Kernels higher than 2.6.10 don't support multiple --to arguments in

DNAT and SNAT targets.  At present, the error is somewhat vague:

# iptables -t nat -A foo -j SNAT --to 1.2.3.4 --to 2.3.4.5
iptables: Invalid argument

But if we want current iptables to work with kernels <= 2.6.10, we
cannot simply disallow this in all cases.

So the below patch adds kernel version checking to iptables, and
utilizes it in [DS]NAT.  Now, users will see a more informative error:

# iptables -t nat -A foo -j SNAT --to 1.2.3.4 --to 2.3.4.5
iptables v1.3.3: Multiple --to-source not supported

This generic infrastructure (shamelessly lifted from procps btw) may
come in handy in the future for other changes.

This fixes bugzilla #367. (Phil Oester)

1 files changed, 18 insertions, 0 deletions

diff --git a/iptables.c b/iptables.c
index 7e8ba59e..aec96137 100644
--- a/iptables.c
+++ b/iptables.c
@@ -39,6 +39,7 @@
 #include <iptables.h>
 #include <fcntl.h>
 #include <sys/wait.h>
+#include <sys/utsname.h>
 
 #ifndef TRUE
 #define TRUE 1
@@ -193,6 +194,8 @@ const char *program_version;
 const char *program_name;
 char *lib_dir;
 
+int kernel_version;
+
 /* Keeping track of external matches and targets: linked lists.  */
 struct iptables_match *iptables_matches = NULL;
 struct iptables_target *iptables_targets = NULL;
@@ -1804,6 +1807,21 @@ static void set_revision(char *name, u_int8_t revision)
 	name[IPT_FUNCTION_MAXNAMELEN - 1] = revision;
 }
 
+void
+get_kernel_version(void) {
+	static struct utsname uts;
+	int x = 0, y = 0, z = 0;
+
+	if (uname(&uts) == -1) {
+		fprintf(stderr, "Unable to retrieve kernel version.\n");
+		free_opts(1);
+		exit(1); 
+	}
+
+	sscanf(uts.release, "%d.%d.%d", &x, &y, &z);
+	kernel_version = LINUX_VERSION(x, y, z);
+}
+
 int do_command(int argc, char *argv[], char **table, iptc_handle_t *handle)
 {
 	struct ipt_entry fw, *e = NULL;