udp.c

/*
 * Copyright (c) 1982, 1986, 1988, 1990, 1993
 *	The Regents of the University of California.  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.
 * 3. All advertising materials mentioning features or use of this software
 *    must display the following acknowledgement:
 *	This product includes software developed by the University of
 *	California, Berkeley and its contributors.
 * 4. Neither the name of the University nor the names of its contributors
 *    may be used to endorse or promote products derived from this software
 *    without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE REGENTS 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 REGENTS 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.
 *
 *	@(#)udp_usrreq.c	8.4 (Berkeley) 1/21/94
 * udp_usrreq.c,v 1.4 1994/10/02 17:48:45 phk Exp
 */

/*
 * Changes and additions relating to SLiRP
 * Copyright (c) 1995 Danny Gasparovski.
 *
 * Please read the file COPYRIGHT for the
 * terms and conditions of the copyright.
 */

#include <slirp.h>
#include "ip_icmp.h"

#ifdef LOG_ENABLED
struct udpstat udpstat;
#endif

struct socket udb;

static u_int8_t udp_tos(struct socket *so);
static void udp_emu(struct socket *so, struct mbuf *m);

/*
 * UDP protocol implementation.
 * Per RFC 768, August, 1980.
 */
#ifndef COMPAT_42
#define UDPCKSUM 1
#else
#define UDPCKSUM 0 /* XXX */
#endif

struct socket *udp_last_so = &udb;

void udp_init()
{
    udb.so_next = udb.so_prev = &udb;
}
/* m->m_data  points at ip packet header
 * m->m_len   length ip packet
 * ip->ip_len length data (IPDU)
 */
void udp_input(m, iphlen) register struct mbuf *m;
int iphlen;
{
    register struct ip *ip;
    register struct udphdr *uh;
    /*	struct mbuf *opts = 0;*/
    int len;
    struct ip save_ip;
    struct socket *so;

    DEBUG_CALL("udp_input");
    DEBUG_ARG("m = %lx", (long)m);
    DEBUG_ARG("iphlen = %d", iphlen);

    STAT(udpstat.udps_ipackets++);

    /*
     * Strip IP options, if any; should skip this,
     * make available to user, and use on returned packets,
     * but we don't yet have a way to check the checksum
     * with options still present.
     */
    if (iphlen > sizeof(struct ip)) {
        ip_stripoptions(m, (struct mbuf *)0);
        iphlen = sizeof(struct ip);
    }

    /*
     * Get IP and UDP header together in first mbuf.
     */
    ip = mtod(m, struct ip *);
    uh = (struct udphdr *)((caddr_t)ip + iphlen);

    /*
     * Make mbuf data length reflect UDP length.
     * If not enough data to reflect UDP length, drop.
     */
    len = ntohs((u_int16_t)uh->uh_ulen);

    if (ip->ip_len != len) {
        if (len > ip->ip_len) {
            STAT(udpstat.udps_badlen++);
            goto bad;
        }
        m_adj(m, len - ip->ip_len);
        ip->ip_len = len;
    }

    /*
     * Save a copy of the IP header in case we want restore it
     * for sending an ICMP error message in response.
     */
    save_ip = *ip;
    save_ip.ip_len += iphlen; /* tcp_input subtracts this */

    /*
     * Checksum extended UDP header and data.
     */
    if (UDPCKSUM && uh->uh_sum) {
        ((struct ipovly *)ip)->ih_next = 0;
        ((struct ipovly *)ip)->ih_prev = 0;
        ((struct ipovly *)ip)->ih_x1 = 0;
        ((struct ipovly *)ip)->ih_len = uh->uh_ulen;
        /* keep uh_sum for ICMP reply
         * uh->uh_sum = cksum(m, len + sizeof (struct ip));
         * if (uh->uh_sum) {
         */
        if (cksum(m, len + sizeof(struct ip))) {
            STAT(udpstat.udps_badsum++);
            goto bad;
        }
    }

    /*
     *  handle DHCP/BOOTP
     */
    if (ntohs(uh->uh_dport) == BOOTP_SERVER) {
        bootp_input(m);
        goto bad;
    }

    /*
     *  handle TFTP
     */
    if (ntohs(uh->uh_dport) == TFTP_SERVER) {
        tftp_input(m);
        goto bad;
    }

    /*
     * Locate pcb for datagram.
     */
    so = udp_last_so;
    if (so->so_lport != uh->uh_sport ||
        so->so_laddr.s_addr != ip->ip_src.s_addr) {
        struct socket *tmp;

        for (tmp = udb.so_next; tmp != &udb; tmp = tmp->so_next) {
            if (tmp->so_lport == uh->uh_sport &&
                tmp->so_laddr.s_addr == ip->ip_src.s_addr) {
                tmp->so_faddr.s_addr = ip->ip_dst.s_addr;
                tmp->so_fport = uh->uh_dport;
                so = tmp;
                break;
            }
        }
        if (tmp == &udb) {
            so = NULL;
        } else {
            STAT(udpstat.udpps_pcbcachemiss++);
            udp_last_so = so;
        }
    }

    if (so == NULL) {
        /*
         * If there's no socket for this packet,
         * create one
         */
        if ((so = socreate()) == NULL)
            goto bad;
        if (udp_attach(so) == -1) {
            DEBUG_MISC(
                (dfd, " udp_attach errno = %d-%s\n", errno, strerror(errno)));
            sofree(so);
            goto bad;
        }

        /*
         * Setup fields
         */
        /* udp_last_so = so; */
        so->so_laddr = ip->ip_src;
        so->so_lport = uh->uh_sport;

        if ((so->so_iptos = udp_tos(so)) == 0)
            so->so_iptos = ip->ip_tos;

        /*
         * XXXXX Here, check if it's in udpexec_list,
         * and if it is, do the fork_exec() etc.
         */
    }

    so->so_faddr = ip->ip_dst; /* XXX */
    so->so_fport = uh->uh_dport; /* XXX */

    iphlen += sizeof(struct udphdr);
    m->m_len -= iphlen;
    m->m_data += iphlen;

    /*
     * Now we sendto() the packet.
     */
    if (so->so_emu)
        udp_emu(so, m);

    if (sosendto(so, m) == -1) {
        m->m_len += iphlen;
        m->m_data -= iphlen;
        *ip = save_ip;
        DEBUG_MISC((dfd, "udp tx errno = %d-%s\n", errno, strerror(errno)));
        icmp_error(m, ICMP_UNREACH, ICMP_UNREACH_NET, 0, strerror(errno));
    }

    m_free(so->so_m); /* used for ICMP if error on sorecvfrom */

    /* restore the orig mbuf packet */
    m->m_len += iphlen;
    m->m_data -= iphlen;
    *ip = save_ip;
    so->so_m = m; /* ICMP backup */

    return;
bad:
    m_freem(m);
    /* if (opts) m_freem(opts); */
    return;
}

int udp_output2(struct socket *so, struct mbuf *m, struct sockaddr_in *saddr,
                struct sockaddr_in *daddr, int iptos)
{
    register struct udpiphdr *ui;
    int error = 0;

    DEBUG_CALL("udp_output");
    DEBUG_ARG("so = %lx", (long)so);
    DEBUG_ARG("m = %lx", (long)m);
    DEBUG_ARG("saddr = %lx", (long)saddr->sin_addr.s_addr);
    DEBUG_ARG("daddr = %lx", (long)daddr->sin_addr.s_addr);

    /*
     * Adjust for header
     */
    m->m_data -= sizeof(struct udpiphdr);
    m->m_len += sizeof(struct udpiphdr);

    /*
     * Fill in mbuf with extended UDP header
     * and addresses and length put into network format.
     */
    ui = mtod(m, struct udpiphdr *);
    ui->ui_next = ui->ui_prev = 0;
    ui->ui_x1 = 0;
    ui->ui_pr = IPPROTO_UDP;
    ui->ui_len =
        htons(m->m_len - sizeof(struct ip)); /* + sizeof (struct udphdr)); */
    /* XXXXX Check for from-one-location sockets, or from-any-location sockets
     */
    ui->ui_src = saddr->sin_addr;
    ui->ui_dst = daddr->sin_addr;
    ui->ui_sport = saddr->sin_port;
    ui->ui_dport = daddr->sin_port;
    ui->ui_ulen = ui->ui_len;

    /*
     * Stuff checksum and output datagram.
     */
    ui->ui_sum = 0;
    if (UDPCKSUM) {
        if ((ui->ui_sum =
                 cksum(m, /* sizeof (struct udpiphdr) + */ m->m_len)) == 0)
            ui->ui_sum = 0xffff;
    }
    ((struct ip *)ui)->ip_len = m->m_len;

    ((struct ip *)ui)->ip_ttl = IPDEFTTL;
    ((struct ip *)ui)->ip_tos = iptos;

    STAT(udpstat.udps_opackets++);

    error = ip_output(so, m);

    return (error);
}

int udp_output(struct socket *so, struct mbuf *m, struct sockaddr_in *addr)

{
    struct sockaddr_in saddr, daddr;

    saddr = *addr;
    if ((so->so_faddr.s_addr & htonl(0xffffff00)) == special_addr.s_addr) {
        saddr.sin_addr.s_addr = so->so_faddr.s_addr;
        if ((so->so_faddr.s_addr & htonl(0x000000ff)) == htonl(0xff))
            saddr.sin_addr.s_addr = alias_addr.s_addr;
    }
    daddr.sin_addr = so->so_laddr;
    daddr.sin_port = so->so_lport;

    return udp_output2(so, m, &saddr, &daddr, so->so_iptos);
}

int udp_attach(so) struct socket *so;
{
    struct sockaddr_in addr;

    if ((so->s = socket(AF_INET, SOCK_DGRAM, 0)) != -1) {
        /*
         * Here, we bind() the socket.  Although not really needed
         * (sendto() on an unbound socket will bind it), it's done
         * here so that emulation of ytalk etc. don't have to do it
         */
        addr.sin_family = AF_INET;
        addr.sin_port = 0;
        addr.sin_addr.s_addr = INADDR_ANY;
        if (bind(so->s, (struct sockaddr *)&addr, sizeof(addr)) < 0) {
            int lasterrno = errno;
            closesocket(so->s);
            so->s = -1;
#ifdef _WIN32
            WSASetLastError(lasterrno);
#else
            errno = lasterrno;
#endif
        } else {
            /* success, insert in queue */
            so->so_expire = curtime + SO_EXPIRE;
            insque(so, &udb);
        }
    }
    return (so->s);
}

void udp_detach(so) struct socket *so;
{
    closesocket(so->s);
    /* if (so->so_m) m_free(so->so_m);    done by sofree */

    sofree(so);
}

static const struct tos_t udptos[] = {
    { 0, 53, IPTOS_LOWDELAY, 0 }, /* DNS */
    { 517, 517, IPTOS_LOWDELAY, EMU_TALK }, /* talk */
    { 518, 518, IPTOS_LOWDELAY, EMU_NTALK }, /* ntalk */
    { 0, 7648, IPTOS_LOWDELAY, EMU_CUSEEME }, /* Cu-Seeme */
    { 0, 0, 0, 0 }
};

static u_int8_t udp_tos(struct socket *so)
{
    int i = 0;

    while (udptos[i].tos) {
        if ((udptos[i].fport && ntohs(so->so_fport) == udptos[i].fport) ||
            (udptos[i].lport && ntohs(so->so_lport) == udptos[i].lport)) {
            so->so_emu = udptos[i].emu;
            return udptos[i].tos;
        }
        i++;
    }

    return 0;
}

#ifdef EMULATE_TALK
#include "talkd.h"
#endif

/*
 * Here, talk/ytalk/ntalk requests must be emulated
 */
static void udp_emu(struct socket *so, struct mbuf *m)
{
    struct sockaddr_in addr;
    int addrlen = sizeof(addr);
#ifdef EMULATE_TALK
    CTL_MSG_OLD *omsg;
    CTL_MSG *nmsg;
    char buff[sizeof(CTL_MSG)];
    u_char type;

    struct talk_request {
        struct talk_request *next;
        struct socket *udp_so;
        struct socket *tcp_so;
    } * req;

    static struct talk_request *req_tbl = 0;

#endif

    struct cu_header {
        uint16_t d_family; // destination family
        uint16_t d_port; // destination port
        uint32_t d_addr; // destination address
        uint16_t s_family; // source family
        uint16_t s_port; // source port
        uint32_t so_addr; // source address
        uint32_t seqn; // sequence number
        uint16_t message; // message
        uint16_t data_type; // data type
        uint16_t pkt_len; // packet length
    } * cu_head;

    switch (so->so_emu) {
#ifdef EMULATE_TALK
    case EMU_TALK:
    case EMU_NTALK:
        /*
         * Talk emulation. We always change the ctl_addr to get
         * some answers from the daemon. When an ANNOUNCE comes,
         * we send LEAVE_INVITE to the local daemons. Also when a
         * DELETE comes, we send copies to the local daemons.
         */
        if (getsockname(so->s, (struct sockaddr *)&addr, &addrlen) < 0)
            return;

#define IS_OLD (so->so_emu == EMU_TALK)

#define COPY_MSG(dest, src)                                 \
    {                                                       \
        dest->type = src->type;                             \
        dest->id_num = src->id_num;                         \
        dest->pid = src->pid;                               \
        dest->addr = src->addr;                             \
        dest->ctl_addr = src->ctl_addr;                     \
        memcpy(&dest->l_name, &src->l_name, NAME_SIZE_OLD); \
        memcpy(&dest->r_name, &src->r_name, NAME_SIZE_OLD); \
        memcpy(&dest->r_tty, &src->r_tty, TTY_SIZE);        \
    }

#define OTOSIN(ptr, field) ((struct sockaddr_in *)&ptr->field)
        /* old_sockaddr to sockaddr_in */


        if (IS_OLD) { /* old talk */
            omsg = mtod(m, CTL_MSG_OLD *);
            nmsg = (CTL_MSG *)buff;
            type = omsg->type;
            OTOSIN(omsg, ctl_addr)->sin_port = addr.sin_port;
            OTOSIN(omsg, ctl_addr)->sin_addr = our_addr;
            strncpy(omsg->l_name, getlogin(), NAME_SIZE_OLD);
        } else { /* new talk */
            omsg = (CTL_MSG_OLD *)buff;
            nmsg = mtod(m, CTL_MSG *);
            type = nmsg->type;
            OTOSIN(nmsg, ctl_addr)->sin_port = addr.sin_port;
            OTOSIN(nmsg, ctl_addr)->sin_addr = our_addr;
            strncpy(nmsg->l_name, getlogin(), NAME_SIZE_OLD);
        }

        if (type == LOOK_UP)
            return; /* for LOOK_UP this is enough */

        if (IS_OLD) { /* make a copy of the message */
            COPY_MSG(nmsg, omsg);
            nmsg->vers = 1;
            nmsg->answer = 0;
        } else
            COPY_MSG(omsg, nmsg);

        /*
         * If if is an ANNOUNCE message, we go through the
         * request table to see if a tcp port has already
         * been redirected for this socket. If not, we solisten()
         * a new socket and add this entry to the table.
         * The port number of the tcp socket and our IP
         * are put to the addr field of the message structures.
         * Then a LEAVE_INVITE is sent to both local daemon
         * ports, 517 and 518. This is why we have two copies
         * of the message, one in old talk and one in new talk
         * format.
         */

        if (type == ANNOUNCE) {
            int s;
            u_short temp_port;

            for (req = req_tbl; req; req = req->next)
                if (so == req->udp_so)
                    break; /* found it */

            if (!req) { /* no entry for so, create new */
                req =
                    (struct talk_request *)malloc(sizeof(struct talk_request));
                req->udp_so = so;
                req->tcp_so =
                    solisten(0, OTOSIN(omsg, addr)->sin_addr.s_addr,
                             OTOSIN(omsg, addr)->sin_port, SS_FACCEPTONCE);
                req->next = req_tbl;
                req_tbl = req;
            }

            /* replace port number in addr field */
            addrlen = sizeof(addr);
            getsockname(req->tcp_so->s, (struct sockaddr *)&addr, &addrlen);
            OTOSIN(omsg, addr)->sin_port = addr.sin_port;
            OTOSIN(omsg, addr)->sin_addr = our_addr;
            OTOSIN(nmsg, addr)->sin_port = addr.sin_port;
            OTOSIN(nmsg, addr)->sin_addr = our_addr;

            /* send LEAVE_INVITEs */
            temp_port = OTOSIN(omsg, ctl_addr)->sin_port;
            OTOSIN(omsg, ctl_addr)->sin_port = 0;
            OTOSIN(nmsg, ctl_addr)->sin_port = 0;
            omsg->type = nmsg->type = LEAVE_INVITE;

            s = socket(AF_INET, SOCK_DGRAM, IPPROTO_IP);
            addr.sin_addr = our_addr;
            addr.sin_family = AF_INET;
            addr.sin_port = htons(517);
            sendto(s, (char *)omsg, sizeof(*omsg), 0, (struct sockaddr *)&addr,
                   sizeof(addr));
            addr.sin_port = htons(518);
            sendto(s, (char *)nmsg, sizeof(*nmsg), 0, (struct sockaddr *)&addr,
                   sizeof(addr));
            closesocket(s);

            omsg->type = nmsg->type = ANNOUNCE;
            OTOSIN(omsg, ctl_addr)->sin_port = temp_port;
            OTOSIN(nmsg, ctl_addr)->sin_port = temp_port;
        }

        /*
         * If it is a DELETE message, we send a copy to the
         * local daemons. Then we delete the entry corresponding
         * to our socket from the request table.
         */

        if (type == DELETE) {
            struct talk_request *temp_req, *req_next;
            int s;
            u_short temp_port;

            temp_port = OTOSIN(omsg, ctl_addr)->sin_port;
            OTOSIN(omsg, ctl_addr)->sin_port = 0;
            OTOSIN(nmsg, ctl_addr)->sin_port = 0;

            s = socket(AF_INET, SOCK_DGRAM, IPPROTO_IP);
            addr.sin_addr = our_addr;
            addr.sin_family = AF_INET;
            addr.sin_port = htons(517);
            sendto(s, (char *)omsg, sizeof(*omsg), 0, (struct sockaddr *)&addr,
                   sizeof(addr));
            addr.sin_port = htons(518);
            sendto(s, (char *)nmsg, sizeof(*nmsg), 0, (struct sockaddr *)&addr,
                   sizeof(addr));
            closesocket(s);

            OTOSIN(omsg, ctl_addr)->sin_port = temp_port;
            OTOSIN(nmsg, ctl_addr)->sin_port = temp_port;

            /* delete table entry */
            if (so == req_tbl->udp_so) {
                temp_req = req_tbl;
                req_tbl = req_tbl->next;
                free(temp_req);
            } else {
                temp_req = req_tbl;
                for (req = req_tbl->next; req; req = req_next) {
                    req_next = req->next;
                    if (so == req->udp_so) {
                        temp_req->next = req_next;
                        free(req);
                        break;
                    } else {
                        temp_req = req;
                    }
                }
            }
        }

        return;
#endif

    case EMU_CUSEEME:

        /*
         * Cu-SeeMe emulation.
         * Hopefully the packet is more that 16 bytes long. We don't
         * do any other tests, just replace the address and port
         * fields.
         */
        if (m->m_len >= sizeof(*cu_head)) {
            if (getsockname(so->s, (struct sockaddr *)&addr, &addrlen) < 0)
                return;
            cu_head = mtod(m, struct cu_header *);
            cu_head->s_port = addr.sin_port;
            cu_head->so_addr = our_addr.s_addr;
        }

        return;
    }
}

struct socket *udp_listen(port, laddr, lport, flags) u_int port;
u_int32_t laddr;
u_int lport;
int flags;
{
    struct sockaddr_in addr;
    struct socket *so;
    int addrlen = sizeof(struct sockaddr_in), opt = 1;

    if ((so = socreate()) == NULL) {
        free(so);
        return NULL;
    }
    so->s = socket(AF_INET, SOCK_DGRAM, 0);
    so->so_expire = curtime + SO_EXPIRE;
    insque(so, &udb);

    addr.sin_family = AF_INET;
    addr.sin_addr.s_addr = INADDR_ANY;
    addr.sin_port = port;

    if (bind(so->s, (struct sockaddr *)&addr, addrlen) < 0) {
        udp_detach(so);
        return NULL;
    }
    setsockopt(so->s, SOL_SOCKET, SO_REUSEADDR, (char *)&opt, sizeof(int));
    /*	setsockopt(so->s,SOL_SOCKET,SO_OOBINLINE,(char *)&opt,sizeof(int)); */

    getsockname(so->s, (struct sockaddr *)&addr, &addrlen);
    so->so_fport = addr.sin_port;
    if (addr.sin_addr.s_addr == 0 ||
        addr.sin_addr.s_addr == loopback_addr.s_addr)
        so->so_faddr = alias_addr;
    else
        so->so_faddr = addr.sin_addr;

    so->so_lport = lport;
    so->so_laddr.s_addr = laddr;
    if (flags != SS_FACCEPTONCE)
        so->so_expire = 0;

    so->so_state = SS_ISFCONNECTED;

    return so;
}