On 5/17/21 12:45 AM, NeilBrown wrote:
>
> Some filesystems cannot be exported without an fsid or uuid.
> tmpfs is the main example.
>
> When mountd (or exportd) creates nfsv4 pseudo-root exports for the path
> leading down to an export point it exports each directory without any
> fsid or uuid. If one of these directories is on tmp, that will fail.
>
> The net result is that exporting a subdirectory of a tmpfs filesystem
> will not work over NFSv4 as the parents within the filesystem cannot be
> exported. It will either fail, or fall-back to NFSv3 (depending on the
> version of the mount.nfs program).
>
> To fix this we need to provide an fsid or uuid for these pseudo-root
> exports. This patch does that by creating an RFC-4122 V5 compatible
> UUID based on an arbitrary seed and the path to the export.
>
> To check if an export needs a uuid, text_export() is moved from exportfs
> to libexport.a, modified slightly and renamed to export_test().
>
> Signed-off-by: NeilBrown <neilb@xxxxxxx>
Committed... (tag: nfs-utils-2-5-4-rc4)
Thanks!
steved.
> ---
>
> This version contains Chuck's suggestion for improving the uuid, and
> general clean-up.
>
> support/export/cache.c | 3 ++-
> support/export/export.c | 29 +++++++++++++++++++++++++++++
> support/export/v4root.c | 23 ++++++++++++++++++++++-
> support/include/exportfs.h | 1 +
> utils/exportd/Makefile.am | 2 +-
> utils/exportfs/exportfs.c | 38 +++-----------------------------------
> utils/mountd/Makefile.am | 2 +-
> 7 files changed, 59 insertions(+), 39 deletions(-)
>
> diff --git a/support/export/cache.c b/support/export/cache.c
> index 3e4f53c0a32e..a5823e92e9f2 100644
> --- a/support/export/cache.c
> +++ b/support/export/cache.c
> @@ -981,7 +981,8 @@ static int dump_to_cache(int f, char *buf, int blen, char *domain,
> write_secinfo(&bp, &blen, exp, flag_mask);
> if (exp->e_uuid == NULL || different_fs) {
> char u[16];
> - if (uuid_by_path(path, 0, 16, u)) {
> + if ((exp->e_flags & flag_mask & NFSEXP_FSID) == 0 &&
> + uuid_by_path(path, 0, 16, u)) {
> qword_add(&bp, &blen, "uuid");
> qword_addhex(&bp, &blen, u, 16);
> }
> diff --git a/support/export/export.c b/support/export/export.c
> index c753f68e4d63..03390dfc1de8 100644
> --- a/support/export/export.c
> +++ b/support/export/export.c
> @@ -10,9 +10,11 @@
> #include <config.h>
> #endif
>
> +#include <unistd.h>
> #include <string.h>
> #include <sys/types.h>
> #include <sys/param.h>
> +#include <fcntl.h>
> #include <netinet/in.h>
> #include <limits.h>
> #include <stdlib.h>
> @@ -420,3 +422,30 @@ export_hash(char *str)
>
> return num % HASH_TABLE_SIZE;
> }
> +
> +int export_test(struct exportent *eep, int with_fsid)
> +{
> + char *path = eep->e_path;
> + int flags = eep->e_flags | (with_fsid ? NFSEXP_FSID : 0);
> + /* beside max path, buf size should take protocol str into account */
> + char buf[NFS_MAXPATHLEN+1+64] = { 0 };
> + char *bp = buf;
> + int len = sizeof(buf);
> + int fd, n;
> +
> + n = snprintf(buf, len, "-test-client- ");
> + bp += n;
> + len -= n;
> + qword_add(&bp, &len, path);
> + if (len < 1)
> + return 0;
> + snprintf(bp, len, " 3 %d 65534 65534 0\n", flags);
> + fd = open("/proc/net/rpc/nfsd.export/channel", O_WRONLY);
> + if (fd < 0)
> + return 0;
> + n = nfsd_path_write(fd, buf, strlen(buf));
> + close(fd);
> + if (n < 0)
> + return 0;
> + return 1;
> +}
> diff --git a/support/export/v4root.c b/support/export/v4root.c
> index 3654bd7c10c0..c12a7d8562b2 100644
> --- a/support/export/v4root.c
> +++ b/support/export/v4root.c
> @@ -20,6 +20,7 @@
>
> #include <unistd.h>
> #include <errno.h>
> +#include <uuid/uuid.h>
>
> #include "xlog.h"
> #include "exportfs.h"
> @@ -89,11 +90,31 @@ v4root_create(char *path, nfs_export *export)
> strncpy(eep.e_path, path, sizeof(eep.e_path)-1);
> if (strcmp(path, "/") != 0)
> eep.e_flags &= ~NFSEXP_FSID;
> +
> + if (strcmp(path, "/") != 0 &&
> + !export_test(&eep, 0)) {
> + /* Need a uuid - base it on path using a fixed seed that
> + * was generated randomly.
> + */
> + const char seed_s[] = "39c6b5c1-3f24-4f4e-977c-7fe6546b8a25";
> + uuid_t seed, uuid;
> + char uuid_s[UUID_STR_LEN];
> + unsigned int i, j;
> +
> + uuid_parse(seed_s, seed);
> + uuid_generate_sha1(uuid, seed, path, strlen(path));
> + uuid_unparse_upper(uuid, uuid_s);
> + /* strip hyhens */
> + for (i = j = 0; uuid_s[i]; i++)
> + if (uuid_s[i] != '-')
> + uuid_s[j++] = uuid_s[i];
> + eep.e_uuid = uuid_s;
> + }
> set_pseudofs_security(&eep);
> exp = export_create(&eep, 0);
> if (exp == NULL)
> return NULL;
> - xlog(D_CALL, "v4root_create: path '%s' flags 0x%x",
> + xlog(D_CALL, "v4root_create: path '%s' flags 0x%x",
> exp->m_export.e_path, exp->m_export.e_flags);
> return &exp->m_export;
> }
> diff --git a/support/include/exportfs.h b/support/include/exportfs.h
> index 81d137210862..7c1b74537186 100644
> --- a/support/include/exportfs.h
> +++ b/support/include/exportfs.h
> @@ -173,5 +173,6 @@ struct export_features {
> struct export_features *get_export_features(void);
> void fix_pseudoflavor_flags(struct exportent *ep);
> char *exportent_realpath(struct exportent *eep);
> +int export_test(struct exportent *eep, int with_fsid);
>
> #endif /* EXPORTFS_H */
> diff --git a/utils/exportd/Makefile.am b/utils/exportd/Makefile.am
> index eb521f15032d..c95bdee76d3f 100644
> --- a/utils/exportd/Makefile.am
> +++ b/utils/exportd/Makefile.am
> @@ -16,7 +16,7 @@ exportd_SOURCES = exportd.c
> exportd_LDADD = ../../support/export/libexport.a \
> ../../support/nfs/libnfs.la \
> ../../support/misc/libmisc.a \
> - $(OPTLIBS) $(LIBBLKID) $(LIBPTHREAD)
> + $(OPTLIBS) $(LIBBLKID) $(LIBPTHREAD) -luuid
>
> exportd_CPPFLAGS = $(AM_CPPFLAGS) $(CPPFLAGS) \
> -I$(top_srcdir)/support/export
> diff --git a/utils/exportfs/exportfs.c b/utils/exportfs/exportfs.c
> index 25d757d8b4b4..bc76aaaf8714 100644
> --- a/utils/exportfs/exportfs.c
> +++ b/utils/exportfs/exportfs.c
> @@ -54,11 +54,6 @@ static int _lockfd = -1;
>
> struct state_paths etab;
>
> -static ssize_t exportfs_write(int fd, const char *buf, size_t len)
> -{
> - return nfsd_path_write(fd, buf, len);
> -}
> -
> /*
> * If we aren't careful, changes made by exportfs can be lost
> * when multiple exports process run at once:
> @@ -510,33 +505,6 @@ static int can_test(void)
> return 1;
> }
>
> -static int test_export(nfs_export *exp, int with_fsid)
> -{
> - char *path = exp->m_export.e_path;
> - int flags = exp->m_export.e_flags | (with_fsid ? NFSEXP_FSID : 0);
> - /* beside max path, buf size should take protocol str into account */
> - char buf[NFS_MAXPATHLEN+1+64] = { 0 };
> - char *bp = buf;
> - int len = sizeof(buf);
> - int fd, n;
> -
> - n = snprintf(buf, len, "-test-client- ");
> - bp += n;
> - len -= n;
> - qword_add(&bp, &len, path);
> - if (len < 1)
> - return 0;
> - snprintf(bp, len, " 3 %d 65534 65534 0\n", flags);
> - fd = open("/proc/net/rpc/nfsd.export/channel", O_WRONLY);
> - if (fd < 0)
> - return 0;
> - n = exportfs_write(fd, buf, strlen(buf));
> - close(fd);
> - if (n < 0)
> - return 0;
> - return 1;
> -}
> -
> static void
> validate_export(nfs_export *exp)
> {
> @@ -568,12 +536,12 @@ validate_export(nfs_export *exp)
>
> if ((exp->m_export.e_flags & NFSEXP_FSID) || exp->m_export.e_uuid ||
> fs_has_fsid) {
> - if ( !test_export(exp, 1)) {
> + if ( !export_test(&exp->m_export, 1)) {
> xlog(L_ERROR, "%s does not support NFS export", path);
> return;
> }
> - } else if ( !test_export(exp, 0)) {
> - if (test_export(exp, 1))
> + } else if ( !export_test(&exp->m_export, 0)) {
> + if (export_test(&exp->m_export, 1))
> xlog(L_ERROR, "%s requires fsid= for NFS export", path);
> else
> xlog(L_ERROR, "%s does not support NFS export", path);
> diff --git a/utils/mountd/Makefile.am b/utils/mountd/Makefile.am
> index 859f28ecd6f3..13b25c90f06e 100644
> --- a/utils/mountd/Makefile.am
> +++ b/utils/mountd/Makefile.am
> @@ -18,7 +18,7 @@ mountd_LDADD = ../../support/export/libexport.a \
> ../../support/nfs/libnfs.la \
> ../../support/misc/libmisc.a \
> $(OPTLIBS) \
> - $(LIBBSD) $(LIBWRAP) $(LIBNSL) $(LIBBLKID) $(LIBTIRPC) \
> + $(LIBBSD) $(LIBWRAP) $(LIBNSL) $(LIBBLKID) -luuid $(LIBTIRPC) \
> $(LIBPTHREAD)
> mountd_CPPFLAGS = $(AM_CPPFLAGS) $(CPPFLAGS) \
> -I$(top_builddir)/support/include \
>
