curl/lib/cfilters.c

/***************************************************************************
 *                                  _   _ ____  _
 *  Project                     ___| | | |  _ \| |
 *                             / __| | | | |_) | |
 *                            | (__| |_| |  _ <| |___
 *                             \___|\___/|_| \_\_____|
 *
 * Copyright (C) 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.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.
 *
 * SPDX-License-Identifier: curl
 *
 ***************************************************************************/

#include "curl_setup.h"

#include "urldata.h"
#include "strerror.h"
#include "cfilters.h"
#include "connect.h"
#include "url.h" /* for Curl_safefree() */
#include "sendf.h"
#include "sockaddr.h" /* required for Curl_sockaddr_storage */
#include "multiif.h"
#include "progress.h"
#include "select.h"
#include "warnless.h"

/* The last 3 #include files should be in this order */
#include "curl_printf.h"
#include "curl_memory.h"
#include "memdebug.h"

#ifndef ARRAYSIZE
#define ARRAYSIZE(A) (sizeof(A)/sizeof((A)[0]))
#endif

#ifdef UNITTESTS
/* used by unit2600.c */
void Curl_cf_def_close(struct Curl_cfilter *cf, struct Curl_easy *data)
{
  cf->connected = FALSE;
  if(cf->next)
    cf->next->cft->do_close(cf->next, data);
}
#endif

CURLcode Curl_cf_def_shutdown(struct Curl_cfilter *cf,
                              struct Curl_easy *data, bool *done)
{
  (void)cf;
  (void)data;
  *done = TRUE;
  return CURLE_OK;
}

static void conn_report_connect_stats(struct Curl_easy *data,
                                      struct connectdata *conn);

void Curl_cf_def_get_host(struct Curl_cfilter *cf, struct Curl_easy *data,
                          const char **phost, const char **pdisplay_host,
                          int *pport)
{
  if(cf->next)
    cf->next->cft->get_host(cf->next, data, phost, pdisplay_host, pport);
  else {
    *phost = cf->conn->host.name;
    *pdisplay_host = cf->conn->host.dispname;
    *pport = cf->conn->primary.remote_port;
  }
}

void Curl_cf_def_adjust_pollset(struct Curl_cfilter *cf,
                                 struct Curl_easy *data,
                                 struct easy_pollset *ps)
{
  /* NOP */
  (void)cf;
  (void)data;
  (void)ps;
}

bool Curl_cf_def_data_pending(struct Curl_cfilter *cf,
                              const struct Curl_easy *data)
{
  return cf->next?
    cf->next->cft->has_data_pending(cf->next, data) : FALSE;
}

ssize_t  Curl_cf_def_send(struct Curl_cfilter *cf, struct Curl_easy *data,
                          const void *buf, size_t len, bool eos,
                          CURLcode *err)
{
  return cf->next?
    cf->next->cft->do_send(cf->next, data, buf, len, eos, err) :
    CURLE_RECV_ERROR;
}

ssize_t  Curl_cf_def_recv(struct Curl_cfilter *cf, struct Curl_easy *data,
                          char *buf, size_t len, CURLcode *err)
{
  return cf->next?
    cf->next->cft->do_recv(cf->next, data, buf, len, err) :
    CURLE_SEND_ERROR;
}

bool Curl_cf_def_conn_is_alive(struct Curl_cfilter *cf,
                               struct Curl_easy *data,
                               bool *input_pending)
{
  return cf->next?
    cf->next->cft->is_alive(cf->next, data, input_pending) :
    FALSE; /* pessimistic in absence of data */
}

CURLcode Curl_cf_def_conn_keep_alive(struct Curl_cfilter *cf,
                                     struct Curl_easy *data)
{
  return cf->next?
    cf->next->cft->keep_alive(cf->next, data) :
    CURLE_OK;
}

CURLcode Curl_cf_def_query(struct Curl_cfilter *cf,
                           struct Curl_easy *data,
                           int query, int *pres1, void *pres2)
{
  return cf->next?
    cf->next->cft->query(cf->next, data, query, pres1, pres2) :
    CURLE_UNKNOWN_OPTION;
}

void Curl_conn_cf_discard_chain(struct Curl_cfilter **pcf,
                                struct Curl_easy *data)
{
  struct Curl_cfilter *cfn, *cf = *pcf;

  if(cf) {
    *pcf = NULL;
    while(cf) {
      cfn = cf->next;
      /* prevent destroying filter to mess with its sub-chain, since
       * we have the reference now and will call destroy on it.
       */
      cf->next = NULL;
      cf->cft->destroy(cf, data);
      free(cf);
      cf = cfn;
    }
  }
}

void Curl_conn_cf_discard_all(struct Curl_easy *data,
                              struct connectdata *conn, int index)
{
  Curl_conn_cf_discard_chain(&conn->cfilter[index], data);
}

void Curl_conn_close(struct Curl_easy *data, int index)
{
  struct Curl_cfilter *cf;

  DEBUGASSERT(data->conn);
  /* it is valid to call that without filters being present */
  cf = data->conn->cfilter[index];
  if(cf) {
    cf->cft->do_close(cf, data);
  }
  Curl_shutdown_clear(data, index);
}

CURLcode Curl_conn_shutdown(struct Curl_easy *data, int sockindex, bool *done)
{
  struct Curl_cfilter *cf;
  CURLcode result = CURLE_OK;
  timediff_t timeout_ms;
  struct curltime now;

  DEBUGASSERT(data->conn);
  /* Get the first connected filter that is not shut down already. */
  cf = data->conn->cfilter[sockindex];
  while(cf && (!cf->connected || cf->shutdown))
    cf = cf->next;

  if(!cf) {
    *done = TRUE;
    return CURLE_OK;
  }

  *done = FALSE;
  now = Curl_now();
  if(!Curl_shutdown_started(data, sockindex)) {
    DEBUGF(infof(data, "shutdown start on%s connection",
           sockindex? " secondary" : ""));
    Curl_shutdown_start(data, sockindex, &now);
  }
  else {
    timeout_ms = Curl_shutdown_timeleft(data->conn, sockindex, &now);
    if(timeout_ms < 0) {
      failf(data, "SSL shutdown timeout");
      return CURLE_OPERATION_TIMEDOUT;
    }
  }

  while(cf) {
    if(!cf->shutdown) {
      bool cfdone = FALSE;
      result = cf->cft->do_shutdown(cf, data, &cfdone);
      if(result) {
        CURL_TRC_CF(data, cf, "shut down failed with %d", result);
        return result;
      }
      else if(!cfdone) {
        CURL_TRC_CF(data, cf, "shut down not done yet");
        return CURLE_OK;
      }
      CURL_TRC_CF(data, cf, "shut down successfully");
      cf->shutdown = TRUE;
    }
    cf = cf->next;
  }
  *done = (!result);
  return result;
}

ssize_t Curl_cf_recv(struct Curl_easy *data, int num, char *buf,
                     size_t len, CURLcode *code)
{
  struct Curl_cfilter *cf;

  DEBUGASSERT(data);
  DEBUGASSERT(data->conn);
  *code = CURLE_OK;
  cf = data->conn->cfilter[num];
  while(cf && !cf->connected) {
    cf = cf->next;
  }
  if(cf) {
    ssize_t nread = cf->cft->do_recv(cf, data, buf, len, code);
    DEBUGASSERT(nread >= 0 || *code);
    DEBUGASSERT(nread < 0 || !*code);
    return nread;
  }
  failf(data, "recv: no filter connected");
  *code = CURLE_FAILED_INIT;
  return -1;
}

ssize_t Curl_cf_send(struct Curl_easy *data, int num,
                     const void *mem, size_t len, bool eos,
                     CURLcode *code)
{
  struct Curl_cfilter *cf;

  DEBUGASSERT(data);
  DEBUGASSERT(data->conn);
  *code = CURLE_OK;
  cf = data->conn->cfilter[num];
  while(cf && !cf->connected) {
    cf = cf->next;
  }
  if(cf) {
    ssize_t nwritten = cf->cft->do_send(cf, data, mem, len, eos, code);
    DEBUGASSERT(nwritten >= 0 || *code);
    DEBUGASSERT(nwritten < 0 || !*code || !len);
    return nwritten;
  }
  failf(data, "send: no filter connected");
  DEBUGASSERT(0);
  *code = CURLE_FAILED_INIT;
  return -1;
}

CURLcode Curl_cf_create(struct Curl_cfilter **pcf,
                        const struct Curl_cftype *cft,
                        void *ctx)
{
  struct Curl_cfilter *cf;
  CURLcode result = CURLE_OUT_OF_MEMORY;

  DEBUGASSERT(cft);
  cf = calloc(1, sizeof(*cf));
  if(!cf)
    goto out;

  cf->cft = cft;
  cf->ctx = ctx;
  result = CURLE_OK;
out:
  *pcf = cf;
  return result;
}

void Curl_conn_cf_add(struct Curl_easy *data,
                      struct connectdata *conn,
                      int index,
                      struct Curl_cfilter *cf)
{
  (void)data;
  DEBUGASSERT(conn);
  DEBUGASSERT(!cf->conn);
  DEBUGASSERT(!cf->next);

  cf->next = conn->cfilter[index];
  cf->conn = conn;
  cf->sockindex = index;
  conn->cfilter[index] = cf;
  CURL_TRC_CF(data, cf, "added");
}

void Curl_conn_cf_insert_after(struct Curl_cfilter *cf_at,
                               struct Curl_cfilter *cf_new)
{
  struct Curl_cfilter *tail, **pnext;

  DEBUGASSERT(cf_at);
  DEBUGASSERT(cf_new);
  DEBUGASSERT(!cf_new->conn);

  tail = cf_at->next;
  cf_at->next = cf_new;
  do {
    cf_new->conn = cf_at->conn;
    cf_new->sockindex = cf_at->sockindex;
    pnext = &cf_new->next;
    cf_new = cf_new->next;
  } while(cf_new);
  *pnext = tail;
}

bool Curl_conn_cf_discard_sub(struct Curl_cfilter *cf,
                              struct Curl_cfilter *discard,
                              struct Curl_easy *data,
                              bool destroy_always)
{
  struct Curl_cfilter **pprev = &cf->next;
  bool found = FALSE;

  /* remove from sub-chain and destroy */
  DEBUGASSERT(cf);
  while(*pprev) {
    if(*pprev == cf) {
      *pprev = discard->next;
      discard->next = NULL;
      found = TRUE;
      break;
    }
    pprev = &((*pprev)->next);
  }
  if(found || destroy_always) {
    discard->next = NULL;
    discard->cft->destroy(discard, data);
    free(discard);
  }
  return found;
}

CURLcode Curl_conn_cf_connect(struct Curl_cfilter *cf,
                              struct Curl_easy *data,
                              bool blocking, bool *done)
{
  if(cf)
    return cf->cft->do_connect(cf, data, blocking, done);
  return CURLE_FAILED_INIT;
}

void Curl_conn_cf_close(struct Curl_cfilter *cf, struct Curl_easy *data)
{
  if(cf)
    cf->cft->do_close(cf, data);
}

ssize_t Curl_conn_cf_send(struct Curl_cfilter *cf, struct Curl_easy *data,
                          const void *buf, size_t len, bool eos,
                          CURLcode *err)
{
  if(cf)
    return cf->cft->do_send(cf, data, buf, len, eos, err);
  *err = CURLE_SEND_ERROR;
  return -1;
}

ssize_t Curl_conn_cf_recv(struct Curl_cfilter *cf, struct Curl_easy *data,
                          char *buf, size_t len, CURLcode *err)
{
  if(cf)
    return cf->cft->do_recv(cf, data, buf, len, err);
  *err = CURLE_RECV_ERROR;
  return -1;
}

CURLcode Curl_conn_connect(struct Curl_easy *data,
                           int sockindex,
                           bool blocking,
                           bool *done)
{
  struct Curl_cfilter *cf;
  CURLcode result = CURLE_OK;

  DEBUGASSERT(data);
  DEBUGASSERT(data->conn);

  cf = data->conn->cfilter[sockindex];
  DEBUGASSERT(cf);
  if(!cf) {
    *done = FALSE;
    return CURLE_FAILED_INIT;
  }

  *done = cf->connected;
  if(!*done) {
    result = cf->cft->do_connect(cf, data, blocking, done);
    if(!result && *done) {
      Curl_conn_ev_update_info(data, data->conn);
      conn_report_connect_stats(data, data->conn);
      data->conn->keepalive = Curl_now();
    }
    else if(result) {
      conn_report_connect_stats(data, data->conn);
    }
  }

  return result;
}

bool Curl_conn_is_connected(struct connectdata *conn, int sockindex)
{
  struct Curl_cfilter *cf;

  cf = conn->cfilter[sockindex];
  return cf && cf->connected;
}

bool Curl_conn_is_ip_connected(struct Curl_easy *data, int sockindex)
{
  struct Curl_cfilter *cf;

  cf = data->conn->cfilter[sockindex];
  while(cf) {
    if(cf->connected)
      return TRUE;
    if(cf->cft->flags & CF_TYPE_IP_CONNECT)
      return FALSE;
    cf = cf->next;
  }
  return FALSE;
}

bool Curl_conn_cf_is_ssl(struct Curl_cfilter *cf)
{
  for(; cf; cf = cf->next) {
    if(cf->cft->flags & CF_TYPE_SSL)
      return TRUE;
    if(cf->cft->flags & CF_TYPE_IP_CONNECT)
      return FALSE;
  }
  return FALSE;
}

bool Curl_conn_is_ssl(struct connectdata *conn, int sockindex)
{
  return conn? Curl_conn_cf_is_ssl(conn->cfilter[sockindex]) : FALSE;
}

bool Curl_conn_is_multiplex(struct connectdata *conn, int sockindex)
{
  struct Curl_cfilter *cf = conn? conn->cfilter[sockindex] : NULL;

  for(; cf; cf = cf->next) {
    if(cf->cft->flags & CF_TYPE_MULTIPLEX)
      return TRUE;
    if(cf->cft->flags & CF_TYPE_IP_CONNECT
       || cf->cft->flags & CF_TYPE_SSL)
      return FALSE;
  }
  return FALSE;
}

bool Curl_conn_data_pending(struct Curl_easy *data, int sockindex)
{
  struct Curl_cfilter *cf;

  (void)data;
  DEBUGASSERT(data);
  DEBUGASSERT(data->conn);

  cf = data->conn->cfilter[sockindex];
  while(cf && !cf->connected) {
    cf = cf->next;
  }
  if(cf) {
    return cf->cft->has_data_pending(cf, data);
  }
  return FALSE;
}

bool Curl_conn_needs_flush(struct Curl_easy *data, int sockindex)
{
  CURLcode result;
  int pending = FALSE;

  struct Curl_cfilter *cf = data->conn->cfilter[sockindex];
  result = cf? cf->cft->query(cf, data, CF_QUERY_NEED_FLUSH,
                              &pending, NULL) : CURLE_UNKNOWN_OPTION;
  return (result || pending == FALSE)? FALSE : TRUE;
}

void Curl_conn_cf_adjust_pollset(struct Curl_cfilter *cf,
                                 struct Curl_easy *data,
                                 struct easy_pollset *ps)
{
  /* Get the lowest not-connected filter, if there are any */
  while(cf && !cf->connected && cf->next && !cf->next->connected)
    cf = cf->next;
  /* Skip all filters that have already shut down */
  while(cf && cf->shutdown)
    cf = cf->next;
  /* From there on, give all filters a chance to adjust the pollset.
   * Lower filters are called later, so they may override */
  while(cf) {
    cf->cft->adjust_pollset(cf, data, ps);
    cf = cf->next;
  }
}

void Curl_conn_adjust_pollset(struct Curl_easy *data,
                               struct easy_pollset *ps)
{
  int i;

  DEBUGASSERT(data);
  DEBUGASSERT(data->conn);
  for(i = 0; i < 2; ++i) {
    Curl_conn_cf_adjust_pollset(data->conn->cfilter[i], data, ps);
  }
}

int Curl_conn_cf_poll(struct Curl_cfilter *cf,
                      struct Curl_easy *data,
                      timediff_t timeout_ms)
{
  struct easy_pollset ps;
  struct pollfd pfds[MAX_SOCKSPEREASYHANDLE];
  unsigned int i, npfds = 0;

  DEBUGASSERT(cf);
  DEBUGASSERT(data);
  DEBUGASSERT(data->conn);
  memset(&ps, 0, sizeof(ps));
  memset(pfds, 0, sizeof(pfds));

  Curl_conn_cf_adjust_pollset(cf, data, &ps);
  DEBUGASSERT(ps.num <= MAX_SOCKSPEREASYHANDLE);
  for(i = 0; i < ps.num; ++i) {
    short events = 0;
    if(ps.actions[i] & CURL_POLL_IN) {
      events |= POLLIN;
    }
    if(ps.actions[i] & CURL_POLL_OUT) {
      events |= POLLOUT;
    }
    if(events) {
      pfds[npfds].fd = ps.sockets[i];
      pfds[npfds].events = events;
      ++npfds;
    }
  }

  if(!npfds)
    DEBUGF(infof(data, "no sockets to poll!"));
  return Curl_poll(pfds, npfds, timeout_ms);
}

void Curl_conn_get_host(struct Curl_easy *data, int sockindex,
                        const char **phost, const char **pdisplay_host,
                        int *pport)
{
  struct Curl_cfilter *cf;

  DEBUGASSERT(data->conn);
  cf = data->conn->cfilter[sockindex];
  if(cf) {
    cf->cft->get_host(cf, data, phost, pdisplay_host, pport);
  }
  else {
    /* Some filter ask during shutdown for this, mainly for debugging
     * purposes. We hand out the defaults, however this is not always
     * accurate, as the connection might be tunneled, etc. But all that
     * state is already gone here. */
    *phost = data->conn->host.name;
    *pdisplay_host = data->conn->host.dispname;
    *pport = data->conn->remote_port;
  }
}

CURLcode Curl_cf_def_cntrl(struct Curl_cfilter *cf,
                                struct Curl_easy *data,
                                int event, int arg1, void *arg2)
{
  (void)cf;
  (void)data;
  (void)event;
  (void)arg1;
  (void)arg2;
  return CURLE_OK;
}

CURLcode Curl_conn_cf_cntrl(struct Curl_cfilter *cf,
                            struct Curl_easy *data,
                            bool ignore_result,
                            int event, int arg1, void *arg2)
{
  CURLcode result = CURLE_OK;

  for(; cf; cf = cf->next) {
    if(Curl_cf_def_cntrl == cf->cft->cntrl)
      continue;
    result = cf->cft->cntrl(cf, data, event, arg1, arg2);
    if(!ignore_result && result)
      break;
  }
  return result;
}

curl_socket_t Curl_conn_cf_get_socket(struct Curl_cfilter *cf,
                                      struct Curl_easy *data)
{
  curl_socket_t sock;
  if(cf && !cf->cft->query(cf, data, CF_QUERY_SOCKET, NULL, &sock))
    return sock;
  return CURL_SOCKET_BAD;
}

curl_socket_t Curl_conn_get_socket(struct Curl_easy *data, int sockindex)
{
  struct Curl_cfilter *cf;

  cf = data->conn? data->conn->cfilter[sockindex] : NULL;
  /* if the top filter has not connected, ask it (and its sub-filters)
   * for the socket. Otherwise conn->sock[sockindex] should have it.
   */
  if(cf && !cf->connected)
    return Curl_conn_cf_get_socket(cf, data);
  return data->conn? data->conn->sock[sockindex] : CURL_SOCKET_BAD;
}

void Curl_conn_forget_socket(struct Curl_easy *data, int sockindex)
{
  if(data->conn) {
    struct Curl_cfilter *cf = data->conn->cfilter[sockindex];
    if(cf)
      (void)Curl_conn_cf_cntrl(cf, data, TRUE,
                               CF_CTRL_FORGET_SOCKET, 0, NULL);
    fake_sclose(data->conn->sock[sockindex]);
    data->conn->sock[sockindex] = CURL_SOCKET_BAD;
  }
}

static CURLcode cf_cntrl_all(struct connectdata *conn,
                             struct Curl_easy *data,
                             bool ignore_result,
                             int event, int arg1, void *arg2)
{
  CURLcode result = CURLE_OK;
  size_t i;

  for(i = 0; i < ARRAYSIZE(conn->cfilter); ++i) {
    result = Curl_conn_cf_cntrl(conn->cfilter[i], data, ignore_result,
                                event, arg1, arg2);
    if(!ignore_result && result)
      break;
  }
  return result;
}

void Curl_conn_ev_data_attach(struct connectdata *conn,
                              struct Curl_easy *data)
{
  cf_cntrl_all(conn, data, TRUE, CF_CTRL_DATA_ATTACH, 0, NULL);
}

void Curl_conn_ev_data_detach(struct connectdata *conn,
                              struct Curl_easy *data)
{
  cf_cntrl_all(conn, data, TRUE, CF_CTRL_DATA_DETACH, 0, NULL);
}

CURLcode Curl_conn_ev_data_setup(struct Curl_easy *data)
{
  return cf_cntrl_all(data->conn, data, FALSE,
                      CF_CTRL_DATA_SETUP, 0, NULL);
}

CURLcode Curl_conn_ev_data_idle(struct Curl_easy *data)
{
  return cf_cntrl_all(data->conn, data, FALSE,
                      CF_CTRL_DATA_IDLE, 0, NULL);
}


CURLcode Curl_conn_flush(struct Curl_easy *data, int sockindex)
{
  return Curl_conn_cf_cntrl(data->conn->cfilter[sockindex], data, FALSE,
                            CF_CTRL_FLUSH, 0, NULL);
}

/**
 * Notify connection filters that the transfer represented by `data`
 * is done with sending data (e.g. has uploaded everything).
 */
void Curl_conn_ev_data_done_send(struct Curl_easy *data)
{
  cf_cntrl_all(data->conn, data, TRUE, CF_CTRL_DATA_DONE_SEND, 0, NULL);
}

/**
 * Notify connection filters that the transfer represented by `data`
 * is finished - eventually premature, e.g. before being complete.
 */
void Curl_conn_ev_data_done(struct Curl_easy *data, bool premature)
{
  cf_cntrl_all(data->conn, data, TRUE, CF_CTRL_DATA_DONE, premature, NULL);
}

CURLcode Curl_conn_ev_data_pause(struct Curl_easy *data, bool do_pause)
{
  return cf_cntrl_all(data->conn, data, FALSE,
                      CF_CTRL_DATA_PAUSE, do_pause, NULL);
}

void Curl_conn_ev_update_info(struct Curl_easy *data,
                              struct connectdata *conn)
{
  cf_cntrl_all(conn, data, TRUE, CF_CTRL_CONN_INFO_UPDATE, 0, NULL);
}

/**
 * Update connection statistics
 */
static void conn_report_connect_stats(struct Curl_easy *data,
                                      struct connectdata *conn)
{
  struct Curl_cfilter *cf = conn->cfilter[FIRSTSOCKET];
  if(cf) {
    struct curltime connected;
    struct curltime appconnected;

    memset(&connected, 0, sizeof(connected));
    cf->cft->query(cf, data, CF_QUERY_TIMER_CONNECT, NULL, &connected);
    if(connected.tv_sec || connected.tv_usec)
      Curl_pgrsTimeWas(data, TIMER_CONNECT, connected);

    memset(&appconnected, 0, sizeof(appconnected));
    cf->cft->query(cf, data, CF_QUERY_TIMER_APPCONNECT, NULL, &appconnected);
    if(appconnected.tv_sec || appconnected.tv_usec)
      Curl_pgrsTimeWas(data, TIMER_APPCONNECT, appconnected);
  }
}

bool Curl_conn_is_alive(struct Curl_easy *data, struct connectdata *conn,
                        bool *input_pending)
{
  struct Curl_cfilter *cf = conn->cfilter[FIRSTSOCKET];
  return cf && !cf->conn->bits.close &&
         cf->cft->is_alive(cf, data, input_pending);
}

CURLcode Curl_conn_keep_alive(struct Curl_easy *data,
                              struct connectdata *conn,
                              int sockindex)
{
  struct Curl_cfilter *cf = conn->cfilter[sockindex];
  return cf? cf->cft->keep_alive(cf, data) : CURLE_OK;
}

size_t Curl_conn_get_max_concurrent(struct Curl_easy *data,
                                     struct connectdata *conn,
                                     int sockindex)
{
  CURLcode result;
  int n = 0;

  struct Curl_cfilter *cf = conn->cfilter[sockindex];
  result = cf? cf->cft->query(cf, data, CF_QUERY_MAX_CONCURRENT,
                              &n, NULL) : CURLE_UNKNOWN_OPTION;
  return (result || n <= 0)? 1 : (size_t)n;
}

int Curl_conn_get_stream_error(struct Curl_easy *data,
                               struct connectdata *conn,
                               int sockindex)
{
  CURLcode result;
  int n = 0;

  struct Curl_cfilter *cf = conn->cfilter[sockindex];
  result = cf? cf->cft->query(cf, data, CF_QUERY_STREAM_ERROR,
                              &n, NULL) : CURLE_UNKNOWN_OPTION;
  return (result || n < 0)? 0 : n;
}

int Curl_conn_sockindex(struct Curl_easy *data, curl_socket_t sockfd)
{
  if(data && data->conn &&
     sockfd != CURL_SOCKET_BAD && sockfd == data->conn->sock[SECONDARYSOCKET])
    return SECONDARYSOCKET;
  return FIRSTSOCKET;
}

CURLcode Curl_conn_recv(struct Curl_easy *data, int sockindex,
                        char *buf, size_t blen, ssize_t *n)
{
  CURLcode result = CURLE_OK;
  ssize_t nread;

  DEBUGASSERT(data->conn);
  nread = data->conn->recv[sockindex](data, sockindex, buf, blen, &result);
  DEBUGASSERT(nread >= 0 || result);
  DEBUGASSERT(nread < 0 || !result);
  *n = (nread >= 0)? (size_t)nread : 0;
  return result;
}

CURLcode Curl_conn_send(struct Curl_easy *data, int sockindex,
                        const void *buf, size_t blen, bool eos,
                        size_t *pnwritten)
{
  size_t write_len = blen;
  ssize_t nwritten;
  CURLcode result = CURLE_OK;
  struct connectdata *conn;

  DEBUGASSERT(sockindex >= 0 && sockindex < 2);
  DEBUGASSERT(pnwritten);
  DEBUGASSERT(data);
  DEBUGASSERT(data->conn);
  conn = data->conn;
#ifdef DEBUGBUILD
  {
    /* Allow debug builds to override this logic to force short sends
    */
    char *p = getenv("CURL_SMALLSENDS");
    if(p) {
      size_t altsize = (size_t)strtoul(p, NULL, 10);
      if(altsize)
        write_len = CURLMIN(write_len, altsize);
    }
  }
#endif
  if(write_len != blen)
    eos = FALSE;
  nwritten = conn->send[sockindex](data, sockindex, buf, write_len, eos,
                                   &result);
  DEBUGASSERT((nwritten >= 0) || result);
  *pnwritten = (nwritten < 0)? 0 : (size_t)nwritten;
  return result;
}

void Curl_pollset_reset(struct Curl_easy *data,
                        struct easy_pollset *ps)
{
  size_t i;
  (void)data;
  memset(ps, 0, sizeof(*ps));
  for(i = 0; i< MAX_SOCKSPEREASYHANDLE; i++)
    ps->sockets[i] = CURL_SOCKET_BAD;
}

/**
 *
 */
void Curl_pollset_change(struct Curl_easy *data,
                       struct easy_pollset *ps, curl_socket_t sock,
                       int add_flags, int remove_flags)
{
  unsigned int i;

  (void)data;
  DEBUGASSERT(VALID_SOCK(sock));
  if(!VALID_SOCK(sock))
    return;

  DEBUGASSERT(add_flags <= (CURL_POLL_IN|CURL_POLL_OUT));
  DEBUGASSERT(remove_flags <= (CURL_POLL_IN|CURL_POLL_OUT));
  DEBUGASSERT((add_flags&remove_flags) == 0); /* no overlap */
  for(i = 0; i < ps->num; ++i) {
    if(ps->sockets[i] == sock) {
      ps->actions[i] &= (unsigned char)(~remove_flags);
      ps->actions[i] |= (unsigned char)add_flags;
      /* all gone? remove socket */
      if(!ps->actions[i]) {
        if((i + 1) < ps->num) {
          memmove(&ps->sockets[i], &ps->sockets[i + 1],
                  (ps->num - (i + 1)) * sizeof(ps->sockets[0]));
          memmove(&ps->actions[i], &ps->actions[i + 1],
                  (ps->num - (i + 1)) * sizeof(ps->actions[0]));
        }
        --ps->num;
      }
      return;
    }
  }
  /* not present */
  if(add_flags) {
    /* Having more SOCKETS per easy handle than what is defined
     * is a programming error. This indicates that we need
     * to raise this limit, making easy_pollset larger.
     * Since we use this in tight loops, we do not want to make
     * the pollset dynamic unnecessarily.
     * The current maximum in practise is HTTP/3 eyeballing where
     * we have up to 4 sockets involved in connection setup.
     */
    DEBUGASSERT(i < MAX_SOCKSPEREASYHANDLE);
    if(i < MAX_SOCKSPEREASYHANDLE) {
      ps->sockets[i] = sock;
      ps->actions[i] = (unsigned char)add_flags;
      ps->num = i + 1;
    }
  }
}

void Curl_pollset_set(struct Curl_easy *data,
                      struct easy_pollset *ps, curl_socket_t sock,
                      bool do_in, bool do_out)
{
  Curl_pollset_change(data, ps, sock,
                      (do_in?CURL_POLL_IN:0)|(do_out?CURL_POLL_OUT:0),
                      (!do_in?CURL_POLL_IN:0)|(!do_out?CURL_POLL_OUT:0));
}

static void ps_add(struct Curl_easy *data, struct easy_pollset *ps,
                   int bitmap, curl_socket_t *socks)
{
  if(bitmap) {
    int i;
    for(i = 0; i < MAX_SOCKSPEREASYHANDLE; ++i) {
      if(!(bitmap & GETSOCK_MASK_RW(i)) || !VALID_SOCK((socks[i]))) {
        break;
      }
      if(bitmap & GETSOCK_READSOCK(i)) {
        if(bitmap & GETSOCK_WRITESOCK(i))
          Curl_pollset_add_inout(data, ps, socks[i]);
        else
          /* is READ, since we checked MASK_RW above */
          Curl_pollset_add_in(data, ps, socks[i]);
      }
      else
        Curl_pollset_add_out(data, ps, socks[i]);
    }
  }
}

void Curl_pollset_add_socks(struct Curl_easy *data,
                            struct easy_pollset *ps,
                            int (*get_socks_cb)(struct Curl_easy *data,
                                                curl_socket_t *socks))
{
  curl_socket_t socks[MAX_SOCKSPEREASYHANDLE];
  int bitmap;

  bitmap = get_socks_cb(data, socks);
  ps_add(data, ps, bitmap, socks);
}

void Curl_pollset_check(struct Curl_easy *data,
                        struct easy_pollset *ps, curl_socket_t sock,
                        bool *pwant_read, bool *pwant_write)
{
  unsigned int i;

  (void)data;
  DEBUGASSERT(VALID_SOCK(sock));
  for(i = 0; i < ps->num; ++i) {
    if(ps->sockets[i] == sock) {
      *pwant_read = !!(ps->actions[i] & CURL_POLL_IN);
      *pwant_write = !!(ps->actions[i] & CURL_POLL_OUT);
      return;
    }
  }
  *pwant_read = *pwant_write = FALSE;
}