ifupdown: code to deconstruct the state_list gracefully

(patch by Gabriel L. Somlo <somlo@cmu.edu>)


git-svn-id: svn://busybox.net/trunk/busybox@18018 69ca8d6d-28ef-0310-b511-8ec308f3f277

3 files changed, 45 insertions, 12 deletions

diff --git a/include/libbb.h b/include/libbb.h
index 4293ae269..809d8446a 100644
--- a/include/libbb.h
+++ b/include/libbb.h
@@ -475,6 +475,7 @@ typedef struct llist_s {
 extern void llist_add_to(llist_t **old_head, void *data);
 extern void llist_add_to_end(llist_t **list_head, void *data);
 extern void *llist_pop(llist_t **elm);
+extern void llist_unlink(llist_t **head, llist_t *elm);
 extern void llist_free(llist_t *elm, void (*freeit)(void *data));
 extern llist_t* llist_rev(llist_t *list);
 
diff --git a/libbb/llist.c b/libbb/llist.c
index 0a5978a26..2b34f762c 100644
--- a/libbb/llist.c
+++ b/libbb/llist.c
@@ -45,21 +45,40 @@ void llist_add_to_end(llist_t ** list_head, void *data)
 /* Remove first element from the list and return it */
 void *llist_pop(llist_t ** head)
 {
-        void *data;
+        void *data, *next;
 
         if (!*head)
-                data = *head;
-        else {
-                void *next = (*head)->link;
+                return NULL;
 
-                data = (*head)->data;
-                free(*head);
-                *head = next;
-        }
+        data = (*head)->data;
+        next = (*head)->link;
+        free(*head);
+        *head = next;
 
         return data;
 }
 
+/* Unlink arbitrary given element from the list */
+void llist_unlink(llist_t **head, llist_t *elm)
+{
+        llist_t *crt;
+
+        if (!(elm && *head))
+                return;
+
+        if (elm == *head) {
+                *head = (*head)->link;
+                return;
+        }
+
+        for (crt = *head; crt; crt = crt->link) {
+                if (crt->link == elm) {
+                        crt->link = elm->link;
+                        return;
+                }
+        }
+}
+
 /* Recursively free all elements in the linked list.  If freeit != NULL
  * call it on each datum in the list */
 void llist_free(llist_t * elm, void (*freeit) (void *data))
diff --git a/networking/ifupdown.c b/networking/ifupdown.c
index ccebecd95..c7cb85350 100644
--- a/networking/ifupdown.c
+++ b/networking/ifupdown.c
@@ -1091,6 +1091,7 @@ int ifupdown_main(int argc, char **argv)
         llist_t *state_list = NULL;
         llist_t *target_list = NULL;
         const char *interfaces = "/etc/network/interfaces";
+        FILE *state_fp;
         int any_failures = 0;
 
         cmds = iface_down;
@@ -1117,6 +1118,19 @@ int ifupdown_main(int argc, char **argv)
         startup_PATH = getenv("PATH");
         if (!startup_PATH) startup_PATH = "";
 
+        /* Read the previous state from the state file */
+        state_fp = fopen_or_warn("/var/run/ifstate", "r");
+        if (state_fp) {
+                char *start, *end_ptr;
+                while ((start = xmalloc_fgets(state_fp)) != NULL) {
+                        /* We should only need to check for a single character */
+                        end_ptr = start + strcspn(start, " \t\n");
+                        *end_ptr = '\0';
+                        llist_add_to(&state_list, start);
+                }
+                fclose(state_fp);
+        }
+
         /* Create a list of interfaces to work on */
         if (DO_ALL) {
                 if (cmds == iface_up) {
@@ -1166,7 +1180,7 @@ int ifupdown_main(int argc, char **argv)
                                 }
                         } else {
                                 /* ifdown */
-                                if (iface_state) {
+                                if (!iface_state) {
                                         bb_error_msg("interface %s not configured", iface);
                                         continue;
                                 }
@@ -1236,7 +1250,8 @@ int ifupdown_main(int argc, char **argv)
                                         iface_state->data = newiface;
                                 }
                         } else {
-                                /* Remove an interface from the linked list */
+                                /* Remove an interface from state_list */
+                                llist_unlink(&state_list, iface_state);
                                 free(llist_pop(&iface_state));
                         }
                 }
@@ -1244,8 +1259,6 @@ int ifupdown_main(int argc, char **argv)
 
         /* Actually write the new state */
         if (!NO_ACT) {
-                FILE *state_fp;
-
                 state_fp = xfopen("/var/run/ifstate", "w");
                 while (state_list) {
                         if (state_list->data) {