1 files changed, 149 insertions, 0 deletions
diff --git a/src/libnetdata/os/system-maps/cached-uid-username.c b/src/libnetdata/os/system-maps/cached-uid-username.c
new file mode 100644
index 000000000..35d93f2f0
--- /dev/null
+++ b/src/libnetdata/os/system-maps/cached-uid-username.c
@@ -0,0 +1,149 @@
+// SPDX-License-Identifier: GPL-3.0-or-later
+
+#include "cached-uid-username.h"
+
+// --------------------------------------------------------------------------------------------------------------------
+// hashtable for caching uid to username mappings
+// key is the uid, value is username (STRING)
+
+#define SIMPLE_HASHTABLE_KEY_TYPE uid_t
+#define SIMPLE_HASHTABLE_VALUE_TYPE CACHED_USERNAME
+#define SIMPLE_HASHTABLE_VALUE2KEY_FUNCTION cached_username_to_uid_ptr
+#define SIMPLE_HASHTABLE_COMPARE_KEYS_FUNCTION compar_uid_ptr
+#define SIMPLE_HASHTABLE_NAME _USERNAMES_CACHE
+#include "libnetdata/simple_hashtable/simple_hashtable.h"
+
+static struct {
+    bool initialized;
+    SPINLOCK spinlock;
+    SIMPLE_HASHTABLE_USERNAMES_CACHE ht;
+} user_cache = {
+    .initialized = false,
+    .spinlock = NETDATA_SPINLOCK_INITIALIZER,
+    .ht = { 0 },
+};
+
+static uid_t *cached_username_to_uid_ptr(CACHED_USERNAME *cu) {
+    return &cu->uid;
+}
+
+static bool compar_uid_ptr(uid_t *a, uid_t *b) {
+    return *a == *b;
+}
+
+void cached_username_populate_by_uid(uid_t uid, const char *username, uint32_t version) {
+    internal_fatal(!user_cache.initialized, "system-users cache needs to be initialized");
+    if(!username || !*username) return;
+
+    spinlock_lock(&user_cache.spinlock);
+
+    XXH64_hash_t hash = XXH3_64bits(&uid, sizeof(uid));
+    SIMPLE_HASHTABLE_SLOT_USERNAMES_CACHE *sl = simple_hashtable_get_slot_USERNAMES_CACHE(&user_cache.ht, hash, &uid, true);
+    CACHED_USERNAME *cu = SIMPLE_HASHTABLE_SLOT_DATA(sl);
+    if(!cu || (cu->version && version > cu->version)) {
+        internal_fatal(cu && cu->uid != uid, "invalid uid matched from cache");
+
+        if(cu)
+            string_freez(cu->username);
+        else
+            cu = callocz(1, sizeof(*cu));
+
+        cu->version = version;
+        cu->uid = uid;
+        cu->username = string_strdupz(username);
+        simple_hashtable_set_slot_USERNAMES_CACHE(&user_cache.ht, sl, hash, cu);
+    }
+
+    spinlock_unlock(&user_cache.spinlock);
+}
+
+CACHED_USERNAME cached_username_get_by_uid(uid_t uid) {
+    internal_fatal(!user_cache.initialized, "system-users cache needs to be initialized");
+
+    spinlock_lock(&user_cache.spinlock);
+
+    XXH64_hash_t hash = XXH3_64bits(&uid, sizeof(uid));
+    SIMPLE_HASHTABLE_SLOT_USERNAMES_CACHE *sl = simple_hashtable_get_slot_USERNAMES_CACHE(&user_cache.ht, hash, &uid, true);
+    CACHED_USERNAME *cu = SIMPLE_HASHTABLE_SLOT_DATA(sl);
+    if(!cu) {
+        cu = callocz(1, sizeof(*cu));
+
+        static char tmp[1024]; // we are inside a global spinlock - it is ok to be static
+        struct passwd pw, *result = NULL;
+
+        if (getpwuid_r(uid, &pw, tmp, sizeof(tmp), &result) != 0 || !result || !pw.pw_name || !(*pw.pw_name)) {
+            char name[UINT64_MAX_LENGTH];
+            print_uint64(name, uid);
+            cu->username = string_strdupz(name);
+        }
+        else
+            cu->username = string_strdupz(pw.pw_name);
+
+        cu->uid = uid;
+        simple_hashtable_set_slot_USERNAMES_CACHE(&user_cache.ht, sl, hash, cu);
+    }
+
+    internal_fatal(cu->uid != uid, "invalid uid matched from cache");
+
+    CACHED_USERNAME rc = {
+        .version = cu->version,
+        .uid = cu->uid,
+        .username = string_dup(cu->username),
+    };
+
+    spinlock_unlock(&user_cache.spinlock);
+    return rc;
+}
+
+void cached_username_release(CACHED_USERNAME cu) {
+    string_freez(cu.username);
+}
+
+void cached_usernames_init(void) {
+    if(user_cache.initialized) return;
+    user_cache.initialized = true;
+
+    spinlock_init(&user_cache.spinlock);
+    simple_hashtable_init_USERNAMES_CACHE(&user_cache.ht, 100);
+}
+
+void cached_usernames_destroy(void) {
+    if(!user_cache.initialized) return;
+
+    spinlock_lock(&user_cache.spinlock);
+
+    for(SIMPLE_HASHTABLE_SLOT_USERNAMES_CACHE *sl = simple_hashtable_first_read_only_USERNAMES_CACHE(&user_cache.ht);
+         sl;
+         sl = simple_hashtable_next_read_only_USERNAMES_CACHE(&user_cache.ht, sl)) {
+        CACHED_USERNAME *u = SIMPLE_HASHTABLE_SLOT_DATA(sl);
+        if(u) {
+            string_freez(u->username);
+            freez(u);
+            // simple_hashtable_del_slot_USERNAMES_CACHE(&uc.ht, sl);
+        }
+    }
+
+    simple_hashtable_destroy_USERNAMES_CACHE(&user_cache.ht);
+    user_cache.initialized = false;
+
+    spinlock_unlock(&user_cache.spinlock);
+}
+
+void cached_usernames_delete_old_versions(uint32_t version) {
+    if(!user_cache.initialized) return;
+
+    spinlock_lock(&user_cache.spinlock);
+
+    for(SIMPLE_HASHTABLE_SLOT_USERNAMES_CACHE *sl = simple_hashtable_first_read_only_USERNAMES_CACHE(&user_cache.ht);
+         sl;
+         sl = simple_hashtable_next_read_only_USERNAMES_CACHE(&user_cache.ht, sl)) {
+        CACHED_USERNAME *cu = SIMPLE_HASHTABLE_SLOT_DATA(sl);
+        if(cu && cu->version && cu->version < version) {
+            string_freez(cu->username);
+            freez(cu);
+            simple_hashtable_del_slot_USERNAMES_CACHE(&user_cache.ht, sl);
+        }
+    }
+
+    spinlock_unlock(&user_cache.spinlock);
+}