util: Helper headers for shared memory cache

1 files changed, 117 insertions, 0 deletions

diff --git a/src/util/mmap_cache.h b/src/util/mmap_cache.h
new file mode 100644
index 00000000..0a4044a7
--- /dev/null
+++ b/src/util/mmap_cache.h
@@ -0,0 +1,117 @@
+/*
+   SSSD
+
+   Mmap Cache Common header
+
+   Copyright (C) Simo Sorce <ssorce@redhat.com>	2011
+
+   This program is free software; you can redistribute it and/or modify
+   it under the terms of the GNU General Public License as published by
+   the Free Software Foundation; either version 3 of the License, or
+   (at your option) any later version.
+
+   This program 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 General Public License for more details.
+
+   You should have received a copy of the GNU General Public License
+   along with this program.  If not, see <http://www.gnu.org/licenses/>.
+*/
+
+#ifndef _MMAP_CACHE_H_
+#define _MMAP_CACHE_H_
+
+#include "util/murmurhash3.h"
+
+
+/* NOTE: all the code here assumes that writing a uint32_t nto mmapped
+ * memory is an atomic operation and can't be split in multiple
+ * non-atomic operations */
+typedef uint32_t rel_ptr_t;
+
+/* align macros */
+#define MC_8 sizeof(uint8_t)
+#define MC_32 sizeof(uint32_t)
+#define MC_64 sizeof(uint64_t)
+#define MC_ALIGN32(size) ( ((size) + MC_32 -1) & (~(MC_32 -1)) )
+#define MC_ALIGN64(size) ( ((size) + MC_64 -1) & (~(MC_64 -1)) )
+#define MC_HEADER_SIZE MC_ALIGN64(sizeof(struct sss_mc_header))
+
+#define MC_HT_SIZE(elems) ( (elems) * MC_32 )
+#define MC_HT_ELEMS(size) ( (size) / MC_32 )
+#define MC_DT_SIZE(elems, payload) ( (elems) * (payload) )
+#define MC_FT_SIZE(elems) ( (elems) / 8 )
+/* ^^ 8 bits per byte so we need just elems/8 bytes to represent all blocks */
+
+#define MC_PTR_ADD(ptr, bytes) (void *)((uint8_t *)(ptr) + (bytes))
+#define MC_PTR_DIFF(ptr, base) ((uint8_t *)(ptr) - (uint8_t *)(base))
+
+#define MC_INVALID_PTR (void *)0xffffffff
+#define MC_INVALID_VAL 0xffffffff
+
+/*
+ * 32 seem a good compromise for slot size
+ * 4 blocks are enough for the average passwd entry of 42 bytes
+ * passwd records have 84 bytes of overhead, 128 - 82 = 46 bytes
+ * 3 blocks can contain a very minimal entry, 96 - 82 = 14 bytes
+ *
+ * 3 blocks are enough for groups w/o users (private user groups)
+ * group records have 68 bytes of overhead, 96 - 66 = 30 bytes
+ */
+#define MC_SLOT_SIZE 32
+#define MC_SIZE_TO_SLOTS(len) (((len) + (MC_SLOT_SIZE - 1)) / MC_SLOT_SIZE)
+#define MC_PTR_TO_SLOT(base, ptr) \
+                    (((uint8_t *)(ptr) - (uint8_t *)(base)) / MC_SLOT_SIZE)
+#define MC_SLOT_TO_PTR(base, slot, type) \
+                                (type *)((base) + ((slot) * MC_SLOT_SIZE))
+
+#define MC_VALID_BARRIER(val) (((val) & 0xff000000) == 0xf0000000)
+
+#define SSS_MC_MAJOR_VNO    0
+#define SSS_MC_MINOR_VNO    4
+
+#define SSS_MC_HEADER_ALIVE     1   /* current and in use */
+#define SSS_MC_HEADER_RECYCLED  2   /* file was recycled, reopen asap */
+
+#pragma pack(1)
+struct sss_mc_header {
+    uint32_t b1;            /* barrier 1 */
+    uint32_t major_vno;     /* major version number */
+    uint32_t minor_vno;     /* minor version number */
+    uint32_t status;        /* database status */
+    uint32_t seed;          /* random seed used to avoid collision attacks */
+    uint32_t dt_size;       /* data table size */
+    uint32_t ft_size;       /* free table size */
+    uint32_t ht_size;       /* hash table size */
+    rel_ptr_t data_table;   /* data table pointer relative to mmap base */
+    rel_ptr_t free_table;   /* free table pointer relative to mmap base */
+    rel_ptr_t hash_table;   /* hash table pointer relative to mmap base */
+    rel_ptr_t reserved;     /* reserved for future changes */
+    uint32_t b2;            /* barrier 2 */
+};
+
+struct sss_mc_rec {
+    uint32_t b1;            /* barrier 1 */
+    uint32_t len;           /* total record length including record data */
+    uint64_t expire;        /* record expiration time (cast to time_t) */
+    rel_ptr_t next;         /* ptr of next record rel to data_table */
+    uint32_t hash1;         /* val of first hash (usually name of record) */
+    uint32_t hash2;         /* val of second hash (usually id of record) */
+    uint32_t b2;            /* barrier 2 - 32 bytes mark, fits a slot */
+    char data[0];
+};
+
+struct sss_mc_pwd_data {
+    rel_ptr_t name;         /* ptr to name string, rel. to struct base addr */
+    uint32_t uid;
+    uint32_t gid;
+    uint32_t strs_len;      /* length of strs */
+    char strs[0];           /* concatenation of all passwd strings, each
+                             * string is zero terminated ordered as follows:
+                             * name, passwd, gecos, dir, shell */
+};
+#pragma pack()
+
+
+#endif /* _MMAP_CACHE_H_ */