netfilter: create audit records for x_tables replaces

The setsockopt() syscall to replace tables is already recorded
in the audit logs. This patch stores additional information
such as table name and netfilter protocol.

Cc: Patrick McHardy <[e-mail]>
Cc: Eric Paris <[e-mail]>
Cc: Al Viro <[e-mail]>
Signed-off-by: Thomas Graf <[e-mail]>
Signed-off-by: Patrick McHardy <[e-mail]>

include/linux/audit.h

···
 #define AUDIT_CAPSET		1322	/* Record showing argument to sys_capset */
 #define AUDIT_MMAP		1323	/* Record showing descriptor and flags in mmap */
 #define AUDIT_NETFILTER_PKT	1324	/* Packets traversing netfilter chains */
+#define AUDIT_NETFILTER_CFG	1325	/* Netfilter chain modifications */
 
 #define AUDIT_AVC		1400	/* SE Linux avc denial or grant */
 #define AUDIT_SELINUX_ERR	1401	/* Internal SE Linux Errors */

net/netfilter/x_tables.c

···
 #include <linux/mutex.h>
 #include <linux/mm.h>
 #include <linux/slab.h>
+#include <linux/audit.h>
 #include <net/net_namespace.h>
 
 #include <linux/netfilter/x_tables.h>
···
 	 * during the get_counters() routine.
 	 */
 	local_bh_enable();
+
+#ifdef CONFIG_AUDIT
+	if (audit_enabled) {
+		struct audit_buffer *ab;
+
+		ab = audit_log_start(current->audit_context, GFP_KERNEL,
+				     AUDIT_NETFILTER_CFG);
+		if (ab) {
+			audit_log_format(ab, "table=%s family=%u entries=%u",
+					 table->name, table->af,
+					 private->number);
+			audit_log_end(ab);
+		}
+	}
+#endif
 
 	return private;
 }