> On May 10, 2022, at 9:32 AM, Steve Dickson <steved@xxxxxxxxxx> wrote:
>
> Hello,
>
> On 5/2/22 4:50 AM, Richard Weinberger wrote:
>> This internal library contains code that will be used by various
>> tools within the nfs-utils package to deal better with NFS re-export,
>> especially cross mounts.
>> Signed-off-by: Richard Weinberger <richard@xxxxxx>
>> ---
>> configure.ac | 12 ++
>> support/Makefile.am | 4 +
>> support/reexport/Makefile.am | 6 +
>> support/reexport/reexport.c | 285 +++++++++++++++++++++++++++++++++++
>> support/reexport/reexport.h | 39 +++++
>> 5 files changed, 346 insertions(+)
>> create mode 100644 support/reexport/Makefile.am
>> create mode 100644 support/reexport/reexport.c
>> create mode 100644 support/reexport/reexport.h
>> diff --git a/configure.ac b/configure.ac
>> index 93626d62..86bf8ba9 100644
>> --- a/configure.ac
>> +++ b/configure.ac
>> @@ -274,6 +274,17 @@ AC_ARG_ENABLE(nfsv4server,
>> fi
>> AM_CONDITIONAL(CONFIG_NFSV4SERVER, [test "$enable_nfsv4server" = "yes" ])
>> +AC_ARG_ENABLE(reexport,
>> + [AC_HELP_STRING([--enable-reexport],
>> + [enable support for re-exporting NFS mounts @<:@default=no@:>@])],
>> + enable_reexport=$enableval,
>> + enable_reexport="no")
>> + if test "$enable_reexport" = yes; then
>> + AC_DEFINE(HAVE_REEXPORT_SUPPORT, 1,
>> + [Define this if you want NFS re-export support compiled in])
>> + fi
>> + AM_CONDITIONAL(CONFIG_REEXPORT, [test "$enable_reexport" = "yes" ])
>> +
> To get this moving I'm going to add a --disable-reexport flag
Hi Steve, no-one has given a reason why disabling support
for re-exports would be necessary. Therefore, can't this
switch just be removed?
> +AC_ARG_ENABLE(reexport,
> + [AC_HELP_STRING([--disable-reexport],
> + [disable support for re-exporting NFS mounts @<:@default=no@:>@])],
> + enable_reexport=$enableval,
> + enable_reexport="yes")
> + if test "$enable_reexport" = yes; then
> + AC_DEFINE(HAVE_REEXPORT_SUPPORT, 1,
> + [Define this if you want NFS re-export support compiled in])
> + fi
> + AM_CONDITIONAL(CONFIG_REEXPORT, [test "$enable_reexport" = "yes" ])
> +
>
> steved.
>
>> dnl Check for TI-RPC library and headers
>> AC_LIBTIRPC
>> @@ -730,6 +741,7 @@ AC_CONFIG_FILES([
>> support/nsm/Makefile
>> support/nfsidmap/Makefile
>> support/nfsidmap/libnfsidmap.pc
>> + support/reexport/Makefile
>> tools/Makefile
>> tools/locktest/Makefile
>> tools/nlmtest/Makefile
>> diff --git a/support/Makefile.am b/support/Makefile.am
>> index c962d4d4..986e9b5f 100644
>> --- a/support/Makefile.am
>> +++ b/support/Makefile.am
>> @@ -10,6 +10,10 @@ if CONFIG_JUNCTION
>> OPTDIRS += junction
>> endif
>> +if CONFIG_REEXPORT
>> +OPTDIRS += reexport
>> +endif
>> +
>> SUBDIRS = export include misc nfs nsm $(OPTDIRS)
>> MAINTAINERCLEANFILES = Makefile.in
>> diff --git a/support/reexport/Makefile.am b/support/reexport/Makefile.am
>> new file mode 100644
>> index 00000000..9d544a8f
>> --- /dev/null
>> +++ b/support/reexport/Makefile.am
>> @@ -0,0 +1,6 @@
>> +## Process this file with automake to produce Makefile.in
>> +
>> +noinst_LIBRARIES = libreexport.a
>> +libreexport_a_SOURCES = reexport.c
>> +
>> +MAINTAINERCLEANFILES = Makefile.in
>> diff --git a/support/reexport/reexport.c b/support/reexport/reexport.c
>> new file mode 100644
>> index 00000000..5474a21f
>> --- /dev/null
>> +++ b/support/reexport/reexport.c
>> @@ -0,0 +1,285 @@
>> +#ifdef HAVE_CONFIG_H
>> +#include <config.h>
>> +#endif
>> +
>> +#include <sqlite3.h>
>> +#include <stdint.h>
>> +#include <stdio.h>
>> +#include <sys/random.h>
>> +#include <sys/stat.h>
>> +#include <sys/types.h>
>> +#include <sys/vfs.h>
>> +#include <unistd.h>
>> +
>> +#include "nfsd_path.h"
>> +#include "nfslib.h"
>> +#include "reexport.h"
>> +#include "xcommon.h"
>> +#include "xlog.h"
>> +
>> +#define REEXPDB_DBFILE NFS_STATEDIR "/reexpdb.sqlite3"
>> +#define REEXPDB_DBFILE_WAIT_USEC (5000)
>> +
>> +static sqlite3 *db;
>> +static int init_done;
>> +
>> +static int prng_init(void)
>> +{
>> + int seed;
>> +
>> + if (getrandom(&seed, sizeof(seed), 0) != sizeof(seed)) {
>> + xlog(L_ERROR, "Unable to obtain seed for PRNG via getrandom()");
>> + return -1;
>> + }
>> +
>> + srand(seed);
>> + return 0;
>> +}
>> +
>> +static void wait_for_dbaccess(void)
>> +{
>> + usleep(REEXPDB_DBFILE_WAIT_USEC + (rand() % REEXPDB_DBFILE_WAIT_USEC));
>> +}
>> +
>> +/*
>> + * reexpdb_init - Initialize reexport database
>> + */
>> +int reexpdb_init(void)
>> +{
>> + char *sqlerr;
>> + int ret;
>> +
>> + if (init_done)
>> + return 0;
>> +
>> + if (prng_init() != 0)
>> + return -1;
>> +
>> + ret = sqlite3_open_v2(REEXPDB_DBFILE, &db, SQLITE_OPEN_READWRITE | SQLITE_OPEN_CREATE | SQLITE_OPEN_FULLMUTEX, NULL);
>> + if (ret != SQLITE_OK) {
>> + xlog(L_ERROR, "Unable to open reexport database: %s", sqlite3_errstr(ret));
>> + return -1;
>> + }
>> +
>> +again:
>> + ret = sqlite3_exec(db, "CREATE TABLE IF NOT EXISTS fsidnums (num INTEGER PRIMARY KEY CHECK (num > 0 AND num < 4294967296), path TEXT UNIQUE); CREATE INDEX IF NOT EXISTS idx_ids_path ON fsidnums (path);", NULL, NULL, &sqlerr);
>> + switch (ret) {
>> + case SQLITE_OK:
>> + init_done = 1;
>> + ret = 0;
>> + break;
>> + case SQLITE_BUSY:
>> + case SQLITE_LOCKED:
>> + wait_for_dbaccess();
>> + goto again;
>> + default:
>> + xlog(L_ERROR, "Unable to init reexport database: %s", sqlite3_errstr(ret));
>> + sqlite3_free(sqlerr);
>> + sqlite3_close_v2(db);
>> + ret = -1;
>> + }
>> +
>> + return ret;
>> +}
>> +
>> +/*
>> + * reexpdb_destroy - Undo reexpdb_init().
>> + */
>> +void reexpdb_destroy(void)
>> +{
>> + if (!init_done)
>> + return;
>> +
>> + sqlite3_close_v2(db);
>> +}
>> +
>> +static int get_fsidnum_by_path(char *path, uint32_t *fsidnum)
>> +{
>> + static const char fsidnum_by_path_sql[] = "SELECT num FROM fsidnums WHERE path = ?1;";
>> + sqlite3_stmt *stmt = NULL;
>> + int found = 0;
>> + int ret;
>> +
>> + ret = sqlite3_prepare_v2(db, fsidnum_by_path_sql, sizeof(fsidnum_by_path_sql), &stmt, NULL);
>> + if (ret != SQLITE_OK) {
>> + xlog(L_WARNING, "Unable to prepare SQL query '%s': %s", fsidnum_by_path_sql, sqlite3_errstr(ret));
>> + goto out;
>> + }
>> +
>> + ret = sqlite3_bind_text(stmt, 1, path, -1, NULL);
>> + if (ret != SQLITE_OK) {
>> + xlog(L_WARNING, "Unable to bind SQL query '%s': %s", fsidnum_by_path_sql, sqlite3_errstr(ret));
>> + goto out;
>> + }
>> +
>> +again:
>> + ret = sqlite3_step(stmt);
>> + switch (ret) {
>> + case SQLITE_ROW:
>> + *fsidnum = sqlite3_column_int(stmt, 0);
>> + found = 1;
>> + break;
>> + case SQLITE_DONE:
>> + /* No hit */
>> + found = 0;
>> + break;
>> + case SQLITE_BUSY:
>> + case SQLITE_LOCKED:
>> + wait_for_dbaccess();
>> + goto again;
>> + default:
>> + xlog(L_WARNING, "Error while looking up '%s' in database: %s", path, sqlite3_errstr(ret));
>> + }
>> +
>> +out:
>> + sqlite3_finalize(stmt);
>> + return found;
>> +}
>> +
>> +static int get_path_by_fsidnum(uint32_t fsidnum, char **path)
>> +{
>> + static const char path_by_fsidnum_sql[] = "SELECT path FROM fsidnums WHERE num = ?1;";
>> + sqlite3_stmt *stmt = NULL;
>> + int found = 0;
>> + int ret;
>> +
>> + ret = sqlite3_prepare_v2(db, path_by_fsidnum_sql, sizeof(path_by_fsidnum_sql), &stmt, NULL);
>> + if (ret != SQLITE_OK) {
>> + xlog(L_WARNING, "Unable to prepare SQL query '%s': %s", path_by_fsidnum_sql, sqlite3_errstr(ret));
>> + goto out;
>> + }
>> +
>> + ret = sqlite3_bind_int(stmt, 1, fsidnum);
>> + if (ret != SQLITE_OK) {
>> + xlog(L_WARNING, "Unable to bind SQL query '%s': %s", path_by_fsidnum_sql, sqlite3_errstr(ret));
>> + goto out;
>> + }
>> +
>> +again:
>> + ret = sqlite3_step(stmt);
>> + switch (ret) {
>> + case SQLITE_ROW:
>> + *path = xstrdup((char *)sqlite3_column_text(stmt, 0));
>> + found = 1;
>> + break;
>> + case SQLITE_DONE:
>> + /* No hit */
>> + found = 0;
>> + break;
>> + case SQLITE_BUSY:
>> + case SQLITE_LOCKED:
>> + wait_for_dbaccess();
>> + goto again;
>> + default:
>> + xlog(L_WARNING, "Error while looking up '%i' in database: %s", fsidnum, sqlite3_errstr(ret));
>> + }
>> +
>> +out:
>> + sqlite3_finalize(stmt);
>> + return found;
>> +}
>> +
>> +static int new_fsidnum_by_path(char *path, uint32_t *fsidnum)
>> +{
>> + /*
>> + * This query is a little tricky. We use SQL to find and claim the smallest free fsid number.
>> + * To find a free fsid the fsidnums is left joined to itself but with an offset of 1.
>> + * Everything after the UNION statement is to handle the corner case where fsidnums
>> + * is empty. In this case we want 1 as first fsid number.
>> + */
>> + static const char new_fsidnum_by_path_sql[] = "INSERT INTO fsidnums VALUES ((SELECT ids1.num + 1 FROM fsidnums AS ids1 LEFT JOIN fsidnums AS ids2 ON ids2.num = ids1.num + 1 WHERE ids2.num IS NULL UNION SELECT 1 WHERE NOT EXISTS (SELECT NULL FROM fsidnums WHERE num = 1) LIMIT 1), ?1) RETURNING num;";
>> +
>> + sqlite3_stmt *stmt = NULL;
>> + int found = 0, check = 0;
>> + int ret;
>> +
>> + ret = sqlite3_prepare_v2(db, new_fsidnum_by_path_sql, sizeof(new_fsidnum_by_path_sql), &stmt, NULL);
>> + if (ret != SQLITE_OK) {
>> + xlog(L_WARNING, "Unable to prepare SQL query '%s': %s", new_fsidnum_by_path_sql, sqlite3_errstr(ret));
>> + goto out;
>> + }
>> +
>> + ret = sqlite3_bind_text(stmt, 1, path, -1, NULL);
>> + if (ret != SQLITE_OK) {
>> + xlog(L_WARNING, "Unable to bind SQL query '%s': %s", new_fsidnum_by_path_sql, sqlite3_errstr(ret));
>> + goto out;
>> + }
>> +
>> +again:
>> + ret = sqlite3_step(stmt);
>> + switch (ret) {
>> + case SQLITE_ROW:
>> + *fsidnum = sqlite3_column_int(stmt, 0);
>> + found = 1;
>> + break;
>> + case SQLITE_CONSTRAINT:
>> + /* Maybe we lost the race against another writer and the path is now present. */
>> + check = 1;
>> + break;
>> + case SQLITE_BUSY:
>> + case SQLITE_LOCKED:
>> + wait_for_dbaccess();
>> + goto again;
>> + default:
>> + xlog(L_WARNING, "Error while looking up '%s' in database: %s", path, sqlite3_errstr(ret));
>> + }
>> +
>> +out:
>> + sqlite3_finalize(stmt);
>> +
>> + if (check) {
>> + found = get_fsidnum_by_path(path, fsidnum);
>> + if (!found)
>> + xlog(L_WARNING, "SQLITE_CONSTRAINT error while inserting '%s' in database", path);
>> + }
>> +
>> + return found;
>> +}
>> +
>> +/*
>> + * reexpdb_fsidnum_by_path - Lookup a fsid by path.
>> + *
>> + * @path: File system path used as lookup key
>> + * @fsidnum: Pointer where found fsid is written to
>> + * @may_create: If non-zero, allocate new fsid if lookup failed
>> + *
>> + */
>> +int reexpdb_fsidnum_by_path(char *path, uint32_t *fsidnum, int may_create)
>> +{
>> + int found;
>> +
>> + found = get_fsidnum_by_path(path, fsidnum);
>> +
>> + if (!found && may_create)
>> + found = new_fsidnum_by_path(path, fsidnum);
>> +
>> + return found;
>> +}
>> +
>> +/*
>> + * reexpdb_uncover_subvolume - Make sure a subvolume is present.
>> + *
>> + * @fsidnum: Numerical fsid number to look for
>> + *
>> + * Subvolumes (NFS cross mounts) get automatically mounted upon first
>> + * access and can vanish after fs.nfs.nfs_mountpoint_timeout seconds.
>> + * Also if the NFS server reboots, clients can still have valid file
>> + * handles for such a subvolume.
>> + *
>> + * If kNFSd asks mountd for the path of a given fsidnum it can
>> + * trigger an automount by calling statfs() on the given path.
>> + */
>> +void reexpdb_uncover_subvolume(uint32_t fsidnum)
>> +{
>> + struct statfs64 st;
>> + char *path = NULL;
>> + int ret;
>> +
>> + if (get_path_by_fsidnum(fsidnum, &path)) {
>> + ret = nfsd_path_statfs64(path, &st);
>> + if (ret == -1)
>> + xlog(L_WARNING, "statfs() failed");
>> + }
>> +
>> + free(path);
>> +}
>> diff --git a/support/reexport/reexport.h b/support/reexport/reexport.h
>> new file mode 100644
>> index 00000000..bb6d2a1b
>> --- /dev/null
>> +++ b/support/reexport/reexport.h
>> @@ -0,0 +1,39 @@
>> +#ifndef REEXPORT_H
>> +#define REEXPORT_H
>> +
>> +enum {
>> + REEXP_NONE = 0,
>> + REEXP_AUTO_FSIDNUM,
>> + REEXP_PREDEFINED_FSIDNUM,
>> +};
>> +
>> +#ifdef HAVE_REEXPORT_SUPPORT
>> +int reexpdb_init(void);
>> +void reexpdb_destroy(void);
>> +int reexpdb_fsidnum_by_path(char *path, uint32_t *fsidnum, int may_create);
>> +int reexpdb_apply_reexport_settings(struct exportent *ep, char *flname, int flline);
>> +void reexpdb_uncover_subvolume(uint32_t fsidnum);
>> +#else
>> +static inline int reexpdb_init(void) { return 0; }
>> +static inline void reexpdb_destroy(void) {}
>> +static inline int reexpdb_fsidnum_by_path(char *path, uint32_t *fsidnum, int may_create)
>> +{
>> + (void)path;
>> + (void)may_create;
>> + *fsidnum = 0;
>> + return 0;
>> +}
>> +static inline int reexpdb_apply_reexport_settings(struct exportent *ep, char *flname, int flline)
>> +{
>> + (void)ep;
>> + (void)flname;
>> + (void)flline;
>> + return 0;
>> +}
>> +static inline void reexpdb_uncover_subvolume(uint32_t fsidnum)
>> +{
>> + (void)fsidnum;
>> +}
>> +#endif /* HAVE_REEXPORT_SUPPORT */
>> +
>> +#endif /* REEXPORT_H */
>
--
Chuck Lever
