--- /dev/null
+/*
+ * nf_nat_pptp.c
+ *
+ * NAT support for PPTP (Point to Point Tunneling Protocol).
+ * PPTP is a a protocol for creating virtual private networks.
+ * It is a specification defined by Microsoft and some vendors
+ * working with Microsoft. PPTP is built on top of a modified
+ * version of the Internet Generic Routing Encapsulation Protocol.
+ * GRE is defined in RFC 1701 and RFC 1702. Documentation of
+ * 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/)
+ *
+ * TODO: - NAT to a unique tuple, not to TCP source port
+ * (needs netfilter tuple reservation)
+ */
+
+#include <linux/module.h>
+#include <linux/tcp.h>
+
+#include <net/netfilter/nf_nat.h>
+#include <net/netfilter/nf_nat_helper.h>
+#include <net/netfilter/nf_nat_rule.h>
+#include <net/netfilter/nf_conntrack_helper.h>
+#include <net/netfilter/nf_conntrack_expect.h>
+#include <linux/netfilter/nf_conntrack_proto_gre.h>
+#include <linux/netfilter/nf_conntrack_pptp.h>
+
+#define NF_NAT_PPTP_VERSION "3.0"
+
+#define REQ_CID(req, off) (*(__be16 *)((char *)(req) + (off)))
+
+MODULE_LICENSE("GPL");
+MODULE_AUTHOR("Harald Welte <laforge@gnumonks.org>");
+MODULE_DESCRIPTION("Netfilter NAT helper module for PPTP");
+MODULE_ALIAS("ip_nat_pptp");
+
+#if 0
+extern const char *pptp_msg_name[];
+#define DEBUGP(format, args...) printk(KERN_DEBUG "%s:%s: " format, __FILE__, \
+ __FUNCTION__, ## args)
+#else
+#define DEBUGP(format, args...)
+#endif
+
+static void pptp_nat_expected(struct nf_conn *ct,
+ struct nf_conntrack_expect *exp)
+{
+ struct nf_conn *master = ct->master;
+ struct nf_conntrack_expect *other_exp;
+ struct nf_conntrack_tuple t;
+ struct nf_ct_pptp_master *ct_pptp_info;
+ struct nf_nat_pptp *nat_pptp_info;
+ struct ip_nat_range range;
+
+ ct_pptp_info = &nfct_help(master)->help.ct_pptp_info;
+ nat_pptp_info = &nfct_nat(master)->help.nat_pptp_info;
+
+ /* And here goes the grand finale of corrosion... */
+ if (exp->dir == IP_CT_DIR_ORIGINAL) {
+ DEBUGP("we are PNS->PAC\n");
+ /* therefore, build tuple for PAC->PNS */
+ t.src.l3num = AF_INET;
+ t.src.u3.ip = master->tuplehash[!exp->dir].tuple.src.u3.ip;
+ t.src.u.gre.key = ct_pptp_info->pac_call_id;
+ t.dst.u3.ip = master->tuplehash[!exp->dir].tuple.dst.u3.ip;
+ t.dst.u.gre.key = ct_pptp_info->pns_call_id;
+ t.dst.protonum = IPPROTO_GRE;
+ } else {
+ DEBUGP("we are PAC->PNS\n");
+ /* build tuple for PNS->PAC */
+ t.src.l3num = AF_INET;
+ t.src.u3.ip = master->tuplehash[!exp->dir].tuple.src.u3.ip;
+ t.src.u.gre.key = nat_pptp_info->pns_call_id;
+ t.dst.u3.ip = master->tuplehash[!exp->dir].tuple.dst.u3.ip;
+ t.dst.u.gre.key = nat_pptp_info->pac_call_id;
+ t.dst.protonum = IPPROTO_GRE;
+ }
+
+ DEBUGP("trying to unexpect other dir: ");
+ NF_CT_DUMP_TUPLE(&t);
+ other_exp = nf_conntrack_expect_find_get(&t);
+ if (other_exp) {
+ nf_conntrack_unexpect_related(other_exp);
+ nf_conntrack_expect_put(other_exp);
+ DEBUGP("success\n");
+ } else {
+ DEBUGP("not found!\n");
+ }
+
+ /* This must be a fresh one. */
+ BUG_ON(ct->status & IPS_NAT_DONE_MASK);
+
+ /* Change src to where master sends to */
+ range.flags = IP_NAT_RANGE_MAP_IPS;
+ range.min_ip = range.max_ip
+ = ct->master->tuplehash[!exp->dir].tuple.dst.u3.ip;
+ if (exp->dir == IP_CT_DIR_ORIGINAL) {
+ range.flags |= IP_NAT_RANGE_PROTO_SPECIFIED;
+ range.min = range.max = exp->saved_proto;
+ }
+ /* hook doesn't matter, but it has to do source manip */
+ nf_nat_setup_info(ct, &range, NF_IP_POST_ROUTING);
+
+ /* For DST manip, map port here to where it's expected. */
+ range.flags = IP_NAT_RANGE_MAP_IPS;
+ range.min_ip = range.max_ip
+ = ct->master->tuplehash[!exp->dir].tuple.src.u3.ip;
+ if (exp->dir == IP_CT_DIR_REPLY) {
+ range.flags |= IP_NAT_RANGE_PROTO_SPECIFIED;
+ range.min = range.max = exp->saved_proto;
+ }
+ /* hook doesn't matter, but it has to do destination manip */
+ nf_nat_setup_info(ct, &range, NF_IP_PRE_ROUTING);
+}
+
+/* outbound packets == from PNS to PAC */
+static int
+pptp_outbound_pkt(struct sk_buff **pskb,
+ struct nf_conn *ct,
+ enum ip_conntrack_info ctinfo,
+ struct PptpControlHeader *ctlh,
+ union pptp_ctrl_union *pptpReq)
+
+{
+ struct nf_ct_pptp_master *ct_pptp_info;
+ struct nf_nat_pptp *nat_pptp_info;
+ u_int16_t msg;
+ __be16 new_callid;
+ unsigned int cid_off;
+
+ ct_pptp_info = &nfct_help(ct)->help.ct_pptp_info;
+ nat_pptp_info = &nfct_nat(ct)->help.nat_pptp_info;
+
+ new_callid = ct_pptp_info->pns_call_id;
+
+ switch (msg = ntohs(ctlh->messageType)) {
+ case PPTP_OUT_CALL_REQUEST:
+ cid_off = offsetof(union pptp_ctrl_union, ocreq.callID);
+ /* FIXME: ideally we would want to reserve a call ID
+ * here. current netfilter NAT core is not able to do
+ * this :( For now we use TCP source port. This breaks
+ * multiple calls within one control session */
+
+ /* save original call ID in nat_info */
+ nat_pptp_info->pns_call_id = ct_pptp_info->pns_call_id;
+
+ /* don't use tcph->source since we are at a DSTmanip
+ * hook (e.g. PREROUTING) and pkt is not mangled yet */
+ new_callid = ct->tuplehash[IP_CT_DIR_REPLY].tuple.dst.u.tcp.port;
+
+ /* save new call ID in ct info */
+ ct_pptp_info->pns_call_id = new_callid;
+ break;
+ case PPTP_IN_CALL_REPLY:
+ cid_off = offsetof(union pptp_ctrl_union, icack.callID);
+ break;
+ case PPTP_CALL_CLEAR_REQUEST:
+ cid_off = offsetof(union pptp_ctrl_union, clrreq.callID);
+ break;
+ default:
+ DEBUGP("unknown outbound packet 0x%04x:%s\n", msg,
+ (msg <= PPTP_MSG_MAX)?
+ pptp_msg_name[msg]:pptp_msg_name[0]);
+ /* fall through */
+ case PPTP_SET_LINK_INFO:
+ /* only need to NAT in case PAC is behind NAT box */
+ case PPTP_START_SESSION_REQUEST:
+ case PPTP_START_SESSION_REPLY:
+ case PPTP_STOP_SESSION_REQUEST:
+ case PPTP_STOP_SESSION_REPLY:
+ case PPTP_ECHO_REQUEST:
+ case PPTP_ECHO_REPLY:
+ /* no need to alter packet */
+ return NF_ACCEPT;
+ }
+
+ /* only OUT_CALL_REQUEST, IN_CALL_REPLY, CALL_CLEAR_REQUEST pass
+ * down to here */
+ DEBUGP("altering call id from 0x%04x to 0x%04x\n",
+ ntohs(REQ_CID(pptpReq, cid_off)), ntohs(new_callid));
+
+ /* mangle packet */
+ if (nf_nat_mangle_tcp_packet(pskb, ct, ctinfo,
+ cid_off + sizeof(struct pptp_pkt_hdr) +
+ sizeof(struct PptpControlHeader),
+ sizeof(new_callid), (char *)&new_callid,
+ sizeof(new_callid)) == 0)
+ return NF_DROP;
+ return NF_ACCEPT;
+}
+
+static void
+pptp_exp_gre(struct nf_conntrack_expect *expect_orig,
+ struct nf_conntrack_expect *expect_reply)
+{
+ struct nf_conn *ct = expect_orig->master;
+ struct nf_ct_pptp_master *ct_pptp_info;
+ struct nf_nat_pptp *nat_pptp_info;
+
+ ct_pptp_info = &nfct_help(ct)->help.ct_pptp_info;
+ nat_pptp_info = &nfct_nat(ct)->help.nat_pptp_info;
+
+ /* save original PAC call ID in nat_info */
+ nat_pptp_info->pac_call_id = ct_pptp_info->pac_call_id;
+
+ /* alter expectation for PNS->PAC direction */
+ expect_orig->saved_proto.gre.key = ct_pptp_info->pns_call_id;
+ expect_orig->tuple.src.u.gre.key = nat_pptp_info->pns_call_id;
+ expect_orig->tuple.dst.u.gre.key = ct_pptp_info->pac_call_id;
+ expect_orig->dir = IP_CT_DIR_ORIGINAL;
+
+ /* alter expectation for PAC->PNS direction */
+ expect_reply->saved_proto.gre.key = nat_pptp_info->pns_call_id;
+ expect_reply->tuple.src.u.gre.key = nat_pptp_info->pac_call_id;
+ expect_reply->tuple.dst.u.gre.key = ct_pptp_info->pns_call_id;
+ expect_reply->dir = IP_CT_DIR_REPLY;
+}
+
+/* inbound packets == from PAC to PNS */
+static int
+pptp_inbound_pkt(struct sk_buff **pskb,
+ struct nf_conn *ct,
+ enum ip_conntrack_info ctinfo,
+ struct PptpControlHeader *ctlh,
+ union pptp_ctrl_union *pptpReq)
+{
+ struct nf_nat_pptp *nat_pptp_info;
+ u_int16_t msg;
+ __be16 new_pcid;
+ unsigned int pcid_off;
+
+ nat_pptp_info = &nfct_nat(ct)->help.nat_pptp_info;
+ new_pcid = nat_pptp_info->pns_call_id;
+
+ switch (msg = ntohs(ctlh->messageType)) {
+ case PPTP_OUT_CALL_REPLY:
+ pcid_off = offsetof(union pptp_ctrl_union, ocack.peersCallID);
+ break;
+ case PPTP_IN_CALL_CONNECT:
+ pcid_off = offsetof(union pptp_ctrl_union, iccon.peersCallID);
+ break;
+ case PPTP_IN_CALL_REQUEST:
+ /* only need to nat in case PAC is behind NAT box */
+ return NF_ACCEPT;
+ case PPTP_WAN_ERROR_NOTIFY:
+ pcid_off = offsetof(union pptp_ctrl_union, wanerr.peersCallID);
+ break;
+ case PPTP_CALL_DISCONNECT_NOTIFY:
+ pcid_off = offsetof(union pptp_ctrl_union, disc.callID);
+ break;
+ case PPTP_SET_LINK_INFO:
+ pcid_off = offsetof(union pptp_ctrl_union, setlink.peersCallID);
+ break;
+ default:
+ DEBUGP("unknown inbound packet %s\n", (msg <= PPTP_MSG_MAX)?
+ pptp_msg_name[msg]:pptp_msg_name[0]);
+ /* fall through */
+ case PPTP_START_SESSION_REQUEST:
+ case PPTP_START_SESSION_REPLY:
+ case PPTP_STOP_SESSION_REQUEST:
+ case PPTP_STOP_SESSION_REPLY:
+ case PPTP_ECHO_REQUEST:
+ case PPTP_ECHO_REPLY:
+ /* no need to alter packet */
+ return NF_ACCEPT;
+ }
+
+ /* only OUT_CALL_REPLY, IN_CALL_CONNECT, IN_CALL_REQUEST,
+ * WAN_ERROR_NOTIFY, CALL_DISCONNECT_NOTIFY pass down here */
+
+ /* mangle packet */
+ DEBUGP("altering peer call id from 0x%04x to 0x%04x\n",
+ ntohs(REQ_CID(pptpReq, pcid_off)), ntohs(new_pcid));
+
+ if (nf_nat_mangle_tcp_packet(pskb, ct, ctinfo,
+ pcid_off + sizeof(struct pptp_pkt_hdr) +
+ sizeof(struct PptpControlHeader),
+ sizeof(new_pcid), (char *)&new_pcid,
+ sizeof(new_pcid)) == 0)
+ return NF_DROP;
+ return NF_ACCEPT;
+}
+
+static int __init nf_nat_helper_pptp_init(void)
+{
+ nf_nat_need_gre();
+
+ BUG_ON(rcu_dereference(nf_nat_pptp_hook_outbound));
+ rcu_assign_pointer(nf_nat_pptp_hook_outbound, pptp_outbound_pkt);
+
+ BUG_ON(rcu_dereference(nf_nat_pptp_hook_inbound));
+ rcu_assign_pointer(nf_nat_pptp_hook_inbound, pptp_inbound_pkt);
+
+ BUG_ON(rcu_dereference(nf_nat_pptp_hook_exp_gre));
+ rcu_assign_pointer(nf_nat_pptp_hook_exp_gre, pptp_exp_gre);
+
+ BUG_ON(rcu_dereference(nf_nat_pptp_hook_expectfn));
+ rcu_assign_pointer(nf_nat_pptp_hook_expectfn, pptp_nat_expected);
+ return 0;
+}
+
+static void __exit nf_nat_helper_pptp_fini(void)
+{
+ rcu_assign_pointer(nf_nat_pptp_hook_expectfn, NULL);
+ rcu_assign_pointer(nf_nat_pptp_hook_exp_gre, NULL);
+ rcu_assign_pointer(nf_nat_pptp_hook_inbound, NULL);
+ rcu_assign_pointer(nf_nat_pptp_hook_outbound, NULL);
+ synchronize_rcu();
+}
+
+module_init(nf_nat_helper_pptp_init);
+module_exit(nf_nat_helper_pptp_fini);
git://git.onelab.eu / linux-2.6.git / blobdiff