intermediate changes

ref:cde9a383711a11544ce7e107a78147fb96cc4029

1 files changed, 1931 insertions, 0 deletions

diff --git a/contrib/libs/curl/lib/transfer.c b/contrib/libs/curl/lib/transfer.c
new file mode 100644
index 00000000000..bfd0218fef7
--- /dev/null
+++ b/contrib/libs/curl/lib/transfer.c
@@ -0,0 +1,1931 @@
+/***************************************************************************
+ *                                  _   _ ____  _
+ *  Project                     ___| | | |  _ \| |
+ *                             / __| | | | |_) | |
+ *                            | (__| |_| |  _ <| |___
+ *                             \___|\___/|_| \_\_____|
+ *
+ * Copyright (C) 1998 - 2020, Daniel Stenberg, <[email protected]>, 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.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.
+ *
+ ***************************************************************************/
+
+#include "curl_setup.h"
+#include "strtoofft.h"
+
+#ifdef HAVE_NETINET_IN_H
+#include <netinet/in.h>
+#endif
+#ifdef HAVE_NETDB_H
+#include <netdb.h>
+#endif
+#ifdef HAVE_ARPA_INET_H
+#include <arpa/inet.h>
+#endif
+#ifdef HAVE_NET_IF_H
+#include <net/if.h>
+#endif
+#ifdef HAVE_SYS_IOCTL_H
+#include <sys/ioctl.h>
+#endif
+#ifdef HAVE_SIGNAL_H
+#include <signal.h>
+#endif
+
+#ifdef HAVE_SYS_PARAM_H
+#include <sys/param.h>
+#endif
+
+#ifdef HAVE_SYS_SELECT_H
+#include <sys/select.h>
+#elif defined(HAVE_UNISTD_H)
+#include <unistd.h>
+#endif
+
+#ifndef HAVE_SOCKET
+#error "We can't compile without socket() support!"
+#endif
+
+#include "urldata.h"
+#include <curl/curl.h>
+#include "netrc.h"
+
+#include "content_encoding.h"
+#include "hostip.h"
+#include "transfer.h"
+#include "sendf.h"
+#include "speedcheck.h"
+#include "progress.h"
+#include "http.h"
+#include "url.h"
+#include "getinfo.h"
+#include "vtls/vtls.h"
+#include "select.h"
+#include "multiif.h"
+#include "connect.h"
+#include "non-ascii.h"
+#include "http2.h"
+#include "mime.h"
+#include "strcase.h"
+#include "urlapi-int.h"
+#include "hsts.h"
+
+/* The last 3 #include files should be in this order */
+#include "curl_printf.h"
+#include "curl_memory.h"
+#include "memdebug.h"
+
+#if !defined(CURL_DISABLE_HTTP) || !defined(CURL_DISABLE_SMTP) || \
+    !defined(CURL_DISABLE_IMAP)
+/*
+ * checkheaders() checks the linked list of custom headers for a
+ * particular header (prefix). Provide the prefix without colon!
+ *
+ * Returns a pointer to the first matching header or NULL if none matched.
+ */
+char *Curl_checkheaders(const struct connectdata *conn,
+                        const char *thisheader)
+{
+  struct curl_slist *head;
+  size_t thislen = strlen(thisheader);
+  struct Curl_easy *data = conn->data;
+
+  for(head = data->set.headers; head; head = head->next) {
+    if(strncasecompare(head->data, thisheader, thislen) &&
+       Curl_headersep(head->data[thislen]) )
+      return head->data;
+  }
+
+  return NULL;
+}
+#endif
+
+CURLcode Curl_get_upload_buffer(struct Curl_easy *data)
+{
+  if(!data->state.ulbuf) {
+    data->state.ulbuf = malloc(data->set.upload_buffer_size);
+    if(!data->state.ulbuf)
+      return CURLE_OUT_OF_MEMORY;
+  }
+  return CURLE_OK;
+}
+
+#ifndef CURL_DISABLE_HTTP
+/*
+ * This function will be called to loop through the trailers buffer
+ * until no more data is available for sending.
+ */
+static size_t Curl_trailers_read(char *buffer, size_t size, size_t nitems,
+                                 void *raw)
+{
+  struct Curl_easy *data = (struct Curl_easy *)raw;
+  struct dynbuf *trailers_buf = &data->state.trailers_buf;
+  size_t bytes_left = Curl_dyn_len(trailers_buf) -
+    data->state.trailers_bytes_sent;
+  size_t to_copy = (size*nitems < bytes_left) ? size*nitems : bytes_left;
+  if(to_copy) {
+    memcpy(buffer,
+           Curl_dyn_ptr(trailers_buf) + data->state.trailers_bytes_sent,
+           to_copy);
+    data->state.trailers_bytes_sent += to_copy;
+  }
+  return to_copy;
+}
+
+static size_t Curl_trailers_left(void *raw)
+{
+  struct Curl_easy *data = (struct Curl_easy *)raw;
+  struct dynbuf *trailers_buf = &data->state.trailers_buf;
+  return Curl_dyn_len(trailers_buf) - data->state.trailers_bytes_sent;
+}
+#endif
+
+/*
+ * This function will call the read callback to fill our buffer with data
+ * to upload.
+ */
+CURLcode Curl_fillreadbuffer(struct connectdata *conn, size_t bytes,
+                             size_t *nreadp)
+{
+  struct Curl_easy *data = conn->data;
+  size_t buffersize = bytes;
+  size_t nread;
+
+  curl_read_callback readfunc = NULL;
+  void *extra_data = NULL;
+
+#ifdef CURL_DOES_CONVERSIONS
+  bool sending_http_headers = FALSE;
+
+  if(conn->handler->protocol&(PROTO_FAMILY_HTTP|CURLPROTO_RTSP)) {
+    const struct HTTP *http = data->req.p.http;
+
+    if(http->sending == HTTPSEND_REQUEST)
+      /* We're sending the HTTP request headers, not the data.
+         Remember that so we don't re-translate them into garbage. */
+      sending_http_headers = TRUE;
+  }
+#endif
+
+#ifndef CURL_DISABLE_HTTP
+  if(data->state.trailers_state == TRAILERS_INITIALIZED) {
+    struct curl_slist *trailers = NULL;
+    CURLcode result;
+    int trailers_ret_code;
+
+    /* at this point we already verified that the callback exists
+       so we compile and store the trailers buffer, then proceed */
+    infof(data,
+          "Moving trailers state machine from initialized to sending.\n");
+    data->state.trailers_state = TRAILERS_SENDING;
+    Curl_dyn_init(&data->state.trailers_buf, DYN_TRAILERS);
+
+    data->state.trailers_bytes_sent = 0;
+    Curl_set_in_callback(data, true);
+    trailers_ret_code = data->set.trailer_callback(&trailers,
+                                                   data->set.trailer_data);
+    Curl_set_in_callback(data, false);
+    if(trailers_ret_code == CURL_TRAILERFUNC_OK) {
+      result = Curl_http_compile_trailers(trailers, &data->state.trailers_buf,
+                                          data);
+    }
+    else {
+      failf(data, "operation aborted by trailing headers callback");
+      *nreadp = 0;
+      result = CURLE_ABORTED_BY_CALLBACK;
+    }
+    if(result) {
+      Curl_dyn_free(&data->state.trailers_buf);
+      curl_slist_free_all(trailers);
+      return result;
+    }
+    infof(data, "Successfully compiled trailers.\r\n");
+    curl_slist_free_all(trailers);
+  }
+#endif
+
+  /* if we are transmitting trailing data, we don't need to write
+     a chunk size so we skip this */
+  if(data->req.upload_chunky &&
+     data->state.trailers_state == TRAILERS_NONE) {
+    /* if chunked Transfer-Encoding */
+    buffersize -= (8 + 2 + 2);   /* 32bit hex + CRLF + CRLF */
+    data->req.upload_fromhere += (8 + 2); /* 32bit hex + CRLF */
+  }
+
+#ifndef CURL_DISABLE_HTTP
+  if(data->state.trailers_state == TRAILERS_SENDING) {
+    /* if we're here then that means that we already sent the last empty chunk
+       but we didn't send a final CR LF, so we sent 0 CR LF. We then start
+       pulling trailing data until we have no more at which point we
+       simply return to the previous point in the state machine as if
+       nothing happened.
+       */
+    readfunc = Curl_trailers_read;
+    extra_data = (void *)data;
+  }
+  else
+#endif
+  {
+    readfunc = data->state.fread_func;
+    extra_data = data->state.in;
+  }
+
+  Curl_set_in_callback(data, true);
+  nread = readfunc(data->req.upload_fromhere, 1,
+                   buffersize, extra_data);
+  Curl_set_in_callback(data, false);
+
+  if(nread == CURL_READFUNC_ABORT) {
+    failf(data, "operation aborted by callback");
+    *nreadp = 0;
+    return CURLE_ABORTED_BY_CALLBACK;
+  }
+  if(nread == CURL_READFUNC_PAUSE) {
+    struct SingleRequest *k = &data->req;
+
+    if(conn->handler->flags & PROTOPT_NONETWORK) {
+      /* protocols that work without network cannot be paused. This is
+         actually only FILE:// just now, and it can't pause since the transfer
+         isn't done using the "normal" procedure. */
+      failf(data, "Read callback asked for PAUSE when not supported!");
+      return CURLE_READ_ERROR;
+    }
+
+    /* CURL_READFUNC_PAUSE pauses read callbacks that feed socket writes */
+    k->keepon |= KEEP_SEND_PAUSE; /* mark socket send as paused */
+    if(data->req.upload_chunky) {
+        /* Back out the preallocation done above */
+      data->req.upload_fromhere -= (8 + 2);
+    }
+    *nreadp = 0;
+
+    return CURLE_OK; /* nothing was read */
+  }
+  else if(nread > buffersize) {
+    /* the read function returned a too large value */
+    *nreadp = 0;
+    failf(data, "read function returned funny value");
+    return CURLE_READ_ERROR;
+  }
+
+  if(!data->req.forbidchunk && data->req.upload_chunky) {
+    /* if chunked Transfer-Encoding
+     *    build chunk:
+     *
+     *        <HEX SIZE> CRLF
+     *        <DATA> CRLF
+     */
+    /* On non-ASCII platforms the <DATA> may or may not be
+       translated based on set.prefer_ascii while the protocol
+       portion must always be translated to the network encoding.
+       To further complicate matters, line end conversion might be
+       done later on, so we need to prevent CRLFs from becoming
+       CRCRLFs if that's the case.  To do this we use bare LFs
+       here, knowing they'll become CRLFs later on.
+     */
+
+    bool added_crlf = FALSE;
+    int hexlen = 0;
+    const char *endofline_native;
+    const char *endofline_network;
+
+    if(
+#ifdef CURL_DO_LINEEND_CONV
+       (data->set.prefer_ascii) ||
+#endif
+       (data->set.crlf)) {
+      /* \n will become \r\n later on */
+      endofline_native  = "\n";
+      endofline_network = "\x0a";
+    }
+    else {
+      endofline_native  = "\r\n";
+      endofline_network = "\x0d\x0a";
+    }
+
+    /* if we're not handling trailing data, proceed as usual */
+    if(data->state.trailers_state != TRAILERS_SENDING) {
+      char hexbuffer[11] = "";
+      hexlen = msnprintf(hexbuffer, sizeof(hexbuffer),
+                         "%zx%s", nread, endofline_native);
+
+      /* move buffer pointer */
+      data->req.upload_fromhere -= hexlen;
+      nread += hexlen;
+
+      /* copy the prefix to the buffer, leaving out the NUL */
+      memcpy(data->req.upload_fromhere, hexbuffer, hexlen);
+
+      /* always append ASCII CRLF to the data unless
+         we have a valid trailer callback */
+#ifndef CURL_DISABLE_HTTP
+      if((nread-hexlen) == 0 &&
+          data->set.trailer_callback != NULL &&
+          data->state.trailers_state == TRAILERS_NONE) {
+        data->state.trailers_state = TRAILERS_INITIALIZED;
+      }
+      else
+#endif
+      {
+        memcpy(data->req.upload_fromhere + nread,
+               endofline_network,
+               strlen(endofline_network));
+        added_crlf = TRUE;
+      }
+    }
+
+#ifdef CURL_DOES_CONVERSIONS
+    {
+      CURLcode result;
+      size_t length;
+      if(data->set.prefer_ascii)
+        /* translate the protocol and data */
+        length = nread;
+      else
+        /* just translate the protocol portion */
+        length = hexlen;
+      if(length) {
+        result = Curl_convert_to_network(data, data->req.upload_fromhere,
+                                         length);
+        /* Curl_convert_to_network calls failf if unsuccessful */
+        if(result)
+          return result;
+      }
+    }
+#endif /* CURL_DOES_CONVERSIONS */
+
+#ifndef CURL_DISABLE_HTTP
+    if(data->state.trailers_state == TRAILERS_SENDING &&
+       !Curl_trailers_left(data)) {
+      Curl_dyn_free(&data->state.trailers_buf);
+      data->state.trailers_state = TRAILERS_DONE;
+      data->set.trailer_data = NULL;
+      data->set.trailer_callback = NULL;
+      /* mark the transfer as done */
+      data->req.upload_done = TRUE;
+      infof(data, "Signaling end of chunked upload after trailers.\n");
+    }
+    else
+#endif
+      if((nread - hexlen) == 0 &&
+         data->state.trailers_state != TRAILERS_INITIALIZED) {
+        /* mark this as done once this chunk is transferred */
+        data->req.upload_done = TRUE;
+        infof(data,
+              "Signaling end of chunked upload via terminating chunk.\n");
+      }
+
+    if(added_crlf)
+      nread += strlen(endofline_network); /* for the added end of line */
+  }
+#ifdef CURL_DOES_CONVERSIONS
+  else if((data->set.prefer_ascii) && (!sending_http_headers)) {
+    CURLcode result;
+    result = Curl_convert_to_network(data, data->req.upload_fromhere, nread);
+    /* Curl_convert_to_network calls failf if unsuccessful */
+    if(result)
+      return result;
+  }
+#endif /* CURL_DOES_CONVERSIONS */
+
+  *nreadp = nread;
+
+  return CURLE_OK;
+}
+
+
+/*
+ * Curl_readrewind() rewinds the read stream. This is typically used for HTTP
+ * POST/PUT with multi-pass authentication when a sending was denied and a
+ * resend is necessary.
+ */
+CURLcode Curl_readrewind(struct connectdata *conn)
+{
+  struct Curl_easy *data = conn->data;
+  curl_mimepart *mimepart = &data->set.mimepost;
+
+  conn->bits.rewindaftersend = FALSE; /* we rewind now */
+
+  /* explicitly switch off sending data on this connection now since we are
+     about to restart a new transfer and thus we want to avoid inadvertently
+     sending more data on the existing connection until the next transfer
+     starts */
+  data->req.keepon &= ~KEEP_SEND;
+
+  /* We have sent away data. If not using CURLOPT_POSTFIELDS or
+     CURLOPT_HTTPPOST, call app to rewind
+  */
+  if(conn->handler->protocol & PROTO_FAMILY_HTTP) {
+    struct HTTP *http = data->req.p.http;
+
+    if(http->sendit)
+      mimepart = http->sendit;
+  }
+  if(data->set.postfields)
+    ; /* do nothing */
+  else if(data->state.httpreq == HTTPREQ_POST_MIME ||
+          data->state.httpreq == HTTPREQ_POST_FORM) {
+    if(Curl_mime_rewind(mimepart)) {
+      failf(data, "Cannot rewind mime/post data");
+      return CURLE_SEND_FAIL_REWIND;
+    }
+  }
+  else {
+    if(data->set.seek_func) {
+      int err;
+
+      Curl_set_in_callback(data, true);
+      err = (data->set.seek_func)(data->set.seek_client, 0, SEEK_SET);
+      Curl_set_in_callback(data, false);
+      if(err) {
+        failf(data, "seek callback returned error %d", (int)err);
+        return CURLE_SEND_FAIL_REWIND;
+      }
+    }
+    else if(data->set.ioctl_func) {
+      curlioerr err;
+
+      Curl_set_in_callback(data, true);
+      err = (data->set.ioctl_func)(data, CURLIOCMD_RESTARTREAD,
+                                   data->set.ioctl_client);
+      Curl_set_in_callback(data, false);
+      infof(data, "the ioctl callback returned %d\n", (int)err);
+
+      if(err) {
+        failf(data, "ioctl callback returned error %d", (int)err);
+        return CURLE_SEND_FAIL_REWIND;
+      }
+    }
+    else {
+      /* If no CURLOPT_READFUNCTION is used, we know that we operate on a
+         given FILE * stream and we can actually attempt to rewind that
+         ourselves with fseek() */
+      if(data->state.fread_func == (curl_read_callback)fread) {
+        if(-1 != fseek(data->state.in, 0, SEEK_SET))
+          /* successful rewind */
+          return CURLE_OK;
+      }
+
+      /* no callback set or failure above, makes us fail at once */
+      failf(data, "necessary data rewind wasn't possible");
+      return CURLE_SEND_FAIL_REWIND;
+    }
+  }
+  return CURLE_OK;
+}
+
+static int data_pending(const struct Curl_easy *data)
+{
+  struct connectdata *conn = data->conn;
+
+#ifdef ENABLE_QUIC
+  if(conn->transport == TRNSPRT_QUIC)
+    return Curl_quic_data_pending(data);
+#endif
+
+  /* in the case of libssh2, we can never be really sure that we have emptied
+     its internal buffers so we MUST always try until we get EAGAIN back */
+  return conn->handler->protocol&(CURLPROTO_SCP|CURLPROTO_SFTP) ||
+#if defined(USE_NGHTTP2)
+    Curl_ssl_data_pending(conn, FIRSTSOCKET) ||
+    /* For HTTP/2, we may read up everything including response body
+       with header fields in Curl_http_readwrite_headers. If no
+       content-length is provided, curl waits for the connection
+       close, which we emulate it using conn->proto.httpc.closed =
+       TRUE. The thing is if we read everything, then http2_recv won't
+       be called and we cannot signal the HTTP/2 stream has closed. As
+       a workaround, we return nonzero here to call http2_recv. */
+    ((conn->handler->protocol&PROTO_FAMILY_HTTP) && conn->httpversion >= 20);
+#else
+    Curl_ssl_data_pending(conn, FIRSTSOCKET);
+#endif
+}
+
+/*
+ * Check to see if CURLOPT_TIMECONDITION was met by comparing the time of the
+ * remote document with the time provided by CURLOPT_TIMEVAL
+ */
+bool Curl_meets_timecondition(struct Curl_easy *data, time_t timeofdoc)
+{
+  if((timeofdoc == 0) || (data->set.timevalue == 0))
+    return TRUE;
+
+  switch(data->set.timecondition) {
+  case CURL_TIMECOND_IFMODSINCE:
+  default:
+    if(timeofdoc <= data->set.timevalue) {
+      infof(data,
+            "The requested document is not new enough\n");
+      data->info.timecond = TRUE;
+      return FALSE;
+    }
+    break;
+  case CURL_TIMECOND_IFUNMODSINCE:
+    if(timeofdoc >= data->set.timevalue) {
+      infof(data,
+            "The requested document is not old enough\n");
+      data->info.timecond = TRUE;
+      return FALSE;
+    }
+    break;
+  }
+
+  return TRUE;
+}
+
+/*
+ * Go ahead and do a read if we have a readable socket or if
+ * the stream was rewound (in which case we have data in a
+ * buffer)
+ *
+ * return '*comeback' TRUE if we didn't properly drain the socket so this
+ * function should get called again without select() or similar in between!
+ */
+static CURLcode readwrite_data(struct Curl_easy *data,
+                               struct connectdata *conn,
+                               struct SingleRequest *k,
+                               int *didwhat, bool *done,
+                               bool *comeback)
+{
+  CURLcode result = CURLE_OK;
+  ssize_t nread; /* number of bytes read */
+  size_t excess = 0; /* excess bytes read */
+  bool readmore = FALSE; /* used by RTP to signal for more data */
+  int maxloops = 100;
+  char *buf = data->state.buffer;
+  DEBUGASSERT(buf);
+
+  *done = FALSE;
+  *comeback = FALSE;
+
+  /* This is where we loop until we have read everything there is to
+     read or we get a CURLE_AGAIN */
+  do {
+    bool is_empty_data = FALSE;
+    size_t buffersize = data->set.buffer_size;
+    size_t bytestoread = buffersize;
+#ifdef USE_NGHTTP2
+    bool is_http2 = ((conn->handler->protocol & PROTO_FAMILY_HTTP) &&
+                     (conn->httpversion == 20));
+#endif
+
+    if(
+#ifdef USE_NGHTTP2
+       /* For HTTP/2, read data without caring about the content
+          length. This is safe because body in HTTP/2 is always
+          segmented thanks to its framing layer. Meanwhile, we have to
+          call Curl_read to ensure that http2_handle_stream_close is
+          called when we read all incoming bytes for a particular
+          stream. */
+       !is_http2 &&
+#endif
+       k->size != -1 && !k->header) {
+      /* make sure we don't read too much */
+      curl_off_t totalleft = k->size - k->bytecount;
+      if(totalleft < (curl_off_t)bytestoread)
+        bytestoread = (size_t)totalleft;
+    }
+
+    if(bytestoread) {
+      /* receive data from the network! */
+      result = Curl_read(conn, conn->sockfd, buf, bytestoread, &nread);
+
+      /* read would've blocked */
+      if(CURLE_AGAIN == result)
+        break; /* get out of loop */
+
+      if(result>0)
+        return result;
+    }
+    else {
+      /* read nothing but since we wanted nothing we consider this an OK
+         situation to proceed from */
+      DEBUGF(infof(data, "readwrite_data: we're done!\n"));
+      nread = 0;
+    }
+
+    if(!k->bytecount) {
+      Curl_pgrsTime(data, TIMER_STARTTRANSFER);
+      if(k->exp100 > EXP100_SEND_DATA)
+        /* set time stamp to compare with when waiting for the 100 */
+        k->start100 = Curl_now();
+    }
+
+    *didwhat |= KEEP_RECV;
+    /* indicates data of zero size, i.e. empty file */
+    is_empty_data = ((nread == 0) && (k->bodywrites == 0)) ? TRUE : FALSE;
+
+    if(0 < nread || is_empty_data) {
+      buf[nread] = 0;
+    }
+    else {
+      /* if we receive 0 or less here, either the http2 stream is closed or the
+         server closed the connection and we bail out from this! */
+#ifdef USE_NGHTTP2
+      if(is_http2 && !nread)
+        DEBUGF(infof(data, "nread == 0, stream closed, bailing\n"));
+      else
+#endif
+        DEBUGF(infof(data, "nread <= 0, server closed connection, bailing\n"));
+      k->keepon &= ~KEEP_RECV;
+      break;
+    }
+
+    /* Default buffer to use when we write the buffer, it may be changed
+       in the flow below before the actual storing is done. */
+    k->str = buf;
+
+    if(conn->handler->readwrite) {
+      result = conn->handler->readwrite(data, conn, &nread, &readmore);
+      if(result)
+        return result;
+      if(readmore)
+        break;
+    }
+
+#ifndef CURL_DISABLE_HTTP
+    /* Since this is a two-state thing, we check if we are parsing
+       headers at the moment or not. */
+    if(k->header) {
+      /* we are in parse-the-header-mode */
+      bool stop_reading = FALSE;
+      result = Curl_http_readwrite_headers(data, conn, &nread, &stop_reading);
+      if(result)
+        return result;
+
+      if(conn->handler->readwrite &&
+         (k->maxdownload <= 0 && nread > 0)) {
+        result = conn->handler->readwrite(data, conn, &nread, &readmore);
+        if(result)
+          return result;
+        if(readmore)
+          break;
+      }
+
+      if(stop_reading) {
+        /* We've stopped dealing with input, get out of the do-while loop */
+
+        if(nread > 0) {
+          infof(data,
+                "Excess found:"
+                " excess = %zd"
+                " url = %s (zero-length body)\n",
+                nread, data->state.up.path);
+        }
+
+        break;
+      }
+    }
+#endif /* CURL_DISABLE_HTTP */
+
+
+    /* This is not an 'else if' since it may be a rest from the header
+       parsing, where the beginning of the buffer is headers and the end
+       is non-headers. */
+    if(!k->header && (nread > 0 || is_empty_data)) {
+
+      if(data->set.opt_no_body) {
+        /* data arrives although we want none, bail out */
+        streamclose(conn, "ignoring body");
+        *done = TRUE;
+        return CURLE_WEIRD_SERVER_REPLY;
+      }
+
+#ifndef CURL_DISABLE_HTTP
+      if(0 == k->bodywrites && !is_empty_data) {
+        /* These checks are only made the first time we are about to
+           write a piece of the body */
+        if(conn->handler->protocol&(PROTO_FAMILY_HTTP|CURLPROTO_RTSP)) {
+          /* HTTP-only checks */
+
+          if(data->req.newurl) {
+            if(conn->bits.close) {
+              /* Abort after the headers if "follow Location" is set
+                 and we're set to close anyway. */
+              k->keepon &= ~KEEP_RECV;
+              *done = TRUE;
+              return CURLE_OK;
+            }
+            /* We have a new url to load, but since we want to be able
+               to re-use this connection properly, we read the full
+               response in "ignore more" */
+            k->ignorebody = TRUE;
+            infof(data, "Ignoring the response-body\n");
+          }
+          if(data->state.resume_from && !k->content_range &&
+             (data->state.httpreq == HTTPREQ_GET) &&
+             !k->ignorebody) {
+
+            if(k->size == data->state.resume_from) {
+              /* The resume point is at the end of file, consider this fine
+                 even if it doesn't allow resume from here. */
+              infof(data, "The entire document is already downloaded");
+              connclose(conn, "already downloaded");
+              /* Abort download */
+              k->keepon &= ~KEEP_RECV;
+              *done = TRUE;
+              return CURLE_OK;
+            }
+
+            /* we wanted to resume a download, although the server doesn't
+             * seem to support this and we did this with a GET (if it
+             * wasn't a GET we did a POST or PUT resume) */
+            failf(data, "HTTP server doesn't seem to support "
+                  "byte ranges. Cannot resume.");
+            return CURLE_RANGE_ERROR;
+          }
+
+          if(data->set.timecondition && !data->state.range) {
+            /* A time condition has been set AND no ranges have been
+               requested. This seems to be what chapter 13.3.4 of
+               RFC 2616 defines to be the correct action for a
+               HTTP/1.1 client */
+
+            if(!Curl_meets_timecondition(data, k->timeofdoc)) {
+              *done = TRUE;
+              /* We're simulating a http 304 from server so we return
+                 what should have been returned from the server */
+              data->info.httpcode = 304;
+              infof(data, "Simulate a HTTP 304 response!\n");
+              /* we abort the transfer before it is completed == we ruin the
+                 re-use ability. Close the connection */
+              connclose(conn, "Simulated 304 handling");
+              return CURLE_OK;
+            }
+          } /* we have a time condition */
+
+        } /* this is HTTP or RTSP */
+      } /* this is the first time we write a body part */
+#endif /* CURL_DISABLE_HTTP */
+
+      k->bodywrites++;
+
+      /* pass data to the debug function before it gets "dechunked" */
+      if(data->set.verbose) {
+        if(k->badheader) {
+          Curl_debug(data, CURLINFO_DATA_IN,
+                     Curl_dyn_ptr(&data->state.headerb),
+                     Curl_dyn_len(&data->state.headerb));
+          if(k->badheader == HEADER_PARTHEADER)
+            Curl_debug(data, CURLINFO_DATA_IN,
+                       k->str, (size_t)nread);
+        }
+        else
+          Curl_debug(data, CURLINFO_DATA_IN,
+                     k->str, (size_t)nread);
+      }
+
+#ifndef CURL_DISABLE_HTTP
+      if(k->chunk) {
+        /*
+         * Here comes a chunked transfer flying and we need to decode this
+         * properly.  While the name says read, this function both reads
+         * and writes away the data. The returned 'nread' holds the number
+         * of actual data it wrote to the client.
+         */
+        CURLcode extra;
+        CHUNKcode res =
+          Curl_httpchunk_read(conn, k->str, nread, &nread, &extra);
+
+        if(CHUNKE_OK < res) {
+          if(CHUNKE_PASSTHRU_ERROR == res) {
+            failf(data, "Failed reading the chunked-encoded stream");
+            return extra;
+          }
+          failf(data, "%s in chunked-encoding", Curl_chunked_strerror(res));
+          return CURLE_RECV_ERROR;
+        }
+        if(CHUNKE_STOP == res) {
+          size_t dataleft;
+          /* we're done reading chunks! */
+          k->keepon &= ~KEEP_RECV; /* read no more */
+
+          /* There are now possibly N number of bytes at the end of the
+             str buffer that weren't written to the client.
+             Push it back to be read on the next pass. */
+
+          dataleft = conn->chunk.dataleft;
+          if(dataleft != 0) {
+            infof(conn->data, "Leftovers after chunking: %zu bytes\n",
+                  dataleft);
+          }
+        }
+        /* If it returned OK, we just keep going */
+      }
+#endif   /* CURL_DISABLE_HTTP */
+
+      /* Account for body content stored in the header buffer */
+      if((k->badheader == HEADER_PARTHEADER) && !k->ignorebody) {
+        size_t headlen = Curl_dyn_len(&data->state.headerb);
+        DEBUGF(infof(data, "Increasing bytecount by %zu\n", headlen));
+        k->bytecount += headlen;
+      }
+
+      if((-1 != k->maxdownload) &&
+         (k->bytecount + nread >= k->maxdownload)) {
+
+        excess = (size_t)(k->bytecount + nread - k->maxdownload);
+        if(excess > 0 && !k->ignorebody) {
+          infof(data,
+                "Excess found in a read:"
+                " excess = %zu"
+                ", size = %" CURL_FORMAT_CURL_OFF_T
+                ", maxdownload = %" CURL_FORMAT_CURL_OFF_T
+                ", bytecount = %" CURL_FORMAT_CURL_OFF_T "\n",
+                excess, k->size, k->maxdownload, k->bytecount);
+          connclose(conn, "excess found in a read");
+        }
+
+        nread = (ssize_t) (k->maxdownload - k->bytecount);
+        if(nread < 0) /* this should be unusual */
+          nread = 0;
+
+        k->keepon &= ~KEEP_RECV; /* we're done reading */
+      }
+
+      k->bytecount += nread;
+
+      Curl_pgrsSetDownloadCounter(data, k->bytecount);
+
+      if(!k->chunk && (nread || k->badheader || is_empty_data)) {
+        /* If this is chunky transfer, it was already written */
+
+        if(k->badheader && !k->ignorebody) {
+          /* we parsed a piece of data wrongly assuming it was a header
+             and now we output it as body instead */
+          size_t headlen = Curl_dyn_len(&data->state.headerb);
+
+          /* Don't let excess data pollute body writes */
+          if(k->maxdownload == -1 || (curl_off_t)headlen <= k->maxdownload)
+            result = Curl_client_write(conn, CLIENTWRITE_BODY,
+                                       Curl_dyn_ptr(&data->state.headerb),
+                                       headlen);
+          else
+            result = Curl_client_write(conn, CLIENTWRITE_BODY,
+                                       Curl_dyn_ptr(&data->state.headerb),
+                                       (size_t)k->maxdownload);
+
+          if(result)
+            return result;
+        }
+        if(k->badheader < HEADER_ALLBAD) {
+          /* This switch handles various content encodings. If there's an
+             error here, be sure to check over the almost identical code
+             in http_chunks.c.
+             Make sure that ALL_CONTENT_ENCODINGS contains all the
+             encodings handled here. */
+          if(conn->data->set.http_ce_skip || !k->writer_stack) {
+            if(!k->ignorebody) {
+#ifndef CURL_DISABLE_POP3
+              if(conn->handler->protocol & PROTO_FAMILY_POP3)
+                result = Curl_pop3_write(conn, k->str, nread);
+              else
+#endif /* CURL_DISABLE_POP3 */
+                result = Curl_client_write(conn, CLIENTWRITE_BODY, k->str,
+                                           nread);
+            }
+          }
+          else if(!k->ignorebody)
+            result = Curl_unencode_write(conn, k->writer_stack, k->str, nread);
+        }
+        k->badheader = HEADER_NORMAL; /* taken care of now */
+
+        if(result)
+          return result;
+      }
+
+    } /* if(!header and data to read) */
+
+    if(conn->handler->readwrite && excess) {
+      /* Parse the excess data */
+      k->str += nread;
+
+      if(&k->str[excess] > &buf[data->set.buffer_size]) {
+        /* the excess amount was too excessive(!), make sure
+           it doesn't read out of buffer */
+        excess = &buf[data->set.buffer_size] - k->str;
+      }
+      nread = (ssize_t)excess;
+
+      result = conn->handler->readwrite(data, conn, &nread, &readmore);
+      if(result)
+        return result;
+
+      if(readmore)
+        k->keepon |= KEEP_RECV; /* we're not done reading */
+      break;
+    }
+
+    if(is_empty_data) {
+      /* if we received nothing, the server closed the connection and we
+         are done */
+      k->keepon &= ~KEEP_RECV;
+    }
+
+    if(k->keepon & KEEP_RECV_PAUSE) {
+      /* this is a paused transfer */
+      break;
+    }
+
+  } while(data_pending(data) && maxloops--);
+
+  if(maxloops <= 0) {
+    /* we mark it as read-again-please */
+    conn->cselect_bits = CURL_CSELECT_IN;
+    *comeback = TRUE;
+  }
+
+  if(((k->keepon & (KEEP_RECV|KEEP_SEND)) == KEEP_SEND) &&
+     conn->bits.close) {
+    /* When we've read the entire thing and the close bit is set, the server
+       may now close the connection. If there's now any kind of sending going
+       on from our side, we need to stop that immediately. */
+    infof(data, "we are done reading and this is set to close, stop send\n");
+    k->keepon &= ~KEEP_SEND; /* no writing anymore either */
+  }
+
+  return CURLE_OK;
+}
+
+CURLcode Curl_done_sending(struct connectdata *conn,
+                           struct SingleRequest *k)
+{
+  k->keepon &= ~KEEP_SEND; /* we're done writing */
+
+  /* These functions should be moved into the handler struct! */
+  Curl_http2_done_sending(conn);
+  Curl_quic_done_sending(conn);
+
+  if(conn->bits.rewindaftersend) {
+    CURLcode result = Curl_readrewind(conn);
+    if(result)
+      return result;
+  }
+  return CURLE_OK;
+}
+
+#if defined(WIN32) && !defined(USE_LWIPSOCK)
+#ifndef SIO_IDEAL_SEND_BACKLOG_QUERY
+#define SIO_IDEAL_SEND_BACKLOG_QUERY 0x4004747B
+#endif
+
+static void win_update_buffer_size(curl_socket_t sockfd)
+{
+  int result;
+  ULONG ideal;
+  DWORD ideallen;
+  result = WSAIoctl(sockfd, SIO_IDEAL_SEND_BACKLOG_QUERY, 0, 0,
+                    &ideal, sizeof(ideal), &ideallen, 0, 0);
+  if(result == 0) {
+    setsockopt(sockfd, SOL_SOCKET, SO_SNDBUF,
+               (const char *)&ideal, sizeof(ideal));
+  }
+}
+#else
+#define win_update_buffer_size(x)
+#endif
+
+/*
+ * Send data to upload to the server, when the socket is writable.
+ */
+static CURLcode readwrite_upload(struct Curl_easy *data,
+                                 struct connectdata *conn,
+                                 int *didwhat)
+{
+  ssize_t i, si;
+  ssize_t bytes_written;
+  CURLcode result;
+  ssize_t nread; /* number of bytes read */
+  bool sending_http_headers = FALSE;
+  struct SingleRequest *k = &data->req;
+
+  if((k->bytecount == 0) && (k->writebytecount == 0))
+    Curl_pgrsTime(data, TIMER_STARTTRANSFER);
+
+  *didwhat |= KEEP_SEND;
+
+  do {
+    /* only read more data if there's no upload data already
+       present in the upload buffer */
+    if(0 == k->upload_present) {
+      result = Curl_get_upload_buffer(data);
+      if(result)
+        return result;
+      /* init the "upload from here" pointer */
+      k->upload_fromhere = data->state.ulbuf;
+
+      if(!k->upload_done) {
+        /* HTTP pollution, this should be written nicer to become more
+           protocol agnostic. */
+        size_t fillcount;
+        struct HTTP *http = k->p.http;
+
+        if((k->exp100 == EXP100_SENDING_REQUEST) &&
+           (http->sending == HTTPSEND_BODY)) {
+          /* If this call is to send body data, we must take some action:
+             We have sent off the full HTTP 1.1 request, and we shall now
+             go into the Expect: 100 state and await such a header */
+          k->exp100 = EXP100_AWAITING_CONTINUE; /* wait for the header */
+          k->keepon &= ~KEEP_SEND;         /* disable writing */
+          k->start100 = Curl_now();       /* timeout count starts now */
+          *didwhat &= ~KEEP_SEND;  /* we didn't write anything actually */
+          /* set a timeout for the multi interface */
+          Curl_expire(data, data->set.expect_100_timeout, EXPIRE_100_TIMEOUT);
+          break;
+        }
+
+        if(conn->handler->protocol&(PROTO_FAMILY_HTTP|CURLPROTO_RTSP)) {
+          if(http->sending == HTTPSEND_REQUEST)
+            /* We're sending the HTTP request headers, not the data.
+               Remember that so we don't change the line endings. */
+            sending_http_headers = TRUE;
+          else
+            sending_http_headers = FALSE;
+        }
+
+        result = Curl_fillreadbuffer(conn, data->set.upload_buffer_size,
+                                     &fillcount);
+        if(result)
+          return result;
+
+        nread = fillcount;
+      }
+      else
+        nread = 0; /* we're done uploading/reading */
+
+      if(!nread && (k->keepon & KEEP_SEND_PAUSE)) {
+        /* this is a paused transfer */
+        break;
+      }
+      if(nread <= 0) {
+        result = Curl_done_sending(conn, k);
+        if(result)
+          return result;
+        break;
+      }
+
+      /* store number of bytes available for upload */
+      k->upload_present = nread;
+
+      /* convert LF to CRLF if so asked */
+      if((!sending_http_headers) && (
+#ifdef CURL_DO_LINEEND_CONV
+         /* always convert if we're FTPing in ASCII mode */
+         (data->set.prefer_ascii) ||
+#endif
+         (data->set.crlf))) {
+        /* Do we need to allocate a scratch buffer? */
+        if(!data->state.scratch) {
+          data->state.scratch = malloc(2 * data->set.upload_buffer_size);
+          if(!data->state.scratch) {
+            failf(data, "Failed to alloc scratch buffer!");
+
+            return CURLE_OUT_OF_MEMORY;
+          }
+        }
+
+        /*
+         * ASCII/EBCDIC Note: This is presumably a text (not binary)
+         * transfer so the data should already be in ASCII.
+         * That means the hex values for ASCII CR (0x0d) & LF (0x0a)
+         * must be used instead of the escape sequences \r & \n.
+         */
+        for(i = 0, si = 0; i < nread; i++, si++) {
+          if(k->upload_fromhere[i] == 0x0a) {
+            data->state.scratch[si++] = 0x0d;
+            data->state.scratch[si] = 0x0a;
+            if(!data->set.crlf) {
+              /* we're here only because FTP is in ASCII mode...
+                 bump infilesize for the LF we just added */
+              if(data->state.infilesize != -1)
+                data->state.infilesize++;
+            }
+          }
+          else
+            data->state.scratch[si] = k->upload_fromhere[i];
+        }
+
+        if(si != nread) {
+          /* only perform the special operation if we really did replace
+             anything */
+          nread = si;
+
+          /* upload from the new (replaced) buffer instead */
+          k->upload_fromhere = data->state.scratch;
+
+          /* set the new amount too */
+          k->upload_present = nread;
+        }
+      }
+
+#ifndef CURL_DISABLE_SMTP
+      if(conn->handler->protocol & PROTO_FAMILY_SMTP) {
+        result = Curl_smtp_escape_eob(conn, nread);
+        if(result)
+          return result;
+      }
+#endif /* CURL_DISABLE_SMTP */
+    } /* if 0 == k->upload_present */
+    else {
+      /* We have a partial buffer left from a previous "round". Use
+         that instead of reading more data */
+    }
+
+    /* write to socket (send away data) */
+    result = Curl_write(conn,
+                        conn->writesockfd,  /* socket to send to */
+                        k->upload_fromhere, /* buffer pointer */
+                        k->upload_present,  /* buffer size */
+                        &bytes_written);    /* actually sent */
+    if(result)
+      return result;
+
+    win_update_buffer_size(conn->writesockfd);
+
+    /* show the data before we change the pointer upload_fromhere */
+    Curl_debug(data, CURLINFO_DATA_OUT, k->upload_fromhere,
+               (size_t)bytes_written);
+
+    k->writebytecount += bytes_written;
+    Curl_pgrsSetUploadCounter(data, k->writebytecount);
+
+    if((!k->upload_chunky || k->forbidchunk) &&
+       (k->writebytecount == data->state.infilesize)) {
+      /* we have sent all data we were supposed to */
+      k->upload_done = TRUE;
+      infof(data, "We are completely uploaded and fine\n");
+    }
+
+    if(k->upload_present != bytes_written) {
+      /* we only wrote a part of the buffer (if anything), deal with it! */
+
+      /* store the amount of bytes left in the buffer to write */
+      k->upload_present -= bytes_written;
+
+      /* advance the pointer where to find the buffer when the next send
+         is to happen */
+      k->upload_fromhere += bytes_written;
+    }
+    else {
+      /* we've uploaded that buffer now */
+      result = Curl_get_upload_buffer(data);
+      if(result)
+        return result;
+      k->upload_fromhere = data->state.ulbuf;
+      k->upload_present = 0; /* no more bytes left */
+
+      if(k->upload_done) {
+        result = Curl_done_sending(conn, k);
+        if(result)
+          return result;
+      }
+    }
+
+
+  } while(0); /* just to break out from! */
+
+  return CURLE_OK;
+}
+
+/*
+ * Curl_readwrite() is the low-level function to be called when data is to
+ * be read and written to/from the connection.
+ *
+ * return '*comeback' TRUE if we didn't properly drain the socket so this
+ * function should get called again without select() or similar in between!
+ */
+CURLcode Curl_readwrite(struct connectdata *conn,
+                        struct Curl_easy *data,
+                        bool *done,
+                        bool *comeback)
+{
+  struct SingleRequest *k = &data->req;
+  CURLcode result;
+  int didwhat = 0;
+
+  curl_socket_t fd_read;
+  curl_socket_t fd_write;
+  int select_res = conn->cselect_bits;
+
+  conn->cselect_bits = 0;
+
+  /* only use the proper socket if the *_HOLD bit is not set simultaneously as
+     then we are in rate limiting state in that transfer direction */
+
+  if((k->keepon & KEEP_RECVBITS) == KEEP_RECV)
+    fd_read = conn->sockfd;
+  else
+    fd_read = CURL_SOCKET_BAD;
+
+  if((k->keepon & KEEP_SENDBITS) == KEEP_SEND)
+    fd_write = conn->writesockfd;
+  else
+    fd_write = CURL_SOCKET_BAD;
+
+  if(conn->data->state.drain) {
+    select_res |= CURL_CSELECT_IN;
+    DEBUGF(infof(data, "Curl_readwrite: forcibly told to drain data\n"));
+  }
+
+  if(!select_res) /* Call for select()/poll() only, if read/write/error
+                     status is not known. */
+    select_res = Curl_socket_check(fd_read, CURL_SOCKET_BAD, fd_write, 0);
+
+  if(select_res == CURL_CSELECT_ERR) {
+    failf(data, "select/poll returned error");
+    return CURLE_SEND_ERROR;
+  }
+
+  /* We go ahead and do a read if we have a readable socket or if
+     the stream was rewound (in which case we have data in a
+     buffer) */
+  if((k->keepon & KEEP_RECV) && (select_res & CURL_CSELECT_IN)) {
+    result = readwrite_data(data, conn, k, &didwhat, done, comeback);
+    if(result || *done)
+      return result;
+  }
+
+  /* If we still have writing to do, we check if we have a writable socket. */
+  if((k->keepon & KEEP_SEND) && (select_res & CURL_CSELECT_OUT)) {
+    /* write */
+
+    result = readwrite_upload(data, conn, &didwhat);
+    if(result)
+      return result;
+  }
+
+  k->now = Curl_now();
+  if(didwhat) {
+    ;
+  }
+  else {
+    /* no read no write, this is a timeout? */
+    if(k->exp100 == EXP100_AWAITING_CONTINUE) {
+      /* This should allow some time for the header to arrive, but only a
+         very short time as otherwise it'll be too much wasted time too
+         often. */
+
+      /* Quoting RFC2616, section "8.2.3 Use of the 100 (Continue) Status":
+
+         Therefore, when a client sends this header field to an origin server
+         (possibly via a proxy) from which it has never seen a 100 (Continue)
+         status, the client SHOULD NOT wait for an indefinite period before
+         sending the request body.
+
+      */
+
+      timediff_t ms = Curl_timediff(k->now, k->start100);
+      if(ms >= data->set.expect_100_timeout) {
+        /* we've waited long enough, continue anyway */
+        k->exp100 = EXP100_SEND_DATA;
+        k->keepon |= KEEP_SEND;
+        Curl_expire_done(data, EXPIRE_100_TIMEOUT);
+        infof(data, "Done waiting for 100-continue\n");
+      }
+    }
+  }
+
+  if(Curl_pgrsUpdate(conn))
+    result = CURLE_ABORTED_BY_CALLBACK;
+  else
+    result = Curl_speedcheck(data, k->now);
+  if(result)
+    return result;
+
+  if(k->keepon) {
+    if(0 > Curl_timeleft(data, &k->now, FALSE)) {
+      if(k->size != -1) {
+        failf(data, "Operation timed out after %" CURL_FORMAT_TIMEDIFF_T
+              " milliseconds with %" CURL_FORMAT_CURL_OFF_T " out of %"
+              CURL_FORMAT_CURL_OFF_T " bytes received",
+              Curl_timediff(k->now, data->progress.t_startsingle),
+              k->bytecount, k->size);
+      }
+      else {
+        failf(data, "Operation timed out after %" CURL_FORMAT_TIMEDIFF_T
+              " milliseconds with %" CURL_FORMAT_CURL_OFF_T " bytes received",
+              Curl_timediff(k->now, data->progress.t_startsingle),
+              k->bytecount);
+      }
+      return CURLE_OPERATION_TIMEDOUT;
+    }
+  }
+  else {
+    /*
+     * The transfer has been performed. Just make some general checks before
+     * returning.
+     */
+
+    if(!(data->set.opt_no_body) && (k->size != -1) &&
+       (k->bytecount != k->size) &&
+#ifdef CURL_DO_LINEEND_CONV
+       /* Most FTP servers don't adjust their file SIZE response for CRLFs,
+          so we'll check to see if the discrepancy can be explained
+          by the number of CRLFs we've changed to LFs.
+       */
+       (k->bytecount != (k->size + data->state.crlf_conversions)) &&
+#endif /* CURL_DO_LINEEND_CONV */
+       !k->newurl) {
+      failf(data, "transfer closed with %" CURL_FORMAT_CURL_OFF_T
+            " bytes remaining to read", k->size - k->bytecount);
+      return CURLE_PARTIAL_FILE;
+    }
+    if(!(data->set.opt_no_body) && k->chunk &&
+       (conn->chunk.state != CHUNK_STOP)) {
+      /*
+       * In chunked mode, return an error if the connection is closed prior to
+       * the empty (terminating) chunk is read.
+       *
+       * The condition above used to check for
+       * conn->proto.http->chunk.datasize != 0 which is true after reading
+       * *any* chunk, not just the empty chunk.
+       *
+       */
+      failf(data, "transfer closed with outstanding read data remaining");
+      return CURLE_PARTIAL_FILE;
+    }
+    if(Curl_pgrsUpdate(conn))
+      return CURLE_ABORTED_BY_CALLBACK;
+  }
+
+  /* Now update the "done" boolean we return */
+  *done = (0 == (k->keepon&(KEEP_RECV|KEEP_SEND|
+                            KEEP_RECV_PAUSE|KEEP_SEND_PAUSE))) ? TRUE : FALSE;
+
+  return CURLE_OK;
+}
+
+/*
+ * Curl_single_getsock() gets called by the multi interface code when the app
+ * has requested to get the sockets for the current connection. This function
+ * will then be called once for every connection that the multi interface
+ * keeps track of. This function will only be called for connections that are
+ * in the proper state to have this information available.
+ */
+int Curl_single_getsock(const struct connectdata *conn,
+                        curl_socket_t *sock)
+{
+  const struct Curl_easy *data = conn->data;
+  int bitmap = GETSOCK_BLANK;
+  unsigned sockindex = 0;
+
+  if(conn->handler->perform_getsock)
+    return conn->handler->perform_getsock(conn, sock);
+
+  /* don't include HOLD and PAUSE connections */
+  if((data->req.keepon & KEEP_RECVBITS) == KEEP_RECV) {
+
+    DEBUGASSERT(conn->sockfd != CURL_SOCKET_BAD);
+
+    bitmap |= GETSOCK_READSOCK(sockindex);
+    sock[sockindex] = conn->sockfd;
+  }
+
+  /* don't include HOLD and PAUSE connections */
+  if((data->req.keepon & KEEP_SENDBITS) == KEEP_SEND) {
+
+    if((conn->sockfd != conn->writesockfd) ||
+       bitmap == GETSOCK_BLANK) {
+      /* only if they are not the same socket and we have a readable
+         one, we increase index */
+      if(bitmap != GETSOCK_BLANK)
+        sockindex++; /* increase index if we need two entries */
+
+      DEBUGASSERT(conn->writesockfd != CURL_SOCKET_BAD);
+
+      sock[sockindex] = conn->writesockfd;
+    }
+
+    bitmap |= GETSOCK_WRITESOCK(sockindex);
+  }
+
+  return bitmap;
+}
+
+/* Curl_init_CONNECT() gets called each time the handle switches to CONNECT
+   which means this gets called once for each subsequent redirect etc */
+void Curl_init_CONNECT(struct Curl_easy *data)
+{
+  data->state.fread_func = data->set.fread_func_set;
+  data->state.in = data->set.in_set;
+}
+
+/*
+ * Curl_pretransfer() is called immediately before a transfer starts, and only
+ * once for one transfer no matter if it has redirects or do multi-pass
+ * authentication etc.
+ */
+CURLcode Curl_pretransfer(struct Curl_easy *data)
+{
+  CURLcode result;
+
+  if(!data->change.url && !data->set.uh) {
+    /* we can't do anything without URL */
+    failf(data, "No URL set!");
+    return CURLE_URL_MALFORMAT;
+  }
+
+  /* since the URL may have been redirected in a previous use of this handle */
+  if(data->change.url_alloc) {
+    /* the already set URL is allocated, free it first! */
+    Curl_safefree(data->change.url);
+    data->change.url_alloc = FALSE;
+  }
+
+  if(!data->change.url && data->set.uh) {
+    CURLUcode uc;
+    free(data->set.str[STRING_SET_URL]);
+    uc = curl_url_get(data->set.uh,
+                      CURLUPART_URL, &data->set.str[STRING_SET_URL], 0);
+    if(uc) {
+      failf(data, "No URL set!");
+      return CURLE_URL_MALFORMAT;
+    }
+  }
+
+  data->state.httpreq = data->set.method;
+  data->change.url = data->set.str[STRING_SET_URL];
+
+  /* Init the SSL session ID cache here. We do it here since we want to do it
+     after the *_setopt() calls (that could specify the size of the cache) but
+     before any transfer takes place. */
+  result = Curl_ssl_initsessions(data, data->set.general_ssl.max_ssl_sessions);
+  if(result)
+    return result;
+
+  data->state.wildcardmatch = data->set.wildcard_enabled;
+  data->set.followlocation = 0; /* reset the location-follow counter */
+  data->state.this_is_a_follow = FALSE; /* reset this */
+  data->state.errorbuf = FALSE; /* no error has occurred */
+  data->state.httpversion = 0; /* don't assume any particular server version */
+
+  data->state.authproblem = FALSE;
+  data->state.authhost.want = data->set.httpauth;
+  data->state.authproxy.want = data->set.proxyauth;
+  Curl_safefree(data->info.wouldredirect);
+
+  if(data->state.httpreq == HTTPREQ_PUT)
+    data->state.infilesize = data->set.filesize;
+  else if((data->state.httpreq != HTTPREQ_GET) &&
+          (data->state.httpreq != HTTPREQ_HEAD)) {
+    data->state.infilesize = data->set.postfieldsize;
+    if(data->set.postfields && (data->state.infilesize == -1))
+      data->state.infilesize = (curl_off_t)strlen(data->set.postfields);
+  }
+  else
+    data->state.infilesize = 0;
+
+  /* If there is a list of cookie files to read, do it now! */
+  if(data->change.cookielist)
+    Curl_cookie_loadfiles(data);
+
+  /* If there is a list of host pairs to deal with */
+  if(data->change.resolve)
+    result = Curl_loadhostpairs(data);
+
+  if(!result) {
+    /* Allow data->set.use_port to set which port to use. This needs to be
+     * disabled for example when we follow Location: headers to URLs using
+     * different ports! */
+    data->state.allow_port = TRUE;
+
+#if defined(HAVE_SIGNAL) && defined(SIGPIPE) && !defined(HAVE_MSG_NOSIGNAL)
+    /*************************************************************
+     * Tell signal handler to ignore SIGPIPE
+     *************************************************************/
+    if(!data->set.no_signal)
+      data->state.prev_signal = signal(SIGPIPE, SIG_IGN);
+#endif
+
+    Curl_initinfo(data); /* reset session-specific information "variables" */
+    Curl_pgrsResetTransferSizes(data);
+    Curl_pgrsStartNow(data);
+
+    /* In case the handle is re-used and an authentication method was picked
+       in the session we need to make sure we only use the one(s) we now
+       consider to be fine */
+    data->state.authhost.picked &= data->state.authhost.want;
+    data->state.authproxy.picked &= data->state.authproxy.want;
+
+#ifndef CURL_DISABLE_FTP
+    if(data->state.wildcardmatch) {
+      struct WildcardData *wc = &data->wildcard;
+      if(wc->state < CURLWC_INIT) {
+        result = Curl_wildcard_init(wc); /* init wildcard structures */
+        if(result)
+          return CURLE_OUT_OF_MEMORY;
+      }
+    }
+#endif
+    Curl_http2_init_state(&data->state);
+    Curl_hsts_loadcb(data, data->hsts);
+  }
+
+  return result;
+}
+
+/*
+ * Curl_posttransfer() is called immediately after a transfer ends
+ */
+CURLcode Curl_posttransfer(struct Curl_easy *data)
+{
+#if defined(HAVE_SIGNAL) && defined(SIGPIPE) && !defined(HAVE_MSG_NOSIGNAL)
+  /* restore the signal handler for SIGPIPE before we get back */
+  if(!data->set.no_signal)
+    signal(SIGPIPE, data->state.prev_signal);
+#else
+  (void)data; /* unused parameter */
+#endif
+
+  return CURLE_OK;
+}
+
+/*
+ * Curl_follow() handles the URL redirect magic. Pass in the 'newurl' string
+ * as given by the remote server and set up the new URL to request.
+ *
+ * This function DOES NOT FREE the given url.
+ */
+CURLcode Curl_follow(struct Curl_easy *data,
+                     char *newurl,    /* the Location: string */
+                     followtype type) /* see transfer.h */
+{
+#ifdef CURL_DISABLE_HTTP
+  (void)data;
+  (void)newurl;
+  (void)type;
+  /* Location: following will not happen when HTTP is disabled */
+  return CURLE_TOO_MANY_REDIRECTS;
+#else
+
+  /* Location: redirect */
+  bool disallowport = FALSE;
+  bool reachedmax = FALSE;
+  CURLUcode uc;
+
+  if(type == FOLLOW_REDIR) {
+    if((data->set.maxredirs != -1) &&
+       (data->set.followlocation >= data->set.maxredirs)) {
+      reachedmax = TRUE;
+      type = FOLLOW_FAKE; /* switch to fake to store the would-be-redirected
+                             to URL */
+    }
+    else {
+      /* mark the next request as a followed location: */
+      data->state.this_is_a_follow = TRUE;
+
+      data->set.followlocation++; /* count location-followers */
+
+      if(data->set.http_auto_referer) {
+        /* We are asked to automatically set the previous URL as the referer
+           when we get the next URL. We pick the ->url field, which may or may
+           not be 100% correct */
+
+        if(data->change.referer_alloc) {
+          Curl_safefree(data->change.referer);
+          data->change.referer_alloc = FALSE;
+        }
+
+        data->change.referer = strdup(data->change.url);
+        if(!data->change.referer)
+          return CURLE_OUT_OF_MEMORY;
+        data->change.referer_alloc = TRUE; /* yes, free this later */
+      }
+    }
+  }
+
+  if(Curl_is_absolute_url(newurl, NULL, MAX_SCHEME_LEN))
+    /* This is an absolute URL, don't allow the custom port number */
+    disallowport = TRUE;
+
+  DEBUGASSERT(data->state.uh);
+  uc = curl_url_set(data->state.uh, CURLUPART_URL, newurl,
+                    (type == FOLLOW_FAKE) ? CURLU_NON_SUPPORT_SCHEME :
+                    ((type == FOLLOW_REDIR) ? CURLU_URLENCODE : 0) );
+  if(uc) {
+    if(type != FOLLOW_FAKE)
+      return Curl_uc_to_curlcode(uc);
+
+    /* the URL could not be parsed for some reason, but since this is FAKE
+       mode, just duplicate the field as-is */
+    newurl = strdup(newurl);
+    if(!newurl)
+      return CURLE_OUT_OF_MEMORY;
+  }
+  else {
+
+    uc = curl_url_get(data->state.uh, CURLUPART_URL, &newurl, 0);
+    if(uc)
+      return Curl_uc_to_curlcode(uc);
+  }
+
+  if(type == FOLLOW_FAKE) {
+    /* we're only figuring out the new url if we would've followed locations
+       but now we're done so we can get out! */
+    data->info.wouldredirect = newurl;
+
+    if(reachedmax) {
+      failf(data, "Maximum (%ld) redirects followed", data->set.maxredirs);
+      return CURLE_TOO_MANY_REDIRECTS;
+    }
+    return CURLE_OK;
+  }
+
+  if(disallowport)
+    data->state.allow_port = FALSE;
+
+  if(data->change.url_alloc)
+    Curl_safefree(data->change.url);
+
+  data->change.url = newurl;
+  data->change.url_alloc = TRUE;
+
+  infof(data, "Issue another request to this URL: '%s'\n", data->change.url);
+
+  /*
+   * We get here when the HTTP code is 300-399 (and 401). We need to perform
+   * differently based on exactly what return code there was.
+   *
+   * News from 7.10.6: we can also get here on a 401 or 407, in case we act on
+   * a HTTP (proxy-) authentication scheme other than Basic.
+   */
+  switch(data->info.httpcode) {
+    /* 401 - Act on a WWW-Authenticate, we keep on moving and do the
+       Authorization: XXXX header in the HTTP request code snippet */
+    /* 407 - Act on a Proxy-Authenticate, we keep on moving and do the
+       Proxy-Authorization: XXXX header in the HTTP request code snippet */
+    /* 300 - Multiple Choices */
+    /* 306 - Not used */
+    /* 307 - Temporary Redirect */
+  default:  /* for all above (and the unknown ones) */
+    /* Some codes are explicitly mentioned since I've checked RFC2616 and they
+     * seem to be OK to POST to.
+     */
+    break;
+  case 301: /* Moved Permanently */
+    /* (quote from RFC7231, section 6.4.2)
+     *
+     * Note: For historical reasons, a user agent MAY change the request
+     * method from POST to GET for the subsequent request.  If this
+     * behavior is undesired, the 307 (Temporary Redirect) status code
+     * can be used instead.
+     *
+     * ----
+     *
+     * Many webservers expect this, so these servers often answers to a POST
+     * request with an error page. To be sure that libcurl gets the page that
+     * most user agents would get, libcurl has to force GET.
+     *
+     * This behaviour is forbidden by RFC1945 and the obsolete RFC2616, and
+     * can be overridden with CURLOPT_POSTREDIR.
+     */
+    if((data->state.httpreq == HTTPREQ_POST
+        || data->state.httpreq == HTTPREQ_POST_FORM
+        || data->state.httpreq == HTTPREQ_POST_MIME)
+       && !(data->set.keep_post & CURL_REDIR_POST_301)) {
+      infof(data, "Switch from POST to GET\n");
+      data->state.httpreq = HTTPREQ_GET;
+    }
+    break;
+  case 302: /* Found */
+    /* (quote from RFC7231, section 6.4.3)
+     *
+     * Note: For historical reasons, a user agent MAY change the request
+     * method from POST to GET for the subsequent request.  If this
+     * behavior is undesired, the 307 (Temporary Redirect) status code
+     * can be used instead.
+     *
+     * ----
+     *
+     * Many webservers expect this, so these servers often answers to a POST
+     * request with an error page. To be sure that libcurl gets the page that
+     * most user agents would get, libcurl has to force GET.
+     *
+     * This behaviour is forbidden by RFC1945 and the obsolete RFC2616, and
+     * can be overridden with CURLOPT_POSTREDIR.
+     */
+    if((data->state.httpreq == HTTPREQ_POST
+        || data->state.httpreq == HTTPREQ_POST_FORM
+        || data->state.httpreq == HTTPREQ_POST_MIME)
+       && !(data->set.keep_post & CURL_REDIR_POST_302)) {
+      infof(data, "Switch from POST to GET\n");
+      data->state.httpreq = HTTPREQ_GET;
+    }
+    break;
+
+  case 303: /* See Other */
+    /* 'See Other' location is not the resource but a substitute for the
+     * resource. In this case we switch the method to GET/HEAD, unless the
+     * method is POST and the user specified to keep it as POST.
+     * https://github.com/curl/curl/issues/5237#issuecomment-614641049
+     */
+    if(data->state.httpreq != HTTPREQ_GET &&
+       ((data->state.httpreq != HTTPREQ_POST &&
+         data->state.httpreq != HTTPREQ_POST_FORM &&
+         data->state.httpreq != HTTPREQ_POST_MIME) ||
+        !(data->set.keep_post & CURL_REDIR_POST_303))) {
+      data->state.httpreq = HTTPREQ_GET;
+      data->set.upload = false;
+      infof(data, "Switch to %s\n",
+            data->set.opt_no_body?"HEAD":"GET");
+    }
+    break;
+  case 304: /* Not Modified */
+    /* 304 means we did a conditional request and it was "Not modified".
+     * We shouldn't get any Location: header in this response!
+     */
+    break;
+  case 305: /* Use Proxy */
+    /* (quote from RFC2616, section 10.3.6):
+     * "The requested resource MUST be accessed through the proxy given
+     * by the Location field. The Location field gives the URI of the
+     * proxy.  The recipient is expected to repeat this single request
+     * via the proxy. 305 responses MUST only be generated by origin
+     * servers."
+     */
+    break;
+  }
+  Curl_pgrsTime(data, TIMER_REDIRECT);
+  Curl_pgrsResetTransferSizes(data);
+
+  return CURLE_OK;
+#endif /* CURL_DISABLE_HTTP */
+}
+
+/* Returns CURLE_OK *and* sets '*url' if a request retry is wanted.
+
+   NOTE: that the *url is malloc()ed. */
+CURLcode Curl_retry_request(struct connectdata *conn,
+                            char **url)
+{
+  struct Curl_easy *data = conn->data;
+  bool retry = FALSE;
+  *url = NULL;
+
+  /* if we're talking upload, we can't do the checks below, unless the protocol
+     is HTTP as when uploading over HTTP we will still get a response */
+  if(data->set.upload &&
+     !(conn->handler->protocol&(PROTO_FAMILY_HTTP|CURLPROTO_RTSP)))
+    return CURLE_OK;
+
+  if((data->req.bytecount + data->req.headerbytecount == 0) &&
+      conn->bits.reuse &&
+      (!data->set.opt_no_body
+        || (conn->handler->protocol & PROTO_FAMILY_HTTP)) &&
+      (data->set.rtspreq != RTSPREQ_RECEIVE))
+    /* We got no data, we attempted to re-use a connection. For HTTP this
+       can be a retry so we try again regardless if we expected a body.
+       For other protocols we only try again only if we expected a body.
+
+       This might happen if the connection was left alive when we were
+       done using it before, but that was closed when we wanted to read from
+       it again. Bad luck. Retry the same request on a fresh connect! */
+    retry = TRUE;
+  else if(data->state.refused_stream &&
+          (data->req.bytecount + data->req.headerbytecount == 0) ) {
+    /* This was sent on a refused stream, safe to rerun. A refused stream
+       error can typically only happen on HTTP/2 level if the stream is safe
+       to issue again, but the nghttp2 API can deliver the message to other
+       streams as well, which is why this adds the check the data counters
+       too. */
+    infof(conn->data, "REFUSED_STREAM, retrying a fresh connect\n");
+    data->state.refused_stream = FALSE; /* clear again */
+    retry = TRUE;
+  }
+  if(retry) {
+#define CONN_MAX_RETRIES 5
+    if(data->state.retrycount++ >= CONN_MAX_RETRIES) {
+      failf(data, "Connection died, tried %d times before giving up",
+            CONN_MAX_RETRIES);
+      data->state.retrycount = 0;
+      return CURLE_SEND_ERROR;
+    }
+    infof(conn->data, "Connection died, retrying a fresh connect\
+(retry count: %d)\n", data->state.retrycount);
+    *url = strdup(conn->data->change.url);
+    if(!*url)
+      return CURLE_OUT_OF_MEMORY;
+
+    connclose(conn, "retry"); /* close this connection */
+    conn->bits.retry = TRUE; /* mark this as a connection we're about
+                                to retry. Marking it this way should
+                                prevent i.e HTTP transfers to return
+                                error just because nothing has been
+                                transferred! */
+
+
+    if(conn->handler->protocol&PROTO_FAMILY_HTTP) {
+      if(data->req.writebytecount) {
+        CURLcode result = Curl_readrewind(conn);
+        if(result) {
+          Curl_safefree(*url);
+          return result;
+        }
+      }
+    }
+  }
+  return CURLE_OK;
+}
+
+/*
+ * Curl_setup_transfer() is called to setup some basic properties for the
+ * upcoming transfer.
+ */
+void
+Curl_setup_transfer(
+  struct Curl_easy *data,   /* transfer */
+  int sockindex,            /* socket index to read from or -1 */
+  curl_off_t size,          /* -1 if unknown at this point */
+  bool getheader,           /* TRUE if header parsing is wanted */
+  int writesockindex        /* socket index to write to, it may very well be
+                               the same we read from. -1 disables */
+  )
+{
+  struct SingleRequest *k = &data->req;
+  struct connectdata *conn = data->conn;
+  struct HTTP *http = data->req.p.http;
+  bool httpsending = ((conn->handler->protocol&PROTO_FAMILY_HTTP) &&
+                      (http->sending == HTTPSEND_REQUEST));
+  DEBUGASSERT(conn != NULL);
+  DEBUGASSERT((sockindex <= 1) && (sockindex >= -1));
+
+  if(conn->bits.multiplex || conn->httpversion == 20 || httpsending) {
+    /* when multiplexing, the read/write sockets need to be the same! */
+    conn->sockfd = sockindex == -1 ?
+      ((writesockindex == -1 ? CURL_SOCKET_BAD : conn->sock[writesockindex])) :
+      conn->sock[sockindex];
+    conn->writesockfd = conn->sockfd;
+    if(httpsending)
+      /* special and very HTTP-specific */
+      writesockindex = FIRSTSOCKET;
+  }
+  else {
+    conn->sockfd = sockindex == -1 ?
+      CURL_SOCKET_BAD : conn->sock[sockindex];
+    conn->writesockfd = writesockindex == -1 ?
+      CURL_SOCKET_BAD:conn->sock[writesockindex];
+  }
+  k->getheader = getheader;
+
+  k->size = size;
+
+  /* The code sequence below is placed in this function just because all
+     necessary input is not always known in do_complete() as this function may
+     be called after that */
+
+  if(!k->getheader) {
+    k->header = FALSE;
+    if(size > 0)
+      Curl_pgrsSetDownloadSize(data, size);
+  }
+  /* we want header and/or body, if neither then don't do this! */
+  if(k->getheader || !data->set.opt_no_body) {
+
+    if(sockindex != -1)
+      k->keepon |= KEEP_RECV;
+
+    if(writesockindex != -1) {
+      /* HTTP 1.1 magic:
+
+         Even if we require a 100-return code before uploading data, we might
+         need to write data before that since the REQUEST may not have been
+         finished sent off just yet.
+
+         Thus, we must check if the request has been sent before we set the
+         state info where we wait for the 100-return code
+      */
+      if((data->state.expect100header) &&
+         (conn->handler->protocol&PROTO_FAMILY_HTTP) &&
+         (http->sending == HTTPSEND_BODY)) {
+        /* wait with write until we either got 100-continue or a timeout */
+        k->exp100 = EXP100_AWAITING_CONTINUE;
+        k->start100 = Curl_now();
+
+        /* Set a timeout for the multi interface. Add the inaccuracy margin so
+           that we don't fire slightly too early and get denied to run. */
+        Curl_expire(data, data->set.expect_100_timeout, EXPIRE_100_TIMEOUT);
+      }
+      else {
+        if(data->state.expect100header)
+          /* when we've sent off the rest of the headers, we must await a
+             100-continue but first finish sending the request */
+          k->exp100 = EXP100_SENDING_REQUEST;
+
+        /* enable the write bit when we're not waiting for continue */
+        k->keepon |= KEEP_SEND;
+      }
+    } /* if(writesockindex != -1) */
+  } /* if(k->getheader || !data->set.opt_no_body) */
+
+}