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curl/lib/select.c

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/***************************************************************************
* _ _ ____ _
* Project ___| | | | _ \| |
* / __| | | | |_) | |
* | (__| |_| | _ <| |___
* \___|\___/|_| \_\_____|
*
* Copyright (C) 1998 - 2021, 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.
*
***************************************************************************/
#include "curl_setup.h"
#include <limits.h>
#ifdef HAVE_SYS_SELECT_H
#include <sys/select.h>
#elif defined(HAVE_UNISTD_H)
#include <unistd.h>
#endif
#if !defined(HAVE_SELECT) && !defined(HAVE_POLL_FINE)
#error "We can't compile without select() or poll() support."
#endif
#if defined(__BEOS__) && !defined(__HAIKU__)
/* BeOS has FD_SET defined in socket.h */
#include <socket.h>
#endif
#ifdef MSDOS
#include <dos.h> /* delay() */
#endif
#ifdef __VXWORKS__
#include <strings.h> /* bzero() in FD_SET */
#endif
#include <curl/curl.h>
#include "urldata.h"
#include "connect.h"
#include "select.h"
#include "timeval.h"
#include "warnless.h"
/*
* Internal function used for waiting a specific amount of ms
* in Curl_socket_check() and Curl_poll() when no file descriptor
* is provided to wait on, just being used to delay execution.
* WinSock select() and poll() timeout mechanisms need a valid
* socket descriptor in a not null file descriptor set to work.
* Waiting indefinitely with this function is not allowed, a
* zero or negative timeout value will return immediately.
* Timeout resolution, accuracy, as well as maximum supported
* value is system dependent, neither factor is a citical issue
* for the intended use of this function in the library.
*
* Return values:
* -1 = system call error, invalid timeout value, or interrupted
* 0 = specified timeout has elapsed
*/
int Curl_wait_ms(timediff_t timeout_ms)
{
int r = 0;
if(!timeout_ms)
return 0;
if(timeout_ms < 0) {
SET_SOCKERRNO(EINVAL);
return -1;
}
#if defined(MSDOS)
delay(timeout_ms);
#elif defined(WIN32)
/* prevent overflow, timeout_ms is typecast to ULONG/DWORD. */
#if TIMEDIFF_T_MAX >= ULONG_MAX
if(timeout_ms >= ULONG_MAX)
timeout_ms = ULONG_MAX-1;
/* don't use ULONG_MAX, because that is equal to INFINITE */
#endif
Sleep((ULONG)timeout_ms);
#else
#if defined(HAVE_POLL_FINE)
/* prevent overflow, timeout_ms is typecast to int. */
#if TIMEDIFF_T_MAX > INT_MAX
if(timeout_ms > INT_MAX)
timeout_ms = INT_MAX;
#endif
r = poll(NULL, 0, (int)timeout_ms);
#else
{
struct timeval pending_tv;
timediff_t tv_sec = timeout_ms / 1000;
timediff_t tv_usec = (timeout_ms % 1000) * 1000; /* max=999999 */
#ifdef HAVE_SUSECONDS_T
#if TIMEDIFF_T_MAX > TIME_T_MAX
/* tv_sec overflow check in case time_t is signed */
if(tv_sec > TIME_T_MAX)
tv_sec = TIME_T_MAX;
#endif
pending_tv.tv_sec = (time_t)tv_sec;
pending_tv.tv_usec = (suseconds_t)tv_usec;
#else
#if TIMEDIFF_T_MAX > INT_MAX
/* tv_sec overflow check in case time_t is signed */
if(tv_sec > INT_MAX)
tv_sec = INT_MAX;
#endif
pending_tv.tv_sec = (int)tv_sec;
pending_tv.tv_usec = (int)tv_usec;
#endif
r = select(0, NULL, NULL, NULL, &pending_tv);
}
#endif /* HAVE_POLL_FINE */
#endif /* USE_WINSOCK */
if(r)
r = -1;
return r;
}
#ifndef HAVE_POLL_FINE
/*
* This is a wrapper around select() to aid in Windows compatibility.
* A negative timeout value makes this function wait indefinitely,
* unless no valid file descriptor is given, when this happens the
* negative timeout is ignored and the function times out immediately.
*
* Return values:
* -1 = system call error or fd >= FD_SETSIZE
* 0 = timeout
* N = number of signalled file descriptors
*/
static int our_select(curl_socket_t maxfd, /* highest socket number */
fd_set *fds_read, /* sockets ready for reading */
fd_set *fds_write, /* sockets ready for writing */
fd_set *fds_err, /* sockets with errors */
timediff_t timeout_ms) /* milliseconds to wait */
{
struct timeval pending_tv;
struct timeval *ptimeout;
#ifdef USE_WINSOCK
/* WinSock select() can't handle zero events. See the comment below. */
if((!fds_read || fds_read->fd_count == 0) &&
(!fds_write || fds_write->fd_count == 0) &&
(!fds_err || fds_err->fd_count == 0)) {
/* no sockets, just wait */
return Curl_wait_ms(timeout_ms);
}
#endif
ptimeout = &pending_tv;
if(timeout_ms < 0) {
ptimeout = NULL;
}
else if(timeout_ms > 0) {
timediff_t tv_sec = timeout_ms / 1000;
timediff_t tv_usec = (timeout_ms % 1000) * 1000; /* max=999999 */
#ifdef HAVE_SUSECONDS_T
#if TIMEDIFF_T_MAX > TIME_T_MAX
/* tv_sec overflow check in case time_t is signed */
if(tv_sec > TIME_T_MAX)
tv_sec = TIME_T_MAX;
#endif
pending_tv.tv_sec = (time_t)tv_sec;
pending_tv.tv_usec = (suseconds_t)tv_usec;
#elif defined(WIN32) /* maybe also others in the future */
#if TIMEDIFF_T_MAX > LONG_MAX
/* tv_sec overflow check on Windows there we know it is long */
if(tv_sec > LONG_MAX)
tv_sec = LONG_MAX;
#endif
pending_tv.tv_sec = (long)tv_sec;
pending_tv.tv_usec = (long)tv_usec;
#else
#if TIMEDIFF_T_MAX > INT_MAX
/* tv_sec overflow check in case time_t is signed */
if(tv_sec > INT_MAX)
tv_sec = INT_MAX;
#endif
pending_tv.tv_sec = (int)tv_sec;
pending_tv.tv_usec = (int)tv_usec;
#endif
}
else {
pending_tv.tv_sec = 0;
pending_tv.tv_usec = 0;
}
#ifdef USE_WINSOCK
/* WinSock select() must not be called with an fd_set that contains zero
fd flags, or it will return WSAEINVAL. But, it also can't be called
with no fd_sets at all! From the documentation:
Any two of the parameters, readfds, writefds, or exceptfds, can be
given as null. At least one must be non-null, and any non-null
descriptor set must contain at least one handle to a socket.
It is unclear why WinSock doesn't just handle this for us instead of
calling this an error. Luckily, with WinSock, we can _also_ ask how
many bits are set on an fd_set. So, let's just check it beforehand.
*/
return select((int)maxfd + 1,
fds_read && fds_read->fd_count ? fds_read : NULL,
fds_write && fds_write->fd_count ? fds_write : NULL,
fds_err && fds_err->fd_count ? fds_err : NULL, ptimeout);
#else
return select((int)maxfd + 1, fds_read, fds_write, fds_err, ptimeout);
#endif
}
#endif
/*
* Wait for read or write events on a set of file descriptors. It uses poll()
* when a fine poll() is available, in order to avoid limits with FD_SETSIZE,
* otherwise select() is used. An error is returned if select() is being used
* and a file descriptor is too large for FD_SETSIZE.
*
* A negative timeout value makes this function wait indefinitely,
* unless no valid file descriptor is given, when this happens the
* negative timeout is ignored and the function times out immediately.
*
* Return values:
* -1 = system call error or fd >= FD_SETSIZE
* 0 = timeout
* [bitmask] = action as described below
*
* CURL_CSELECT_IN - first socket is readable
* CURL_CSELECT_IN2 - second socket is readable
* CURL_CSELECT_OUT - write socket is writable
* CURL_CSELECT_ERR - an error condition occurred
*/
int Curl_socket_check(curl_socket_t readfd0, /* two sockets to read from */
curl_socket_t readfd1,
curl_socket_t writefd, /* socket to write to */
timediff_t timeout_ms) /* milliseconds to wait */
{
struct pollfd pfd[3];
int num;
int r;
if((readfd0 == CURL_SOCKET_BAD) && (readfd1 == CURL_SOCKET_BAD) &&
(writefd == CURL_SOCKET_BAD)) {
/* no sockets, just wait */
return Curl_wait_ms(timeout_ms);
}
/* Avoid initial timestamp, avoid Curl_now() call, when elapsed
time in this function does not need to be measured. This happens
when function is called with a zero timeout or a negative timeout
value indicating a blocking call should be performed. */
num = 0;
if(readfd0 != CURL_SOCKET_BAD) {
pfd[num].fd = readfd0;
pfd[num].events = POLLRDNORM|POLLIN|POLLRDBAND|POLLPRI;
pfd[num].revents = 0;
num++;
}
if(readfd1 != CURL_SOCKET_BAD) {
pfd[num].fd = readfd1;
pfd[num].events = POLLRDNORM|POLLIN|POLLRDBAND|POLLPRI;
pfd[num].revents = 0;
num++;
}
if(writefd != CURL_SOCKET_BAD) {
pfd[num].fd = writefd;
pfd[num].events = POLLWRNORM|POLLOUT|POLLPRI;
pfd[num].revents = 0;
num++;
}
r = Curl_poll(pfd, num, timeout_ms);
if(r <= 0)
return r;
r = 0;
num = 0;
if(readfd0 != CURL_SOCKET_BAD) {
if(pfd[num].revents & (POLLRDNORM|POLLIN|POLLERR|POLLHUP))
r |= CURL_CSELECT_IN;
if(pfd[num].revents & (POLLRDBAND|POLLPRI|POLLNVAL))
r |= CURL_CSELECT_ERR;
num++;
}
if(readfd1 != CURL_SOCKET_BAD) {
if(pfd[num].revents & (POLLRDNORM|POLLIN|POLLERR|POLLHUP))
r |= CURL_CSELECT_IN2;
if(pfd[num].revents & (POLLRDBAND|POLLPRI|POLLNVAL))
r |= CURL_CSELECT_ERR;
num++;
}
if(writefd != CURL_SOCKET_BAD) {
if(pfd[num].revents & (POLLWRNORM|POLLOUT))
r |= CURL_CSELECT_OUT;
if(pfd[num].revents & (POLLERR|POLLHUP|POLLPRI|POLLNVAL))
r |= CURL_CSELECT_ERR;
}
return r;
}
/*
* This is a wrapper around poll(). If poll() does not exist, then
* select() is used instead. An error is returned if select() is
* being used and a file descriptor is too large for FD_SETSIZE.
* A negative timeout value makes this function wait indefinitely,
* unless no valid file descriptor is given, when this happens the
* negative timeout is ignored and the function times out immediately.
*
* Return values:
* -1 = system call error or fd >= FD_SETSIZE
* 0 = timeout
* N = number of structures with non zero revent fields
*/
int Curl_poll(struct pollfd ufds[], unsigned int nfds, timediff_t timeout_ms)
{
#ifdef HAVE_POLL_FINE
int pending_ms;
#else
fd_set fds_read;
fd_set fds_write;
fd_set fds_err;
curl_socket_t maxfd;
#endif
bool fds_none = TRUE;
unsigned int i;
int r;
if(ufds) {
for(i = 0; i < nfds; i++) {
if(ufds[i].fd != CURL_SOCKET_BAD) {
fds_none = FALSE;
break;
}
}
}
if(fds_none) {
/* no sockets, just wait */
return Curl_wait_ms(timeout_ms);
}
/* Avoid initial timestamp, avoid Curl_now() call, when elapsed
time in this function does not need to be measured. This happens
when function is called with a zero timeout or a negative timeout
value indicating a blocking call should be performed. */
#ifdef HAVE_POLL_FINE
/* prevent overflow, timeout_ms is typecast to int. */
#if TIMEDIFF_T_MAX > INT_MAX
if(timeout_ms > INT_MAX)
timeout_ms = INT_MAX;
#endif
if(timeout_ms > 0)
pending_ms = (int)timeout_ms;
else if(timeout_ms < 0)
pending_ms = -1;
else
pending_ms = 0;
r = poll(ufds, nfds, pending_ms);
if(r <= 0)
return r;
for(i = 0; i < nfds; i++) {
if(ufds[i].fd == CURL_SOCKET_BAD)
continue;
if(ufds[i].revents & POLLHUP)
ufds[i].revents |= POLLIN;
if(ufds[i].revents & POLLERR)
ufds[i].revents |= POLLIN|POLLOUT;
}
#else /* HAVE_POLL_FINE */
FD_ZERO(&fds_read);
FD_ZERO(&fds_write);
FD_ZERO(&fds_err);
maxfd = (curl_socket_t)-1;
for(i = 0; i < nfds; i++) {
ufds[i].revents = 0;
if(ufds[i].fd == CURL_SOCKET_BAD)
continue;
VERIFY_SOCK(ufds[i].fd);
if(ufds[i].events & (POLLIN|POLLOUT|POLLPRI|
POLLRDNORM|POLLWRNORM|POLLRDBAND)) {
if(ufds[i].fd > maxfd)
maxfd = ufds[i].fd;
if(ufds[i].events & (POLLRDNORM|POLLIN))
FD_SET(ufds[i].fd, &fds_read);
if(ufds[i].events & (POLLWRNORM|POLLOUT))
FD_SET(ufds[i].fd, &fds_write);
if(ufds[i].events & (POLLRDBAND|POLLPRI))
FD_SET(ufds[i].fd, &fds_err);
}
}
/*
Note also that WinSock ignores the first argument, so we don't worry
about the fact that maxfd is computed incorrectly with WinSock (since
curl_socket_t is unsigned in such cases and thus -1 is the largest
value).
*/
r = our_select(maxfd, &fds_read, &fds_write, &fds_err, timeout_ms);
if(r <= 0)
return r;
r = 0;
for(i = 0; i < nfds; i++) {
ufds[i].revents = 0;
if(ufds[i].fd == CURL_SOCKET_BAD)
continue;
if(FD_ISSET(ufds[i].fd, &fds_read)) {
if(ufds[i].events & POLLRDNORM)
ufds[i].revents |= POLLRDNORM;
if(ufds[i].events & POLLIN)
ufds[i].revents |= POLLIN;
}
if(FD_ISSET(ufds[i].fd, &fds_write)) {
if(ufds[i].events & POLLWRNORM)
ufds[i].revents |= POLLWRNORM;
if(ufds[i].events & POLLOUT)
ufds[i].revents |= POLLOUT;
}
if(FD_ISSET(ufds[i].fd, &fds_err)) {
if(ufds[i].events & POLLRDBAND)
ufds[i].revents |= POLLRDBAND;
if(ufds[i].events & POLLPRI)
ufds[i].revents |= POLLPRI;
}
if(ufds[i].revents != 0)
r++;
}
#endif /* HAVE_POLL_FINE */
return r;
}
#ifdef TPF
/*
* This is a replacement for select() on the TPF platform.
* It is used whenever libcurl calls select().
* The call below to tpf_process_signals() is required because
* TPF's select calls are not signal interruptible.
*
* Return values are the same as select's.
*/
int tpf_select_libcurl(int maxfds, fd_set *reads, fd_set *writes,
fd_set *excepts, struct timeval *tv)
{
int rc;
rc = tpf_select_bsd(maxfds, reads, writes, excepts, tv);
tpf_process_signals();
return rc;
}
#endif /* TPF */
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