[PATCH v3 24/25] tools/xenstore: rework get_node()

[Juergen Gross <jgross@xxxxxxxx>]

Today get_node_canonicalized() is the only caller of get_node().

In order to prepare introducing a get_node() variant returning a
pointer to const struct node, do the following restructuring:

- move the call of read_node() from get_node() into
  get_node_canonicalized()

- rename get_node() to get_node_chk_perm()

- rename get_node_canonicalized() to get_node()

Signed-off-by: Juergen Gross <jgross@xxxxxxxx>
---
V3:
- new patch
---
 tools/xenstore/xenstored_core.c | 57 +++++++++++++++------------------
 1 file changed, 25 insertions(+), 32 deletions(-)

diff --git a/tools/xenstore/xenstored_core.c b/tools/xenstore/xenstored_core.c
index ec20bc042d..fa07bc0c31 100644
--- a/tools/xenstore/xenstored_core.c
+++ b/tools/xenstore/xenstored_core.c
@@ -996,27 +996,26 @@ static int errno_from_parents(struct connection *conn, 
const void *ctx,
  * If it fails, returns NULL and sets errno.
  * Temporary memory allocations are done with ctx.
  */
-static struct node *get_node(struct connection *conn,
-                            const void *ctx,
-                            const char *name,
-                            unsigned int perm)
+static bool get_node_chk_perm(struct connection *conn, const void *ctx,
+                             const struct node *node, const char *name,
+                             unsigned int perm)
 {
-       struct node *node;
        struct node_perms perms;
+       bool err = false;
 
-       node = read_node(conn, ctx, name);
        /* If we don't have permission, we don't have node. */
        if (node) {
                node_to_node_perms(node, &perms);
                if ((perm_for_conn(conn, &perms) & perm) != perm) {
                        errno = EACCES;
-                       node = NULL;
+                       err = true;
                }
        }
        /* Clean up errno if they weren't supposed to know. */
-       if (!node && !read_node_can_propagate_errno())
+       if (err && !read_node_can_propagate_errno())
                errno = errno_from_parents(conn, ctx, name, errno, perm);
-       return node;
+
+       return err;
 }
 
 static struct buffered_data *new_buffer(void *ctx)
@@ -1285,14 +1284,12 @@ const char *canonicalize(struct connection *conn, const 
void *ctx,
        return name;
 }
 
-static struct node *get_node_canonicalized(struct connection *conn,
-                                          const void *ctx,
-                                          const char *name,
-                                          const char **canonical_name,
-                                          unsigned int perm,
-                                          bool allow_special)
+static struct node *get_node(struct connection *conn, const void *ctx,
+                            const char *name, const char **canonical_name,
+                            unsigned int perm, bool allow_special)
 {
        const char *tmp_name;
+       struct node *node;
 
        if (!canonical_name)
                canonical_name = &tmp_name;
@@ -1300,7 +1297,10 @@ static struct node *get_node_canonicalized(struct 
connection *conn,
        if (!*canonical_name)
                return NULL;
 
-       return get_node(conn, ctx, *canonical_name, perm);
+       node = read_node(conn, ctx, *canonical_name);
+
+       return get_node_chk_perm(conn, ctx, node, *canonical_name, perm)
+              ? NULL : node;
 }
 
 static int send_directory(const void *ctx, struct connection *conn,
@@ -1308,8 +1308,7 @@ static int send_directory(const void *ctx, struct 
connection *conn,
 {
        struct node *node;
 
-       node = get_node_canonicalized(conn, ctx, onearg(in), NULL,
-                                     XS_PERM_READ, false);
+       node = get_node(conn, ctx, onearg(in), NULL, XS_PERM_READ, false);
        if (!node)
                return errno;
 
@@ -1330,8 +1329,7 @@ static int send_directory_part(const void *ctx, struct 
connection *conn,
                return EINVAL;
 
        /* First arg is node name. */
-       node = get_node_canonicalized(conn, ctx, in->buffer, NULL,
-                                     XS_PERM_READ, false);
+       node = get_node(conn, ctx, in->buffer, NULL, XS_PERM_READ, false);
        if (!node)
                return errno;
 
@@ -1380,8 +1378,7 @@ static int do_read(const void *ctx, struct connection 
*conn,
 {
        struct node *node;
 
-       node = get_node_canonicalized(conn, ctx, onearg(in), NULL,
-                                     XS_PERM_READ, false);
+       node = get_node(conn, ctx, onearg(in), NULL, XS_PERM_READ, false);
        if (!node)
                return errno;
 
@@ -1595,8 +1592,7 @@ static int do_write(const void *ctx, struct connection 
*conn,
        offset = strlen(vec[0]) + 1;
        datalen = in->used - offset;
 
-       node = get_node_canonicalized(conn, ctx, vec[0], &name, XS_PERM_WRITE,
-                                     false);
+       node = get_node(conn, ctx, vec[0], &name, XS_PERM_WRITE, false);
        if (!node) {
                /* No permissions, invalid input? */
                if (errno != ENOENT)
@@ -1624,8 +1620,7 @@ static int do_mkdir(const void *ctx, struct connection 
*conn,
        struct node *node;
        const char *name;
 
-       node = get_node_canonicalized(conn, ctx, onearg(in), &name,
-                                     XS_PERM_WRITE, false);
+       node = get_node(conn, ctx, onearg(in), &name, XS_PERM_WRITE, false);
 
        /* If it already exists, fine. */
        if (!node) {
@@ -1754,8 +1749,7 @@ static int do_rm(const void *ctx, struct connection *conn,
        const char *name;
        char *parentname;
 
-       node = get_node_canonicalized(conn, ctx, onearg(in), &name,
-                                     XS_PERM_WRITE, false);
+       node = get_node(conn, ctx, onearg(in), &name, XS_PERM_WRITE, false);
        if (!node) {
                /* Didn't exist already?  Fine, if parent exists. */
                if (errno == ENOENT) {
@@ -1797,8 +1791,7 @@ static int do_get_perms(const void *ctx, struct 
connection *conn,
        unsigned int len;
        struct node_perms perms;
 
-       node = get_node_canonicalized(conn, ctx, onearg(in), NULL, XS_PERM_READ,
-                                     true);
+       node = get_node(conn, ctx, onearg(in), NULL, XS_PERM_READ, true);
        if (!node)
                return errno;
 
@@ -1842,8 +1835,8 @@ static int do_set_perms(const void *ctx, struct 
connection *conn,
                return ENOENT;
 
        /* We must own node to do this (tools can do this too). */
-       node = get_node_canonicalized(conn, ctx, in->buffer, &name,
-                                     XS_PERM_WRITE | XS_PERM_OWNER, true);
+       node = get_node(conn, ctx, in->buffer, &name,
+                       XS_PERM_WRITE | XS_PERM_OWNER, true);
        if (!node)
                return errno;
 
-- 
2.35.3