IPC ready for more commands?  This would mean that the last
	// command was ack'd and that we don't have any queued up to still send.
	// Some uses might want to defer sending a command until the IPC is
	// settled.
	virtual int FetchReadyState();

	pid_t FetchSpawnPid() {
		return ipc_pid;
	}

	int FetchErrno() { return exit_errno; }

	virtual int FetchIPCSynced() { return ipc_synced; }

	// Pollable system
	virtual int MergeSet(int in_max_fd, fd_set *out_rset, fd_set *out_wset);
	virtual int Poll(fd_set& in_rset, fd_set& in_wset);

	struct ipc_cmd_rec {
		void *auxptr;
		IPCmdCallback callback;
		string name;
		int id;
	};

protected:
	// Child process that never returns
	virtual void IPC_Child_Loop();

	// Internal die functions
	virtual void IPCDie();

	virtual int CheckPidVec();
	
	GlobalRegistry *globalreg;

	// This isn't a ringbuf since it's dgram single-tx frames
	list<ipc_packet *> cmd_buf;

	// Name of the process we'll use in the child
	string procname;

	int next_cmdid;

	// Pair used to talk to the Other Half
	int sockpair[2];

	// PID of the child process
	pid_t ipc_pid;

	// Have we spawned a subproc?  Blow up on setup commands if
	// we have.
	int ipc_spawned;

	map<unsigned int, ipc_cmd_rec *> ipc_cmd_map;
	// Normally this would be a vec but it's a lot cheaper for ram and code size
	// to re-use the template
	map<unsigned int, ipc_cmd_rec *> ipc_sync_map;

	// Cmd to run instead of a copy of ourself. 
	string child_cmd;
	int child_exec_mode;

	friend class IPC_MessageClient;
	friend int ipc_die_callback(IPC_CMD_PARMS);
	friend int ipc_ack_callback(IPC_CMD_PARMS);

	// Reason we're exiting
	int exit_errno;

	// Have we been synced?  (child)
	int ipc_synced;
};

// Special IPCremote class for root control binary, used by IPC remote and
// tuntap control, among others
class RootIPCRemote : public IPCRemote {
public:
	RootIPCRemote() { IPCRemote(); }
	RootIPCRemote(GlobalRegistry *in_globalreg, string procname);
	virtual ~RootIPCRemote() { IPCDie(); }

	virtual void CatchSigChild(int status) {
		if (!globalreg->spindown) {
			_MSG("Suid-root control binary failed: " + 
				 string(strerror(WEXITSTATUS(status))), MSGFLAG_FATAL);
		}

		// globalreg->fatal_condition = 1;
		IPCRemote::CatchSigChild(status);
	}

	virtual int OpenFDPassSock();

	// Send a descriptor
	virtual int SendDescriptor(int in_fd);
	// Get a descriptor - there is no way to sync names or something to them,
	// so these should be called in pairs - send one, send a ipc command to
	// the other side to read it, and get it read.  If commands are stacked in
	// order it should be fine.
	virtual int ReceiveDescriptor();

	virtual int SyncIPC();

	virtual int SyncRoot() {
		ipc_packet *pack =
			(ipc_packet *) malloc(sizeof(ipc_packet));
		pack->data_len = 0;
		pack->ipc_cmdnum = rootipcsync_cmd;
		pack->ipc_ack = 0;
		return SendIPC(pack);
	}

	virtual int ShutdownIPC(ipc_packet *pack);

	virtual int FetchReadyState();

	virtual void RootIPCSynced() { root_ipc_synced = 1; }
	virtual int FetchRootIPCSynced() { return root_ipc_synced; }

protected:
	virtual void IPCDie();
	virtual void ShutdownIPCPassFD();

#ifdef SYS_LINUX
	// Descriptor to the file descriptor passer (if one exists)
	int ipc_fd_fd;
	struct sockaddr_un unixsock;
#endif

	int fdpass_cmd, rootipcsync_cmd;

	int root_ipc_synced;

};

#endif