netfilter: nf_log: use an array of loggers instead of list

Now that legacy ulog targets are not available anymore in the tree, we
can have up to two possible loggers:

1) The plain text logging via kernel logging ring.
2) The nfnetlink_log infrastructure which delivers log messages
   to userspace.

This patch replaces the list of loggers by an array of two pointers
per family for each possible logger and it also introduces a new field
to the nf_logger structure which indicates the position in the logger
array (based on the logger type).

This prepares a follow up patch that consolidates the nf_log_packet()
interface by allowing to specify the logger as parameter.

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

1 files changed, 24 insertions, 26 deletions

diff --git a/net/netfilter/nf_log.c b/net/netfilter/nf_log.c
index 85296d4eac0e..7a29a3a46172 100644
--- a/net/netfilter/nf_log.c
+++ b/net/netfilter/nf_log.c
@@ -16,16 +16,22 @@
 #define NF_LOG_PREFIXLEN		128
 #define NFLOGGER_NAME_LEN		64
 
-static struct list_head nf_loggers_l[NFPROTO_NUMPROTO] __read_mostly;
+static struct nf_logger __rcu *loggers[NFPROTO_NUMPROTO][NF_LOG_TYPE_MAX] __read_mostly;
 static DEFINE_MUTEX(nf_log_mutex);
 
 static struct nf_logger *__find_logger(int pf, const char *str_logger)
 {
-	struct nf_logger *t;
+	struct nf_logger *log;
+	int i;
+
+	for (i = 0; i < NF_LOG_TYPE_MAX; i++) {
+		if (loggers[pf][i] == NULL)
+			continue;
 
-	list_for_each_entry(t, &nf_loggers_l[pf], list[pf]) {
-		if (!strnicmp(str_logger, t->name, strlen(t->name)))
-			return t;
+		log = rcu_dereference_protected(loggers[pf][i],
+						lockdep_is_held(&nf_log_mutex));
+		if (!strnicmp(str_logger, log->name, strlen(log->name)))
+			return log;
 	}
 
 	return NULL;
@@ -73,17 +79,14 @@ int nf_log_register(u_int8_t pf, struct nf_logger *logger)
 	if (pf >= ARRAY_SIZE(init_net.nf.nf_loggers))
 		return -EINVAL;
 
-	for (i = 0; i < ARRAY_SIZE(logger->list); i++)
-		INIT_LIST_HEAD(&logger->list[i]);
-
 	mutex_lock(&nf_log_mutex);
 
 	if (pf == NFPROTO_UNSPEC) {
 		for (i = NFPROTO_UNSPEC; i < NFPROTO_NUMPROTO; i++)
-			list_add_tail(&(logger->list[i]), &(nf_loggers_l[i]));
+			rcu_assign_pointer(loggers[i][logger->type], logger);
 	} else {
 		/* register at end of list to honor first register win */
-		list_add_tail(&logger->list[pf], &nf_loggers_l[pf]);
+		rcu_assign_pointer(loggers[pf][logger->type], logger);
 	}
 
 	mutex_unlock(&nf_log_mutex);
@@ -98,7 +101,7 @@ void nf_log_unregister(struct nf_logger *logger)
 
 	mutex_lock(&nf_log_mutex);
 	for (i = 0; i < NFPROTO_NUMPROTO; i++)
-		list_del(&logger->list[i]);
+		RCU_INIT_POINTER(loggers[i][logger->type], NULL);
 	mutex_unlock(&nf_log_mutex);
 }
 EXPORT_SYMBOL(nf_log_unregister);
@@ -188,8 +191,7 @@ static int seq_show(struct seq_file *s, void *v)
 {
 	loff_t *pos = v;
 	const struct nf_logger *logger;
-	struct nf_logger *t;
-	int ret;
+	int i, ret;
 	struct net *net = seq_file_net(s);
 
 	logger = rcu_dereference_protected(net->nf.nf_loggers[*pos],
@@ -203,11 +205,16 @@ static int seq_show(struct seq_file *s, void *v)
 	if (ret < 0)
 		return ret;
 
-	list_for_each_entry(t, &nf_loggers_l[*pos], list[*pos]) {
-		ret = seq_printf(s, "%s", t->name);
+	for (i = 0; i < NF_LOG_TYPE_MAX; i++) {
+		if (loggers[*pos][i] == NULL)
+			continue;
+
+		logger = rcu_dereference_protected(loggers[*pos][i],
+					   lockdep_is_held(&nf_log_mutex));
+		ret = seq_printf(s, "%s", logger->name);
 		if (ret < 0)
 			return ret;
-		if (&t->list[*pos] != nf_loggers_l[*pos].prev) {
+		if (i == 0 && loggers[*pos][i + 1] != NULL) {
 			ret = seq_printf(s, ",");
 			if (ret < 0)
 				return ret;
@@ -389,14 +396,5 @@ static struct pernet_operations nf_log_net_ops = {
 
 int __init netfilter_log_init(void)
 {
-	int i, ret;
-
-	ret = register_pernet_subsys(&nf_log_net_ops);
-	if (ret < 0)
-		return ret;
-
-	for (i = NFPROTO_UNSPEC; i < NFPROTO_NUMPROTO; i++)
-		INIT_LIST_HEAD(&(nf_loggers_l[i]));
-
-	return 0;
+	return register_pernet_subsys(&nf_log_net_ops);
 }