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diff --git a/nsock/src/nsock_proxy.h b/nsock/src/nsock_proxy.h
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+/***************************************************************************
+ * nsock_proxy.h -- PRIVATE interface definitions for proxy handling.      *
+ *                                                                         *
+ ***********************IMPORTANT NSOCK LICENSE TERMS***********************
+ *
+ * The nsock parallel socket event library is (C) 1999-2023 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 */
+