/***************************************************************************
 * nsock_proxy.h -- PRIVATE interface definitions for proxy handling.      *
 *                                                                         *
 ***********************IMPORTANT NSOCK LICENSE TERMS***********************
 *
 * The nsock parallel socket event library is (C) 1999-2024 Nmap Software LLC
 * This library is free software; you may redistribute and/or modify it under
 * the terms of the GNU General Public License as published by the Free Software
 * Foundation; Version 2. This guarantees your right to use, modify, and
 * redistribute this software under certain conditions. If this license is
 * unacceptable to you, Nmap Software LLC may be willing to sell alternative
 * licenses (contact sales@nmap.com ).
 *
 * As a special exception to the GPL terms, Nmap Software LLC grants permission
 * to link the code of this program with any version of the OpenSSL library
 * which is distributed under a license identical to that listed in the included
 * docs/licenses/OpenSSL.txt file, and distribute linked combinations including
 * the two. You must obey the GNU GPL in all respects for all of the code used
 * other than OpenSSL. If you modify this file, you may extend this exception to
 * your version of the file, but you are not obligated to do so.
 *
 * If you received these files with a written license agreement stating terms
 * other than the (GPL) terms above, then that alternative license agreement
 * takes precedence over this comment.
 *
 * Source is provided to this software because we believe users have a right to
 * know exactly what a program is going to do before they run it. This also
 * allows you to audit the software for security holes.
 *
 * Source code also allows you to port Nmap to new platforms, fix bugs, and add
 * new features. You are highly encouraged to send your changes to the
 * dev@nmap.org mailing list for possible incorporation into the main
 * distribution. By sending these changes to Fyodor or one of the Insecure.Org
 * development mailing lists, or checking them into the Nmap source code
 * repository, it is understood (unless you specify otherwise) that you are
 * offering the Nmap Project (Nmap Software LLC) the unlimited, non-exclusive
 * right to reuse, modify, and relicense the code. Nmap will always be available
 * Open Source, but this is important because the inability to relicense code
 * has caused devastating problems for other Free Software projects (such as KDE
 * and NASM). We also occasionally relicense the code to third parties as
 * discussed above. If you wish to specify special license conditions of your
 * contributions, just say so when you send them.
 *
 * 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 v2.0 for more
 * details (http://www.gnu.org/licenses/gpl-2.0.html).
 *
 ***************************************************************************/

/* $Id$ */

#ifndef NSOCK_PROXY_H
#define NSOCK_PROXY_H

#include "gh_list.h"

#if HAVE_NETDB_H
#include <netdb.h>
#endif

#include <nsock.h>
#include <errno.h>


/* ------------------- CONSTANTS ------------------- */
enum nsock_proxy_type {
  PROXY_TYPE_HTTP = 0,
  PROXY_TYPE_SOCKS4,
  PROXY_TYPE_COUNT,
};

enum nsock_proxy_state {
  /* Common initial state for all proxy types. */
  PROXY_STATE_INITIAL,

  /* HTTP proxy states. */
  PROXY_STATE_HTTP_TCP_CONNECTED,
  PROXY_STATE_HTTP_TUNNEL_ESTABLISHED,

  /* SOCKS 4 proxy states. */
  PROXY_STATE_SOCKS4_TCP_CONNECTED,
  PROXY_STATE_SOCKS4_TUNNEL_ESTABLISHED,
};


/* ------------------- STRUCTURES ------------------- */

struct uri {
  char *scheme;
  char *user;
  char *pass;
  char *host;
  char *path;
  int port;
};

/* Static information about a proxy node in the chain. This is generated by
 * parsing the proxy specification string given by user. Those structures are
 * then read-only and stored in the nsock_pool. */
struct proxy_node {
  const struct proxy_spec *spec;

  struct sockaddr_storage ss;
  size_t sslen;
  unsigned short port;
  char *nodestr; /* used for log messages */
  gh_lnode_t nodeq;
};

/* Ordered list of proxy nodes, as specified in the proxy specification string. */
struct proxy_chain {
  gh_list_t nodes;
};

/* IOD-specific context. For each IOD we establish a tunnel through the chain of
 * proxies. This structure stores all the related information. */
struct proxy_chain_context {
  const struct proxy_chain *px_chain;

  /* Nodes iterator in px_chain->nodes */
  struct proxy_node *px_current;

  /* Current node connection state. */
  enum nsock_proxy_state px_state;

  /* Those fields are used to store information about the final target
   * to reach. */
  enum nse_type target_ev_type;
  struct sockaddr_storage target_ss;
  size_t target_sslen;
  unsigned short target_port;
  nsock_ev_handler target_handler;
};

struct proxy_op {
  int (*node_new)(struct proxy_node **node, const struct uri *uri);
  void (*node_delete)(struct proxy_node *node);
  void (*handler)(nsock_pool nspool, nsock_event nsevent, void *udata);
};

struct proxy_spec {
  const char *prefix;
  enum nsock_proxy_type type;
  const struct proxy_op *ops;
};


/* ------------------- UTIL FUNCTIONS ------------------- */
int proxy_resolve(const char *host, struct sockaddr *addr, size_t *addrlen, int ai_family);

static inline struct proxy_node *proxy_ctx_node_next(struct proxy_chain_context *ctx) {
  gh_lnode_t *next;

  assert(ctx);
  assert(ctx->px_current);

  next = gh_lnode_next(&ctx->px_current->nodeq);
  if (!next)
    return NULL;

  return container_of(next, struct proxy_node, nodeq);
}


/* ------------------- PROTOTYPES ------------------- */

struct proxy_chain_context *proxy_chain_context_new(nsock_pool nspool);
void proxy_chain_context_delete(struct proxy_chain_context *ctx);

void nsock_proxy_ev_dispatch(nsock_pool nspool, nsock_event nsevent, void *udata);
void forward_event(nsock_pool nspool, nsock_event nse, void *udata);


#endif /* NSOCK_PROXY_H */