urldata.h

#ifndef HEADER_CURL_URLDATA_H
#define HEADER_CURL_URLDATA_H
/***************************************************************************
 *                                  _   _ ____  _
 *  Project                     ___| | | |  _ \| |
 *                             / __| | | | |_) | |
 *                            | (__| |_| |  _ <| |___
 *                             \___|\___/|_| \_\_____|
 *
 * Copyright (C) 1998 - 2017, Daniel Stenberg, <daniel@haxx.se>, et al.
 *
 * This software is licensed as described in the file COPYING, which
 * you should have received as part of this distribution. The terms
 * are also available at https://curl.haxx.se/docs/copyright.html.
 *
 * You may opt to use, copy, modify, merge, publish, distribute and/or sell
 * copies of the Software, and permit persons to whom the Software is
 * furnished to do so, under the terms of the COPYING file.
 *
 * This software is distributed on an "AS IS" basis, WITHOUT WARRANTY OF ANY
 * KIND, either express or implied.
 *
 ***************************************************************************/

/* This file is for lib internal stuff */

#include "curl_setup.h"

#define PORT_FTP 21
#define PORT_FTPS 990
#define PORT_TELNET 23
#define PORT_HTTP 80
#define PORT_HTTPS 443
#define PORT_DICT 2628
#define PORT_LDAP 389
#define PORT_LDAPS 636
#define PORT_TFTP 69
#define PORT_SSH 22
#define PORT_IMAP 143
#define PORT_IMAPS 993
#define PORT_POP3 110
#define PORT_POP3S 995
#define PORT_SMB 445
#define PORT_SMBS 445
#define PORT_SMTP 25
#define PORT_SMTPS 465 /* sometimes called SSMTP */
#define PORT_RTSP 554
#define PORT_RTMP 1935
#define PORT_RTMPT PORT_HTTP
#define PORT_RTMPS PORT_HTTPS
#define PORT_GOPHER 70

#define DICT_MATCH "/MATCH:"
#define DICT_MATCH2 "/M:"
#define DICT_MATCH3 "/FIND:"
#define DICT_DEFINE "/DEFINE:"
#define DICT_DEFINE2 "/D:"
#define DICT_DEFINE3 "/LOOKUP:"

#define CURL_DEFAULT_USER "anonymous"
#define CURL_DEFAULT_PASSWORD "ftp@example.com"

/* Convenience defines for checking protocols or their SSL based version. Each
   protocol handler should only ever have a single CURLPROTO_ in its protocol
   field. */
#define PROTO_FAMILY_HTTP (CURLPROTO_HTTP|CURLPROTO_HTTPS)
#define PROTO_FAMILY_FTP  (CURLPROTO_FTP|CURLPROTO_FTPS)
#define PROTO_FAMILY_POP3 (CURLPROTO_POP3|CURLPROTO_POP3S)
#define PROTO_FAMILY_SMB  (CURLPROTO_SMB|CURLPROTO_SMBS)
#define PROTO_FAMILY_SMTP (CURLPROTO_SMTP|CURLPROTO_SMTPS)

#define DEFAULT_CONNCACHE_SIZE 5

/* length of longest IPv6 address string including the trailing null */
#define MAX_IPADR_LEN sizeof("ffff:ffff:ffff:ffff:ffff:ffff:255.255.255.255")

/* Default FTP/IMAP etc response timeout in milliseconds.
   Symbian OS panics when given a timeout much greater than 1/2 hour.
*/
#define RESP_TIMEOUT (1800*1000)

#include "cookie.h"
#include "formdata.h"

#ifdef HAVE_NETINET_IN_H
#include <netinet/in.h>
#endif

#include "timeval.h"

#ifdef HAVE_ZLIB_H
#include <zlib.h>               /* for content-encoding */
#ifdef __SYMBIAN32__
/* zlib pollutes the namespace with this definition */
#undef WIN32
#endif
#endif

#include <curl/curl.h>

#include "http_chunks.h" /* for the structs and enum stuff */
#include "hostip.h"
#include "hash.h"
#include "splay.h"

#include "mime.h"
#include "imap.h"
#include "pop3.h"
#include "smtp.h"
#include "ftp.h"
#include "file.h"
#include "ssh.h"
#include "http.h"
#include "rtsp.h"
#include "smb.h"
#include "wildcard.h"
#include "multihandle.h"

#ifdef HAVE_GSSAPI
# ifdef HAVE_GSSGNU
#  include <gss.h>
# elif defined HAVE_GSSMIT
#  include <gssapi/gssapi.h>
#  include <gssapi/gssapi_generic.h>
# else
#  include <gssapi.h>
# endif
#endif

#ifdef HAVE_LIBSSH2_H
#include <libssh2.h>
#include <libssh2_sftp.h>
#endif /* HAVE_LIBSSH2_H */

/* The upload buffer size, should not be smaller than CURL_MAX_WRITE_SIZE, as
   it needs to hold a full buffer as could be sent in a write callback */
#define UPLOAD_BUFSIZE CURL_MAX_WRITE_SIZE

/* The "master buffer" is for HTTP pipelining */
#define MASTERBUF_SIZE 16384

/* Initial size of the buffer to store headers in, it'll be enlarged in case
   of need. */
#define HEADERSIZE 256

#define CURLEASY_MAGIC_NUMBER 0xc0dedbadU
#define GOOD_EASY_HANDLE(x) \
  ((x) && ((x)->magic == CURLEASY_MAGIC_NUMBER))

/* Some convenience macros to get the larger/smaller value out of two given.
   We prefix with CURL to prevent name collisions. */
#define CURLMAX(x,y) ((x)>(y)?(x):(y))
#define CURLMIN(x,y) ((x)<(y)?(x):(y))

#ifdef HAVE_GSSAPI
/* Types needed for krb5-ftp connections */
struct krb5buffer {
  void *data;
  size_t size;
  size_t index;
  int eof_flag;
};

enum protection_level {
  PROT_NONE, /* first in list */
  PROT_CLEAR,
  PROT_SAFE,
  PROT_CONFIDENTIAL,
  PROT_PRIVATE,
  PROT_CMD,
  PROT_LAST /* last in list */
};
#endif

/* enum for the nonblocking SSL connection state machine */
typedef enum {
  ssl_connect_1,
  ssl_connect_2,
  ssl_connect_2_reading,
  ssl_connect_2_writing,
  ssl_connect_3,
  ssl_connect_done
} ssl_connect_state;

typedef enum {
  ssl_connection_none,
  ssl_connection_negotiating,
  ssl_connection_complete
} ssl_connection_state;

/* SSL backend-specific data; declared differently by each SSL backend */
struct ssl_backend_data;

/* struct for data related to each SSL connection */
struct ssl_connect_data {
  /* Use ssl encrypted communications TRUE/FALSE, not necessarily using it atm
     but at least asked to or meaning to use it. See 'state' for the exact
     current state of the connection. */
  bool use;
  ssl_connection_state state;
  ssl_connect_state connecting_state;
#if defined(USE_SSL)
  struct ssl_backend_data *backend;
#endif
};

struct ssl_primary_config {
  long version;          /* what version the client wants to use */
  long version_max;      /* max supported version the client wants to use*/
  bool verifypeer;       /* set TRUE if this is desired */
  bool verifyhost;       /* set TRUE if CN/SAN must match hostname */
  bool verifystatus;     /* set TRUE if certificate status must be checked */
  bool sessionid;        /* cache session IDs or not */
  char *CApath;          /* certificate dir (doesn't work on windows) */
  char *CAfile;          /* certificate to verify peer against */
  char *clientcert;
  char *random_file;     /* path to file containing "random" data */
  char *egdsocket;       /* path to file containing the EGD daemon socket */
  char *cipher_list;     /* list of ciphers to use */
};

struct ssl_config_data {
  struct ssl_primary_config primary;
  bool enable_beast; /* especially allow this flaw for interoperability's
                        sake*/
  bool no_revoke;    /* disable SSL certificate revocation checks */
  long certverifyresult; /* result from the certificate verification */
  char *CRLfile;   /* CRL to check certificate revocation */
  char *issuercert;/* optional issuer certificate filename */
  curl_ssl_ctx_callback fsslctx; /* function to initialize ssl ctx */
  void *fsslctxp;        /* parameter for call back */
  bool certinfo;         /* gather lots of certificate info */
  bool falsestart;

  char *cert; /* client certificate file name */
  char *cert_type; /* format for certificate (default: PEM)*/
  char *key; /* private key file name */
  char *key_type; /* format for private key (default: PEM) */
  char *key_passwd; /* plain text private key password */

#ifdef USE_TLS_SRP
  char *username; /* TLS username (for, e.g., SRP) */
  char *password; /* TLS password (for, e.g., SRP) */
  enum CURL_TLSAUTH authtype; /* TLS authentication type (default SRP) */
#endif
};

struct ssl_general_config {
  size_t max_ssl_sessions; /* SSL session id cache size */
};

/* information stored about one single SSL session */
struct curl_ssl_session {
  char *name;       /* host name for which this ID was used */
  char *conn_to_host; /* host name for the connection (may be NULL) */
  const char *scheme; /* protocol scheme used */
  void *sessionid;  /* as returned from the SSL layer */
  size_t idsize;    /* if known, otherwise 0 */
  long age;         /* just a number, the higher the more recent */
  int remote_port;  /* remote port */
  int conn_to_port; /* remote port for the connection (may be -1) */
  struct ssl_primary_config ssl_config; /* setup for this session */
};

#ifdef USE_WINDOWS_SSPI
#include "curl_sspi.h"
#endif

/* Struct used for Digest challenge-response authentication */
struct digestdata {
#if defined(USE_WINDOWS_SSPI)
  BYTE *input_token;
  size_t input_token_len;
  CtxtHandle *http_context;
  /* copy of user/passwd used to make the identity for http_context.
     either may be NULL. */
  char *user;
  char *passwd;
#else
  char *nonce;
  char *cnonce;
  char *realm;
  int algo;
  bool stale; /* set true for re-negotiation */
  char *opaque;
  char *qop;
  char *algorithm;
  int nc; /* nounce count */
  bool userhash;
#endif
};

typedef enum {
  NTLMSTATE_NONE,
  NTLMSTATE_TYPE1,
  NTLMSTATE_TYPE2,
  NTLMSTATE_TYPE3,
  NTLMSTATE_LAST
} curlntlm;

#if defined(CURL_DOES_CONVERSIONS) && defined(HAVE_ICONV)
#include <iconv.h>
#endif

/* Struct used for GSSAPI (Kerberos V5) authentication */
#if defined(USE_KERBEROS5)
struct kerberos5data {
#if defined(USE_WINDOWS_SSPI)
  CredHandle *credentials;
  CtxtHandle *context;
  TCHAR *spn;
  SEC_WINNT_AUTH_IDENTITY identity;
  SEC_WINNT_AUTH_IDENTITY *p_identity;
  size_t token_max;
  BYTE *output_token;
#else
  gss_ctx_id_t context;
  gss_name_t spn;
#endif
};
#endif

/* Struct used for NTLM challenge-response authentication */
#if defined(USE_NTLM)
struct ntlmdata {
  curlntlm state;
#ifdef USE_WINDOWS_SSPI
  CredHandle *credentials;
  CtxtHandle *context;
  SEC_WINNT_AUTH_IDENTITY identity;
  SEC_WINNT_AUTH_IDENTITY *p_identity;
  size_t token_max;
  BYTE *output_token;
  BYTE *input_token;
  size_t input_token_len;
#else
  unsigned int flags;
  unsigned char nonce[8];
  void *target_info; /* TargetInfo received in the ntlm type-2 message */
  unsigned int target_info_len;
#endif
};
#endif

#ifdef USE_SPNEGO
struct negotiatedata {
  /* When doing Negotiate (SPNEGO) auth, we first need to send a token
     and then validate the received one. */
  enum { GSS_AUTHNONE, GSS_AUTHRECV, GSS_AUTHSENT } state;
#ifdef HAVE_GSSAPI
  OM_uint32 status;
  gss_ctx_id_t context;
  gss_name_t spn;
  gss_buffer_desc output_token;
#else
#ifdef USE_WINDOWS_SSPI
  DWORD status;
  CredHandle *credentials;
  CtxtHandle *context;
  SEC_WINNT_AUTH_IDENTITY identity;
  SEC_WINNT_AUTH_IDENTITY *p_identity;
  TCHAR *spn;
  size_t token_max;
  BYTE *output_token;
  size_t output_token_length;
#endif
#endif
};
#endif


/*
 * Boolean values that concerns this connection.
 */
struct ConnectBits {
  /* always modify bits.close with the connclose() and connkeep() macros! */
  bool close; /* if set, we close the connection after this request */
  bool reuse; /* if set, this is a re-used connection */
  bool conn_to_host; /* if set, this connection has a "connect to host"
                        that overrides the host in the URL */
  bool conn_to_port; /* if set, this connection has a "connect to port"
                        that overrides the port in the URL (remote port) */
  bool proxy; /* if set, this transfer is done through a proxy - any type */
  bool httpproxy;    /* if set, this transfer is done through a http proxy */
  bool socksproxy;   /* if set, this transfer is done through a socks proxy */
  bool user_passwd;    /* do we use user+password for this connection? */
  bool proxy_user_passwd; /* user+password for the proxy? */
  bool ipv6_ip; /* we communicate with a remote site specified with pure IPv6
                   IP address */
  bool ipv6;    /* we communicate with a site using an IPv6 address */

  bool do_more; /* this is set TRUE if the ->curl_do_more() function is
                   supposed to be called, after ->curl_do() */
  bool tcpconnect[2]; /* the TCP layer (or similar) is connected, this is set
                         the first time on the first connect function call */
  bool protoconnstart;/* the protocol layer has STARTED its operation after
                         the TCP layer connect */

  bool retry;         /* this connection is about to get closed and then
                         re-attempted at another connection. */
  bool tunnel_proxy;  /* if CONNECT is used to "tunnel" through the proxy.
                         This is implicit when SSL-protocols are used through
                         proxies, but can also be enabled explicitly by
                         apps */
  bool authneg;       /* TRUE when the auth phase has started, which means
                         that we are creating a request with an auth header,
                         but it is not the final request in the auth
                         negotiation. */
  bool rewindaftersend;/* TRUE when the sending couldn't be stopped even
                          though it will be discarded. When the whole send
                          operation is done, we must call the data rewind
                          callback. */
  bool ftp_use_epsv;  /* As set with CURLOPT_FTP_USE_EPSV, but if we find out
                         EPSV doesn't work we disable it for the forthcoming
                         requests */

  bool ftp_use_eprt;  /* As set with CURLOPT_FTP_USE_EPRT, but if we find out
                         EPRT doesn't work we disable it for the forthcoming
                         requests */
  bool ftp_use_data_ssl; /* Enabled SSL for the data connection */
  bool netrc;         /* name+password provided by netrc */
  bool userpwd_in_url; /* name+password found in url */
  bool stream_was_rewound; /* Indicates that the stream was rewound after a
                              request read past the end of its response byte
                              boundary */
  bool proxy_connect_closed; /* set true if a proxy disconnected the
                                connection in a CONNECT request with auth, so
                                that libcurl should reconnect and continue. */
  bool bound; /* set true if bind() has already been done on this socket/
                 connection */
  bool type_set;  /* type= was used in the URL */
  bool multiplex; /* connection is multiplexed */

  bool tcp_fastopen; /* use TCP Fast Open */
  bool tls_enable_npn;  /* TLS NPN extension? */
  bool tls_enable_alpn; /* TLS ALPN extension? */
  bool proxy_ssl_connected[2]; /* TRUE when SSL initialization for HTTPS proxy
                                  is complete */
  bool socksproxy_connecting; /* connecting through a socks proxy */
};

struct hostname {
  char *rawalloc; /* allocated "raw" version of the name */
  char *encalloc; /* allocated IDN-encoded version of the name */
  char *name;     /* name to use internally, might be encoded, might be raw */
  const char *dispname; /* name to display, as 'name' might be encoded */
};

/*
 * Flags on the keepon member of the Curl_transfer_keeper
 */

#define KEEP_NONE  0
#define KEEP_RECV  (1<<0)     /* there is or may be data to read */
#define KEEP_SEND (1<<1)     /* there is or may be data to write */
#define KEEP_RECV_HOLD (1<<2) /* when set, no reading should be done but there
                                 might still be data to read */
#define KEEP_SEND_HOLD (1<<3) /* when set, no writing should be done but there
                                  might still be data to write */
#define KEEP_RECV_PAUSE (1<<4) /* reading is paused */
#define KEEP_SEND_PAUSE (1<<5) /* writing is paused */

#define KEEP_RECVBITS (KEEP_RECV | KEEP_RECV_HOLD | KEEP_RECV_PAUSE)
#define KEEP_SENDBITS (KEEP_SEND | KEEP_SEND_HOLD | KEEP_SEND_PAUSE)


#ifdef HAVE_LIBZ
typedef enum {
  ZLIB_UNINIT,          /* uninitialized */
  ZLIB_INIT,            /* initialized */
  ZLIB_GZIP_HEADER,     /* reading gzip header */
  ZLIB_GZIP_INFLATING,  /* inflating gzip stream */
  ZLIB_INIT_GZIP        /* initialized in transparent gzip mode */
} zlibInitState;
#endif

#ifdef CURLRES_ASYNCH
struct Curl_async {
  char *hostname;
  int port;
  struct Curl_dns_entry *dns;
  bool done;  /* set TRUE when the lookup is complete */
  int status; /* if done is TRUE, this is the status from the callback */
  void *os_specific;  /* 'struct thread_data' for Windows */
};
#endif

#define FIRSTSOCKET     0
#define SECONDARYSOCKET 1

/* These function pointer types are here only to allow easier typecasting
   within the source when we need to cast between data pointers (such as NULL)
   and function pointers. */
typedef CURLcode (*Curl_do_more_func)(struct connectdata *, int *);
typedef CURLcode (*Curl_done_func)(struct connectdata *, CURLcode, bool);

enum expect100 {
  EXP100_SEND_DATA,           /* enough waiting, just send the body now */
  EXP100_AWAITING_CONTINUE,   /* waiting for the 100 Continue header */
  EXP100_SENDING_REQUEST,     /* still sending the request but will wait for
                                 the 100 header once done with the request */
  EXP100_FAILED               /* used on 417 Expectation Failed */
};

enum upgrade101 {
  UPGR101_INIT,               /* default state */
  UPGR101_REQUESTED,          /* upgrade requested */
  UPGR101_RECEIVED,           /* response received */
  UPGR101_WORKING             /* talking upgraded protocol */
};

/*
 * Request specific data in the easy handle (Curl_easy).  Previously,
 * these members were on the connectdata struct but since a conn struct may
 * now be shared between different Curl_easys, we store connection-specific
 * data here. This struct only keeps stuff that's interesting for *this*
 * request, as it will be cleared between multiple ones
 */
struct SingleRequest {
  curl_off_t size;        /* -1 if unknown at this point */
  curl_off_t *bytecountp; /* return number of bytes read or NULL */

  curl_off_t maxdownload; /* in bytes, the maximum amount of data to fetch,
                             -1 means unlimited */
  curl_off_t *writebytecountp; /* return number of bytes written or NULL */

  curl_off_t bytecount;         /* total number of bytes read */
  curl_off_t writebytecount;    /* number of bytes written */

  long headerbytecount;         /* only count received headers */
  long deductheadercount; /* this amount of bytes doesn't count when we check
                             if anything has been transferred at the end of a
                             connection. We use this counter to make only a
                             100 reply (without a following second response
                             code) result in a CURLE_GOT_NOTHING error code */

  struct curltime start;         /* transfer started at this time */
  struct curltime now;           /* current time */
  bool header;                  /* incoming data has HTTP header */
  enum {
    HEADER_NORMAL,              /* no bad header at all */
    HEADER_PARTHEADER,          /* part of the chunk is a bad header, the rest
                                   is normal data */
    HEADER_ALLBAD               /* all was believed to be header */
  } badheader;                  /* the header was deemed bad and will be
                                   written as body */
  int headerline;               /* counts header lines to better track the
                                   first one */
  char *hbufp;                  /* points at *end* of header line */
  size_t hbuflen;
  char *str;                    /* within buf */
  char *str_start;              /* within buf */
  char *end_ptr;                /* within buf */
  char *p;                      /* within headerbuff */
  bool content_range;           /* set TRUE if Content-Range: was found */
  curl_off_t offset;            /* possible resume offset read from the
                                   Content-Range: header */
  int httpcode;                 /* error code from the 'HTTP/1.? XXX' or
                                   'RTSP/1.? XXX' line */
  struct curltime start100;      /* time stamp to wait for the 100 code from */
  enum expect100 exp100;        /* expect 100 continue state */
  enum upgrade101 upgr101;      /* 101 upgrade state */

  int auto_decoding;            /* What content encoding. sec 3.5, RFC2616. */

#define IDENTITY 0              /* No encoding */
#define DEFLATE 1               /* zlib deflate [RFC 1950 & 1951] */
#define GZIP 2                  /* gzip algorithm [RFC 1952] */

#ifdef HAVE_LIBZ
  zlibInitState zlib_init;      /* possible zlib init state;
                                   undefined if Content-Encoding header. */
  z_stream z;                   /* State structure for zlib. */
#endif

  time_t timeofdoc;
  long bodywrites;

  char *buf;
  curl_socket_t maxfd;

  int keepon;

  bool upload_done; /* set to TRUE when doing chunked transfer-encoding upload
                       and we're uploading the last chunk */

  bool ignorebody;  /* we read a response-body but we ignore it! */
  bool ignorecl;    /* This HTTP response has no body so we ignore the Content-
                       Length: header */

  char *location;   /* This points to an allocated version of the Location:
                       header data */
  char *newurl;     /* Set to the new URL to use when a redirect or a retry is
                       wanted */

  /* 'upload_present' is used to keep a byte counter of how much data there is
     still left in the buffer, aimed for upload. */
  ssize_t upload_present;

   /* 'upload_fromhere' is used as a read-pointer when we uploaded parts of a
      buffer, so the next read should read from where this pointer points to,
      and the 'upload_present' contains the number of bytes available at this
      position */
  char *upload_fromhere;

  bool chunk; /* if set, this is a chunked transfer-encoding */
  bool upload_chunky; /* set TRUE if we are doing chunked transfer-encoding
                         on upload */
  bool getheader;     /* TRUE if header parsing is wanted */

  bool forbidchunk;   /* used only to explicitly forbid chunk-upload for
                         specific upload buffers. See readmoredata() in
                         http.c for details. */

  void *protop;       /* Allocated protocol-specific data. Each protocol
                         handler makes sure this points to data it needs. */
};

/*
 * Specific protocol handler.
 */

struct Curl_handler {
  const char *scheme;        /* URL scheme name. */

  /* Complement to setup_connection_internals(). */
  CURLcode (*setup_connection)(struct connectdata *);

  /* These two functions MUST be set to be protocol dependent */
  CURLcode (*do_it)(struct connectdata *, bool *done);
  Curl_done_func done;

  /* If the curl_do() function is better made in two halves, this
   * curl_do_more() function will be called afterwards, if set. For example
   * for doing the FTP stuff after the PASV/PORT command.
   */
  Curl_do_more_func do_more;

  /* This function *MAY* be set to a protocol-dependent function that is run
   * after the connect() and everything is done, as a step in the connection.
   * The 'done' pointer points to a bool that should be set to TRUE if the
   * function completes before return. If it doesn't complete, the caller
   * should call the curl_connecting() function until it is.
   */
  CURLcode (*connect_it)(struct connectdata *, bool *done);

  /* See above. Currently only used for FTP. */
  CURLcode (*connecting)(struct connectdata *, bool *done);
  CURLcode (*doing)(struct connectdata *, bool *done);

  /* Called from the multi interface during the PROTOCONNECT phase, and it
     should then return a proper fd set */
  int (*proto_getsock)(struct connectdata *conn,
                       curl_socket_t *socks,
                       int numsocks);

  /* Called from the multi interface during the DOING phase, and it should
     then return a proper fd set */
  int (*doing_getsock)(struct connectdata *conn,
                       curl_socket_t *socks,
                       int numsocks);

  /* Called from the multi interface during the DO_MORE phase, and it should
     then return a proper fd set */
  int (*domore_getsock)(struct connectdata *conn,
                        curl_socket_t *socks,
                        int numsocks);

  /* Called from the multi interface during the DO_DONE, PERFORM and
     WAITPERFORM phases, and it should then return a proper fd set. Not setting
     this will make libcurl use the generic default one. */
  int (*perform_getsock)(const struct connectdata *conn,
                         curl_socket_t *socks,
                         int numsocks);

  /* This function *MAY* be set to a protocol-dependent function that is run
   * by the curl_disconnect(), as a step in the disconnection.  If the handler
   * is called because the connection has been considered dead, dead_connection
   * is set to TRUE.
   */
  CURLcode (*disconnect)(struct connectdata *, bool dead_connection);

  /* If used, this function gets called from transfer.c:readwrite_data() to
     allow the protocol to do extra reads/writes */
  CURLcode (*readwrite)(struct Curl_easy *data, struct connectdata *conn,
                        ssize_t *nread, bool *readmore);

  /* This function can perform various checks on the connection. See
     CONNCHECK_* for more information about the checks that can be performed,
     and CONNRESULT_* for the results that can be returned. */
  unsigned int (*connection_check)(struct connectdata *conn,
                                   unsigned int checks_to_perform);

  long defport;           /* Default port. */
  unsigned int protocol;  /* See CURLPROTO_* - this needs to be the single
                             specific protocol bit */
  unsigned int flags;     /* Extra particular characteristics, see PROTOPT_* */
};

#define PROTOPT_NONE 0             /* nothing extra */
#define PROTOPT_SSL (1<<0)         /* uses SSL */
#define PROTOPT_DUAL (1<<1)        /* this protocol uses two connections */
#define PROTOPT_CLOSEACTION (1<<2) /* need action before socket close */
/* some protocols will have to call the underlying functions without regard to
   what exact state the socket signals. IE even if the socket says "readable",
   the send function might need to be called while uploading, or vice versa.
*/
#define PROTOPT_DIRLOCK (1<<3)
#define PROTOPT_NONETWORK (1<<4)   /* protocol doesn't use the network! */
#define PROTOPT_NEEDSPWD (1<<5)    /* needs a password, and if none is set it
                                      gets a default */
#define PROTOPT_NOURLQUERY (1<<6)   /* protocol can't handle
                                        url query strings (?foo=bar) ! */
#define PROTOPT_CREDSPERREQUEST (1<<7) /* requires login credentials per
                                          request instead of per connection */
#define PROTOPT_ALPN_NPN (1<<8) /* set ALPN and/or NPN for this */
#define PROTOPT_STREAM (1<<9) /* a protocol with individual logical streams */
#define PROTOPT_URLOPTIONS (1<<10) /* allow options part in the userinfo field
                                      of the URL */
#define PROTOPT_PROXY_AS_HTTP (1<<11) /* allow this non-HTTP scheme over a
                                         HTTP proxy as HTTP proxies may know
                                         this protocol and act as a gateway */
#define PROTOPT_WILDCARD (1<<12) /* protocol supports wildcard matching */

#define CONNCHECK_NONE 0                 /* No checks */
#define CONNCHECK_ISDEAD (1<<0)          /* Check if the connection is dead. */

#define CONNRESULT_NONE 0                /* No extra information. */
#define CONNRESULT_DEAD (1<<0)           /* The connection is dead. */

/* return the count of bytes sent, or -1 on error */
typedef ssize_t (Curl_send)(struct connectdata *conn, /* connection data */
                            int sockindex,            /* socketindex */
                            const void *buf,          /* data to write */
                            size_t len,               /* max amount to write */
                            CURLcode *err);           /* error to return */

/* return the count of bytes read, or -1 on error */
typedef ssize_t (Curl_recv)(struct connectdata *conn, /* connection data */
                            int sockindex,            /* socketindex */
                            char *buf,                /* store data here */
                            size_t len,               /* max amount to read */
                            CURLcode *err);           /* error to return */

#ifdef USE_RECV_BEFORE_SEND_WORKAROUND
struct postponed_data {
  char *buffer;          /* Temporal store for received data during
                            sending, must be freed */
  size_t allocated_size; /* Size of temporal store */
  size_t recv_size;      /* Size of received data during sending */
  size_t recv_processed; /* Size of processed part of postponed data */
#ifdef DEBUGBUILD
  curl_socket_t bindsock;/* Structure must be bound to specific socket,
                            used only for DEBUGASSERT */
#endif /* DEBUGBUILD */
};
#endif /* USE_RECV_BEFORE_SEND_WORKAROUND */

struct proxy_info {
  struct hostname host;
  long port;
  curl_proxytype proxytype; /* what kind of proxy that is in use */
  char *user;    /* proxy user name string, allocated */
  char *passwd;  /* proxy password string, allocated */
};

#define CONNECT_BUFFER_SIZE 16384

/* struct for HTTP CONNECT state data */
struct http_connect_state {
  char connect_buffer[CONNECT_BUFFER_SIZE];
  int perline; /* count bytes per line */
  int keepon;
  char *line_start;
  char *ptr; /* where to store more data */
  curl_off_t cl; /* size of content to read and ignore */
  bool chunked_encoding;
  enum {
    TUNNEL_INIT,    /* init/default/no tunnel state */
    TUNNEL_CONNECT, /* CONNECT has been sent off */
    TUNNEL_COMPLETE /* CONNECT response received completely */
  } tunnel_state;
};

/*
 * The connectdata struct contains all fields and variables that should be
 * unique for an entire connection.
 */
struct connectdata {
  /* 'data' is the CURRENT Curl_easy using this connection -- take great
     caution that this might very well vary between different times this
     connection is used! */
  struct Curl_easy *data;

  struct curl_llist_element bundle_node; /* conncache */

  /* chunk is for HTTP chunked encoding, but is in the general connectdata
     struct only because we can do just about any protocol through a HTTP proxy
     and a HTTP proxy may in fact respond using chunked encoding */
  struct Curl_chunker chunk;

  curl_closesocket_callback fclosesocket; /* function closing the socket(s) */
  void *closesocket_client;

  bool inuse; /* This is a marker for the connection cache logic. If this is
                 TRUE this handle is being used by an easy handle and cannot
                 be used by any other easy handle without careful
                 consideration (== only for pipelining). */

  /**** Fields set when inited and not modified again */
  long connection_id; /* Contains a unique number to make it easier to
                         track the connections in the log output */

  /* 'dns_entry' is the particular host we use. This points to an entry in the
     DNS cache and it will not get pruned while locked. It gets unlocked in
     Curl_done(). This entry will be NULL if the connection is re-used as then
     there is no name resolve done. */
  struct Curl_dns_entry *dns_entry;

  /* 'ip_addr' is the particular IP we connected to. It points to a struct
     within the DNS cache, so this pointer is only valid as long as the DNS
     cache entry remains locked. It gets unlocked in Curl_done() */
  Curl_addrinfo *ip_addr;
  Curl_addrinfo *tempaddr[2]; /* for happy eyeballs */

  /* 'ip_addr_str' is the ip_addr data as a human readable string.
     It remains available as long as the connection does, which is longer than
     the ip_addr itself. */
  char ip_addr_str[MAX_IPADR_LEN];

  unsigned int scope_id;  /* Scope id for IPv6 */

  int socktype;  /* SOCK_STREAM or SOCK_DGRAM */

  struct hostname host;
  char *secondaryhostname; /* secondary socket host name (ftp) */
  struct hostname conn_to_host; /* the host to connect to. valid only if
                                   bits.conn_to_host is set */

  struct proxy_info socks_proxy;
  struct proxy_info http_proxy;

  long port;       /* which port to use locally */
  int remote_port; /* the remote port, not the proxy port! */
  int conn_to_port; /* the remote port to connect to. valid only if
                       bits.conn_to_port is set */
  unsigned short secondary_port; /* secondary socket remote port to connect to
                                    (ftp) */

  /* 'primary_ip' and 'primary_port' get filled with peer's numerical
     ip address and port number whenever an outgoing connection is
     *attempted* from the primary socket to a remote address. When more
     than one address is tried for a connection these will hold data
     for the last attempt. When the connection is actually established
     these are updated with data which comes directly from the socket. */

  char primary_ip[MAX_IPADR_LEN];
  long primary_port;

  /* 'local_ip' and 'local_port' get filled with local's numerical
     ip address and port number whenever an outgoing connection is
     **established** from the primary socket to a remote address. */

  char local_ip[MAX_IPADR_LEN];
  long local_port;

  char *user;    /* user name string, allocated */
  char *passwd;  /* password string, allocated */
  char *options; /* options string, allocated */

  char *oauth_bearer; /* bearer token for OAuth 2.0, allocated */

  int httpversion;        /* the HTTP version*10 reported by the server */
  int rtspversion;        /* the RTSP version*10 reported by the server */

  struct curltime now;     /* "current" time */
  struct curltime created; /* creation time */
  curl_socket_t sock[2]; /* two sockets, the second is used for the data
                            transfer when doing FTP */
  curl_socket_t tempsock[2]; /* temporary sockets for happy eyeballs */
  bool sock_accepted[2]; /* TRUE if the socket on this index was created with
                            accept() */
  Curl_recv *recv[2];
  Curl_send *send[2];

#ifdef USE_RECV_BEFORE_SEND_WORKAROUND
  struct postponed_data postponed[2]; /* two buffers for two sockets */
#endif /* USE_RECV_BEFORE_SEND_WORKAROUND */
  struct ssl_connect_data ssl[2]; /* this is for ssl-stuff */
  struct ssl_connect_data proxy_ssl[2]; /* this is for proxy ssl-stuff */
  struct ssl_primary_config ssl_config;
  struct ssl_primary_config proxy_ssl_config;
  bool tls_upgraded;

  struct ConnectBits bits;    /* various state-flags for this connection */

 /* connecttime: when connect() is called on the current IP address. Used to
    be able to track when to move on to try next IP - but only when the multi
    interface is used. */
  struct curltime connecttime;
  /* The two fields below get set in Curl_connecthost */
  int num_addr; /* number of addresses to try to connect to */
  time_t timeoutms_per_addr; /* how long time in milliseconds to spend on
                                trying to connect to each IP address */

  const struct Curl_handler *handler; /* Connection's protocol handler */
  const struct Curl_handler *given;   /* The protocol first given */

  long ip_version; /* copied from the Curl_easy at creation time */

  /**** curl_get() phase fields */

  curl_socket_t sockfd;   /* socket to read from or CURL_SOCKET_BAD */
  curl_socket_t writesockfd; /* socket to write to, it may very
                                well be the same we read from.
                                CURL_SOCKET_BAD disables */

  /** Dynamicly allocated strings, MUST be freed before this **/
  /** struct is killed.                                      **/
  struct dynamically_allocated_data {
    char *proxyuserpwd;
    char *uagent;
    char *accept_encoding;
    char *userpwd;
    char *rangeline;
    char *ref;
    char *host;
    char *cookiehost;
    char *rtsp_transport;
    char *te; /* TE: request header */
  } allocptr;

#ifdef HAVE_GSSAPI
  int sec_complete; /* if Kerberos is enabled for this connection */
  enum protection_level command_prot;
  enum protection_level data_prot;
  enum protection_level request_data_prot;
  size_t buffer_size;
  struct krb5buffer in_buffer;
  void *app_data;
  const struct Curl_sec_client_mech *mech;
  struct sockaddr_in local_addr;
#endif

#if defined(USE_KERBEROS5)    /* Consider moving some of the above GSS-API */
  struct kerberos5data krb5;  /* variables into the structure definition, */
#endif                        /* however, some of them are ftp specific. */

  /* the two following *_inuse fields are only flags, not counters in any way.
     If TRUE it means the channel is in use, and if FALSE it means the channel
     is up for grabs by one. */

  bool readchannel_inuse;  /* whether the read channel is in use by an easy
                              handle */
  bool writechannel_inuse; /* whether the write channel is in use by an easy
                              handle */
  struct curl_llist send_pipe; /* List of handles waiting to send on this
                                  pipeline */
  struct curl_llist recv_pipe; /* List of handles waiting to read their
                                  responses on this pipeline */
  char *master_buffer; /* The master buffer allocated on-demand;
                          used for pipelining. */
  size_t read_pos; /* Current read position in the master buffer */
  size_t buf_len; /* Length of the buffer?? */


  curl_seek_callback seek_func; /* function that seeks the input */
  void *seek_client;            /* pointer to pass to the seek() above */

  /*************** Request - specific items ************/

#if defined(USE_NTLM)
  struct ntlmdata ntlm;     /* NTLM differs from other authentication schemes
                               because it authenticates connections, not
                               single requests! */
  struct ntlmdata proxyntlm; /* NTLM data for proxy */

#if defined(NTLM_WB_ENABLED)
  /* used for communication with Samba's winbind daemon helper ntlm_auth */
  curl_socket_t ntlm_auth_hlpr_socket;
  pid_t ntlm_auth_hlpr_pid;
  char *challenge_header;
  char *response_header;
#endif
#endif

  char syserr_buf [256]; /* buffer for Curl_strerror() */

#ifdef CURLRES_ASYNCH
  /* data used for the asynch name resolve callback */
  struct Curl_async async;
#endif

  /* These three are used for chunked-encoding trailer support */
  char *trailer; /* allocated buffer to store trailer in */
  int trlMax;    /* allocated buffer size */
  int trlPos;    /* index of where to store data */

  union {
    struct ftp_conn ftpc;