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#ifndef _GNU_SOURCE
#define _GNU_SOURCE
#endif
#include <dlfcn.h>
#include <stdio.h>
#include <unistd.h>
#include <stdlib.h>
#include <fcntl.h>
#include <string.h>
#include <errno.h>
typedef ssize_t (*pread_t)(int, void *, size_t, off_t);
typedef ssize_t (*pwrite_t)(int, const void *, size_t, off_t);
typedef int (*close_t)(int);
typedef int (*fsync_t)(int);
#define FILENAME_BUFSIZE 1024
#define COMMAND_BUFSIZE FILENAME_BUFSIZE
// only files with this substring in their name ale influenced by this library
#define FILENAME_TRIGGER "/chunk_"
// offset in a file used in some scenarios
#define FAR_OFFSET_THRESHOLD 102400
// for files which match FILENAME_TRIGGER, this library will cause the following functions to fail:
// * pread always fails with EIO if file name contains "pread_EIO"
// * pwrite always fails with EIO if file name contains "pwrite_EIO"
// * close always fails with EIO if file name contains "close_EIO"
// * fsync always fails with EIO if file name contains "fsync_EIO"
// * pread fails with EIO if offset>FAR_OFFSET_THRESHOLD and file name contains "pread_far_EIO"
// * pwrite fails with EIO if offset>FAR_OFFSET_THRESHOLD and file name contains "pwrite_far_EIO"
static char *read_filename(int fd, char *buf, int bufsize) {
char fdpath[COMMAND_BUFSIZE] = {0};
int procfd;
sprintf(fdpath, "/proc/self/fd/%d", fd);
memset(buf, 0, bufsize);
readlink(fdpath, buf, bufsize);
return buf;
}
static int err_on_operation(int fd, const char* opname, size_t offset) {
char filename[FILENAME_BUFSIZE] = {0};
char always_eio_trigger[COMMAND_BUFSIZE] = {0};
char far_eio_trigger[COMMAND_BUFSIZE] = {0};
read_filename(fd, filename, FILENAME_BUFSIZE);
if (!strstr(filename, FILENAME_TRIGGER)) {
return 0;
}
// prepare substrings of the filename which trigger errors in various scenarios
sprintf(always_eio_trigger, "%s_EIO", opname);
sprintf(far_eio_trigger, "%s_far_EIO", opname);
if (strstr(filename, always_eio_trigger)) {
return EIO;
} else if (strstr(filename, far_eio_trigger) && offset > FAR_OFFSET_THRESHOLD) {
return EIO;
} else {
return 0;
}
}
// define functions overridden by this library
ssize_t pread(int fd, void *buf, size_t count, off_t offset) {
int err;
static pread_t _pread = NULL;
err = err_on_operation(fd, "pread", offset);
if (err) {
errno = err;
return -1;
}
if (!_pread) {
_pread = (pread_t)dlsym(RTLD_NEXT, "pread");
}
return _pread(fd, buf, count, offset);
}
ssize_t pwrite(int fd, const void *buf, size_t count, off_t offset) {
int err;
static pwrite_t _pwrite = NULL;
err = err_on_operation(fd, "pwrite", offset);
if (err) {
errno = err;
return -1;
}
if (!_pwrite) {
_pwrite = (pwrite_t)dlsym(RTLD_NEXT, "pwrite");
}
return _pwrite(fd, buf, count, offset);
}
int close(int fd) {
int err;
static close_t _close = NULL;
err = err_on_operation(fd, "close", 0);
if (err) {
errno = err;
return -1;
}
if (!_close) {
_close = (close_t)dlsym(RTLD_NEXT, "close");
}
return _close(fd);
}
int fsync(int fd) {
int err;
static fsync_t _fsync = NULL;
err = err_on_operation(fd, "fsync", 0);
if (err) {
errno = err;
return -1;
}
if (!_fsync) {
_fsync = (fsync_t)dlsym(RTLD_NEXT, "fsync");
}
return _fsync(fd);
}
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