--- /dev/null
+/*
+ * ip_nat_proto_gre.c - Version 2.0
+ *
+ * NAT protocol helper module for GRE.
+ *
+ * GRE is a generic encapsulation protocol, which is generally not very
+ * suited for NAT, as it has no protocol-specific part as port numbers.
+ *
+ * It has an optional key field, which may help us distinguishing two
+ * connections between the same two hosts.
+ *
+ * GRE is defined in RFC 1701 and RFC 1702, as well as RFC 2784
+ *
+ * PPTP is built on top of a modified version of GRE, and has a mandatory
+ * field called "CallID", which serves us for the same purpose as the key
+ * field in plain GRE.
+ *
+ * Documentation about PPTP can be found in RFC 2637
+ *
+ * (C) 2000-2004 by Harald Welte <laforge@gnumonks.org>
+ *
+ * Development of this code funded by Astaro AG (http://www.astaro.com/)
+ *
+ */
+
+#include <linux/config.h>
+#include <linux/module.h>
+#include <linux/ip.h>
+#include <linux/netfilter_ipv4/ip_nat.h>
+#include <linux/netfilter_ipv4/ip_nat_rule.h>
+#include <linux/netfilter_ipv4/ip_nat_protocol.h>
+#include <linux/netfilter_ipv4/ip_conntrack_proto_gre.h>
+
+MODULE_LICENSE("GPL");
+MODULE_AUTHOR("Harald Welte <laforge@gnumonks.org>");
+MODULE_DESCRIPTION("Netfilter NAT protocol helper module for GRE");
+
+#if 0
+#define DEBUGP(format, args...) printk(KERN_DEBUG __FILE__ ":" __FUNCTION__ \
+ ": " format, ## args)
+#else
+#define DEBUGP(x, args...)
+#endif
+
+/* is key in given range between min and max */
+static int
+gre_in_range(const struct ip_conntrack_tuple *tuple,
+ enum ip_nat_manip_type maniptype,
+ const union ip_conntrack_manip_proto *min,
+ const union ip_conntrack_manip_proto *max)
+{
+ u_int32_t key;
+
+ if (maniptype == IP_NAT_MANIP_SRC)
+ key = tuple->src.u.gre.key;
+ else
+ key = tuple->dst.u.gre.key;
+
+ return ntohl(key) >= ntohl(min->gre.key)
+ && ntohl(key) <= ntohl(max->gre.key);
+}
+
+/* generate unique tuple ... */
+static int
+gre_unique_tuple(struct ip_conntrack_tuple *tuple,
+ const struct ip_nat_range *range,
+ enum ip_nat_manip_type maniptype,
+ const struct ip_conntrack *conntrack)
+{
+ u_int32_t min, i, range_size;
+ u_int32_t key = 0, *keyptr;
+
+ if (maniptype == IP_NAT_MANIP_SRC)
+ keyptr = &tuple->src.u.gre.key;
+ else
+ keyptr = &tuple->dst.u.gre.key;
+
+ if (!(range->flags & IP_NAT_RANGE_PROTO_SPECIFIED)) {
+ DEBUGP("%p: NATing GRE PPTP\n", conntrack);
+ min = 1;
+ range_size = 0xffff;
+ } else {
+ min = ntohl(range->min.gre.key);
+ range_size = ntohl(range->max.gre.key) - min + 1;
+ }
+
+ DEBUGP("min = %u, range_size = %u\n", min, range_size);
+
+ for (i = 0; i < range_size; i++, key++) {
+ *keyptr = htonl(min + key % range_size);
+ if (!ip_nat_used_tuple(tuple, conntrack))
+ return 1;
+ }
+
+ DEBUGP("%p: no NAT mapping\n", conntrack);
+
+ return 0;
+}
+
+/* manipulate a GRE packet according to maniptype */
+static int
+gre_manip_pkt(struct sk_buff **pskb,
+ unsigned int hdroff,
+ const struct ip_conntrack_manip *manip,
+ enum ip_nat_manip_type maniptype)
+{
+ struct gre_hdr *greh;
+ struct gre_hdr_pptp *pgreh;
+
+ if (!skb_ip_make_writable(pskb, hdroff + sizeof(*pgreh)))
+ return 0;
+
+ greh = (void *)(*pskb)->data + hdroff;
+ pgreh = (struct gre_hdr_pptp *) greh;
+
+ /* we only have destination manip of a packet, since 'source key'
+ * is not present in the packet itself */
+ if (maniptype == IP_NAT_MANIP_DST) {
+ /* key manipulation is always dest */
+ switch (greh->version) {
+ case 0:
+ if (!greh->key) {
+ DEBUGP("can't nat GRE w/o key\n");
+ break;
+ }
+ if (greh->csum) {
+ /* FIXME: Never tested this code... */
+ *(gre_csum(greh)) =
+ ip_nat_cheat_check(~*(gre_key(greh)),
+ manip->u.gre.key,
+ *(gre_csum(greh)));
+ }
+ *(gre_key(greh)) = manip->u.gre.key;
+ break;
+ case GRE_VERSION_PPTP:
+ DEBUGP("call_id -> 0x%04x\n",
+ ntohl(manip->u.gre.key));
+ pgreh->call_id = htons(ntohl(manip->u.gre.key));
+ break;
+ default:
+ DEBUGP("can't nat unknown GRE version\n");
+ return 0;
+ break;
+ }
+ }
+ return 1;
+}
+
+/* print out a nat tuple */
+static unsigned int
+gre_print(char *buffer,
+ const struct ip_conntrack_tuple *match,
+ const struct ip_conntrack_tuple *mask)
+{
+ unsigned int len = 0;
+
+ if (mask->src.u.gre.key)
+ len += sprintf(buffer + len, "srckey=0x%x ",
+ ntohl(match->src.u.gre.key));
+
+ if (mask->dst.u.gre.key)
+ len += sprintf(buffer + len, "dstkey=0x%x ",
+ ntohl(match->src.u.gre.key));
+
+ return len;
+}
+
+/* print a range of keys */
+static unsigned int
+gre_print_range(char *buffer, const struct ip_nat_range *range)
+{
+ if (range->min.gre.key != 0
+ || range->max.gre.key != 0xFFFF) {
+ if (range->min.gre.key == range->max.gre.key)
+ return sprintf(buffer, "key 0x%x ",
+ ntohl(range->min.gre.key));
+ else
+ return sprintf(buffer, "keys 0x%u-0x%u ",
+ ntohl(range->min.gre.key),
+ ntohl(range->max.gre.key));
+ } else
+ return 0;
+}
+
+/* nat helper struct */
+static struct ip_nat_protocol gre = {
+ .name = "GRE",
+ .protonum = IPPROTO_GRE,
+ .manip_pkt = gre_manip_pkt,
+ .in_range = gre_in_range,
+ .unique_tuple = gre_unique_tuple,
+ .print = gre_print,
+ .print_range = gre_print_range
+};
+
+static int __init init(void)
+{
+ if (ip_nat_protocol_register(&gre))
+ return -EIO;
+
+ return 0;
+}
+
+static void __exit fini(void)
+{
+ ip_nat_protocol_unregister(&gre);
+}
+
+module_init(init);
+module_exit(fini);
git://git.onelab.eu / linux-2.6.git / blobdiff