1. 根目录:
2. net
3. netfilter
4. nf_log.c

#include <linux/kernel.h>
#include <linux/init.h>
#include <linux/module.h>
#include <linux/proc_fs.h>
#include <linux/skbuff.h>
#include <linux/netfilter.h>
#include <linux/seq_file.h>
#include <net/protocol.h>
#include <net/netfilter/nf_log.h>

#include "nf_internals.h"

/* Internal logging interface, which relies on the real
   LOG target modules */

#define NF_LOG_PREFIXLEN		128
#define NFLOGGER_NAME_LEN		64

static struct nf_logger __rcu *loggers[NFPROTO_NUMPROTO][NF_LOG_TYPE_MAX] __read_mostly;
static DEFINE_MUTEX(nf_log_mutex);

#define nft_log_dereference(logger) \
	rcu_dereference_protected(logger, lockdep_is_held(&nf_log_mutex))

static struct nf_logger *__find_logger(int pf, const char *str_logger)
{
	struct nf_logger *log;
	int i;

	for (i = 0; i < NF_LOG_TYPE_MAX; i++) {
		if (loggers[pf][i] == NULL)
			continue;

		log = nft_log_dereference(loggers[pf][i]);
		if (!strncasecmp(str_logger, log->name, strlen(log->name)))
			return log;
	}

	return NULL;
}

void nf_log_set(struct net *net, u_int8_t pf, const struct nf_logger *logger)
{
	const struct nf_logger *log;

	if (pf == NFPROTO_UNSPEC)
		return;

	mutex_lock(&nf_log_mutex);
	log = nft_log_dereference(net->nf.nf_loggers[pf]);
	if (log == NULL)
		rcu_assign_pointer(net->nf.nf_loggers[pf], logger);

	mutex_unlock(&nf_log_mutex);
}
EXPORT_SYMBOL(nf_log_set);

void nf_log_unset(struct net *net, const struct nf_logger *logger)
{
	int i;
	const struct nf_logger *log;

	mutex_lock(&nf_log_mutex);
	for (i = 0; i < NFPROTO_NUMPROTO; i++) {
		log = nft_log_dereference(net->nf.nf_loggers[i]);
		if (log == logger)
			RCU_INIT_POINTER(net->nf.nf_loggers[i], NULL);
	}
	mutex_unlock(&nf_log_mutex);
	synchronize_rcu();
}
EXPORT_SYMBOL(nf_log_unset);

/* return EEXIST if the same logger is registered, 0 on success. */
int nf_log_register(u_int8_t pf, struct nf_logger *logger)
{
	int i;
	int ret = 0;

	if (pf >= ARRAY_SIZE(init_net.nf.nf_loggers))
		return -EINVAL;

	mutex_lock(&nf_log_mutex);

	if (pf == NFPROTO_UNSPEC) {
		for (i = NFPROTO_UNSPEC; i < NFPROTO_NUMPROTO; i++) {
			if (rcu_access_pointer(loggers[i][logger->type])) {
				ret = -EEXIST;
				goto unlock;
			}
		}
		for (i = NFPROTO_UNSPEC; i < NFPROTO_NUMPROTO; i++)
			rcu_assign_pointer(loggers[i][logger->type], logger);
	} else {
		if (rcu_access_pointer(loggers[pf][logger->type])) {
			ret = -EEXIST;
			goto unlock;
		}
		rcu_assign_pointer(loggers[pf][logger->type], logger);
	}

unlock:
	mutex_unlock(&nf_log_mutex);
	return ret;
}
EXPORT_SYMBOL(nf_log_register);

void nf_log_unregister(struct nf_logger *logger)
{
	const struct nf_logger *log;
	int i;

	mutex_lock(&nf_log_mutex);
	for (i = 0; i < NFPROTO_NUMPROTO; i++) {
		log = nft_log_dereference(loggers[i][logger->type]);
		if (log == logger)
			RCU_INIT_POINTER(loggers[i][logger->type], NULL);
	}
	mutex_unlock(&nf_log_mutex);
	synchronize_rcu();
}
EXPORT_SYMBOL(nf_log_unregister);

int nf_log_bind_pf(struct net *net, u_int8_t pf,
		   const struct nf_logger *logger)
{
	if (pf >= ARRAY_SIZE(net->nf.nf_loggers))
		return -EINVAL;
	mutex_lock(&nf_log_mutex);
	if (__find_logger(pf, logger->name) == NULL) {
		mutex_unlock(&nf_log_mutex);
		return -ENOENT;
	}
	rcu_assign_pointer(net->nf.nf_loggers[pf], logger);
	mutex_unlock(&nf_log_mutex);
	return 0;
}
EXPORT_SYMBOL(nf_log_bind_pf);

void nf_log_unbind_pf(struct net *net, u_int8_t pf)
{
	if (pf >= ARRAY_SIZE(net->nf.nf_loggers))
		return;
	mutex_lock(&nf_log_mutex);
	RCU_INIT_POINTER(net->nf.nf_loggers[pf], NULL);
	mutex_unlock(&nf_log_mutex);
}
EXPORT_SYMBOL(nf_log_unbind_pf);

void nf_logger_request_module(int pf, enum nf_log_type type)
{
	if (loggers[pf][type] == NULL)
		request_module("nf-logger-%u-%u", pf, type);
}
EXPORT_SYMBOL_GPL(nf_logger_request_module);

int nf_logger_find_get(int pf, enum nf_log_type type)
{
	struct nf_logger *logger;
	int ret = -ENOENT;

	if (rcu_access_pointer(loggers[pf][type]) == 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,
		   const struct sk_buff *skb,
		   const struct net_device *in,
		   const struct net_device *out,
		   const struct nf_loginfo *loginfo,
		   const char *fmt, ...)
{
	va_list args;
	char prefix[NF_LOG_PREFIXLEN];
	const struct nf_logger *logger;

	rcu_read_lock();
	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);
		va_end(args);
		logger->logfn(net, pf, hooknum, skb, in, out, loginfo, prefix);
	}
	rcu_read_unlock();
}
EXPORT_SYMBOL(nf_log_packet);

void nf_log_trace(struct net *net,
		  u_int8_t pf,
		  unsigned int hooknum,
		  const struct sk_buff *skb,
		  const struct net_device *in,
		  const struct net_device *out,
		  const struct nf_loginfo *loginfo, const char *fmt, ...)
{
	va_list args;
	char prefix[NF_LOG_PREFIXLEN];
	const struct nf_logger *logger;

	rcu_read_lock();
	logger = rcu_dereference(net->nf.nf_loggers[pf]);
	if (logger) {
		va_start(args, fmt);
		vsnprintf(prefix, sizeof(prefix), fmt, args);
		va_end(args);
		logger->logfn(net, pf, hooknum, skb, in, out, loginfo, prefix);
	}
	rcu_read_unlock();
}
EXPORT_SYMBOL(nf_log_trace);

#define S_SIZE (1024 - (sizeof(unsigned int) + 1))

struct nf_log_buf {
	unsigned int	count;
	char		buf[S_SIZE + 1];
};
static struct nf_log_buf emergency, *emergency_ptr = &emergency;

__printf(2, 3) int nf_log_buf_add(struct nf_log_buf *m, const char *f, ...)
{
	va_list args;
	int len;

	if (likely(m->count < S_SIZE)) {
		va_start(args, f);
		len = vsnprintf(m->buf + m->count, S_SIZE - m->count, f, args);
		va_end(args);
		if (likely(m->count + len < S_SIZE)) {
			m->count += len;
			return 0;
		}
	}
	m->count = S_SIZE;
	printk_once(KERN_ERR KBUILD_MODNAME " please increase S_SIZE\n");
	return -1;
}
EXPORT_SYMBOL_GPL(nf_log_buf_add);

struct nf_log_buf *nf_log_buf_open(void)
{
	struct nf_log_buf *m = kmalloc(sizeof(*m), GFP_ATOMIC);

	if (unlikely(!m)) {
		local_bh_disable();
		do {
			m = xchg(&emergency_ptr, NULL);
		} while (!m);
	}
	m->count = 0;
	return m;
}
EXPORT_SYMBOL_GPL(nf_log_buf_open);

void nf_log_buf_close(struct nf_log_buf *m)
{
	m->buf[m->count] = 0;
	printk("%s\n", m->buf);

	if (likely(m != &emergency))
		kfree(m);
	else {
		emergency_ptr = m;
		local_bh_enable();
	}
}
EXPORT_SYMBOL_GPL(nf_log_buf_close);

#ifdef CONFIG_PROC_FS
static void *seq_start(struct seq_file *seq, loff_t *pos)
{
	struct net *net = seq_file_net(seq);

	mutex_lock(&nf_log_mutex);

	if (*pos >= ARRAY_SIZE(net->nf.nf_loggers))
		return NULL;

	return pos;
}

static void *seq_next(struct seq_file *s, void *v, loff_t *pos)
{
	struct net *net = seq_file_net(s);

	(*pos)++;

	if (*pos >= ARRAY_SIZE(net->nf.nf_loggers))
		return NULL;

	return pos;
}

static void seq_stop(struct seq_file *s, void *v)
{
	mutex_unlock(&nf_log_mutex);
}

static int seq_show(struct seq_file *s, void *v)
{
	loff_t *pos = v;
	const struct nf_logger *logger;
	int i;
	struct net *net = seq_file_net(s);

	logger = nft_log_dereference(net->nf.nf_loggers[*pos]);

	if (!logger)
		seq_printf(s, "%2lld NONE (", *pos);
	else
		seq_printf(s, "%2lld %s (", *pos, logger->name);

	if (seq_has_overflowed(s))
		return -ENOSPC;

	for (i = 0; i < NF_LOG_TYPE_MAX; i++) {
		if (loggers[*pos][i] == NULL)
			continue;

		logger = nft_log_dereference(loggers[*pos][i]);
		seq_printf(s, "%s", logger->name);
		if (i == 0 && loggers[*pos][i + 1] != NULL)
			seq_printf(s, ",");

		if (seq_has_overflowed(s))
			return -ENOSPC;
	}

	seq_printf(s, ")\n");

	if (seq_has_overflowed(s))
		return -ENOSPC;
	return 0;
}

static const struct seq_operations nflog_seq_ops = {
	.start	= seq_start,
	.next	= seq_next,
	.stop	= seq_stop,
	.show	= seq_show,
};

static int nflog_open(struct inode *inode, struct file *file)
{
	return seq_open_net(inode, file, &nflog_seq_ops,
			    sizeof(struct seq_net_private));
}

static const struct file_operations nflog_file_ops = {
	.owner	 = THIS_MODULE,
	.open	 = nflog_open,
	.read	 = seq_read,
	.llseek	 = seq_lseek,
	.release = seq_release_net,
};


#endif /* PROC_FS */

#ifdef CONFIG_SYSCTL
static char nf_log_sysctl_fnames[NFPROTO_NUMPROTO-NFPROTO_UNSPEC][3];
static struct ctl_table nf_log_sysctl_table[NFPROTO_NUMPROTO+1];

static int nf_log_proc_dostring(struct ctl_table *table, int write,
			 void __user *buffer, size_t *lenp, loff_t *ppos)
{
	const struct nf_logger *logger;
	char buf[NFLOGGER_NAME_LEN];
	size_t size = *lenp;
	int r = 0;
	int tindex = (unsigned long)table->extra1;
	struct net *net = current->nsproxy->net_ns;

	if (write) {
		if (size > sizeof(buf))
			size = sizeof(buf);
		if (copy_from_user(buf, buffer, size))
			return -EFAULT;

		if (!strcmp(buf, "NONE")) {
			nf_log_unbind_pf(net, tindex);
			return 0;
		}
		mutex_lock(&nf_log_mutex);
		logger = __find_logger(tindex, buf);
		if (logger == NULL) {
			mutex_unlock(&nf_log_mutex);
			return -ENOENT;
		}
		rcu_assign_pointer(net->nf.nf_loggers[tindex], logger);
		mutex_unlock(&nf_log_mutex);
	} else {
		mutex_lock(&nf_log_mutex);
		logger = nft_log_dereference(net->nf.nf_loggers[tindex]);
		if (!logger)
			table->data = "NONE";
		else
			table->data = logger->name;
		r = proc_dostring(table, write, buffer, lenp, ppos);
		mutex_unlock(&nf_log_mutex);
	}

	return r;
}

static int netfilter_log_sysctl_init(struct net *net)
{
	int i;
	struct ctl_table *table;

	table = nf_log_sysctl_table;
	if (!net_eq(net, &init_net)) {
		table = kmemdup(nf_log_sysctl_table,
				 sizeof(nf_log_sysctl_table),
				 GFP_KERNEL);
		if (!table)
			goto err_alloc;
	} else {
		for (i = NFPROTO_UNSPEC; i < NFPROTO_NUMPROTO; i++) {
			snprintf(nf_log_sysctl_fnames[i],
				 3, "%d", i);
			nf_log_sysctl_table[i].procname	=
				nf_log_sysctl_fnames[i];
			nf_log_sysctl_table[i].data = NULL;
			nf_log_sysctl_table[i].maxlen = NFLOGGER_NAME_LEN;
			nf_log_sysctl_table[i].mode = 0644;
			nf_log_sysctl_table[i].proc_handler =
				nf_log_proc_dostring;
			nf_log_sysctl_table[i].extra1 =
				(void *)(unsigned long) i;
		}
	}

	net->nf.nf_log_dir_header = register_net_sysctl(net,
						"net/netfilter/nf_log",
						table);
	if (!net->nf.nf_log_dir_header)
		goto err_reg;

	return 0;

err_reg:
	if (!net_eq(net, &init_net))
		kfree(table);
err_alloc:
	return -ENOMEM;
}

static void netfilter_log_sysctl_exit(struct net *net)
{
	struct ctl_table *table;

	table = net->nf.nf_log_dir_header->ctl_table_arg;
	unregister_net_sysctl_table(net->nf.nf_log_dir_header);
	if (!net_eq(net, &init_net))
		kfree(table);
}
#else
static int netfilter_log_sysctl_init(struct net *net)
{
	return 0;
}

static void netfilter_log_sysctl_exit(struct net *net)
{
}
#endif /* CONFIG_SYSCTL */

static int __net_init nf_log_net_init(struct net *net)
{
	int ret = -ENOMEM;

#ifdef CONFIG_PROC_FS
	if (!proc_create("nf_log", S_IRUGO,
			 net->nf.proc_netfilter, &nflog_file_ops))
		return ret;
#endif
	ret = netfilter_log_sysctl_init(net);
	if (ret < 0)
		goto out_sysctl;

	return 0;

out_sysctl:
#ifdef CONFIG_PROC_FS
	remove_proc_entry("nf_log", net->nf.proc_netfilter);
#endif
	return ret;
}

static void __net_exit nf_log_net_exit(struct net *net)
{
	netfilter_log_sysctl_exit(net);
#ifdef CONFIG_PROC_FS
	remove_proc_entry("nf_log", net->nf.proc_netfilter);
#endif
}

static struct pernet_operations nf_log_net_ops = {
	.init = nf_log_net_init,
	.exit = nf_log_net_exit,
};

int __init netfilter_log_init(void)
{
	return register_pernet_subsys(&nf_log_net_ops);
}