v4 [PATCH 2/6] <nss_action.h>: New abstraction for combining NSS modules and NSS actions
DJ Delorie
dj@redhat.com
Tue Nov 10 21:46:02 GMT 2020
>From 9cb4fd5df60173d7009b3ea0b6731493d23c402e Mon Sep 17 00:00:00 2001
From: Florian Weimer <fweimer@redhat.com>
Date: Thu, 20 Feb 2020 09:32:27 +0100
Subject: [PATCH 2/6] <nss_action.h>: New abstraction for combining NSS modules
and NSS actions
---
nss/Makefile | 3 +-
nss/nss_action.c | 116 ++++++++++++++++++++++++
nss/nss_action.h | 108 ++++++++++++++++++++++
nss/nss_action_parse.c | 197 +++++++++++++++++++++++++++++++++++++++++
4 files changed, 423 insertions(+), 1 deletion(-)
create mode 100644 nss/nss_action.c
create mode 100644 nss/nss_action.h
create mode 100644 nss/nss_action_parse.c
diff --git a/nss/Makefile b/nss/Makefile
index 18035a4fb4..f3e555066b 100644
--- a/nss/Makefile
+++ b/nss/Makefile
@@ -30,7 +30,8 @@ routines = nsswitch getnssent getnssent_r digits_dots \
$(addsuffix -lookup,$(databases)) \
compat-lookup nss_hash nss_files_fopen \
nss_readline nss_parse_line_result \
- nss_fgetent_r nss_module
+ nss_fgetent_r nss_module nss_action \
+ nss_action_parse
# These are the databases that go through nss dispatch.
# Caution: if you add a database here, you must add its real name
diff --git a/nss/nss_action.c b/nss/nss_action.c
new file mode 100644
index 0000000000..b9c3b93fea
--- /dev/null
+++ b/nss/nss_action.c
@@ -0,0 +1,116 @@
+/* NSS actions, elements in a nsswitch.conf configuration line.
+ Copyright (c) 2020 Free Software Foundation, Inc.
+ This file is part of the GNU C Library.
+
+ The GNU C Library is free software; you can redistribute it and/or
+ modify it under the terms of the GNU Lesser General Public
+ License as published by the Free Software Foundation; either
+ version 2.1 of the License, or (at your option) any later version.
+
+ The GNU C Library is distributed in the hope that it will be useful,
+ but WITHOUT ANY WARRANTY; without even the implied warranty of
+ MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+ Lesser General Public License for more details.
+
+ You should have received a copy of the GNU Lesser General Public
+ License along with the GNU C Library; if not, see
+ <https://www.gnu.org/licenses/>. */
+
+#include <nss_action.h>
+
+#include <string.h>
+#include <libc-lock.h>
+
+/* Maintain a global list of NSS action lists. Since most databases
+ use the same list of actions, this list is usually short.
+ Deduplication in __nss_action_allocate ensures that the list does
+ not grow without bounds. */
+
+struct nss_action_list_wrapper
+{
+ /* The next element of the list. */
+ struct nss_action_list_wrapper *next;
+
+ /* Number of elements in the list (excluding the terminator). */
+ size_t count;
+
+ /* NULL-terminated list of actions. */
+ struct nss_action actions[];
+};
+
+/* Toplevel list of allocated NSS action lists. */
+static struct nss_action_list_wrapper *nss_actions;
+
+/* Lock covers the nss_actions list. */
+__libc_lock_define (static, nss_actions_lock);
+
+/* Returns true if the actions are equal (same module, same actions
+ array). */
+static bool
+actions_equal (const struct nss_action *a, const struct nss_action *b)
+{
+ return a->module == b->module && a->action_bits == b->action_bits;
+}
+
+
+/* Returns true if COUNT actions at A and B are equal (according to
+ actions_equal above). Caller must ensure that either A or B have at
+ least COUNT actions. */
+static bool
+action_lists_equal (const struct nss_action *a, const struct nss_action *b,
+ size_t count)
+{
+ for (size_t i = 0; i < count; ++i)
+ if (!actions_equal (a + i, b + i))
+ return false;
+ return true;
+}
+
+/* Returns a pre-allocated action list for COUNT actions at ACTIONS,
+ or NULL if no such list exists. */
+static nss_action_list
+find_allocated (struct nss_action *actions, size_t count)
+{
+ for (struct nss_action_list_wrapper *p = nss_actions; p != NULL; p = p->next)
+ if (p->count == count && action_lists_equal (p->actions, actions, count))
+ return p->actions;
+ return NULL;
+}
+
+nss_action_list
+__nss_action_allocate (struct nss_action *actions, size_t count)
+{
+ nss_action_list result = NULL;
+ __libc_lock_lock (nss_actions_lock);
+
+ result = find_allocated (actions, count);
+ if (result == NULL)
+ {
+ struct nss_action_list_wrapper *wrapper
+ = malloc (sizeof (*wrapper) + sizeof (*actions) * count);
+ if (wrapper != NULL)
+ {
+ wrapper->next = nss_actions;
+ wrapper->count = count;
+ memcpy (wrapper->actions, actions, sizeof (*actions) * count);
+ nss_actions = wrapper;
+ result = wrapper->actions;
+ }
+ }
+
+ __libc_lock_unlock (nss_actions_lock);
+ return result;
+}
+
+void __libc_freeres_fn_section
+__nss_action_freeres (void)
+{
+ struct nss_action_list_wrapper *current = nss_actions;
+ while (current != NULL)
+ {
+ struct nss_action_list_wrapper *next = current->next;
+ free (current);
+ current = next;
+ }
+ nss_actions = NULL;
+}
diff --git a/nss/nss_action.h b/nss/nss_action.h
new file mode 100644
index 0000000000..fa280afd05
--- /dev/null
+++ b/nss/nss_action.h
@@ -0,0 +1,108 @@
+/* NSS actions, elements in a nsswitch.conf configuration line.
+ Copyright (c) 2020 Free Software Foundation, Inc.
+ This file is part of the GNU C Library.
+
+ The GNU C Library is free software; you can redistribute it and/or
+ modify it under the terms of the GNU Lesser General Public
+ License as published by the Free Software Foundation; either
+ version 2.1 of the License, or (at your option) any later version.
+
+ The GNU C Library is distributed in the hope that it will be useful,
+ but WITHOUT ANY WARRANTY; without even the implied warranty of
+ MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+ Lesser General Public License for more details.
+
+ You should have received a copy of the GNU Lesser General Public
+ License along with the GNU C Library; if not, see
+ <https://www.gnu.org/licenses/>. */
+
+#ifndef _NSS_ACTION_H
+#define _NSS_ACTION_H
+
+#include <stddef.h>
+
+/* See nss_database.h for a summary of how this relates. */
+
+#include "nsswitch.h" /* For lookup_actions. */
+
+struct nss_module;
+
+/* A NSS action pairs a service module with the action for each result
+ state. */
+struct nss_action
+{
+ /* The service module that provides the functionality (potentially
+ not yet loaded). */
+ struct nss_module *module;
+
+ /* Action according to result. Two bits for each lookup_actions
+ value (from nsswitch.h), indexed by enum nss_status (from nss.h). */
+ unsigned int action_bits;
+};
+
+/* Value to add to first nss_status value to get zero. */
+#define NSS_STATUS_BIAS 2
+/* Number of bits per lookup action. */
+#define NSS_BPL 2
+#define NSS_BPL_MASK ((1 << NSS_BPL) - 1)
+
+/* Index in actions of an NSS status. Note that in nss/nss.h the
+ status starts at -2, and we shift that up to zero by adding 2.
+ Thus for example NSS_STATUS_TRYAGAIN, which is -2, would index into
+ the 0th bit place as expected. */
+static inline int
+nss_actions_bits_index (enum nss_status status)
+{
+ return NSS_BPL * (NSS_STATUS_BIAS + status);
+}
+
+/* Returns the lookup_action value for STATUS in ACTION. */
+static inline lookup_actions
+nss_action_get (const struct nss_action *action, enum nss_status status)
+{
+ return ((action->action_bits >> nss_actions_bits_index (status))
+ & NSS_BPL_MASK);
+}
+
+/* Sets the lookup_action value for STATUS in ACTION. */
+static inline void
+nss_action_set (struct nss_action *action,
+ enum nss_status status, lookup_actions actions)
+{
+ int offset = nss_actions_bits_index (status);
+ unsigned int mask = NSS_BPL_MASK << offset;
+ action->action_bits = ((action->action_bits & ~mask)
+ | ((unsigned int) actions << offset));
+}
+
+static inline void
+nss_action_set_all (struct nss_action *action, lookup_actions actions)
+{
+ unsigned int bits = actions & NSS_BPL_MASK;
+ action->action_bits = ( bits
+ | (bits << (NSS_BPL * 1))
+ | (bits << (NSS_BPL * 2))
+ | (bits << (NSS_BPL * 3))
+ | (bits << (NSS_BPL * 4))
+ );
+}
+
+/* A list of struct nss_action objects in array terminated by an
+ action with a NULL module. */
+typedef struct nss_action *nss_action_list;
+
+/* Returns a pointer to an allocated NSS action list that has COUNT
+ actions that matches the array at ACTIONS. */
+nss_action_list __nss_action_allocate (struct nss_action *actions,
+ size_t count) attribute_hidden;
+
+/* Returns a pointer to a list allocated by __nss_action_allocate, or
+ NULL on error. ENOMEM means a (temporary) memory allocation error,
+ EINVAL means that LINE is syntactically invalid. */
+nss_action_list __nss_action_parse (const char *line);
+
+/* Called from __libc_freeres. */
+void __nss_action_freeres (void) attribute_hidden;
+
+
+#endif /* _NSS_ACTION_H */
diff --git a/nss/nss_action_parse.c b/nss/nss_action_parse.c
new file mode 100644
index 0000000000..52acdbd9f2
--- /dev/null
+++ b/nss/nss_action_parse.c
@@ -0,0 +1,197 @@
+/* Parse a service line from nsswitch.conf.
+ Copyright (c) 1996-2020 Free Software Foundation, Inc.
+ This file is part of the GNU C Library.
+
+ The GNU C Library is free software; you can redistribute it and/or
+ modify it under the terms of the GNU Lesser General Public
+ License as published by the Free Software Foundation; either
+ version 2.1 of the License, or (at your option) any later version.
+
+ The GNU C Library is distributed in the hope that it will be useful,
+ but WITHOUT ANY WARRANTY; without even the implied warranty of
+ MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+ Lesser General Public License for more details.
+
+ You should have received a copy of the GNU Lesser General Public
+ License along with the GNU C Library; if not, see
+ <https://www.gnu.org/licenses/>. */
+
+#include "nss_action.h"
+#include "nss_module.h"
+
+#include <ctype.h>
+#include <string.h>
+#include <stdbool.h>
+
+/* Staging area during parsing. */
+#define DYNARRAY_STRUCT action_list
+#define DYNARRAY_ELEMENT struct nss_action
+#define DYNARRAY_PREFIX action_list_
+#include <malloc/dynarray-skeleton.c>
+
+/* Skip whitespace in line[]. */
+#define SKIP_WS() \
+ while (line[0] != '\0' && isspace (line[0])) \
+ ++line;
+
+/* Read the source names:
+ `( <source> ( "[" "!"? (<status> "=" <action> )+ "]" )? )*'
+ */
+static bool
+nss_action_parse (const char *line, struct action_list *result)
+{
+ while (1)
+ {
+ SKIP_WS ();
+ if (line[0] == '\0')
+ /* No more sources specified. */
+ return true;
+
+ /* Read <source> identifier. */
+ const char *name = line;
+ while (line[0] != '\0' && !isspace (line[0]) && line[0] != '[')
+ ++line;
+ if (name == line)
+ return true;
+
+ struct nss_action new_service
+ = { .module = __nss_module_allocate (name, line - name), };
+ if (new_service.module == NULL)
+ {
+ /* Memory allocation error. */
+ action_list_mark_failed (result);
+ return false;
+ }
+ nss_action_set_all (&new_service, NSS_ACTION_CONTINUE);
+ nss_action_set (&new_service, NSS_STATUS_SUCCESS, NSS_ACTION_RETURN);
+ nss_action_set (&new_service, NSS_STATUS_RETURN, NSS_ACTION_RETURN);
+
+ SKIP_WS ();
+
+ if (line[0] == '[')
+ {
+ /* Read criterions. */
+
+ /* Skip the '['. */
+ ++ line;
+ SKIP_WS ();
+
+ do
+ {
+ int not;
+ enum nss_status status;
+ lookup_actions action;
+
+ /* Grok ! before name to mean all statuses but that one. */
+ not = line[0] == '!';
+ if (not)
+ ++line;
+
+ /* Read status name. */
+ name = line;
+ while (line[0] != '\0' && !isspace (line[0]) && line[0] != '='
+ && line[0] != ']')
+ ++line;
+
+ /* Compare with known statuses. */
+ if (line - name == 7)
+ {
+ if (__strncasecmp (name, "SUCCESS", 7) == 0)
+ status = NSS_STATUS_SUCCESS;
+ else if (__strncasecmp (name, "UNAVAIL", 7) == 0)
+ status = NSS_STATUS_UNAVAIL;
+ else
+ return false;
+ }
+ else if (line - name == 8)
+ {
+ if (__strncasecmp (name, "NOTFOUND", 8) == 0)
+ status = NSS_STATUS_NOTFOUND;
+ else if (__strncasecmp (name, "TRYAGAIN", 8) == 0)
+ status = NSS_STATUS_TRYAGAIN;
+ else
+ return false;
+ }
+ else
+ return false;
+
+ SKIP_WS ();
+ if (line[0] != '=')
+ return false;
+
+ /* Skip the '='. */
+ ++ line;
+ SKIP_WS ();
+ name = line;
+ while (line[0] != '\0' && !isspace (line[0]) && line[0] != '='
+ && line[0] != ']')
+ ++line;
+
+ if (line - name == 6 && __strncasecmp (name, "RETURN", 6) == 0)
+ action = NSS_ACTION_RETURN;
+ else if (line - name == 8
+ && __strncasecmp (name, "CONTINUE", 8) == 0)
+ action = NSS_ACTION_CONTINUE;
+ else if (line - name == 5
+ && __strncasecmp (name, "MERGE", 5) == 0)
+ action = NSS_ACTION_MERGE;
+ else
+ return false;
+
+ if (not)
+ {
+ /* Save the current action setting for this status,
+ set them all to the given action, and reset this one. */
+ const lookup_actions save
+ = nss_action_get (&new_service, status);
+ nss_action_set_all (&new_service, action);
+ nss_action_set (&new_service, status, save);
+ }
+ else
+ nss_action_set (&new_service, status, action);
+
+ SKIP_WS ();
+ }
+ while (line[0] != ']');
+
+ /* Skip the ']'. */
+ ++line;
+ }
+
+ action_list_add (result, new_service);
+ }
+}
+
+nss_action_list
+ __nss_action_parse (const char *line)
+{
+ struct action_list list;
+ action_list_init (&list);
+ if (nss_action_parse (line, &list))
+ {
+ size_t size = action_list_size (&list);
+ nss_action_list result
+ = malloc (sizeof (*result) * (size + 1));
+ if (result == NULL)
+ {
+ action_list_free (&list);
+ return NULL;
+ }
+ memcpy (result, action_list_begin (&list), sizeof (*result) * size);
+ /* Sentinel. */
+ result[size].module = NULL;
+ return result;
+ }
+ else if (action_list_has_failed (&list))
+ {
+ /* Memory allocation error. */
+ __set_errno (ENOMEM);
+ return NULL;
+ }
+ else
+ {
+ /* Parse error. */
+ __set_errno (EINVAL);
+ return NULL;
+ }
+}
--
2.21.1
More information about the Libc-alpha
mailing list