extensions: DNAT: Rename from libipt to libxt

Prepare for merge of libipt and libip6t DNAT extensions, allow for
better code review.

Signed-off-by: Phil Sutter <phil@nwl.cc>

1 files changed, 370 insertions, 0 deletions

diff --git a/extensions/libxt_DNAT.c b/extensions/libxt_DNAT.c
new file mode 100644
index 00000000..9a179919
--- /dev/null
+++ b/extensions/libxt_DNAT.c
@@ -0,0 +1,370 @@
+#include <stdio.h>
+#include <netdb.h>
+#include <string.h>
+#include <stdlib.h>
+#include <xtables.h>
+#include <iptables.h> /* get_kernel_version */
+#include <limits.h> /* INT_MAX in ip_tables.h */
+#include <arpa/inet.h>
+#include <linux/netfilter_ipv4/ip_tables.h>
+#include <linux/netfilter/nf_nat.h>
+
+#define TO_IPV4_MRC(ptr) ((const struct nf_nat_ipv4_multi_range_compat *)(ptr))
+#define RANGE2_INIT_FROM_IPV4_MRC(ptr) {			\
+	.flags		= TO_IPV4_MRC(ptr)->range[0].flags,	\
+	.min_addr.ip	= TO_IPV4_MRC(ptr)->range[0].min_ip,	\
+	.max_addr.ip	= TO_IPV4_MRC(ptr)->range[0].max_ip,	\
+	.min_proto	= TO_IPV4_MRC(ptr)->range[0].min,	\
+	.max_proto	= TO_IPV4_MRC(ptr)->range[0].max,	\
+};
+
+enum {
+	O_TO_DEST = 0,
+	O_RANDOM,
+	O_PERSISTENT,
+	F_TO_DEST = 1 << O_TO_DEST,
+	F_RANDOM  = 1 << O_RANDOM,
+};
+
+static void DNAT_help(void)
+{
+	printf(
+"DNAT target options:\n"
+" --to-destination [<ipaddr>[-<ipaddr>]][:port[-port]]\n"
+"				Address to map destination to.\n"
+"[--random] [--persistent]\n");
+}
+
+static void DNAT_help_v2(void)
+{
+	printf(
+"DNAT target options:\n"
+" --to-destination [<ipaddr>[-<ipaddr>]][:port[-port[/port]]]\n"
+"				Address to map destination to.\n"
+"[--random] [--persistent]\n");
+}
+
+static const struct xt_option_entry DNAT_opts[] = {
+	{.name = "to-destination", .id = O_TO_DEST, .type = XTTYPE_STRING,
+	 .flags = XTOPT_MAND},
+	{.name = "random", .id = O_RANDOM, .type = XTTYPE_NONE},
+	{.name = "persistent", .id = O_PERSISTENT, .type = XTTYPE_NONE},
+	XTOPT_TABLEEND,
+};
+
+/* Parses ports */
+static void
+parse_ports(const char *arg, bool portok, struct nf_nat_range2 *range)
+{
+	unsigned int port, maxport, baseport;
+	char *end = NULL;
+
+	if (!portok)
+		xtables_error(PARAMETER_PROBLEM,
+			      "Need TCP, UDP, SCTP or DCCP with port specification");
+
+	range->flags |= NF_NAT_RANGE_PROTO_SPECIFIED;
+
+	if (!xtables_strtoui(arg, &end, &port, 1, UINT16_MAX))
+		xtables_error(PARAMETER_PROBLEM,
+			      "Port `%s' not valid", arg);
+
+	switch (*end) {
+	case '\0':
+		range->min_proto.tcp.port
+			= range->max_proto.tcp.port
+			= htons(port);
+		return;
+	case '-':
+		arg = end + 1;
+		break;
+	case ':':
+		xtables_error(PARAMETER_PROBLEM,
+			      "Invalid port:port syntax - use dash");
+	default:
+		xtables_error(PARAMETER_PROBLEM,
+			      "Garbage after port value: `%s'", end);
+	}
+
+	if (!xtables_strtoui(arg, &end, &maxport, 1, UINT16_MAX))
+		xtables_error(PARAMETER_PROBLEM,
+			      "Port `%s' not valid", arg);
+
+	if (maxport < port)
+		/* People are stupid. */
+		xtables_error(PARAMETER_PROBLEM,
+			   "Port range `%s' funky", arg);
+
+	range->min_proto.tcp.port = htons(port);
+	range->max_proto.tcp.port = htons(maxport);
+
+	switch (*end) {
+	case '\0':
+		return;
+	case '/':
+		arg = end + 1;
+		break;
+	default:
+		xtables_error(PARAMETER_PROBLEM,
+			      "Garbage after port range: `%s'", end);
+	}
+
+	if (!xtables_strtoui(arg, &end, &baseport, 1, UINT16_MAX))
+		xtables_error(PARAMETER_PROBLEM,
+			      "Port `%s' not valid", arg);
+
+	range->flags |= NF_NAT_RANGE_PROTO_OFFSET;
+	range->base_proto.tcp.port = htons(baseport);
+}
+
+/* Ranges expected in network order. */
+static void
+parse_to(const char *orig_arg, bool portok, struct nf_nat_range2 *range)
+{
+	char *arg, *colon, *dash;
+
+	arg = xtables_strdup(orig_arg);
+	colon = strchr(arg, ':');
+
+	if (colon) {
+		parse_ports(colon + 1, portok, range);
+
+		/* Starts with a colon? No IP info...*/
+		if (colon == arg) {
+			free(arg);
+			return;
+		}
+		*colon = '\0';
+	}
+
+	range->flags |= NF_NAT_RANGE_MAP_IPS;
+	dash = strchr(arg, '-');
+	if (colon && dash && dash > colon)
+		dash = NULL;
+
+	if (dash)
+		*dash = '\0';
+
+	if (!inet_pton(AF_INET, arg, &range->min_addr))
+		xtables_error(PARAMETER_PROBLEM,
+			      "Bad IP address \"%s\"\n", arg);
+	if (dash) {
+		if (!inet_pton(AF_INET, dash + 1, &range->max_addr))
+			xtables_error(PARAMETER_PROBLEM,
+				      "Bad IP address \"%s\"\n", dash + 1);
+	} else {
+		range->max_addr = range->min_addr;
+	}
+	free(arg);
+	return;
+}
+
+static void __DNAT_parse(struct xt_option_call *cb, __u16 proto,
+			 struct nf_nat_range2 *range)
+{
+	bool portok = proto == IPPROTO_TCP ||
+		      proto == IPPROTO_UDP ||
+		      proto == IPPROTO_SCTP ||
+		      proto == IPPROTO_DCCP ||
+		      proto == IPPROTO_ICMP;
+
+	xtables_option_parse(cb);
+	switch (cb->entry->id) {
+	case O_TO_DEST:
+		parse_to(cb->arg, portok, range);
+		break;
+	case O_PERSISTENT:
+		range->flags |= NF_NAT_RANGE_PERSISTENT;
+		break;
+	}
+}
+
+static void DNAT_parse(struct xt_option_call *cb)
+{
+	struct nf_nat_ipv4_multi_range_compat *mr = (void *)cb->data;
+	const struct ipt_entry *entry = cb->xt_entry;
+	struct nf_nat_range2 range = {};
+
+	__DNAT_parse(cb, entry->ip.proto, &range);
+
+	switch (cb->entry->id) {
+	case O_TO_DEST:
+		mr->range->min_ip = range.min_addr.ip;
+		mr->range->max_ip = range.max_addr.ip;
+		mr->range->min = range.min_proto;
+		mr->range->max = range.max_proto;
+		/* fall through */
+	case O_PERSISTENT:
+		mr->range->flags |= range.flags;
+		break;
+	}
+}
+
+static void DNAT_fcheck(struct xt_fcheck_call *cb)
+{
+	static const unsigned int f = F_TO_DEST | F_RANDOM;
+	struct nf_nat_ipv4_multi_range_compat *mr = cb->data;
+
+	if ((cb->xflags & f) == f)
+		mr->range[0].flags |= NF_NAT_RANGE_PROTO_RANDOM;
+
+	mr->rangesize = 1;
+
+	if (mr->range[0].flags & NF_NAT_RANGE_PROTO_OFFSET)
+		xtables_error(PARAMETER_PROBLEM,
+			      "Shifted portmap ranges not supported with this kernel");
+}
+
+static char *sprint_range(const struct nf_nat_range2 *r)
+{
+	static char buf[INET_ADDRSTRLEN * 2 + 1 + 6 * 3];
+
+	if (r->flags & NF_NAT_RANGE_MAP_IPS) {
+		sprintf(buf, "%s", xtables_ipaddr_to_numeric(&r->min_addr.in));
+		if (memcmp(&r->min_addr, &r->max_addr, sizeof(r->min_addr)))
+			sprintf(buf + strlen(buf), "-%s",
+				xtables_ipaddr_to_numeric(&r->max_addr.in));
+	} else {
+		buf[0] = '\0';
+	}
+	if (r->flags & NF_NAT_RANGE_PROTO_SPECIFIED) {
+		sprintf(buf + strlen(buf), ":%hu",
+			ntohs(r->min_proto.tcp.port));
+		if (r->max_proto.tcp.port != r->min_proto.tcp.port)
+			sprintf(buf + strlen(buf), "-%hu",
+				ntohs(r->max_proto.tcp.port));
+		if (r->flags & NF_NAT_RANGE_PROTO_OFFSET)
+			sprintf(buf + strlen(buf), "/%hu",
+				ntohs(r->base_proto.tcp.port));
+	}
+	return buf;
+}
+
+static void __DNAT_print(const struct nf_nat_range2 *r, bool save)
+{
+	const char *dashdash = save ? "--" : "";
+
+	printf(" %s%s", save ? "--to-destination " : "to:", sprint_range(r));
+	if (r->flags & NF_NAT_RANGE_PROTO_RANDOM)
+		printf(" %srandom", dashdash);
+	if (r->flags & NF_NAT_RANGE_PERSISTENT)
+		printf(" %spersistent", dashdash);
+}
+
+static void DNAT_print(const void *ip, const struct xt_entry_target *target,
+                       int numeric)
+{
+	struct nf_nat_range2 range = RANGE2_INIT_FROM_IPV4_MRC(target->data);
+
+	__DNAT_print(&range, false);
+}
+
+static void DNAT_save(const void *ip, const struct xt_entry_target *target)
+{
+	struct nf_nat_range2 range = RANGE2_INIT_FROM_IPV4_MRC(target->data);
+
+	__DNAT_print(&range, true);
+}
+
+static int __DNAT_xlate(struct xt_xlate *xl, const struct nf_nat_range2 *r)
+{
+	char *range_str = sprint_range(r);
+	const char *sep = " ";
+
+	/* shifted portmap ranges are not supported by nftables */
+	if (r->flags & NF_NAT_RANGE_PROTO_OFFSET)
+		return 0;
+
+	xt_xlate_add(xl, "dnat");
+	if (strlen(range_str))
+		xt_xlate_add(xl, " to %s", range_str);
+	if (r->flags & NF_NAT_RANGE_PROTO_RANDOM) {
+		xt_xlate_add(xl, "%srandom", sep);
+		sep = ",";
+	}
+	if (r->flags & NF_NAT_RANGE_PERSISTENT) {
+		xt_xlate_add(xl, "%spersistent", sep);
+		sep = ",";
+	}
+	return 1;
+}
+
+static int DNAT_xlate(struct xt_xlate *xl,
+		      const struct xt_xlate_tg_params *params)
+{
+	struct nf_nat_range2 range =
+		RANGE2_INIT_FROM_IPV4_MRC(params->target->data);
+
+	return __DNAT_xlate(xl, &range);
+}
+
+static void DNAT_parse_v2(struct xt_option_call *cb)
+{
+	const struct ipt_entry *entry = cb->xt_entry;
+
+	__DNAT_parse(cb, entry->ip.proto, cb->data);
+}
+
+static void DNAT_fcheck_v2(struct xt_fcheck_call *cb)
+{
+	static const unsigned int f = F_TO_DEST | F_RANDOM;
+	struct nf_nat_range2 *range = cb->data;
+
+	if ((cb->xflags & f) == f)
+		range->flags |= NF_NAT_RANGE_PROTO_RANDOM;
+}
+
+static void DNAT_print_v2(const void *ip, const struct xt_entry_target *target,
+                       int numeric)
+{
+	__DNAT_print((const void *)target->data, false);
+}
+
+static void DNAT_save_v2(const void *ip, const struct xt_entry_target *target)
+{
+	__DNAT_print((const void *)target->data, true);
+}
+
+static int DNAT_xlate_v2(struct xt_xlate *xl,
+		      const struct xt_xlate_tg_params *params)
+{
+	return __DNAT_xlate(xl, (const void *)params->target->data);
+}
+
+static struct xtables_target dnat_tg_reg[] = {
+	{
+		.name		= "DNAT",
+		.version	= XTABLES_VERSION,
+		.family		= NFPROTO_IPV4,
+		.revision	= 0,
+		.size		= XT_ALIGN(sizeof(struct nf_nat_ipv4_multi_range_compat)),
+		.userspacesize	= XT_ALIGN(sizeof(struct nf_nat_ipv4_multi_range_compat)),
+		.help		= DNAT_help,
+		.print		= DNAT_print,
+		.save		= DNAT_save,
+		.x6_parse	= DNAT_parse,
+		.x6_fcheck	= DNAT_fcheck,
+		.x6_options	= DNAT_opts,
+		.xlate		= DNAT_xlate,
+	},
+	{
+		.name		= "DNAT",
+		.version	= XTABLES_VERSION,
+		.family		= NFPROTO_IPV4,
+		.revision	= 2,
+		.size		= XT_ALIGN(sizeof(struct nf_nat_range2)),
+		.userspacesize	= XT_ALIGN(sizeof(struct nf_nat_range2)),
+		.help		= DNAT_help_v2,
+		.print		= DNAT_print_v2,
+		.save		= DNAT_save_v2,
+		.x6_parse	= DNAT_parse_v2,
+		.x6_fcheck	= DNAT_fcheck_v2,
+		.x6_options	= DNAT_opts,
+		.xlate		= DNAT_xlate_v2,
+	},
+};
+
+void _init(void)
+{
+	xtables_register_targets(dnat_tg_reg, ARRAY_SIZE(dnat_tg_reg));
+}