netfilter: log: nf_log_packet() as real unified interface

Before this patch, the nf_loginfo parameter specified the logging
configuration in case the specified default logger was loaded. This
patch updates the semantics of the nf_loginfo parameter in
nf_log_packet() which now indicates the logger that you explicitly
want to use.

Thus, nf_log_packet() is exposed as an unified interface which
internally routes the log message to the corresponding logger type
by family.

The module dependencies are expressed by the new nf_logger_find_get()
and nf_logger_put() functions which bump the logger module refcount.
Thus, you can not remove logger modules that are used by rules anymore.

Another important effect of this change is that the family specific
module is only loaded when required. Therefore, xt_LOG and nft_log
will just trigger the autoload of the nf_log_{ip,ip6} modules
according to the family.

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

1 files changed, 40 insertions, 1 deletions

diff --git a/net/netfilter/nf_log.c b/net/netfilter/nf_log.c
index 0b6b2c874199..0b2161c689e0 100644
--- a/net/netfilter/nf_log.c
+++ b/net/netfilter/nf_log.c
@@ -132,6 +132,41 @@ void nf_log_unbind_pf(struct net *net, u_int8_t pf)
 }
 EXPORT_SYMBOL(nf_log_unbind_pf);
 
+int nf_logger_find_get(int pf, enum nf_log_type type)
+{
+	struct nf_logger *logger;
+	int ret = -ENOENT;
+
+	logger = loggers[pf][type];
+	if (logger == NULL)
+		request_module("nf-logger-%u-%u", pf, type);
+
+	rcu_read_lock();
+	logger = rcu_dereference(loggers[pf][type]);
+	if (logger == NULL)
+		goto out;
+
+	if (logger && try_module_get(logger->me))
+		ret = 0;
+out:
+	rcu_read_unlock();
+	return ret;
+}
+EXPORT_SYMBOL_GPL(nf_logger_find_get);
+
+void nf_logger_put(int pf, enum nf_log_type type)
+{
+	struct nf_logger *logger;
+
+	BUG_ON(loggers[pf][type] == NULL);
+
+	rcu_read_lock();
+	logger = rcu_dereference(loggers[pf][type]);
+	module_put(logger->me);
+	rcu_read_unlock();
+}
+EXPORT_SYMBOL_GPL(nf_logger_put);
+
 void nf_log_packet(struct net *net,
 		   u_int8_t pf,
 		   unsigned int hooknum,
@@ -146,7 +181,11 @@ void nf_log_packet(struct net *net,
 	const struct nf_logger *logger;
 
 	rcu_read_lock();
-	logger = rcu_dereference(net->nf.nf_loggers[pf]);
+	if (loginfo != NULL)
+		logger = rcu_dereference(loggers[pf][loginfo->type]);
+	else
+		logger = rcu_dereference(net->nf.nf_loggers[pf]);
+
 	if (logger) {
 		va_start(args, fmt);
 		vsnprintf(prefix, sizeof(prefix), fmt, args);