--- /dev/null
+/*
+ * nf_nat_proto_gre.c
+ *
+ * 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) 2000-2005 by Harald Welte <laforge@gnumonks.org>
+ *
+ * Development of this code funded by Astaro AG (http://www.astaro.com/)
+ *
+ */
+
+#include <linux/module.h>
+#include <linux/skbuff.h>
+#include <linux/ip.h>
+
+#include <net/netfilter/nf_nat.h>
+#include <net/netfilter/nf_nat_rule.h>
+#include <net/netfilter/nf_nat_protocol.h>
+#include <linux/netfilter/nf_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 "%s:%s: " format, __FILE__, \
+ __FUNCTION__, ## args)
+#else
+#define DEBUGP(x, args...)
+#endif
+
+/* is key in given range between min and max */
+static int
+gre_in_range(const struct nf_conntrack_tuple *tuple,
+ enum nf_nat_manip_type maniptype,
+ const union nf_conntrack_man_proto *min,
+ const union nf_conntrack_man_proto *max)
+{
+ __be16 key;
+
+ if (maniptype == IP_NAT_MANIP_SRC)
+ key = tuple->src.u.gre.key;
+ else
+ key = tuple->dst.u.gre.key;
+
+ return ntohs(key) >= ntohs(min->gre.key) &&
+ ntohs(key) <= ntohs(max->gre.key);
+}
+
+/* generate unique tuple ... */
+static int
+gre_unique_tuple(struct nf_conntrack_tuple *tuple,
+ const struct nf_nat_range *range,
+ enum nf_nat_manip_type maniptype,
+ const struct nf_conn *conntrack)
+{
+ static u_int16_t key;
+ __be16 *keyptr;
+ unsigned int min, i, range_size;
+
+ 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 = ntohs(range->min.gre.key);
+ range_size = ntohs(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 = htons(min + key % range_size);
+ if (!nf_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 iphdroff,
+ const struct nf_conntrack_tuple *tuple,
+ enum nf_nat_manip_type maniptype)
+{
+ struct gre_hdr *greh;
+ struct gre_hdr_pptp *pgreh;
+ struct iphdr *iph = (struct iphdr *)((*pskb)->data + iphdroff);
+ unsigned int hdroff = iphdroff + iph->ihl * 4;
+
+ /* pgreh includes two optional 32bit fields which are not required
+ * to be there. That's where the magic '8' comes from */
+ if (!skb_make_writable(pskb, hdroff + sizeof(*pgreh) - 8))
+ 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)
+ return 1;
+ 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... */
+ nf_proto_csum_replace4(gre_csum(greh), *pskb,
+ *(gre_key(greh)),
+ tuple->dst.u.gre.key, 0);
+ }
+ *(gre_key(greh)) = tuple->dst.u.gre.key;
+ break;
+ case GRE_VERSION_PPTP:
+ DEBUGP("call_id -> 0x%04x\n", ntohs(tuple->dst.u.gre.key));
+ pgreh->call_id = tuple->dst.u.gre.key;
+ break;
+ default:
+ DEBUGP("can't nat unknown GRE version\n");
+ return 0;
+ }
+ return 1;
+}
+
+static struct nf_nat_protocol gre __read_mostly = {
+ .name = "GRE",
+ .protonum = IPPROTO_GRE,
+ .manip_pkt = gre_manip_pkt,
+ .in_range = gre_in_range,
+ .unique_tuple = gre_unique_tuple,
+#if defined(CONFIG_NF_CT_NETLINK) || defined(CONFIG_NF_CT_NETLINK_MODULE)
+ .range_to_nfattr = nf_nat_port_range_to_nfattr,
+ .nfattr_to_range = nf_nat_port_nfattr_to_range,
+#endif
+};
+
+int __init nf_nat_proto_gre_init(void)
+{
+ return nf_nat_protocol_register(&gre);
+}
+
+void __exit nf_nat_proto_gre_fini(void)
+{
+ nf_nat_protocol_unregister(&gre);
+}
+
+module_init(nf_nat_proto_gre_init);
+module_exit(nf_nat_proto_gre_fini);
+
+void nf_nat_need_gre(void)
+{
+ return;
+}
+EXPORT_SYMBOL_GPL(nf_nat_need_gre);
git://git.onelab.eu / linux-2.6.git / blobdiff