ip_conntrack_helper_pptp.c

linux-2.6.15.6

		}

		/* server accepted call, we now expect GRE frames */
		if (info->sstate != PPTP_SESSION_CONFIRMED) {
			DEBUGP("%s but no session\n", pptp_msg_name[msg]);
			break;
		}
		if (info->cstate != PPTP_CALL_OUT_REQ &&
		    info->cstate != PPTP_CALL_OUT_CONF) {
			DEBUGP("%s without OUTCALL_REQ\n", pptp_msg_name[msg]);
			break;
		}
		if (pptpReq->ocack.resultCode != PPTP_OUTCALL_CONNECT) {
			info->cstate = PPTP_CALL_NONE;
			break;
		}

		cid = &pptpReq->ocack.callID;
		pcid = &pptpReq->ocack.peersCallID;

		info->pac_call_id = ntohs(*cid);
		
		if (htons(info->pns_call_id) != *pcid) {
			DEBUGP("%s for unknown callid %u\n",
				pptp_msg_name[msg], ntohs(*pcid));
			break;
		}

		DEBUGP("%s, CID=%X, PCID=%X\n", pptp_msg_name[msg], 
			ntohs(*cid), ntohs(*pcid));
		
		info->cstate = PPTP_CALL_OUT_CONF;

		seq = ntohl(tcph->seq) + sizeof(struct pptp_pkt_hdr)
				       + sizeof(struct PptpControlHeader)
				       + ((void *)pcid - (void *)pptpReq);
			
		if (exp_gre(ct, seq, *cid, *pcid) != 0)
			printk("ip_conntrack_pptp: error during exp_gre\n");
		break;

	case PPTP_IN_CALL_REQUEST:
		if (reqlen < sizeof(_pptpReq.icack)) {
			DEBUGP("%s: short packet\n", pptp_msg_name[msg]);
			break;
		}

		/* server tells us about incoming call request */
		if (info->sstate != PPTP_SESSION_CONFIRMED) {
			DEBUGP("%s but no session\n", pptp_msg_name[msg]);
			break;
		}
		pcid = &pptpReq->icack.peersCallID;
		DEBUGP("%s, PCID=%X\n", pptp_msg_name[msg], ntohs(*pcid));
		info->cstate = PPTP_CALL_IN_REQ;
		info->pac_call_id = ntohs(*pcid);
		break;

	case PPTP_IN_CALL_CONNECT:
		if (reqlen < sizeof(_pptpReq.iccon)) {
			DEBUGP("%s: short packet\n", pptp_msg_name[msg]);
			break;
		}

		/* server tells us about incoming call established */
		if (info->sstate != PPTP_SESSION_CONFIRMED) {
			DEBUGP("%s but no session\n", pptp_msg_name[msg]);
			break;
		}
		if (info->sstate != PPTP_CALL_IN_REP
		    && info->sstate != PPTP_CALL_IN_CONF) {
			DEBUGP("%s but never sent IN_CALL_REPLY\n",
				pptp_msg_name[msg]);
			break;
		}

		pcid = &pptpReq->iccon.peersCallID;
		cid = &info->pac_call_id;

		if (info->pns_call_id != ntohs(*pcid)) {
			DEBUGP("%s for unknown CallID %u\n", 
				pptp_msg_name[msg], ntohs(*pcid));
			break;
		}

		DEBUGP("%s, PCID=%X\n", pptp_msg_name[msg], ntohs(*pcid));
		info->cstate = PPTP_CALL_IN_CONF;

		/* we expect a GRE connection from PAC to PNS */
		seq = ntohl(tcph->seq) + sizeof(struct pptp_pkt_hdr)
				       + sizeof(struct PptpControlHeader)
				       + ((void *)pcid - (void *)pptpReq);
			
		if (exp_gre(ct, seq, *cid, *pcid) != 0)
			printk("ip_conntrack_pptp: error during exp_gre\n");

		break;

	case PPTP_CALL_DISCONNECT_NOTIFY:
		if (reqlen < sizeof(_pptpReq.disc)) {
			DEBUGP("%s: short packet\n", pptp_msg_name[msg]);
			break;
		}

		/* server confirms disconnect */
		cid = &pptpReq->disc.callID;
		DEBUGP("%s, CID=%X\n", pptp_msg_name[msg], ntohs(*cid));
		info->cstate = PPTP_CALL_NONE;

		/* untrack this call id, unexpect GRE packets */
		pptp_destroy_siblings(ct);
		break;

	case PPTP_WAN_ERROR_NOTIFY:
		break;

	case PPTP_ECHO_REQUEST:
	case PPTP_ECHO_REPLY:
		/* I don't have to explain these ;) */
		break;
	default:
		DEBUGP("invalid %s (TY=%d)\n", (msg <= PPTP_MSG_MAX)
			? pptp_msg_name[msg]:pptp_msg_name[0], msg);
		break;
	}


	if (ip_nat_pptp_hook_inbound)
		return ip_nat_pptp_hook_inbound(pskb, ct, ctinfo, ctlh,
						pptpReq);

	return NF_ACCEPT;

}

static inline int
pptp_outbound_pkt(struct sk_buff **pskb,
		  struct tcphdr *tcph,
		  unsigned int nexthdr_off,
		  unsigned int datalen,
		  struct ip_conntrack *ct,
		  enum ip_conntrack_info ctinfo)
{
	struct PptpControlHeader _ctlh, *ctlh;
	unsigned int reqlen;
	union pptp_ctrl_union _pptpReq, *pptpReq;
	struct ip_ct_pptp_master *info = &ct->help.ct_pptp_info;
	u_int16_t msg;
	__be16 *cid, *pcid;

	ctlh = skb_header_pointer(*pskb, nexthdr_off, sizeof(_ctlh), &_ctlh);
	if (!ctlh)
		return NF_ACCEPT;
	nexthdr_off += sizeof(_ctlh);
	datalen -= sizeof(_ctlh);
	
	reqlen = datalen;
	if (reqlen > sizeof(*pptpReq))
		reqlen = sizeof(*pptpReq);
	pptpReq = skb_header_pointer(*pskb, nexthdr_off, reqlen, &_pptpReq);
	if (!pptpReq)
		return NF_ACCEPT;

	msg = ntohs(ctlh->messageType);
	DEBUGP("outbound control message %s\n", pptp_msg_name[msg]);

	switch (msg) {
	case PPTP_START_SESSION_REQUEST:
		/* client requests for new control session */
		if (info->sstate != PPTP_SESSION_NONE) {
			DEBUGP("%s but we already have one",
				pptp_msg_name[msg]);
		}
		info->sstate = PPTP_SESSION_REQUESTED;
		break;
	case PPTP_STOP_SESSION_REQUEST:
		/* client requests end of control session */
		info->sstate = PPTP_SESSION_STOPREQ;
		break;

	case PPTP_OUT_CALL_REQUEST:
		if (reqlen < sizeof(_pptpReq.ocreq)) {
			DEBUGP("%s: short packet\n", pptp_msg_name[msg]);
			/* FIXME: break; */
		}

		/* client initiating connection to server */
		if (info->sstate != PPTP_SESSION_CONFIRMED) {
			DEBUGP("%s but no session\n",
				pptp_msg_name[msg]);
			break;
		}
		info->cstate = PPTP_CALL_OUT_REQ;
		/* track PNS call id */
		cid = &pptpReq->ocreq.callID;
		DEBUGP("%s, CID=%X\n", pptp_msg_name[msg], ntohs(*cid));
		info->pns_call_id = ntohs(*cid);
		break;
	case PPTP_IN_CALL_REPLY:
		if (reqlen < sizeof(_pptpReq.icack)) {
			DEBUGP("%s: short packet\n", pptp_msg_name[msg]);
			break;
		}

		/* client answers incoming call */
		if (info->cstate != PPTP_CALL_IN_REQ
		    && info->cstate != PPTP_CALL_IN_REP) {
			DEBUGP("%s without incall_req\n", 
				pptp_msg_name[msg]);
			break;
		}
		if (pptpReq->icack.resultCode != PPTP_INCALL_ACCEPT) {
			info->cstate = PPTP_CALL_NONE;
			break;
		}
		pcid = &pptpReq->icack.peersCallID;
		if (info->pac_call_id != ntohs(*pcid)) {
			DEBUGP("%s for unknown call %u\n", 
				pptp_msg_name[msg], ntohs(*pcid));
			break;
		}
		DEBUGP("%s, CID=%X\n", pptp_msg_name[msg], ntohs(*pcid));
		/* part two of the three-way handshake */
		info->cstate = PPTP_CALL_IN_REP;
		info->pns_call_id = ntohs(pptpReq->icack.callID);
		break;

	case PPTP_CALL_CLEAR_REQUEST:
		/* client requests hangup of call */
		if (info->sstate != PPTP_SESSION_CONFIRMED) {
			DEBUGP("CLEAR_CALL but no session\n");
			break;
		}
		/* FUTURE: iterate over all calls and check if
		 * call ID is valid.  We don't do this without newnat,
		 * because we only know about last call */
		info->cstate = PPTP_CALL_CLEAR_REQ;
		break;
	case PPTP_SET_LINK_INFO:
		break;
	case PPTP_ECHO_REQUEST:
	case PPTP_ECHO_REPLY:
		/* I don't have to explain these ;) */
		break;
	default:
		DEBUGP("invalid %s (TY=%d)\n", (msg <= PPTP_MSG_MAX)? 
			pptp_msg_name[msg]:pptp_msg_name[0], msg);
		/* unknown: no need to create GRE masq table entry */
		break;
	}
	
	if (ip_nat_pptp_hook_outbound)
		return ip_nat_pptp_hook_outbound(pskb, ct, ctinfo, ctlh,
						 pptpReq);

	return NF_ACCEPT;
}


/* track caller id inside control connection, call expect_related */
static int 
conntrack_pptp_help(struct sk_buff **pskb,
		    struct ip_conntrack *ct, enum ip_conntrack_info ctinfo)

{
	struct pptp_pkt_hdr _pptph, *pptph;
	struct tcphdr _tcph, *tcph;
	u_int32_t tcplen = (*pskb)->len - (*pskb)->nh.iph->ihl * 4;
	u_int32_t datalen;
	int dir = CTINFO2DIR(ctinfo);
	struct ip_ct_pptp_master *info = &ct->help.ct_pptp_info;
	unsigned int nexthdr_off;

	int oldsstate, oldcstate;
	int ret;

	/* don't do any tracking before tcp handshake complete */
	if (ctinfo != IP_CT_ESTABLISHED 
	    && ctinfo != IP_CT_ESTABLISHED+IP_CT_IS_REPLY) {
		DEBUGP("ctinfo = %u, skipping\n", ctinfo);
		return NF_ACCEPT;
	}
	
	nexthdr_off = (*pskb)->nh.iph->ihl*4;
	tcph = skb_header_pointer(*pskb, nexthdr_off, sizeof(_tcph), &_tcph);
	BUG_ON(!tcph);
	nexthdr_off += tcph->doff * 4;
 	datalen = tcplen - tcph->doff * 4;

	if (tcph->fin || tcph->rst) {
		DEBUGP("RST/FIN received, timeouting GRE\n");
		/* can't do this after real newnat */
		info->cstate = PPTP_CALL_NONE;

		/* untrack this call id, unexpect GRE packets */
		pptp_destroy_siblings(ct);
	}

	pptph = skb_header_pointer(*pskb, nexthdr_off, sizeof(_pptph), &_pptph);
	if (!pptph) {
		DEBUGP("no full PPTP header, can't track\n");
		return NF_ACCEPT;
	}
	nexthdr_off += sizeof(_pptph);
	datalen -= sizeof(_pptph);

	/* if it's not a control message we can't do anything with it */
	if (ntohs(pptph->packetType) != PPTP_PACKET_CONTROL ||
	    ntohl(pptph->magicCookie) != PPTP_MAGIC_COOKIE) {
		DEBUGP("not a control packet\n");
		return NF_ACCEPT;
	}

	oldsstate = info->sstate;
	oldcstate = info->cstate;

	spin_lock_bh(&ip_pptp_lock);

	/* FIXME: We just blindly assume that the control connection is always
	 * established from PNS->PAC.  However, RFC makes no guarantee */
	if (dir == IP_CT_DIR_ORIGINAL)
		/* client -> server (PNS -> PAC) */
		ret = pptp_outbound_pkt(pskb, tcph, nexthdr_off, datalen, ct,
					ctinfo);
	else
		/* server -> client (PAC -> PNS) */
		ret = pptp_inbound_pkt(pskb, tcph, nexthdr_off, datalen, ct,
				       ctinfo);
	DEBUGP("sstate: %d->%d, cstate: %d->%d\n",
		oldsstate, info->sstate, oldcstate, info->cstate);
	spin_unlock_bh(&ip_pptp_lock);

	return ret;
}

/* control protocol helper */
static struct ip_conntrack_helper pptp = { 
	.list = { NULL, NULL },
	.name = "pptp", 
	.me = THIS_MODULE,
	.max_expected = 2,
	.timeout = 5 * 60,
	.tuple = { .src = { .ip = 0, 
		 	    .u = { .tcp = { .port =  
				    __constant_htons(PPTP_CONTROL_PORT) } } 
			  }, 
		   .dst = { .ip = 0, 
			    .u = { .all = 0 },
			    .protonum = IPPROTO_TCP
			  } 
		 },
	.mask = { .src = { .ip = 0, 
			   .u = { .tcp = { .port = __constant_htons(0xffff) } } 
			 }, 
		  .dst = { .ip = 0, 
			   .u = { .all = 0 },
			   .protonum = 0xff 
		 	 } 
		},
	.help = conntrack_pptp_help
};

extern void __exit ip_ct_proto_gre_fini(void);
extern int __init ip_ct_proto_gre_init(void);

/* ip_conntrack_pptp initialization */
static int __init init(void)
{
	int retcode;
 
	retcode = ip_ct_proto_gre_init();
	if (retcode < 0)
		return retcode;

	DEBUGP(" registering helper\n");
	if ((retcode = ip_conntrack_helper_register(&pptp))) {
		printk(KERN_ERR "Unable to register conntrack application "
				"helper for pptp: %d\n", retcode);
		ip_ct_proto_gre_fini();
		return retcode;
	}

	printk("ip_conntrack_pptp version %s loaded\n", IP_CT_PPTP_VERSION);
	return 0;
}

static void __exit fini(void)
{
	ip_conntrack_helper_unregister(&pptp);
	ip_ct_proto_gre_fini();
	printk("ip_conntrack_pptp version %s unloaded\n", IP_CT_PPTP_VERSION);
}

module_init(init);
module_exit(fini);

EXPORT_SYMBOL(ip_nat_pptp_hook_outbound);
EXPORT_SYMBOL(ip_nat_pptp_hook_inbound);
EXPORT_SYMBOL(ip_nat_pptp_hook_exp_gre);
EXPORT_SYMBOL(ip_nat_pptp_hook_expectfn);