plugins: only dlopen() each plugin once. dlcose() in destructor

plugin.c

@@ -0,0 +1,82 @@
+#include "plugin.h"
+
+#include <string.h>
+#include <dlfcn.h>
+
+#define LOG_MODULE "plugin"
+#define LOG_ENABLE_DBG 0
+#include "log.h"
+#include "config.h"
+#include "tllist.h"
+
+struct plugin {
+    char *name;
+    void *lib;
+};
+
+static tll(struct plugin) libs = tll_init();
+
+static void __attribute__((destructor))
+fini(void)
+{
+    tll_foreach(libs, plug) {
+        dlerror();
+        dlclose(plug->item.lib);
+
+        const char *dl_error = dlerror();
+        if (dl_error != NULL)
+            LOG_ERR("%s: dlclose(): %s", plug->item.name, dl_error);
+
+        free(plug->item.name);
+    }
+
+    tll_free(libs);
+}
+
+const struct module_info *
+plugin_load_module(const char *name)
+{
+    char path[128];
+    snprintf(path, sizeof(path), "./modules/lib%s.so", name);
+
+    void *lib = NULL;
+
+    /* Have we already loaded it? */
+    tll_foreach(libs, plug) {
+        if (strcmp(plug->item.name, name) == 0) {
+            lib = plug->item.lib;
+            LOG_DBG("%s already loaded: %p", name, lib);
+            break;
+        }
+    }
+
+    if (lib == NULL) {
+        /* Not loaded - do it now */
+        lib = dlopen(path, RTLD_LOCAL | RTLD_NOW);
+        LOG_DBG("%s: dlopened to %p", name, lib);
+
+        if (lib == NULL) {
+            LOG_ERR("%s: dlopen: %s", name, dlerror());
+            return NULL;
+        }
+
+        tll_push_back(libs, ((struct plugin){strdup(name), lib}));
+    }
+
+    /* TODO: use same name in all modules */
+    char sym[128];
+    snprintf(sym, sizeof(sym), "module_%s", name);
+
+    /* TODO: cache symbol */
+    dlerror(); /* Clear previous error */
+    const struct module_info *info = dlsym(lib, sym);
+
+    const char *dlsym_error = dlerror();
+    if (dlsym_error != NULL) {
+        LOG_ERR("%s: dlsym: %s", name, dlsym_error);
+        return NULL;
+    }
+
+    assert(info != NULL);
+    return info;
+}