unit: add minimal condition checker for unit startup

1 files changed, 158 insertions, 0 deletions

diff --git a/src/condition.c b/src/condition.c
new file mode 100644
index 0000000000..8c2db2d3e9
--- /dev/null
+++ b/src/condition.c
@@ -0,0 +1,158 @@
+/*-*- Mode: C; c-basic-offset: 8; indent-tabs-mode: nil -*-*/
+
+/***
+  This file is part of systemd.
+
+  Copyright 2010 ProFUSION embedded systems
+
+  systemd 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 2 of the License, or
+  (at your option) any later version.
+
+  systemd 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 systemd; If not, see <http://www.gnu.org/licenses/>.
+***/
+
+#include <stdlib.h>
+#include <errno.h>
+#include <string.h>
+#include <unistd.h>
+
+#include "util.h"
+#include "condition.h"
+
+Condition* condition_new(ConditionType type, const char *parameter, bool negate) {
+        Condition *c;
+
+        c = new0(Condition, 1);
+        c->type = type;
+        c->negate = negate;
+
+        if (!(c->parameter = strdup(parameter))) {
+                free(c);
+                return NULL;
+        }
+
+        return c;
+}
+
+void condition_free(Condition *c) {
+        assert(c);
+
+        free(c->parameter);
+        free(c);
+}
+
+void condition_free_list(Condition *first) {
+        Condition *c, *n;
+
+        LIST_FOREACH_SAFE(conditions, c, n, first)
+                condition_free(c);
+}
+
+static bool test_kernel_command_line(const char *parameter) {
+        char *line, *w, *state, *word = NULL;
+        bool equal;
+        int r;
+        size_t l, pl;
+        bool found = false;
+
+        if ((r = read_one_line_file("/proc/cmdline", &line)) < 0) {
+                log_warning("Failed to read /proc/cmdline, ignoring: %s", strerror(-r));
+                return false;
+        }
+
+        equal = !!strchr(parameter, '=');
+        pl = strlen(parameter);
+
+        FOREACH_WORD_QUOTED(w, l, line, state) {
+
+                free(word);
+                if (!(word = strndup(w, l)))
+                        break;
+
+                if (equal) {
+                        if (streq(word, parameter)) {
+                                found = true;
+                                break;
+                        }
+                } else {
+                        if (startswith(word, parameter) && (word[pl] == '=' || word[pl] == 0)) {
+                                found = true;
+                                break;
+                        }
+                }
+
+        }
+
+        free(word);
+        free(line);
+
+        return found;
+}
+
+bool condition_test(Condition *c) {
+        assert(c);
+
+        switch(c->type) {
+
+        case CONDITION_PATH_EXISTS:
+                return (access(c->parameter, F_OK) >= 0) == !c->negate;
+
+        case CONDITION_KERNEL_COMMAND_LINE:
+                return !!test_kernel_command_line(c->parameter) == !c->negate;
+
+        default:
+                assert_not_reached("Invalid condition type.");
+        }
+}
+
+bool condition_test_list(Condition *first) {
+        Condition *c;
+
+        /* If the condition list is empty, then it is true */
+        if (!first)
+                return true;
+
+        /* Otherwise, if any of the conditions apply we return true */
+        LIST_FOREACH(conditions, c, first)
+                if (condition_test(c))
+                        return true;
+
+        return false;
+}
+
+void condition_dump(Condition *c, FILE *f, const char *prefix) {
+        assert(c);
+        assert(f);
+
+        if (!prefix)
+                prefix = "";
+
+        fprintf(f,
+                "%s%s: %s%s\n",
+                prefix,
+                condition_type_to_string(c->type),
+                c->negate ? "!" : "",
+                c->parameter);
+}
+
+void condition_dump_list(Condition *first, FILE *f, const char *prefix) {
+        Condition *c;
+
+        LIST_FOREACH(conditions, c, first)
+                condition_dump(c, f, prefix);
+}
+
+static const char* const condition_type_table[_CONDITION_TYPE_MAX] = {
+        [CONDITION_KERNEL_COMMAND_LINE] = "ConditionKernelCommandLine",
+        [CONDITION_PATH_EXISTS] = "ConditionPathExists"
+};
+
+DEFINE_STRING_TABLE_LOOKUP(condition_type, ConditionType);