freebsd-dev/lib/libc_r/uthread/uthread_sendfile.c
Alfred Perlstein a9ee9c593d Fix a number of subtle and evil bugs in the libc_r wrapping of sendfile(2).
o) Since we unwrap the sendfile syscall, check the return value of
   writev(2) to see if it didn't complete all the data.
   Previously if only a partial writev() succeeded, it would proceed
   to sendfile(2) even though the headers weren't completely sent.

o) Properly adjust the "bytes to send" to take into account sendfile(2)'s
   behaviour of counting the headers against the bytes to be transfered
   from the file.

o) Correct the problem where EAGAIN was being returned from _sys_sendfile(2)
   however the wrapper didn't update the 'sent bytes' parameter to take into
   account for it.  This is because sendfile can return EAGAIN even though
   it has actually transfered data.

Special thanks to Justin Erenkrantz <jerenkrantz@apache.org> for bringing
this to my attention and giving an excellent way to reproduce the problem.

PR: kern/32684
MFC After: 1 week
2001-12-12 08:02:24 +00:00

202 lines
5.3 KiB
C

/*
* Copyright (C) 2000 Jason Evans <jasone@freebsd.org>.
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
* notice(s), this list of conditions and the following disclaimer as
* the first lines of this file unmodified other than the possible
* addition of one or more copyright notices.
* 2. Redistributions in binary form must reproduce the above copyright
* notice(s), this list of conditions and the following disclaimer in
* the documentation and/or other materials provided with the
* distribution.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDER(S) ``AS IS'' AND ANY
* EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
* PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER(S) BE
* LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
* CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
* SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR
* BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY,
* WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE
* OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE,
* EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*
* $FreeBSD$
*/
#include <sys/fcntl.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <sys/uio.h>
#include <errno.h>
#include <pthread.h>
#include "pthread_private.h"
__weak_reference(_sendfile, sendfile);
int
_sendfile(int fd, int s, off_t offset, size_t nbytes, struct sf_hdtr *hdtr,
off_t *sbytes, int flags)
{
struct pthread *curthread = _get_curthread();
int ret, type, blocking;
ssize_t wvret, num = 0;
off_t n, nwritten = 0;
/*
* Write the headers if any.
* If some data is written but not all we must return here.
*/
if ((hdtr != NULL) && (hdtr->headers != NULL)) {
if ((wvret = writev(s, hdtr->headers, hdtr->hdr_cnt)) == -1) {
ret = -1;
goto ERROR;
} else {
int i;
ssize_t hdrtot;
nwritten += wvret;
for (i = 0, hdrtot = 0; i < hdtr->hdr_cnt; i++)
hdrtot += hdtr->headers[i].iov_len;
if (wvret < hdrtot)
goto SHORT_WRITE;
}
}
/* Lock the descriptors. */
if ((ret = _FD_LOCK(fd, FD_READ, NULL)) != 0) {
ret = -1;
errno = EBADF;
goto ERROR;
}
if ((ret = _FD_LOCK(s, FD_WRITE, NULL)) != 0) {
ret = -1;
errno = EBADF;
goto ERROR_1;
}
/* Check the descriptor access modes. */
type = _thread_fd_table[fd]->flags & O_ACCMODE;
if (type != O_RDONLY && type != O_RDWR) {
/* File is not open for read. */
ret = -1;
errno = EBADF;
goto ERROR_2;
}
type = _thread_fd_table[s]->flags & O_ACCMODE;
if (type != O_WRONLY && type != O_RDWR) {
/* File is not open for write. */
ret = -1;
errno = EBADF;
goto ERROR_2;
}
/* Check if file operations are to block */
blocking = ((_thread_fd_table[s]->flags & O_NONBLOCK) == 0);
/*
* Emulate sendfile(2) weirdness, sendfile doesn't actually send
* nbytes of the file, it really sends (nbytes - headers_size) of
* the file. If (nbytes - headers_size) == 0 we just send trailers.
*/
if (nbytes != 0) {
nbytes -= nwritten;
if (nbytes <= 0)
goto ERROR_2;
}
/*
* Loop while no error occurs and until the expected number of bytes are
* written.
*/
for (;;) {
/* Perform a non-blocking sendfile syscall. */
ret = __sys_sendfile(fd, s, offset + num, nbytes - num,
NULL, &n, flags);
/*
* We have to handle the sideways return path of sendfile.
*
* If the result is 0, we're done.
* If the result is anything else check the errno.
* If the errno is not EGAIN return the error.
* Otherwise, take into account how much
* sendfile may have written for us because sendfile can
* return EAGAIN even though it has written data.
*
* We don't clear 'ret' because the sendfile(2) syscall
* would not have either.
*/
if (ret == 0) {
/* Writing completed. */
num += n;
break;
} else if ((ret == -1) && (errno == EAGAIN)) {
/*
* Some bytes were written but there are still more to
* write.
*/
/* Update the count of bytes written. */
num += n;
/*
* If we're not blocking then return.
*/
if (!blocking)
goto SHORT_WRITE;
/*
* Otherwise wait on the fd.
*/
curthread->data.fd.fd = fd;
_thread_kern_set_timeout(NULL);
/* Reset the interrupted operation flag. */
curthread->interrupted = 0;
_thread_kern_sched_state(PS_FDW_WAIT, __FILE__,
__LINE__);
if (curthread->interrupted) {
/* Interrupted by a signal. Return an error. */
break;
}
} else {
/* Incomplete non-blocking syscall, or error. */
break;
}
}
ERROR_2:
_FD_UNLOCK(s, FD_WRITE);
ERROR_1:
_FD_UNLOCK(fd, FD_READ);
ERROR:
if (ret == 0) {
/* Write the trailers, if any. */
if ((hdtr != NULL) && (hdtr->trailers != NULL)) {
if ((wvret = writev(s, hdtr->trailers, hdtr->trl_cnt))
== -1)
ret = -1;
else
nwritten += wvret;
}
}
SHORT_WRITE:
if (sbytes != NULL) {
/*
* Number of bytes written in headers/trailers, plus in the main
* sendfile() loop.
*/
*sbytes = nwritten + num;
}
return ret;
}