Archipelago » qemu

/*

 * libslirp glue

 *

 * Copyright (c) 2004-2008 Fabrice Bellard

 *

 * Permission is hereby granted, free of charge, to any person obtaining a copy

 * of this software and associated documentation files (the "Software"), to deal

 * in the Software without restriction, including without limitation the rights

 * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell

 * copies of the Software, and to permit persons to whom the Software is

 * furnished to do so, subject to the following conditions:

 *

 * The above copyright notice and this permission notice shall be included in

 * all copies or substantial portions of the Software.

 *

 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR

 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,

 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL

 * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER

 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,

 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN

 * THE SOFTWARE.

 */

#include "qemu-common.h"

#include "qemu-timer.h"

#include "qemu-char.h"

#include "slirp.h"

#include "hw/hw.h"

/* host loopback address */

struct in_addr loopback_addr;

/* emulated hosts use the MAC addr 52:55:IP:IP:IP:IP */

static const uint8_t special_ethaddr[6] = {

    0x52, 0x55, 0x00, 0x00, 0x00, 0x00

};

static const uint8_t zero_ethaddr[6] = { 0, 0, 0, 0, 0, 0 };

/* XXX: suppress those select globals */

fd_set *global_readfds, *global_writefds, *global_xfds;

u_int curtime;

static u_int time_fasttimo, last_slowtimo;

static int do_slowtimo;

static QTAILQ_HEAD(slirp_instances, Slirp) slirp_instances =

    QTAILQ_HEAD_INITIALIZER(slirp_instances);

static struct in_addr dns_addr;

static u_int dns_addr_time;

#ifdef _WIN32

int get_dns_addr(struct in_addr *pdns_addr)

{

    FIXED_INFO *FixedInfo=NULL;

    ULONG    BufLen;

    DWORD    ret;

    IP_ADDR_STRING *pIPAddr;

    struct in_addr tmp_addr;

    if (dns_addr.s_addr != 0 && (curtime - dns_addr_time) < 1000) {

        *pdns_addr = dns_addr;

        return 0;

    }

    FixedInfo = (FIXED_INFO *)GlobalAlloc(GPTR, sizeof(FIXED_INFO));

    BufLen = sizeof(FIXED_INFO);

    if (ERROR_BUFFER_OVERFLOW == GetNetworkParams(FixedInfo, &BufLen)) {

        if (FixedInfo) {

            GlobalFree(FixedInfo);

            FixedInfo = NULL;

        }

        FixedInfo = GlobalAlloc(GPTR, BufLen);

    }

    if ((ret = GetNetworkParams(FixedInfo, &BufLen)) != ERROR_SUCCESS) {

        printf("GetNetworkParams failed. ret = %08x\n", (u_int)ret );

        if (FixedInfo) {

            GlobalFree(FixedInfo);

            FixedInfo = NULL;

        }

        return -1;

    }

    pIPAddr = &(FixedInfo->DnsServerList);

    inet_aton(pIPAddr->IpAddress.String, &tmp_addr);

    *pdns_addr = tmp_addr;

    dns_addr = tmp_addr;

    dns_addr_time = curtime;

    if (FixedInfo) {

        GlobalFree(FixedInfo);

        FixedInfo = NULL;

    }

    return 0;

}

static void winsock_cleanup(void)

{

    WSACleanup();

}

#else

static struct stat dns_addr_stat;

int get_dns_addr(struct in_addr *pdns_addr)

{

    char buff[512];

    char buff2[257];

    FILE *f;

    int found = 0;

    struct in_addr tmp_addr;

    if (dns_addr.s_addr != 0) {

        struct stat old_stat;

        if ((curtime - dns_addr_time) < 1000) {

            *pdns_addr = dns_addr;

            return 0;

        }

        old_stat = dns_addr_stat;

        if (stat("/etc/resolv.conf", &dns_addr_stat) != 0)

            return -1;

        if ((dns_addr_stat.st_dev == old_stat.st_dev)

            && (dns_addr_stat.st_ino == old_stat.st_ino)

            && (dns_addr_stat.st_size == old_stat.st_size)

            && (dns_addr_stat.st_mtime == old_stat.st_mtime)) {

            *pdns_addr = dns_addr;

            return 0;

        }

    }

    f = fopen("/etc/resolv.conf", "r");

    if (!f)

        return -1;

#ifdef DEBUG

    lprint("IP address of your DNS(s): ");

#endif

    while (fgets(buff, 512, f) != NULL) {

        if (sscanf(buff, "nameserver%*[ \t]%256s", buff2) == 1) {

            if (!inet_aton(buff2, &tmp_addr))

                continue;

            /* If it's the first one, set it to dns_addr */

            if (!found) {

                *pdns_addr = tmp_addr;

                dns_addr = tmp_addr;

                dns_addr_time = curtime;

            }

#ifdef DEBUG

            else

                lprint(", ");

#endif

            if (++found > 3) {

#ifdef DEBUG

                lprint("(more)");

#endif

                break;

            }

#ifdef DEBUG

            else

                lprint("%s", inet_ntoa(tmp_addr));

#endif

        }

    }

    fclose(f);

    if (!found)

        return -1;

    return 0;

}

#endif

static void slirp_init_once(void)

{

    static int initialized;

#ifdef _WIN32

    WSADATA Data;

#endif

    if (initialized) {

        return;

    }

    initialized = 1;

#ifdef _WIN32

    WSAStartup(MAKEWORD(2,0), &Data);

    atexit(winsock_cleanup);

#endif

    loopback_addr.s_addr = htonl(INADDR_LOOPBACK);

}

static void slirp_state_save(QEMUFile *f, void *opaque);

static int slirp_state_load(QEMUFile *f, void *opaque, int version_id);

Slirp *slirp_init(int restricted, struct in_addr vnetwork,

                  struct in_addr vnetmask, struct in_addr vhost,

                  const char *vhostname, const char *tftp_path,

                  const char *bootfile, struct in_addr vdhcp_start,

                  struct in_addr vnameserver, void *opaque)

{

    Slirp *slirp = qemu_mallocz(sizeof(Slirp));

    slirp_init_once();

    slirp->restricted = restricted;

    if_init(slirp);

    ip_init(slirp);

    /* Initialise mbufs *after* setting the MTU */

    m_init(slirp);

    slirp->vnetwork_addr = vnetwork;

    slirp->vnetwork_mask = vnetmask;

    slirp->vhost_addr = vhost;

    if (vhostname) {

        pstrcpy(slirp->client_hostname, sizeof(slirp->client_hostname),

                vhostname);

    }

    if (tftp_path) {

        slirp->tftp_prefix = qemu_strdup(tftp_path);

    }

    if (bootfile) {

        slirp->bootp_filename = qemu_strdup(bootfile);

    }

    slirp->vdhcp_startaddr = vdhcp_start;

    slirp->vnameserver_addr = vnameserver;

    slirp->opaque = opaque;

    register_savevm(NULL, "slirp", 0, 3,

                    slirp_state_save, slirp_state_load, slirp);

    QTAILQ_INSERT_TAIL(&slirp_instances, slirp, entry);

    return slirp;

}

void slirp_cleanup(Slirp *slirp)

{

    QTAILQ_REMOVE(&slirp_instances, slirp, entry);

    unregister_savevm(NULL, "slirp", slirp);

    qemu_free(slirp->tftp_prefix);

    qemu_free(slirp->bootp_filename);

    qemu_free(slirp);

}

#define CONN_CANFSEND(so) (((so)->so_state & (SS_FCANTSENDMORE|SS_ISFCONNECTED)) == SS_ISFCONNECTED)

#define CONN_CANFRCV(so) (((so)->so_state & (SS_FCANTRCVMORE|SS_ISFCONNECTED)) == SS_ISFCONNECTED)

#define UPD_NFDS(x) if (nfds < (x)) nfds = (x)

void slirp_select_fill(int *pnfds,

                       fd_set *readfds, fd_set *writefds, fd_set *xfds)

{

    Slirp *slirp;

    struct socket *so, *so_next;

    int nfds;

    if (QTAILQ_EMPTY(&slirp_instances)) {

        return;

    }

    /* fail safe */

    global_readfds = NULL;

    global_writefds = NULL;

    global_xfds = NULL;

    nfds = *pnfds;

        /*

         * First, TCP sockets

         */

        do_slowtimo = 0;

        QTAILQ_FOREACH(slirp, &slirp_instances, entry) {

                /*

                 * *_slowtimo needs calling if there are IP fragments

                 * in the fragment queue, or there are TCP connections active

                 */

                do_slowtimo |= ((slirp->tcb.so_next != &slirp->tcb) ||

                    (&slirp->ipq.ip_link != slirp->ipq.ip_link.next));

                for (so = slirp->tcb.so_next; so != &slirp->tcb;

                     so = so_next) {

                        so_next = so->so_next;

                        /*

                         * See if we need a tcp_fasttimo

                         */

                        if (time_fasttimo == 0 && so->so_tcpcb->t_flags & TF_DELACK)

                           time_fasttimo = curtime; /* Flag when we want a fasttimo */

                        /*

                         * NOFDREF can include still connecting to local-host,

                         * newly socreated() sockets etc. Don't want to select these.

                          */

                        if (so->so_state & SS_NOFDREF || so->s == -1)

                           continue;

                        /*

                         * Set for reading sockets which are accepting

                         */

                        if (so->so_state & SS_FACCEPTCONN) {

                                FD_SET(so->s, readfds);

                                UPD_NFDS(so->s);

                                continue;

                        }

                        /*

                         * Set for writing sockets which are connecting

                         */

                        if (so->so_state & SS_ISFCONNECTING) {

                                FD_SET(so->s, writefds);

                                UPD_NFDS(so->s);

                                continue;

                        }

                        /*

                         * Set for writing if we are connected, can send more, and

                         * we have something to send

                         */

                        if (CONN_CANFSEND(so) && so->so_rcv.sb_cc) {

                                FD_SET(so->s, writefds);

                                UPD_NFDS(so->s);

                        }

                        /*

                         * Set for reading (and urgent data) if we are connected, can

                         * receive more, and we have room for it XXX /2 ?

                         */

                        if (CONN_CANFRCV(so) && (so->so_snd.sb_cc < (so->so_snd.sb_datalen/2))) {

                                FD_SET(so->s, readfds);

                                FD_SET(so->s, xfds);

                                UPD_NFDS(so->s);

                        }

                }

                /*

                 * UDP sockets

                 */

                for (so = slirp->udb.so_next; so != &slirp->udb;

                     so = so_next) {

                        so_next = so->so_next;

                        /*

                         * See if it's timed out

                         */

                        if (so->so_expire) {

                                if (so->so_expire <= curtime) {

                                        udp_detach(so);

                                        continue;

                                } else

                                        do_slowtimo = 1; /* Let socket expire */

                        }

                        /*

                         * When UDP packets are received from over the

                         * link, they're sendto()'d straight away, so

                         * no need for setting for writing

                         * Limit the number of packets queued by this session

                         * to 4.  Note that even though we try and limit this

                         * to 4 packets, the session could have more queued

                         * if the packets needed to be fragmented

                         * (XXX <= 4 ?)

                         */

                        if ((so->so_state & SS_ISFCONNECTED) && so->so_queued <= 4) {

                                FD_SET(so->s, readfds);

                                UPD_NFDS(so->s);

                        }

                }

                /*

                 * ICMP sockets

                 */

                for (so = slirp->icmp.so_next; so != &slirp->icmp;

                     so = so_next) {

                    so_next = so->so_next;

                    /*

                     * See if it's timed out

                     */

                    if (so->so_expire) {

                        if (so->so_expire <= curtime) {

                            icmp_detach(so);

                            continue;

                        } else {

                            do_slowtimo = 1; /* Let socket expire */

                        }

                    }

                    if (so->so_state & SS_ISFCONNECTED) {

                        FD_SET(so->s, readfds);

                        UPD_NFDS(so->s);

                    }

                }

        }

        *pnfds = nfds;

}

void slirp_select_poll(fd_set *readfds, fd_set *writefds, fd_set *xfds,

                       int select_error)

{

    Slirp *slirp;

    struct socket *so, *so_next;

    int ret;

    if (QTAILQ_EMPTY(&slirp_instances)) {

        return;

    }

    global_readfds = readfds;

    global_writefds = writefds;

    global_xfds = xfds;

    curtime = qemu_get_clock_ms(rt_clock);

    QTAILQ_FOREACH(slirp, &slirp_instances, entry) {

        /*

         * See if anything has timed out

         */

                if (time_fasttimo && ((curtime - time_fasttimo) >= 2)) {

                        tcp_fasttimo(slirp);

                        time_fasttimo = 0;

                }

                if (do_slowtimo && ((curtime - last_slowtimo) >= 499)) {

                        ip_slowtimo(slirp);

                        tcp_slowtimo(slirp);

                        last_slowtimo = curtime;

                }

        /*

         * Check sockets

         */

        if (!select_error) {

                /*

                 * Check TCP sockets

                 */

                for (so = slirp->tcb.so_next; so != &slirp->tcb;

                     so = so_next) {

                        so_next = so->so_next;

                        /*

                         * FD_ISSET is meaningless on these sockets

                         * (and they can crash the program)

                         */

                        if (so->so_state & SS_NOFDREF || so->s == -1)

                           continue;

                        /*

                         * Check for URG data

                         * This will soread as well, so no need to

                         * test for readfds below if this succeeds

                         */

                        if (FD_ISSET(so->s, xfds))

                           sorecvoob(so);

                        /*

                         * Check sockets for reading

                         */

                        else if (FD_ISSET(so->s, readfds)) {

                                /*

                                 * Check for incoming connections

                                 */

                                if (so->so_state & SS_FACCEPTCONN) {

                                        tcp_connect(so);

                                        continue;

                                } /* else */

                                ret = soread(so);

                                /* Output it if we read something */

                                if (ret > 0)

                                   tcp_output(sototcpcb(so));

                        }

                        /*

                         * Check sockets for writing

                         */

                        if (FD_ISSET(so->s, writefds)) {

                          /*

                           * Check for non-blocking, still-connecting sockets

                           */

                          if (so->so_state & SS_ISFCONNECTING) {

                            /* Connected */

                            so->so_state &= ~SS_ISFCONNECTING;

                            ret = send(so->s, (const void *) &ret, 0, 0);

                            if (ret < 0) {

                              /* XXXXX Must fix, zero bytes is a NOP */

                              if (errno == EAGAIN || errno == EWOULDBLOCK ||

                                  errno == EINPROGRESS || errno == ENOTCONN)

                                continue;

                              /* else failed */

                              so->so_state &= SS_PERSISTENT_MASK;

                              so->so_state |= SS_NOFDREF;

                            }

                            /* else so->so_state &= ~SS_ISFCONNECTING; */

                            /*

                             * Continue tcp_input

                             */

                            tcp_input((struct mbuf *)NULL, sizeof(struct ip), so);

                            /* continue; */

                          } else

                            ret = sowrite(so);

                          /*

                           * XXXXX If we wrote something (a lot), there

                           * could be a need for a window update.

                           * In the worst case, the remote will send

                           * a window probe to get things going again

                           */

                        }

                        /*

                         * Probe a still-connecting, non-blocking socket

                         * to check if it's still alive

                           */

#ifdef PROBE_CONN

                        if (so->so_state & SS_ISFCONNECTING) {

                          ret = recv(so->s, (char *)&ret, 0,0);

                          if (ret < 0) {

                            /* XXX */

                            if (errno == EAGAIN || errno == EWOULDBLOCK ||

                                errno == EINPROGRESS || errno == ENOTCONN)

                              continue; /* Still connecting, continue */

                            /* else failed */

                            so->so_state &= SS_PERSISTENT_MASK;

                            so->so_state |= SS_NOFDREF;

                            /* tcp_input will take care of it */

                          } else {

                            ret = send(so->s, &ret, 0,0);

                            if (ret < 0) {

                              /* XXX */

                              if (errno == EAGAIN || errno == EWOULDBLOCK ||

                                  errno == EINPROGRESS || errno == ENOTCONN)

                                continue;

                              /* else failed */

                              so->so_state &= SS_PERSISTENT_MASK;

                              so->so_state |= SS_NOFDREF;

                            } else

                              so->so_state &= ~SS_ISFCONNECTING;

                          }

                          tcp_input((struct mbuf *)NULL, sizeof(struct ip),so);

                        } /* SS_ISFCONNECTING */

#endif

                }

                /*

                 * Now UDP sockets.

                 * Incoming packets are sent straight away, they're not buffered.

                 * Incoming UDP data isn't buffered either.

                 */

                for (so = slirp->udb.so_next; so != &slirp->udb;

                     so = so_next) {

                        so_next = so->so_next;

                        if (so->s != -1 && FD_ISSET(so->s, readfds)) {

                            sorecvfrom(so);

                        }

                }

                /*

                 * Check incoming ICMP relies.

                 */

                for (so = slirp->icmp.so_next; so != &slirp->icmp;

                     so = so_next) {

                     so_next = so->so_next;

                    if (so->s != -1 && FD_ISSET(so->s, readfds)) {

                        icmp_receive(so);

                    }

                }

        }

        /*

         * See if we can start outputting

         */

        if (slirp->if_queued) {

            if_start(slirp);

        }

    }

        /* clear global file descriptor sets.

         * these reside on the stack in vl.c

         * so they're unusable if we're not in

         * slirp_select_fill or slirp_select_poll.

         */

         global_readfds = NULL;

         global_writefds = NULL;

         global_xfds = NULL;

}

#define ETH_ALEN 6

#define ETH_HLEN 14

#define ETH_P_IP        0x0800                /* Internet Protocol packet        */

#define ETH_P_ARP        0x0806                /* Address Resolution packet        */

#define        ARPOP_REQUEST        1                /* ARP request                        */

#define        ARPOP_REPLY        2                /* ARP reply                        */

struct ethhdr

{

        unsigned char        h_dest[ETH_ALEN];        /* destination eth addr        */

        unsigned char        h_source[ETH_ALEN];        /* source ether addr        */

        unsigned short        h_proto;                /* packet type ID field        */

};

struct arphdr

{

        unsigned short        ar_hrd;                /* format of hardware address        */

        unsigned short        ar_pro;                /* format of protocol address        */

        unsigned char        ar_hln;                /* length of hardware address        */

        unsigned char        ar_pln;                /* length of protocol address        */

        unsigned short        ar_op;                /* ARP opcode (command)                */

         /*

          *         Ethernet looks like this : This bit is variable sized however...

          */

        unsigned char                ar_sha[ETH_ALEN];        /* sender hardware address        */

        uint32_t                ar_sip;                        /* sender IP address                */

        unsigned char                ar_tha[ETH_ALEN];        /* target hardware address        */

        uint32_t                ar_tip        ;                /* target IP address                */

} __attribute__((packed));

static void arp_input(Slirp *slirp, const uint8_t *pkt, int pkt_len)

{

    struct ethhdr *eh = (struct ethhdr *)pkt;

    struct arphdr *ah = (struct arphdr *)(pkt + ETH_HLEN);

    uint8_t arp_reply[max(ETH_HLEN + sizeof(struct arphdr), 64)];

    struct ethhdr *reh = (struct ethhdr *)arp_reply;

    struct arphdr *rah = (struct arphdr *)(arp_reply + ETH_HLEN);

    int ar_op;

    struct ex_list *ex_ptr;

    ar_op = ntohs(ah->ar_op);

    switch(ar_op) {

    case ARPOP_REQUEST:

        if ((ah->ar_tip & slirp->vnetwork_mask.s_addr) ==

            slirp->vnetwork_addr.s_addr) {

            if (ah->ar_tip == slirp->vnameserver_addr.s_addr ||

                ah->ar_tip == slirp->vhost_addr.s_addr)

                goto arp_ok;

            for (ex_ptr = slirp->exec_list; ex_ptr; ex_ptr = ex_ptr->ex_next) {

                if (ex_ptr->ex_addr.s_addr == ah->ar_tip)

                    goto arp_ok;

            }

            return;

        arp_ok:

            memset(arp_reply, 0, sizeof(arp_reply));

            /* XXX: make an ARP request to have the client address */

            memcpy(slirp->client_ethaddr, eh->h_source, ETH_ALEN);

            /* ARP request for alias/dns mac address */

            memcpy(reh->h_dest, pkt + ETH_ALEN, ETH_ALEN);

            memcpy(reh->h_source, special_ethaddr, ETH_ALEN - 4);

            memcpy(&reh->h_source[2], &ah->ar_tip, 4);

            reh->h_proto = htons(ETH_P_ARP);

            rah->ar_hrd = htons(1);

            rah->ar_pro = htons(ETH_P_IP);

            rah->ar_hln = ETH_ALEN;

            rah->ar_pln = 4;

            rah->ar_op = htons(ARPOP_REPLY);

            memcpy(rah->ar_sha, reh->h_source, ETH_ALEN);

            rah->ar_sip = ah->ar_tip;

            memcpy(rah->ar_tha, ah->ar_sha, ETH_ALEN);

            rah->ar_tip = ah->ar_sip;

            slirp_output(slirp->opaque, arp_reply, sizeof(arp_reply));

        }

        break;

    case ARPOP_REPLY:

        /* reply to request of client mac address ? */

        if (!memcmp(slirp->client_ethaddr, zero_ethaddr, ETH_ALEN) &&

            ah->ar_sip == slirp->client_ipaddr.s_addr) {

            memcpy(slirp->client_ethaddr, ah->ar_sha, ETH_ALEN);

        }

        break;

    default:

        break;

    }

}

void slirp_input(Slirp *slirp, const uint8_t *pkt, int pkt_len)

{

    struct mbuf *m;

    int proto;

    if (pkt_len < ETH_HLEN)

        return;

    proto = ntohs(*(uint16_t *)(pkt + 12));

    switch(proto) {

    case ETH_P_ARP:

        arp_input(slirp, pkt, pkt_len);

        break;

    case ETH_P_IP:

        m = m_get(slirp);

        if (!m)

            return;

        /* Note: we add to align the IP header */

        if (M_FREEROOM(m) < pkt_len + 2) {

            m_inc(m, pkt_len + 2);

        }

        m->m_len = pkt_len + 2;

        memcpy(m->m_data + 2, pkt, pkt_len);

        m->m_data += 2 + ETH_HLEN;

        m->m_len -= 2 + ETH_HLEN;

        ip_input(m);

        break;

    default:

        break;

    }

}

/* output the IP packet to the ethernet device */

void if_encap(Slirp *slirp, const uint8_t *ip_data, int ip_data_len)

{

    uint8_t buf[1600];

    struct ethhdr *eh = (struct ethhdr *)buf;

    if (ip_data_len + ETH_HLEN > sizeof(buf))

        return;

    if (!memcmp(slirp->client_ethaddr, zero_ethaddr, ETH_ALEN)) {

        uint8_t arp_req[ETH_HLEN + sizeof(struct arphdr)];

        struct ethhdr *reh = (struct ethhdr *)arp_req;

        struct arphdr *rah = (struct arphdr *)(arp_req + ETH_HLEN);

        const struct ip *iph = (const struct ip *)ip_data;

        /* If the client addr is not known, there is no point in

           sending the packet to it. Normally the sender should have

           done an ARP request to get its MAC address. Here we do it

           in place of sending the packet and we hope that the sender

           will retry sending its packet. */

        memset(reh->h_dest, 0xff, ETH_ALEN);

        memcpy(reh->h_source, special_ethaddr, ETH_ALEN - 4);

        memcpy(&reh->h_source[2], &slirp->vhost_addr, 4);

        reh->h_proto = htons(ETH_P_ARP);

        rah->ar_hrd = htons(1);

        rah->ar_pro = htons(ETH_P_IP);

        rah->ar_hln = ETH_ALEN;

        rah->ar_pln = 4;

        rah->ar_op = htons(ARPOP_REQUEST);

        /* source hw addr */

        memcpy(rah->ar_sha, special_ethaddr, ETH_ALEN - 4);

        memcpy(&rah->ar_sha[2], &slirp->vhost_addr, 4);

        /* source IP */

        rah->ar_sip = slirp->vhost_addr.s_addr;

        /* target hw addr (none) */

        memset(rah->ar_tha, 0, ETH_ALEN);

        /* target IP */

        rah->ar_tip = iph->ip_dst.s_addr;

        slirp->client_ipaddr = iph->ip_dst;

        slirp_output(slirp->opaque, arp_req, sizeof(arp_req));

    } else {

        memcpy(eh->h_dest, slirp->client_ethaddr, ETH_ALEN);

        memcpy(eh->h_source, special_ethaddr, ETH_ALEN - 4);

        /* XXX: not correct */

        memcpy(&eh->h_source[2], &slirp->vhost_addr, 4);

        eh->h_proto = htons(ETH_P_IP);

        memcpy(buf + sizeof(struct ethhdr), ip_data, ip_data_len);

        slirp_output(slirp->opaque, buf, ip_data_len + ETH_HLEN);

    }

}

/* Drop host forwarding rule, return 0 if found. */

int slirp_remove_hostfwd(Slirp *slirp, int is_udp, struct in_addr host_addr,

                         int host_port)

{

    struct socket *so;

    struct socket *head = (is_udp ? &slirp->udb : &slirp->tcb);

    struct sockaddr_in addr;

    int port = htons(host_port);

    socklen_t addr_len;

    for (so = head->so_next; so != head; so = so->so_next) {

        addr_len = sizeof(addr);

        if ((so->so_state & SS_HOSTFWD) &&

            getsockname(so->s, (struct sockaddr *)&addr, &addr_len) == 0 &&

            addr.sin_addr.s_addr == host_addr.s_addr &&

            addr.sin_port == port) {

            close(so->s);

            sofree(so);

            return 0;

        }

    }

    return -1;

}

int slirp_add_hostfwd(Slirp *slirp, int is_udp, struct in_addr host_addr,

                      int host_port, struct in_addr guest_addr, int guest_port)

{

    if (!guest_addr.s_addr) {

        guest_addr = slirp->vdhcp_startaddr;

    }

    if (is_udp) {

        if (!udp_listen(slirp, host_addr.s_addr, htons(host_port),

                        guest_addr.s_addr, htons(guest_port), SS_HOSTFWD))

            return -1;

    } else {

        if (!tcp_listen(slirp, host_addr.s_addr, htons(host_port),

                        guest_addr.s_addr, htons(guest_port), SS_HOSTFWD))

            return -1;

    }

    return 0;

}

int slirp_add_exec(Slirp *slirp, int do_pty, const void *args,

                   struct in_addr *guest_addr, int guest_port)

{

    if (!guest_addr->s_addr) {

        guest_addr->s_addr = slirp->vnetwork_addr.s_addr |

            (htonl(0x0204) & ~slirp->vnetwork_mask.s_addr);

    }

    if ((guest_addr->s_addr & slirp->vnetwork_mask.s_addr) !=

        slirp->vnetwork_addr.s_addr ||

        guest_addr->s_addr == slirp->vhost_addr.s_addr ||

        guest_addr->s_addr == slirp->vnameserver_addr.s_addr) {

        return -1;

    }

    return add_exec(&slirp->exec_list, do_pty, (char *)args, *guest_addr,

                    htons(guest_port));

}

ssize_t slirp_send(struct socket *so, const void *buf, size_t len, int flags)

{

        if (so->s == -1 && so->extra) {

                qemu_chr_write(so->extra, buf, len);

                return len;

        }

        return send(so->s, buf, len, flags);

}

static struct socket *

slirp_find_ctl_socket(Slirp *slirp, struct in_addr guest_addr, int guest_port)

{

    struct socket *so;

    for (so = slirp->tcb.so_next; so != &slirp->tcb; so = so->so_next) {

        if (so->so_faddr.s_addr == guest_addr.s_addr &&

            htons(so->so_fport) == guest_port) {

            return so;

        }

    }

    return NULL;

}

size_t slirp_socket_can_recv(Slirp *slirp, struct in_addr guest_addr,

                             int guest_port)

{

        struct iovec iov[2];

        struct socket *so;

        so = slirp_find_ctl_socket(slirp, guest_addr, guest_port);

        if (!so || so->so_state & SS_NOFDREF)

                return 0;

        if (!CONN_CANFRCV(so) || so->so_snd.sb_cc >= (so->so_snd.sb_datalen/2))

                return 0;

        return sopreprbuf(so, iov, NULL);

}

void slirp_socket_recv(Slirp *slirp, struct in_addr guest_addr, int guest_port,

                       const uint8_t *buf, int size)

{

    int ret;

    struct socket *so = slirp_find_ctl_socket(slirp, guest_addr, guest_port);

    if (!so)

        return;

    ret = soreadbuf(so, (const char *)buf, size);

    if (ret > 0)

        tcp_output(sototcpcb(so));

}

static void slirp_tcp_save(QEMUFile *f, struct tcpcb *tp)

{

    int i;

    qemu_put_sbe16(f, tp->t_state);