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Began test implementation of DDLP-A

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This commit is contained in:
Thomas Schmitt 2007-04-15 16:46:47 +00:00
parent 998333ae78
commit 218b525c55
2 changed files with 701 additions and 0 deletions
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537
libburn/trunk/libburn/ddlpa.c Normal file
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/* ddlpa
Implementation of Delicate Device Locking Protocol level A.
Copyright (C) 2007 Thomas Schmitt <scdbackup@gmx.net>
Provided under any of the following licenses: GPL, LGPL, BSD. Choose one.
*/
#include <stdio.h>
#include <sys/types.h>
#include <unistd.h>
#include <string.h>
#include <stdlib.h>
#include <errno.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <sys/ioctl.h>
#include <scsi/scsi.h>
/* No getter functions. This makes the compiled code leaner. */
#define DDLPA_H_NOT_ENCAPSULATED 1
/* All callers of ddlpa must do this */
#include "ddlpa.h"
/* 1 = Enable progress message on stderr, 0 = normal silent operation */
static int ddlpa_debug_mode = 1;
/* ----------------------- private -------------------- */
static int ddlpa_new(struct ddlpa_lock **lck, int o_flags, int ddlpa_flags)
{
int i;
struct ddlpa_lock *o;
o = *lck = (struct ddlpa_lock *) malloc(sizeof(struct ddlpa_lock));
if (o == NULL)
return ENOMEM;
for (i = 0; i < sizeof(struct ddlpa_lock); i++)
((char *) o)[i] = 0;
o->path = NULL;
o->fd = -1;
for (i = 0; i < DDLPA_MAX_SIBLINGS; i++)
o->sibling_fds[i] = -1;
o->errmsg = NULL;
o->o_flags = o_flags;
o->ddlpa_flags = ddlpa_flags;
return 0;
}
static int ddlpa_enumerate(struct ddlpa_lock *o, int *idx,
char path[DDLPA_MAX_STD_LEN + 1])
{
if (*idx < 0)
*idx = 0;
if (*idx < 26)
sprintf(path, "/dev/hd%c", 'a' + *idx);
else if (*idx < 256 + 26)
sprintf(path, "/dev/sr%d", *idx - 26);
else if (*idx < 2 * 256 + 26)
sprintf(path, "/dev/scd%d", *idx - 256 - 26);
else if (*idx < 3 * 256 + 26)
sprintf(path, "/dev/sg%d", *idx - 2 * 256 - 26);
else
return 1;
(*idx)++;
return 0;
}
static int ddlpa_std_by_rdev(struct ddlpa_lock *o)
{
int idx = 0;
char try_path[DDLPA_MAX_STD_LEN+1];
struct stat path_stbuf, try_stbuf;
if (!o->path_is_valid)
return EFAULT;
if (stat(o->path, &path_stbuf) == -1)
return errno;
while (ddlpa_enumerate(o, &idx, try_path) == 0) {
if (stat(try_path, &try_stbuf) == -1)
continue;
if (path_stbuf.st_rdev != try_stbuf.st_rdev)
continue;
strcpy(o->std_path, try_path);
if (ddlpa_debug_mode)
fprintf(stderr,
"DDLPA_DEBUG: ddlpa_std_by_rdev(\"%s\") = \"%s\"\n",
o->path, o->std_path);
return 0;
}
return ENOENT;
}
/* Caution : these tests are valid only with standard paths */
static int ddlpa_is_scsi(struct ddlpa_lock *o, char *path)
{
return (strncmp(path, "/dev/s", 6) == 0);
}
static int ddlpa_is_sg(struct ddlpa_lock *o, char *path)
{
return (strncmp(path, "/dev/sg", 7) == 0);
}
static int ddlpa_is_sr(struct ddlpa_lock *o, char *path)
{
return (strncmp(path, "/dev/sr", 7) == 0);
}
static int ddlpa_is_scd(struct ddlpa_lock *o, char *path)
{
return (strncmp(path, "/dev/scd", 8) == 0);
}
static int ddlpa_fcntl_lock(struct ddlpa_lock *o, int fd, int l_type)
{
struct flock lockthing;
int ret;
memset(&lockthing, 0, sizeof(lockthing));
lockthing.l_type = l_type;
lockthing.l_whence = SEEK_SET;
lockthing.l_start = 0;
lockthing.l_len = 0;
ret = fcntl(fd, F_SETLK, &lockthing);
if (ret == -1)
return EBUSY;
return 0;
}
static int ddlpa_occupy(struct ddlpa_lock *o, char *path, int *fd,
int no_o_excl)
{
int ret, o_flags = O_RDWR | O_NDELAY;
if(!no_o_excl)
o_flags |= O_EXCL;
*fd = open(path, o_flags);
if (*fd == -1) {
o->errmsg = malloc(strlen(path)+160);
if (o->errmsg)
sprintf(o->errmsg,
"Failed to open O_RDWR | O_NDELAY %s: '%s'",
(no_o_excl ? "" : "| O_EXCL "), path);
return (errno ? errno : EBUSY);
}
ret = ddlpa_fcntl_lock(o, *fd, F_WRLCK);
if (ret) {
o->errmsg = malloc(strlen(path)+160);
if (o->errmsg)
sprintf(o->errmsg,
"Failed to lock fcntl(F_WRLCK) : '%s'",path);
close(*fd);
*fd = -1;
return ret;
}
if (ddlpa_debug_mode)
fprintf(stderr, "DDLPA_DEBUG: ddlpa_occupy() %s: '%s'\n",
(no_o_excl ? " " : "O_EXCL "), path);
return 0;
}
static int ddlpa_obtain_scsi_adr(struct ddlpa_lock *o, char *path,
int *bus, int *host, int *channel, int *id, int *lun)
{
int fd, ret, open_mode = O_RDONLY | O_NDELAY;
struct my_scsi_idlun {
int x;
int host_unique_id;
};
struct my_scsi_idlun idlun;
if (!ddlpa_is_scsi(o, o->std_path))
return EFAULT;
fd = open(path, open_mode);
if (fd == -1)
return (errno ? errno : EBUSY);
if (!(o->ddlpa_flags & DDLPA_ALLOW_ROGUE_BUSIDLUN)) {
ret = ddlpa_fcntl_lock(o, fd, F_RDLCK);
if (ret) {
if (ddlpa_debug_mode)
fprintf(stderr,
"DDLPA_DEBUG: fcntl '%s' errno=%d ret=%d\n",
path, errno, ret);
return ret;
}
}
if (ioctl(fd, SCSI_IOCTL_GET_BUS_NUMBER, bus) == -1)
*bus = -1;
ret = ioctl(fd, SCSI_IOCTL_GET_IDLUN, &idlun);
close(fd);
if (ret == -1)
return (errno ? errno : EIO);
*host = (idlun.x >> 24) & 255;
*channel = (idlun.x >> 16) & 255;
*id = (idlun.x) & 255;
*lun = (idlun.x >> 8 ) & 255;
return 0;
}
static int ddlpa_collect_siblings(struct ddlpa_lock *o)
{
int idx = 0, ret, have_sg = 0, have_sr = 0, have_scd = 0;
dev_t path_dev;
ino_t path_inode;
struct stat stbuf;
char *path, try_path[DDLPA_MAX_STD_LEN+1];
int p_bus, p_host, p_channel, p_id, p_lun;
int t_bus, t_host, t_channel, t_id, t_lun;
if (o->ddlpa_flags & DDLPA_OPEN_GIVEN_PATH)
path = o->path;
else
path = o->std_path;
if (path[0] == 0 || o->num_siblings != 0)
return EFAULT;
if (!ddlpa_is_scsi(o, o->std_path))
return EFAULT;
if (stat(path, &stbuf) == -1)
return errno;
path_inode = stbuf.st_ino;
path_dev = stbuf.st_dev;
o->rdev = stbuf.st_rdev;
o->dev = stbuf.st_dev;
o->ino = stbuf.st_ino;
ret = ddlpa_obtain_scsi_adr(o, path,
&p_bus, &p_host, &p_channel, &p_id, &p_lun);
if (ret) {
o->errmsg = strdup(
"Cannot obtain SCSI parameters host,channel,id,lun");
return ret;
}
while (ddlpa_enumerate(o, &idx, try_path) == 0) {
if (!ddlpa_is_scsi(o, try_path))
continue;
if (stat(try_path, &stbuf) == -1)
continue;
ret = ddlpa_obtain_scsi_adr(o, try_path,
&t_bus, &t_host, &t_channel, &t_id, &t_lun);
if (ret) {
/* >>> interpret error, memorize busy, no permission */
continue;
}
if (t_host != p_host || t_channel != p_channel ||
t_id != p_id || t_lun != p_lun)
continue;
if (o->num_siblings >= DDLPA_MAX_SIBLINGS) {
o->errmsg =
strdup("Too many matching device files found");
return ERANGE;
}
if (ddlpa_is_sg(o, try_path))
have_sg = 1;
else if (ddlpa_is_sr(o, try_path))
have_sr = 1;
else if (ddlpa_is_scd(o, try_path))
have_scd = 1;
strcpy(o->sibling_paths[o->num_siblings], try_path);
o->sibling_rdevs[o->num_siblings] = stbuf.st_rdev;
o->sibling_devs[o->num_siblings] = stbuf.st_dev;
o->sibling_inodes[o->num_siblings] = stbuf.st_ino;
if (ddlpa_debug_mode)
fprintf(stderr,
"DDLPA_DEBUG: ddlpa_collect_siblings() found \"%s\"\n",
try_path);
(o->num_siblings)++;
}
if (have_sg && have_sr && have_scd)
return 0;
if (o->ddlpa_flags & DDLPA_ALLOW_MISSING_SGRCD)
return 0;
o->errmsg = strdup("Did not find enough siblings");
/* >>> add more info about busy and forbidden paths */
return EBUSY;
}
static int ddlpa_open_all(struct ddlpa_lock *o)
{
int i, j, ret, no_o_excl;
if (ddlpa_is_scsi(o, o->std_path)) {
ret = ddlpa_collect_siblings(o);
if (ret)
return ret;
for (i = 0; i < o->num_siblings; i++) {
/* Watch out for the main personality of the drive. */
/* No need to occupy identical path or softlink path */
if (o->sibling_devs[i] == o->dev &&
o->sibling_inodes[i] == o->ino)
continue;
/* There may be the same rdev but different inode. */
no_o_excl = (o->sibling_rdevs[i] == o->rdev);
/* Look for multiply registered device drivers */
for (j = 0; j < i; j++) {
if (o->sibling_devs[j] == o->sibling_devs[i] &&
o->sibling_inodes[j] == o->sibling_inodes[i])
break;
if (o->sibling_rdevs[j] == o->sibling_rdevs[i])
no_o_excl = 1;
}
if (j < i)
continue; /* inode is already occupied */
ret = ddlpa_occupy(o, o->sibling_paths[i],
&(o->sibling_fds[i]), no_o_excl);
if (ret)
return ret;
}
}
if (o->ddlpa_flags & DDLPA_OPEN_GIVEN_PATH)
ret = ddlpa_occupy(o, o->path, &(o->fd), 0);
else
ret = ddlpa_occupy(o, o->std_path, &(o->fd), 0);
if (ret)
return ret;
/* >>> use fcntl() to adjust O_NONBLOCK */;
return 0;
}
/* ----------------------- public -------------------- */
int ddlpa_destroy(struct ddlpa_lock **lockbundle)
{
struct ddlpa_lock *o;
int i;
o= *lockbundle;
if (o == NULL)
return 0;
for (i = 0; i < o->num_siblings; i++)
if (o->sibling_fds[i] != -1)
close(o->sibling_fds[i]);
if(o->fd != -1)
close(o->fd);
if (o->path != NULL)
free(o->path);
if (o->errmsg != NULL)
free(o->errmsg);
free((char *) o);
*lockbundle = NULL;
return 0;
}
int ddlpa_lock_path(char *path, int o_flags, int ddlpa_flags,
struct ddlpa_lock **lockbundle, char **errmsg)
{
struct ddlpa_lock *o;
int ret;
*errmsg = NULL;
if (ddlpa_new(&o, o_flags, ddlpa_flags))
return ENOMEM;
*lockbundle = o;
o->path = strdup(path);
if (o->path == NULL)
return ENOMEM;
o->path_is_valid = 1;
ret = ddlpa_std_by_rdev(o);
if (ret) {
*errmsg = strdup(
"Cannot find equivalent of given path among standard paths");
return ret;
}
ret = ddlpa_open_all(o);
if (ret) {
*errmsg = o->errmsg;
o->errmsg = NULL;
ddlpa_destroy(&o);
}
return ret;
}
int ddlpa_lock_btl(int bus, int target, int lun,
int o_flags, int ddlpa_flags,
struct ddlpa_lock **lockbundle, char **errmsg)
{
/* >>> */
*errmsg = strdup("Function ddlpa_lock_btl() not implemented yet.");
return ENOSYS;
}
#ifndef DDLPA_H_NOT_ENCAPSULATED
int ddlpa_get_fd(struct ddlpa_lock *lockbundle)
{
/* >>> */
return -1;
}
char *ddlpa_get_fd_path(struct ddlpa_lock *lockbundle)
{
/* >>> */
return "none";
}
int ddlpa_get_siblings(struct ddlpa_lock *lockbundle,
char **std_path, int *num_siblings,
char ***sibling_paths, int **sibling_fds)
{
*num_siblings = 0;
/* >>> */
return 1;
}
#endif /* ! DDLPA_H_NOT_ENCAPSULATED */
/* ----------------------------- Test / Demo -------------------------- */
#ifdef DDLPA_C_STANDALONE
int main(int argc, char **argv)
{
struct ddlpa_lock *lck = NULL;
char *errmsg = NULL, *opened_path = NULL, *my_path = NULL;
int i, ret, fd = -1, duration = -1;
if (argc < 3) {
usage:;
fprintf(stderr, "usage: %s device_path duration\n", argv[0]);
exit(1);
}
my_path = argv[1];
sscanf(argv[2], "%d", &duration);
if (duration < 0)
goto usage;
/* This substitutes for:
fd = open(my_path, O_RDWR | O_EXCL);
*/
ret = ddlpa_lock_path(my_path, O_RDWR, DDLPA_ALLOW_ROGUE_BUSIDLUN,
&lck, &errmsg);
if (ret) {
fprintf(stderr, "Cannot exclusively open '%s'\n", my_path);
if (errmsg != NULL)
fprintf(stderr, "Reason given : %s\n",
errmsg);
free(errmsg);
fprintf(stderr, "Error condition : %d '%s'\n",
errno, strerror(errno));
exit(2);
}
fd = lck->fd;
printf("---------------------------------------------- Lock gained\n");
/* Use fd for the usual operations on the device depicted by my_path.
*/
/* This prints an overview of the impact of the lock */
if (lck->ddlpa_flags & DDLPA_OPEN_GIVEN_PATH)
opened_path = lck->path;
else
opened_path = lck->std_path;
printf("ddlpa: opened %s", opened_path);
if (strcmp(opened_path, lck->std_path) != 0)
printf(" (an alias of '%s')", lck->std_path);
printf("\n");
if (lck->num_siblings > 0) {
printf("ddlpa: opened siblings:");
for (i = 0; i < lck->num_siblings; i++)
if (lck->sibling_fds[i] != -1)
printf(" %s", lck->sibling_paths[i]);
printf("\n");
}
/* This example waits a while. So other lock candidates can collide. */
for (i = 0; i < duration; i++) {
sleep(1);
fprintf(stderr, "\rslept %d seconds of %d", i + 1, duration);
}
fprintf(stderr, "\n");
/* When finally done with the drive, this substitutes for:
close(fd);
*/
if (ddlpa_destroy(&lck)) {
/* Well, man 2 close says it can fail. */
exit(3);
}
exit(0);
}
#endif /* DDLPA_C_STANDALONE */

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libburn/trunk/libburn/ddlpa.h Normal file
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/* ddlpa
Implementation of Delicate Device Locking Protocol level A.
Copyright (C) 2007 Thomas Schmitt <scdbackup@gmx.net>
Provided under any of the following licenses: GPL, LGPL, BSD. Choose one.
*/
#ifndef DDLPA_H_INCLUDED
#define DDLPA_H_INCLUDED 1
/* >>> For now : do not encapsulate the details of struct ddlpa_lock */
#ifndef DDLPA_H_NOT_ENCAPSULATED
#define DDLPA_H_NOT_ENCAPSULATED 1
#endif
#ifndef DDLPA_H_NOT_ENCAPSULATED
/** Container for locking state and parameters.
*/
struct ddlpa_lock;
#else /* ! DDLPA_H_NOT_ENCAPSULATED */
/* An upper limit for the length of standard paths and sibling paths */
#define DDLPA_MAX_STD_LEN 15
/* An upper limit for the number of siblings */
#define DDLPA_MAX_SIBLINGS 5
struct ddlpa_lock {
/* Recorded input parameters of locking call */
char *path;
int path_is_valid;
int in_bus, in_target, in_lun;
int inbtl_is_valid;
int ddlpa_flags;
int o_flags;
/* Result of locking call */
char std_path[DDLPA_MAX_STD_LEN + 1];
int fd;
dev_t rdev;
dev_t dev;
ino_t ino;
int host, channel, id, lun, bus;
int hcilb_is_valid;
int num_siblings;
char sibling_paths[DDLPA_MAX_SIBLINGS][DDLPA_MAX_STD_LEN + 1];
int sibling_fds[DDLPA_MAX_SIBLINGS];
dev_t sibling_rdevs[DDLPA_MAX_SIBLINGS];
dev_t sibling_devs[DDLPA_MAX_SIBLINGS];
ino_t sibling_inodes[DDLPA_MAX_SIBLINGS];
/* Is NULL if all goes well. Else it may contain a text message. */
char *errmsg;
};
#endif /* DDLPA_H_NOT_ENCAPSULATED */
/** Lock a recorder by naming a device file path. Allocate a new container.
@param path Gives the file system path of the recorder
as known to the calling program.
@param o_flags flags for open(2)
@param ddlpa_flags 0 = default behavior: the standard path will be opened
and treated by fcntl(F_SETLK)
DDLPA_OPEN_GIVEN_PATH causes the input parameter "path"
to be used with open(2) and fcntl(2). Caution: This
weakens the fcntl part of DDLP-A.
DDLPA_ALLOW_MISSING_SGRCD allows to grant a lock
although not both, a sg and a sr|scd device, have been
found during sibling search. Normally this is counted
as failure due to EBUSY.
DDLPA_ALLOW_ROGUE_BUSIDLUN allows to perform the ioctls
SCSI_IOCTL_GET_BUS_NUMBER and SCSI_IOCTL_GET_IDLUN
without prior fcntl lock. This is expected to be
harmless. It helps to detect and report drives which
are really busy.
@param lockbundle gets allocated and then represents the locking state
@param errmsg if *errmsg is not NULL after the call, it contains an
error message. Then to be released by free(3).
It is NULL in case of success or lack of memory.
@return 0=success , 1=failure
*/
int ddlpa_lock_path(char *path, int o_flags, int ddlpa_flags,
struct ddlpa_lock **lockbundle, char **errmsg);
/** Lock a recorder by naming a Bus,Target,Lun number triple.
Allocate a new container.
@param bus parameter to match ioctl(SCSI_IOCTL_GET_BUS_NUMBER)
@param target parameter to match ioctl(SCSI_IOCTL_GET_IDLUN) &0xff
@param lun parameter to match ioctl(SCSI_IOCTL_GET_IDLUN) &0xff00
@param o_flags flags for open(2)
@param ddlpa_flags see ddlpa_lock_path(). Flag DDLPA_OPEN_GIVEN_PATH
will be ignored.
@param lockbundle see ddlpa_lock_path().
@param errmsg see ddlpa_lock_path().
@return 0=success , 1=failure
*/
int ddlpa_lock_btl(int bus, int target, int lun,
int o_flags, int ddlpa_flags,
struct ddlpa_lock **lockbundle, char **errmsg);
/** Release the lock by closing all filedescriptors and freeing memory.
@param lockbundle the lock which is to be released.
*lockbundle will be set to NULL by this call.
@return 0=success , 1=failure
*/
int ddlpa_destroy(struct ddlpa_lock **lockbundle);
#ifndef DDLPA_H_NOT_ENCAPSULATED
/** Obtain the file descriptor for doing serious work on the recorder.
@param lockbundle the lock which has been activated either by
ddlpa_lock_path() or ddlpa_lock_btl()
@return the file descriptor
*/
int ddlpa_get_fd(struct ddlpa_lock *lockbundle);
/** Obtain the path which was used to open the file descriptor.
@param lockbundle the lock
@return a pointer to the path string.
Do not alter that string ! Do not free(3) it !
*/
char *ddlpa_get_fd_path(struct ddlpa_lock *lockbundle);
/* Obtain info about the standard path and eventual locked siblings.
@param lockbundle the lock to inquire
@param std_path a pointer to the string with the standard path.
Do not alter that string ! Do not free(3) it !
@param num_siblings Tells the number of elements in sibling_*[].
0 and 1 will be the most frequent values.
@param sibling_paths Tells the device file paths of the opened sibling
device representations
Do not alter those strings ! Do not free(3) them !
@param sibling_fds Contains the opened file descriptors on sibling_paths
@return 0=success , 1=failure (will hardly happen)
*/
int ddlpa_get_siblings(struct ddlpa_lock *lockbundle,
char **std_path, int *num_siblings,
char ***sibling_paths, int **sibling_fds);
#endif /* ! DDLPA_H_NOT_ENCAPSULATED */
/** Definitions of macros used in above functions */
#define DDLPA_OPEN_GIVEN_PATH 1
#define DDLPA_ALLOW_MISSING_SGRCD 2
#define DDLPA_ALLOW_ROGUE_BUSIDLUN 4
#endif /* DDLPA_H_INCLUDED */