gNFS : make it possible to mount a subdir that actually is a symlink

We are using the function to export all sub-directories in a gluster volume via nfs.
For real directories it works fine but if we have a symbolic link which points to the
directory, it is not possible to mount that directory via nfs and the nameof the link.
Kernel nfs resolves symlink handle to directoryhandle , similar gluster nfs should
resolve the symbolic link handle into directory handle.

Change-Id: I8bd07534ba9474f0b863f2335b2fd222ab625dba
BUG: 1157223
Signed-off-by: jiffin tony thottan <jthottan@redhat.com>
Reviewed-on: http://review.gluster.org/9052
Reviewed-by: soumya k <skoduri@redhat.com>
Tested-by: Gluster Build System <jenkins@build.gluster.com>
Reviewed-by: Jeff Darcy <jdarcy@redhat.com>
Reviewed-by: Niels de Vos <ndevos@redhat.com>

4 files changed, 398 insertions, 1 deletions

diff --git a/libglusterfs/src/common-utils.c b/libglusterfs/src/common-utils.c
index 0f1aceec39b..1318c4d49a6 100644
--- a/libglusterfs/src/common-utils.c
+++ b/libglusterfs/src/common-utils.c
@@ -3429,3 +3429,130 @@ fop_log_level (glusterfs_fop_t fop, int op_errno)
 
         return GF_LOG_ERROR;
 }
+
+/* This function will build absolute path of file/directory from the
+ * current location and relative path given from the current location
+ * For example consider our current path is /a/b/c/ and relative path
+ * from current location is ./../x/y/z .After parsing through this
+ * function the absolute path becomes /a/b/x/y/z/.
+ *
+ * The function gives a pointer to absolute path if it is successful
+ * and also returns zero.
+ * Otherwise function gives NULL pointer with returning an err value.
+ *
+ * So the user need to free memory allocated for path.
+ *
+ */
+
+int32_t
+gf_build_absolute_path (char *current_path, char *relative_path, char **path)
+{
+        char                    *absolute_path          = NULL;
+        char                    *token                  = NULL;
+        char                    *component              = NULL;
+        char                    *saveptr                = NULL;
+        char                    *end                    = NULL;
+        int                     ret                     = 0;
+        size_t                  relativepath_len        = 0;
+        size_t                  currentpath_len         = 0;
+        size_t                  max_absolutepath_len    = 0;
+
+        GF_ASSERT (current_path);
+        GF_ASSERT (relative_path);
+        GF_ASSERT (path);
+
+        if (!path || !current_path || !relative_path) {
+                ret = -EFAULT;
+                goto err;
+        }
+        /* Check for current and relative path
+         * current path should be absolute one and  start from '/'
+         * relative path should not start from '/'
+         */
+        currentpath_len = strlen (current_path);
+        if (current_path[0] != '/' || (currentpath_len > PATH_MAX)) {
+                gf_log (THIS->name, GF_LOG_ERROR, "Wrong value for"
+                                   " current path %s", current_path);
+                ret = -EINVAL;
+                goto err;
+        }
+
+        relativepath_len = strlen (relative_path);
+        if (relative_path[0] == '/' || (relativepath_len > PATH_MAX)) {
+                gf_log (THIS->name, GF_LOG_ERROR, "Wrong value for"
+                                   " relative path %s", relative_path);
+                ret = -EINVAL;
+                goto err;
+        }
+
+        /* It is maximum possible value for absolute path */
+        max_absolutepath_len = currentpath_len + relativepath_len + 2;
+
+        absolute_path = GF_CALLOC (1, max_absolutepath_len, gf_common_mt_char);
+        if (!absolute_path) {
+                ret = -ENOMEM;
+                goto err;
+        }
+        absolute_path[0] = '\0';
+
+        /* If current path is root i.e contains only "/", we do not
+         * need to copy it
+         */
+        if (strcmp (current_path, "/") != 0) {
+                strcpy (absolute_path, current_path);
+
+                /* We trim '/' at the end for easier string manipulation */
+                gf_path_strip_trailing_slashes (absolute_path);
+        }
+
+        /* Used to spilt relative path based on '/' */
+        component = gf_strdup (relative_path);
+        if (!component) {
+                ret = -ENOMEM;
+                goto err;
+        }
+
+        /* In the relative path, we want to consider ".." and "."
+         * if token is ".." , we just need to reduce one level hierarchy
+         * if token is "." , we just ignore it
+         * if token is NULL , end of relative path
+         * if absolute path becomes '\0' and still "..", then it is a bad
+         * relative path,  it points to out of boundary area and stop
+         * building the absolute path
+         * All other cases we just concatenate token to the absolute path
+         */
+        for (token = strtok_r (component,  "/", &saveptr),
+             end = strchr (absolute_path, '\0'); token;
+             token = strtok_r (NULL, "/", &saveptr)) {
+                if (strcmp (token, ".") == 0)
+                        continue;
+
+                else if (strcmp (token, "..") == 0) {
+
+                        if (absolute_path[0] == '\0') {
+                                ret = -EACCES;
+                                goto err;
+                         }
+
+                         end = strrchr (absolute_path, '/');
+                         *end = '\0';
+                } else {
+                        ret = snprintf (end, max_absolutepath_len -
+                                        strlen (absolute_path), "/%s", token);
+                        end = strchr (absolute_path , '\0');
+                }
+        }
+
+        if (strlen (absolute_path) > PATH_MAX) {
+                ret = -EINVAL;
+                goto err;
+        }
+        *path = gf_strdup (absolute_path);
+
+err:
+        if (component)
+                GF_FREE (component);
+        if (absolute_path)
+                GF_FREE (absolute_path);
+        return ret;
+}
diff --git a/libglusterfs/src/common-utils.h b/libglusterfs/src/common-utils.h
index 0d5abb42ec2..d2bc42b9662 100644
--- a/libglusterfs/src/common-utils.h
+++ b/libglusterfs/src/common-utils.h
@@ -653,4 +653,8 @@ gf_backtrace_done (char *buf);
 
 gf_loglevel_t
 fop_log_level (glusterfs_fop_t fop, int op_errno);
+
+int32_t
+gf_build_absolute_path (char *current_path, char *relative_path, char **path);
+
 #endif /* _COMMON_UTILS_H */
diff --git a/tests/bugs/bug-1157223-symlink-mounting.t b/tests/bugs/bug-1157223-symlink-mounting.t
new file mode 100644
index 00000000000..4ebc3453889
--- /dev/null
+++ b/tests/bugs/bug-1157223-symlink-mounting.t
@@ -0,0 +1,124 @@
+#!/bin/bash
+
+. $(dirname $0)/../include.rc
+. $(dirname $0)/../nfs.rc
+
+cleanup;
+
+## Start and create a volume
+TEST glusterd
+TEST pidof glusterd
+
+TEST $CLI volume info;
+TEST $CLI volume create $V0  $H0:$B0/$V0
+
+TEST $CLI volume start $V0;
+
+## Wait for volume to register with rpc.mountd
+EXPECT_WITHIN $NFS_EXPORT_TIMEOUT "1" is_nfs_export_available;
+
+## Mount NFS
+TEST mount_nfs $H0:/$V0 $N0 nolock;
+
+mkdir $N0/dir1;
+mkdir $N0/dir2;
+pushd $N0/ ;
+
+##link created using relative path
+ln -s dir1 symlink1;
+
+##relative path contains ".."
+ln -s ../dir1 dir2/symlink2;
+
+##link created using absolute path
+ln -s $N0/dir1 symlink3;
+
+##link pointing to another symlinks
+ln -s symlink1 symlink4
+ln -s symlink3 symlink5
+
+##dead links
+ln -s does/not/exist symlink6
+
+##link which contains ".." points out of glusterfs
+ln -s ../../ symlink7
+
+##links pointing to unauthorized area
+ln -s .glusterfs symlink8
+
+popd ;
+
+##Umount the volume
+EXPECT_WITHIN $UMOUNT_TIMEOUT "Y" umount_nfs $N0
+
+## Mount and umount NFS via directory
+TEST mount_nfs $H0:/$V0/dir1 $N0 nolock;
+EXPECT_WITHIN $UMOUNT_TIMEOUT "Y" umount_nfs $N0
+
+## Mount and umount NFS via symlink1
+TEST mount_nfs $H0:/$V0/symlink1 $N0 nolock;
+EXPECT_WITHIN $UMOUNT_TIMEOUT "Y" umount_nfs $N0
+
+## Mount and umount NFS via symlink2
+TEST  mount_nfs $H0:/$V0/dir2/symlink2 $N0 nolock;
+EXPECT_WITHIN $UMOUNT_TIMEOUT "Y" umount_nfs $N0
+
+## Mount NFS via symlink3 should fail
+TEST ! mount_nfs $H0:/$V0/symlink3 $N0 nolock;
+
+## Mount and umount NFS via symlink4
+TEST  mount_nfs $H0:/$V0/symlink4 $N0 nolock;
+EXPECT_WITHIN $UMOUNT_TIMEOUT "Y" umount_nfs $N0
+
+## Mount NFS via symlink5 should fail
+TEST ! mount_nfs $H0:/$V0/symlink5 $N0 nolock;
+
+## Mount NFS via symlink6 should fail
+TEST ! mount_nfs $H0:/$V0/symlink6 $N0 nolock;
+
+## Mount NFS via symlink7 should fail
+TEST ! mount_nfs $H0:/$V0/symlink7 $N0 nolock;
+
+## Mount NFS via symlink8 should fail
+TEST ! mount_nfs $H0:/$V0/symlink8 $N0 nolock;
+
+##Similar check for udp mount
+$CLI volume stop $V0
+TEST $CLI volume set $V0 nfs.mount-udp on
+$CLI volume start $V0
+
+## Wait for volume to register with rpc.mountd
+EXPECT_WITHIN $NFS_EXPORT_TIMEOUT "1" is_nfs_export_available;
+
+## Mount and umount NFS via directory
+TEST mount_nfs $H0:/$V0/dir1 $N0 nolock,mountproto=udp,proto=tcp;
+EXPECT_WITHIN $UMOUNT_TIMEOUT "Y" umount_nfs $N0
+
+## Mount and umount NFS via symlink1
+TEST mount_nfs $H0:/$V0/symlink1 $N0 nolock,mountproto=udp,proto=tcp;
+EXPECT_WITHIN $UMOUNT_TIMEOUT "Y" umount_nfs $N0
+
+## Mount and umount NFS via symlink2
+TEST  mount_nfs $H0:/$V0/dir2/symlink2 $N0 nolock,mountproto=udp,proto=tcp;
+EXPECT_WITHIN $UMOUNT_TIMEOUT "Y" umount_nfs $N0
+
+## Mount NFS via symlink3 should fail
+TEST ! mount_nfs $H0:/$V0/symlink3 $N0 nolock,mountproto=udp,proto=tcp;
+
+## Mount and umount NFS via symlink4
+TEST  mount_nfs $H0:/$V0/symlink4 $N0 nolock,mountproto=udp,proto=tcp;
+EXPECT_WITHIN $UMOUNT_TIMEOUT "Y" umount_nfs $N0
+
+## Mount NFS via symlink5 should fail
+TEST ! mount_nfs $H0:/$V0/symlink5 $N0 nolock,mountproto=udp,proto=tcp;
+
+## Mount NFS via symlink6 should fail
+TEST ! mount_nfs $H0:/$V0/symlink6 $N0 nolock,mountproto=udp,proto=tcp;
+
+##symlink7 is not check here, because in udp mount ../../ resolves into root '/'
+
+## Mount NFS via symlink8 should fail
+TEST ! mount_nfs $H0:/$V0/symlink8 $N0 nolock,mountproto=udp,proto=tcp;
+
+rm -rf $H0:$B0/
+cleanup;
diff --git a/xlators/nfs/server/src/mount3.c b/xlators/nfs/server/src/mount3.c
index 6be856ba92a..f76c1c41ff2 100644
--- a/xlators/nfs/server/src/mount3.c
+++ b/xlators/nfs/server/src/mount3.c
@@ -845,6 +845,15 @@ mnt3_resolve_subdir_cbk (call_frame_t *frame, void *cookie, xlator_t *this,
                          struct iatt *buf, dict_t *xattr,
                          struct iatt *postparent);
 
+int
+mnt3_parse_dir_exports (rpcsvc_request_t *req, struct mount3_state *ms,
+                        char *subdir);
+
+int32_t
+mnt3_readlink_cbk (call_frame_t *frame, void *cookie, xlator_t *this,
+                   int32_t op_ret, int32_t op_errno, const char *path,
+                   struct iatt *buf, dict_t *xdata);
+
 /* There are multiple components in the directory export path and each one
  * needs to be looked up one after the other.
  */
@@ -880,6 +889,13 @@ __mnt3_resolve_export_subdir_comp (mnt3_resolve_t *mres)
         }
 
         nfs_request_user_init (&nfu, mres->req);
+        if (IA_ISLNK (mres->resolveloc.inode->ia_type)) {
+                ret = nfs_readlink (mres->mstate->nfsx, mres->exp->vol, &nfu,
+                                    &mres->resolveloc, mnt3_readlink_cbk, mres);
+                gf_log (GF_MNT, GF_LOG_DEBUG, "Symlink found , need to resolve"
+                                              " into directory handle");
+                goto err;
+        }
         ret = nfs_lookup (mres->mstate->nfsx, mres->exp->vol, &nfu,
                           &mres->resolveloc, mnt3_resolve_subdir_cbk, mres);
 
@@ -954,7 +970,124 @@ err:
         return 0;
 }
 
+/* This function resolves symbolic link into directory path from
+ * the mount and restart the parsing process from the begining
+ *
+ * Note : Path specified in the symlink should be relative to the
+ *        symlink, because that is the one which is consistent throught
+ *        out the file system.
+ *        If the symlink resolves into another symlink ,then same process
+ *        will be repeated.
+ *        If symbolic links points outside the file system are not considered
+ *        here.
+ *
+ * TODO : 1.) This function cannot handle symlinks points to path which
+ *            goes out of the filesystem and comes backs again to same.
+ *            For example, consider vol is exported volume.It contains
+ *            dir,
+ *            symlink1 which points to ../vol/dir,
+ *            symlink2 which points to ../mnt/../vol/dir,
+ *            symlink1 and symlink2 are not handled right now.
+ *
+ *        2.) udp mount routine is much simpler from tcp routine and resolves
+ *            symlink directly.May be ,its better we change this routine
+ *            similar to udp
+ */
+int32_t
+mnt3_readlink_cbk (call_frame_t *frame, void *cookie, xlator_t *this,
+                   int32_t op_ret, int32_t op_errno, const char *path,
+                   struct iatt *buf, dict_t *xdata)
+{
+        mnt3_resolve_t           *mres            = NULL;
+        int                      ret              = -EFAULT;
+        char                     *real_loc        = NULL;
+        size_t                   path_len         = 0;
+        size_t                   parent_path_len  = 0;
+        char                     *parent_path     = NULL;
+        char                     *absolute_path   = NULL;
+        char                     *relative_path   = NULL;
+        int                      mntstat          = 0;
+
+        GF_ASSERT (frame);
+
+        mres = frame->local;
+        if (!mres || !path || (path[0] == '/') || (op_ret < 0))
+                goto mnterr;
 
+        /* Finding current location of symlink */
+        parent_path_len = strlen (mres->resolveloc.path) - strlen (mres->resolveloc.name);
+        parent_path = gf_strndup (mres->resolveloc.path, parent_path_len);
+        if (!parent_path) {
+                ret = -ENOMEM;
+                goto mnterr;
+        }
+
+        relative_path = gf_strdup (path);
+        if (!relative_path) {
+                ret = -ENOMEM;
+                goto mnterr;
+        }
+        /* Resolving into absolute path */
+        ret = gf_build_absolute_path (parent_path, relative_path, &absolute_path);
+        if (ret < 0) {
+                gf_log (GF_MNT, GF_LOG_ERROR, "Cannot resolve symlink, path"
+                               "is out of boundary from current location %s"
+                               "and with relative path %s pointed by symlink",
+                                parent_path, relative_path);
+
+                goto mnterr;
+        }
+
+        /* Building the actual mount path to be mounted */
+        path_len = strlen (mres->exp->vol->name) +  strlen (absolute_path)
+                   + strlen (mres->remainingdir) + 1;
+        real_loc = GF_CALLOC (1, path_len, gf_nfs_mt_char);
+        if (!real_loc) {
+                ret = -ENOMEM;
+                goto mnterr;
+        }
+        sprintf (real_loc , "%s%s", mres->exp->vol->name, absolute_path);
+        gf_path_strip_trailing_slashes (real_loc);
+
+        /* There may entries after symlink in the mount path,
+         * we should include remaining entries too */
+        if (strlen (mres->remainingdir) > 0)
+                strcat (real_loc, mres->remainingdir);
+
+        gf_log (GF_MNT, GF_LOG_DEBUG, "Resolved path is : %s%s "
+                        "and actual mount path is %s",
+                        absolute_path, mres->remainingdir, real_loc);
+
+        /* After the resolving the symlink , parsing should be done
+         * for the populated mount path
+         */
+        ret = mnt3_parse_dir_exports (mres->req, mres->mstate, real_loc);
+
+        if (ret) {
+                gf_log (GF_MNT, GF_LOG_ERROR,
+                        "Resolved into an unknown path %s%s "
+                        "from the current location of symlink %s",
+                         absolute_path, mres->remainingdir, parent_path);
+        }
+
+        GF_FREE (real_loc);
+        GF_FREE (absolute_path);
+        GF_FREE (parent_path);
+        GF_FREE (relative_path);
+
+        return ret;
+
+mnterr:
+        mntstat = mnt3svc_errno_to_mnterr (-ret);
+        mnt3svc_mnt_error_reply (mres->req, mntstat);
+        if (absolute_path)
+                GF_FREE (absolute_path);
+        if (parent_path)
+                GF_FREE (parent_path);
+        if (relative_path)
+                GF_FREE (relative_path);
+        return ret;
+}
 
 /* We will always have to perform a hard lookup on all the components of a
  * directory export for a mount request because in the mount reply we need the
@@ -996,6 +1129,13 @@ __mnt3_resolve_subdir (mnt3_resolve_t *mres)
         }
 
         nfs_request_user_init (&nfu, mres->req);
+        if (IA_ISLNK (mres->resolveloc.inode->ia_type)) {
+                ret = nfs_readlink (mres->mstate->nfsx, mres->exp->vol, &nfu,
+                                    &mres->resolveloc, mnt3_readlink_cbk, mres);
+                gf_log (GF_MNT, GF_LOG_DEBUG, "Symlink found , need to resolve "
+                                              "into directory handle");
+                goto err;
+        }
         ret = nfs_lookup (mres->mstate->nfsx, mres->exp->vol, &nfu,
                           &mres->resolveloc, mnt3_resolve_subdir_cbk, mres);
 
@@ -2054,13 +2194,15 @@ __mnt3udp_get_export_subdir_inode (struct svc_req *req, char *subdir,
          * TODO: Instead of linking against libgfapi.so, just for one API
          * i.e. glfs_resolve_at(), It would be cleaner if PATH name to
          * inode resolution code can be moved to libglusterfs.so or so.
+         * refer bugzilla for more details :
+         * https://bugzilla.redhat.com/show_bug.cgi?id=1161573
          */
         fs = glfs_new_from_ctx (exp->vol->ctx);
         if (!fs)
                 return NULL;
 
         ret = glfs_resolve_at (fs, exp->vol, NULL, subdir,
-                               &loc, &buf, 0 /* Follow link */,
+                               &loc, &buf, 1 /* Follow link */,
                                0 /* Hard lookup */);
 
         glfs_free_from_ctx (fs);