conntrackd: add child process infrastructure

This patch adds a simple infrastructure that allows to account
the child processes that have been forked. This also includes
a callback handler that can be registered that is called once
the child process finishes.

We can extended this later to include an alarm to limit the
maximum lifetime of a forked child process. This is good to
ensure that child processes behave timely.

Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>

4 files changed, 66 insertions, 6 deletions

diff --git a/src/Makefile.am b/src/Makefile.am
index 8a45bf9..decc545 100644
--- a/src/Makefile.am
+++ b/src/Makefile.am
@@ -12,7 +12,7 @@ conntrack_LDFLAGS = $(all_libraries) @LIBNETFILTER_CONNTRACK_LIBS@
 
 conntrackd_SOURCES = alarm.c main.c run.c hash.c queue.c rbtree.c \
 		    local.c log.c mcast.c udp.c netlink.c vector.c \
-		    filter.c fds.c event.c \
+		    filter.c fds.c event.c process.c \
 		    cache.c cache_iterators.c \
 		    cache_timer.c cache_wt.c \
 		    sync-mode.c sync-alarm.c sync-ftfw.c sync-notrack.c \
diff --git a/src/process.c b/src/process.c
new file mode 100644
index 0000000..a89f388
--- /dev/null
+++ b/src/process.c
@@ -0,0 +1,55 @@
+/*
+ * (C) 2009 by Pablo Neira Ayuso <pablo@netfilter.org>
+ * 
+ * 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 2 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, write to the Free Software
+ * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
+ */
+
+#include "conntrackd.h"
+#include "process.h"
+
+static LIST_HEAD(process_list);
+
+int fork_process_new(void (*cb)(void *data), void *data)
+{
+	struct child_process *c;
+
+	c = calloc(sizeof(struct child_process), 1);
+	if (c == NULL)
+		return -1;
+
+	c->cb = cb;
+	c->data = data;
+
+	list_add(&c->head, &process_list);
+
+	return fork();
+}
+
+int fork_process_delete(int pid)
+{
+	struct child_process *this, *tmp;
+
+	list_for_each_entry_safe(this, tmp, &process_list, head) {
+		if (this->pid == pid) {
+			list_del(&this->head);
+			if (this->cb) {
+				this->cb(this->data);
+			}
+			free(this);
+			return 1;
+		}
+	}
+	return 0;
+}
diff --git a/src/run.c b/src/run.c
index 6465699..09e2ae9 100644
--- a/src/run.c
+++ b/src/run.c
@@ -25,6 +25,7 @@
 #include "alarm.h"
 #include "fds.h"
 #include "traffic_stats.h"
+#include "process.h"
 
 #include <errno.h>
 #include <signal.h>
@@ -77,6 +78,9 @@ static void child(int foo)
 			STATE(stats).wait_failed++;
 			break;
 		}
+		/* delete process from list and run the callback */
+		fork_process_delete(ret);
+
 		if (!WIFSIGNALED(status))
 			continue;
 
diff --git a/src/sync-mode.c b/src/sync-mode.c
index 298fcd2..0d35923 100644
--- a/src/sync-mode.c
+++ b/src/sync-mode.c
@@ -26,6 +26,7 @@
 #include "fds.h"
 #include "event.h"
 #include "queue.h"
+#include "process.h"
 
 #include <errno.h>
 #include <unistd.h>
@@ -391,28 +392,28 @@ static int local_handler_sync(int fd, int type, void *data)
 
 	switch(type) {
 	case DUMP_INTERNAL:
-		ret = fork();
+		ret = fork_process_new(NULL, NULL);
 		if (ret == 0) {
 			cache_dump(STATE_SYNC(internal), fd, NFCT_O_PLAIN);
 			exit(EXIT_SUCCESS);
 		}
 		break;
 	case DUMP_EXTERNAL:
-		ret = fork();
+		ret = fork_process_new(NULL, NULL);
 		if (ret == 0) {
 			cache_dump(STATE_SYNC(external), fd, NFCT_O_PLAIN);
 			exit(EXIT_SUCCESS);
 		} 
 		break;
 	case DUMP_INT_XML:
-		ret = fork();
+		ret = fork_process_new(NULL, NULL);
 		if (ret == 0) {
 			cache_dump(STATE_SYNC(internal), fd, NFCT_O_XML);
 			exit(EXIT_SUCCESS);
 		}
 		break;
 	case DUMP_EXT_XML:
-		ret = fork();
+		ret = fork_process_new(NULL, NULL);
 		if (ret == 0) {
 			cache_dump(STATE_SYNC(external), fd, NFCT_O_XML);
 			exit(EXIT_SUCCESS);
@@ -421,7 +422,7 @@ static int local_handler_sync(int fd, int type, void *data)
 	case COMMIT:
 		/* delete the reset alarm if any before committing */
 		del_alarm(&STATE_SYNC(reset_cache_alarm));
-		ret = fork();
+		ret = fork_process_new(NULL, NULL);
 		if (ret == 0) {
 			dlog(LOG_NOTICE, "committing external cache");
 			cache_commit(STATE_SYNC(external));