alias_skinny.c

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/*-
 * alias_skinny.c
 *
 * SPDX-License-Identifier: BSD-2-Clause-FreeBSD
 *
 * Copyright (c) 2002, 2003 MarcusCom, Inc.
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 *
 * Author: Joe Marcus Clarke <marcus@FreeBSD.org>
 *
 * $FreeBSD$
 */
 
#ifdef _KERNEL
#include <sys/param.h>
#include <sys/kernel.h>
#include <sys/module.h>
#else
#include <errno.h>
#include <stdio.h>
#include <unistd.h>
#endif
 
#include <netinet/in_systm.h>
#include <netinet/in.h>
#include <netinet/ip.h>
#include <netinet/tcp.h>
 
#ifdef _KERNEL
#include <netinet/libalias/alias_local.h>
#include <netinet/libalias/alias_mod.h>
#else
#include "alias_local.h"
#include "alias_mod.h"
#endif
 
static void
AliasHandleSkinny(struct libalias *, struct ip *, struct alias_link *);
 
static int
fingerprint(struct libalias *la, struct alias_data *ah)
{
        if (ah->dport == NULL || ah->sport == NULL || ah->lnk == NULL)
                return (-1);
        if (la->skinnyPort != 0 && (ntohs(*ah->sport) == la->skinnyPort ||
                                    ntohs(*ah->dport) == la->skinnyPort))
                return (0);
        return (-1);
}
 
static int
protohandler(struct libalias *la, struct ip *pip, struct alias_data *ah)
{
        AliasHandleSkinny(la, pip, ah->lnk);
        return (0);
}
 
struct proto_handler handlers[] = {
        {
          .pri = 110,
          .dir = IN|OUT,
          .proto = TCP,
          .fingerprint = &fingerprint,
          .protohandler = &protohandler
        },
        { EOH }
};
 
static int
mod_handler(module_t mod, int type, void *data)
{
        int error;
 
        switch (type) {
        case MOD_LOAD:
                error = 0;
                LibAliasAttachHandlers(handlers);
                break;
        case MOD_UNLOAD:
                error = 0;
                LibAliasDetachHandlers(handlers);
                break;
        default:
                error = EINVAL;
        }
        return (error);
}
 
#ifdef _KERNEL
static
#endif
moduledata_t alias_mod = {
       "alias_skinny", mod_handler, NULL
};
 
#ifdef _KERNEL
DECLARE_MODULE(alias_skinny, alias_mod, SI_SUB_DRIVERS, SI_ORDER_SECOND);
MODULE_VERSION(alias_skinny, 1);
MODULE_DEPEND(alias_skinny, libalias, 1, 1, 1);
#endif
 
/*
 * alias_skinny.c handles the translation for the Cisco Skinny Station
 * protocol.  Skinny typically uses TCP port 2000 to set up calls between
 * a Cisco Call Manager and a Cisco IP phone.  When a phone comes on line,
 * it first needs to register with the Call Manager.  To do this it sends
 * a registration message.  This message contains the IP address of the
 * IP phone.  This message must then be translated to reflect our global
 * IP address.  Along with the registration message (and usually in the
 * same packet), the phone sends an IP port message.  This message indicates
 * the TCP port over which it will communicate.
 *
 * When a call is placed from the phone, the Call Manager will send an
 * Open Receive Channel message to the phone to let the caller know someone
 * has answered.  The phone then sends back an Open Receive Channel
 * Acknowledgement.  In this packet, the phone sends its IP address again,
 * and the UDP port over which the voice traffic should flow.  These values
 * need translation.  Right after the Open Receive Channel Acknowledgement,
 * the Call Manager sends a Start Media Transmission message indicating the
 * call is connected.  This message contains the IP address and UDP port
 * number of the remote (called) party.  Once this message is translated, the
 * call can commence.  The called part sends the first UDP packet to the
 * calling phone at the pre-arranged UDP port in the Open Receive Channel
 * Acknowledgement.
 *
 * Skinny is a Cisco-proprietary protocol and is a trademark of Cisco Systems,
 * Inc.  All rights reserved.
*/
 
/* #define LIBALIAS_DEBUG 1 */
 
/* Message types that need translating */
#define REG_MSG         0x00000001
#define IP_PORT_MSG     0x00000002
#define OPNRCVCH_ACK    0x00000022
#define START_MEDIATX   0x0000008a
 
struct skinny_header {
        u_int32_t       len;
        u_int32_t       reserved;
        u_int32_t       msgId;
};
 
struct RegisterMessage {
        u_int32_t       msgId;
        char            devName   [16];
        u_int32_t       uid;
        u_int32_t       instance;
        u_int32_t       ipAddr;
        u_char          devType;
        u_int32_t       maxStreams;
};
 
struct IpPortMessage {
        u_int32_t       msgId;
        u_int32_t       stationIpPort;  /* Note: Skinny uses 32-bit port
                                         * numbers */
};
 
struct OpenReceiveChannelAck {
        u_int32_t       msgId;
        u_int32_t       status;
        u_int32_t       ipAddr;
        u_int32_t       port;
        u_int32_t       passThruPartyID;
};
 
struct StartMediaTransmission {
        u_int32_t       msgId;
        u_int32_t       conferenceID;
        u_int32_t       passThruPartyID;
        u_int32_t       remoteIpAddr;
        u_int32_t       remotePort;
        u_int32_t       MSPacket;
        u_int32_t       payloadCap;
        u_int32_t       precedence;
        u_int32_t       silenceSuppression;
        u_short         maxFramesPerPacket;
        u_int32_t       G723BitRate;
};
 
typedef enum {
        ClientToServer = 0,
        ServerToClient = 1
} ConvDirection;
 
static int
alias_skinny_reg_msg(struct RegisterMessage *reg_msg, struct ip *pip,
    struct tcphdr *tc, struct alias_link *lnk,
    ConvDirection direction)
{
        (void)direction;
 
        reg_msg->ipAddr = (u_int32_t)GetAliasAddress(lnk).s_addr;
 
        tc->th_sum = 0;
#ifdef _KERNEL
        tc->th_x2 = 1;
#else
        tc->th_sum = TcpChecksum(pip);
#endif
 
        return (0);
}
 
static int
alias_skinny_startmedia(struct StartMediaTransmission *start_media,
    struct ip *pip, struct tcphdr *tc,
    struct alias_link *lnk, u_int32_t localIpAddr,
    ConvDirection direction)
{
        struct in_addr dst, src;
 
        (void)pip;
        (void)tc;
        (void)lnk;
        (void)direction;
 
        dst.s_addr = start_media->remoteIpAddr;
        src.s_addr = localIpAddr;
 
        /*
         * XXX I should probably handle in bound global translations as
         * well.
         */
 
        return (0);
}
 
static int
alias_skinny_port_msg(struct IpPortMessage *port_msg, struct ip *pip,
    struct tcphdr *tc, struct alias_link *lnk,
    ConvDirection direction)
{
        (void)direction;
 
        port_msg->stationIpPort = (u_int32_t)ntohs(GetAliasPort(lnk));
 
        tc->th_sum = 0;
#ifdef _KERNEL
        tc->th_x2 = 1;
#else
        tc->th_sum = TcpChecksum(pip);
#endif
        return (0);
}
 
static int
alias_skinny_opnrcvch_ack(struct libalias *la, struct OpenReceiveChannelAck *opnrcvch_ack,
    struct ip *pip, struct tcphdr *tc,
    struct alias_link *lnk, u_int32_t * localIpAddr,
    ConvDirection direction)
{
        struct in_addr null_addr;
        struct alias_link *opnrcv_lnk;
        u_int32_t localPort;
 
        (void)lnk;
        (void)direction;
 
        *localIpAddr = (u_int32_t)opnrcvch_ack->ipAddr;
        localPort = opnrcvch_ack->port;
 
        null_addr.s_addr = INADDR_ANY;
        opnrcv_lnk = FindUdpTcpOut(la, pip->ip_src, null_addr,
            htons((u_short) opnrcvch_ack->port), 0,
            IPPROTO_UDP, 1);
        opnrcvch_ack->ipAddr = (u_int32_t)GetAliasAddress(opnrcv_lnk).s_addr;
        opnrcvch_ack->port = (u_int32_t)ntohs(GetAliasPort(opnrcv_lnk));
 
        tc->th_sum = 0;
#ifdef _KERNEL
        tc->th_x2 = 1;
#else
        tc->th_sum = TcpChecksum(pip);
#endif
        return (0);
}
 
static void
AliasHandleSkinny(struct libalias *la, struct ip *pip, struct alias_link *lnk)
{
        size_t hlen, tlen, dlen;
        struct tcphdr *tc;
        u_int32_t msgId, t, len, lip;
        struct skinny_header *sd;
        size_t orig_len, skinny_hdr_len = sizeof(struct skinny_header);
        ConvDirection direction;
 
        lip = -1;
        tc = (struct tcphdr *)ip_next(pip);
        hlen = (pip->ip_hl + tc->th_off) << 2;
        tlen = ntohs(pip->ip_len);
        dlen = tlen - hlen;
 
        sd = (struct skinny_header *)tcp_next(tc);
 
        /*
         * XXX This direction is reserved for future use.  I still need to
         * handle the scenario where the call manager is on the inside, and
         * the calling phone is on the global outside.
         */
        if (ntohs(tc->th_dport) == la->skinnyPort)
                direction = ClientToServer;
        else if (ntohs(tc->th_sport) == la->skinnyPort)
                direction = ServerToClient;
        else {
#ifdef LIBALIAS_DEBUG
                fprintf(stderr,
                    "PacketAlias/Skinny: Invalid port number, not a Skinny packet\n");
#endif
                return;
        }
 
        orig_len = dlen;
        /*
         * Skinny packets can contain many messages.  We need to loop
         * through the packet using len to determine message boundaries.
         * This comes into play big time with port messages being in the
         * same packet as register messages.  Also, open receive channel
         * acks are usually buried in a packet some 400 bytes long.
         */
        while (dlen >= skinny_hdr_len) {
                len = (sd->len);
                msgId = (sd->msgId);
                t = len;
 
                if (t > orig_len || t > dlen) {
#ifdef LIBALIAS_DEBUG
                        fprintf(stderr,
                            "PacketAlias/Skinny: Not a skinny packet, invalid length \n");
#endif
                        return;
                }
                switch (msgId) {
                case REG_MSG: {
                        struct RegisterMessage *reg_mesg;
 
                        if (len < (int)sizeof(struct RegisterMessage)) {
#ifdef LIBALIAS_DEBUG
                                fprintf(stderr,
                                    "PacketAlias/Skinny: Not a skinny packet, bad registration message\n");
#endif
                                return;
                        }
                        reg_mesg = (struct RegisterMessage *)&sd->msgId;
#ifdef LIBALIAS_DEBUG
                        fprintf(stderr,
                            "PacketAlias/Skinny: Received a register message");
#endif
                        alias_skinny_reg_msg(reg_mesg, pip, tc, lnk, direction);
                        break;
                }
                case IP_PORT_MSG: {
                        struct IpPortMessage *port_mesg;
 
                        if (len < (int)sizeof(struct IpPortMessage)) {
#ifdef LIBALIAS_DEBUG
                                fprintf(stderr,
                                    "PacketAlias/Skinny: Not a skinny packet, port message\n");
#endif
                                return;
                        }
#ifdef LIBALIAS_DEBUG
                        fprintf(stderr,
                            "PacketAlias/Skinny: Received ipport message\n");
#endif
                        port_mesg = (struct IpPortMessage *)&sd->msgId;
                        alias_skinny_port_msg(port_mesg, pip, tc, lnk, direction);
                        break;
                }
                case OPNRCVCH_ACK: {
                        struct OpenReceiveChannelAck *opnrcvchn_ack;
 
                        if (len < (int)sizeof(struct OpenReceiveChannelAck)) {
#ifdef LIBALIAS_DEBUG
                                fprintf(stderr,
                                    "PacketAlias/Skinny: Not a skinny packet, packet,OpnRcvChnAckMsg\n");
#endif
                                return;
                        }
#ifdef LIBALIAS_DEBUG
                        fprintf(stderr,
                            "PacketAlias/Skinny: Received open rcv channel msg\n");
#endif
                        opnrcvchn_ack = (struct OpenReceiveChannelAck *)&sd->msgId;
                        alias_skinny_opnrcvch_ack(la, opnrcvchn_ack, pip, tc, lnk, &lip, direction);
                        break;
                }
                case START_MEDIATX: {
                        struct StartMediaTransmission *startmedia_tx;
 
                        if (len < (int)sizeof(struct StartMediaTransmission)) {
#ifdef LIBALIAS_DEBUG
                                fprintf(stderr,
                                    "PacketAlias/Skinny: Not a skinny packet,StartMediaTx Message\n");
#endif
                                return;
                        }
                        if (lip == -1) {
#ifdef LIBALIAS_DEBUG
                                fprintf(stderr,
                                    "PacketAlias/Skinny: received a"
                                    " packet,StartMediaTx Message before"
                                    " packet,OpnRcvChnAckMsg\n"
#endif
                                return;
                        }
 
#ifdef LIBALIAS_DEBUG
                        fprintf(stderr,
                            "PacketAlias/Skinny: Received start media trans msg\n");
#endif
                        startmedia_tx = (struct StartMediaTransmission *)&sd->msgId;
                        alias_skinny_startmedia(startmedia_tx, pip, tc, lnk, lip, direction);
                        break;
                }
                default:
                        break;
                }
                /* Place the pointer at the next message in the packet. */
                dlen -= len + (skinny_hdr_len - sizeof(msgId));
                sd = (struct skinny_header *)(((char *)&sd->msgId) + len);
        }
}