qemu/slirp/slirp.c

/*
 * 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-char.h"
#include "slirp.h"
#include "hw/hw.h"

/* host address */
struct in_addr our_addr;
/* host dns address */
struct in_addr dns_addr;
/* 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;

TAILQ_HEAD(slirp_instances, Slirp) slirp_instances =
    TAILQ_HEAD_INITIALIZER(slirp_instances);

#ifdef _WIN32

static 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;

    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;
    if (FixedInfo) {
        GlobalFree(FixedInfo);
        FixedInfo = NULL;
    }
    return 0;
}

static void winsock_cleanup(void)
{
    WSACleanup();
}

#else

static 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;

    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 (tmp_addr.s_addr == loopback_addr.s_addr)
                tmp_addr = our_addr;
            /* If it's the first one, set it to dns_addr */
            if (!found)
                *pdns_addr = tmp_addr;
#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;
    struct hostent *he;
    char our_name[256];
#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);

    /* FIXME: This address may change during runtime */
    if (gethostname(our_name, sizeof(our_name)) == 0) {
        he = gethostbyname(our_name);
        if (he) {
            our_addr = *(struct in_addr *)he->h_addr;
        }
    }
    if (our_addr.s_addr == 0) {
        our_addr = loopback_addr;
    }

    /* FIXME: This address may change during runtime */
    if (get_dns_addr(&dns_addr) < 0) {
        dns_addr = loopback_addr;
    }
}

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("slirp", 0, 3, slirp_state_save, slirp_state_load, slirp);

    TAILQ_INSERT_TAIL(&slirp_instances, slirp, entry);

    return slirp;
}

void slirp_cleanup(Slirp *slirp)
{
    TAILQ_REMOVE(&slirp_instances, slirp, entry);

    unregister_savevm("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)

/*
 * curtime kept to an accuracy of 1ms
 */
#ifdef _WIN32
static void updtime(void)
{
    struct _timeb tb;

    _ftime(&tb);

    curtime = tb.time * 1000 + tb.millitm;
}
#else
static void updtime(void)
{
    struct timeval tv;

    gettimeofday(&tv, NULL);

    curtime = tv.tv_sec * 1000 + tv.tv_usec / 1000;
}
#endif

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 (TAILQ_EMPTY(&slirp_instances)) {
        return;
    }

    /* fail safe */
    global_readfds = NULL;
    global_writefds = NULL;
    global_xfds = NULL;

    nfds = *pnfds;
	/*
	 * First, TCP sockets
	 */
	do_slowtimo = 0;

	TAILQ_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);
			}
		}
	}

        *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 (TAILQ_EMPTY(&slirp_instances)) {
        return;
    }

    global_readfds = readfds;
    global_writefds = writefds;
    global_xfds = xfds;

	/* Update time */
	updtime();

    TAILQ_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);
                        }
		}
	}

	/*
	 * 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[ETH_HLEN + sizeof(struct arphdr)];
    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:
            /* 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);
    for (i = 0; i < TCPT_NTIMERS; i++)
        qemu_put_sbe16(f, tp->t_timer[i]);
    qemu_put_sbe16(f, tp->t_rxtshift);
    qemu_put_sbe16(f, tp->t_rxtcur);
    qemu_put_sbe16(f, tp->t_dupacks);
    qemu_put_be16(f, tp->t_maxseg);
    qemu_put_sbyte(f, tp->t_force);
    qemu_put_be16(f, tp->t_flags);
    qemu_put_be32(f, tp->snd_una);
    qemu_put_be32(f, tp->snd_nxt);
    qemu_put_be32(f, tp->snd_up);
    qemu_put_be32(f, tp->snd_wl1);
    qemu_put_be32(f, tp->snd_wl2);
    qemu_put_be32(f, tp->iss);
    qemu_put_be32(f, tp->snd_wnd);
    qemu_put_be32(f, tp->rcv_wnd);
    qemu_put_be32(f, tp->rcv_nxt);
    qemu_put_be32(f, tp->rcv_up);
    qemu_put_be32(f, tp->irs);
    qemu_put_be32(f, tp->rcv_adv);
    qemu_put_be32(f, tp->snd_max);
    qemu_put_be32(f, tp->snd_cwnd);
    qemu_put_be32(f, tp->snd_ssthresh);
    qemu_put_sbe16(f, tp->t_idle);
    qemu_put_sbe16(f, tp->t_rtt);
    qemu_put_be32(f, tp->t_rtseq);
    qemu_put_sbe16(f, tp->t_srtt);
    qemu_put_sbe16(f, tp->t_rttvar);
    qemu_put_be16(f, tp->t_rttmin);
    qemu_put_be32(f, tp->max_sndwnd);
    qemu_put_byte(f, tp->t_oobflags);
    qemu_put_byte(f, tp->t_iobc);
    qemu_put_sbe16(f, tp->t_softerror);
    qemu_put_byte(f, tp->snd_scale);
    qemu_put_byte(f, tp->rcv_scale);
    qemu_put_byte(f, tp->request_r_scale);
    qemu_put_byte(f, tp->requested_s_scale);
    qemu_put_be32(f, tp->ts_recent);
    qemu_put_be32(f, tp->ts_recent_age);
    qemu_put_be32(f, tp->last_ack_sent);
}

static void slirp_sbuf_save(QEMUFile *f, struct sbuf *sbuf)
{
    uint32_t off;

    qemu_put_be32(f, sbuf->sb_cc);
    qemu_put_be32(f, sbuf->sb_datalen);
    off = (uint32_t)(sbuf->sb_wptr - sbuf->sb_data);
    qemu_put_sbe32(f, off);
    off = (uint32_t)(sbuf->sb_rptr - sbuf->sb_data);
    qemu_put_sbe32(f, off);
    qemu_put_buffer(f, (unsigned char*)sbuf->sb_data, sbuf->sb_datalen);
}

static void slirp_socket_save(QEMUFile *f, struct socket *so)
{
    qemu_put_be32(f, so->so_urgc);
    qemu_put_be32(f, so->so_faddr.s_addr);
    qemu_put_be32(f, so->so_laddr.s_addr);
    qemu_put_be16(f, so->so_fport);
    qemu_put_be16(f, so->so_lport);
    qemu_put_byte(f, so->so_iptos);
    qemu_put_byte(f, so->so_emu);
    qemu_put_byte(f, so->so_type);
    qemu_put_be32(f, so->so_state);
    slirp_sbuf_save(f, &so->so_rcv);
    slirp_sbuf_save(f, &so->so_snd);
    slirp_tcp_save(f, so->so_tcpcb);
}

static void slirp_bootp_save(QEMUFile *f, Slirp *slirp)
{
    int i;

    for (i = 0; i < NB_BOOTP_CLIENTS; i++) {
        qemu_put_be16(f, slirp->bootp_clients[i].allocated);
        qemu_put_buffer(f, slirp->bootp_clients[i].macaddr, 6);
    }
}

static void slirp_state_save(QEMUFile *f, void *opaque)
{
    Slirp *slirp = opaque;
    struct ex_list *ex_ptr;

    for (ex_ptr = slirp->exec_list; ex_ptr; ex_ptr = ex_ptr->ex_next)
        if (ex_ptr->ex_pty == 3) {
            struct socket *so;
            so = slirp_find_ctl_socket(slirp, ex_ptr->ex_addr,
                                       ntohs(ex_ptr->ex_fport));
            if (!so)
                continue;

            qemu_put_byte(f, 42);
            slirp_socket_save(f, so);
        }
    qemu_put_byte(f, 0);

    qemu_put_be16(f, slirp->ip_id);

    slirp_bootp_save(f, slirp);
}

static void slirp_tcp_load(QEMUFile *f, struct tcpcb *tp)
{
    int i;

    tp->t_state = qemu_get_sbe16(f);
    for (i = 0; i < TCPT_NTIMERS; i++)
        tp->t_timer[i] = qemu_get_sbe16(f);
    tp->t_rxtshift = qemu_get_sbe16(f);
    tp->t_rxtcur = qemu_get_sbe16(f);
    tp->t_dupacks = qemu_get_sbe16(f);
    tp->t_maxseg = qemu_get_be16(f);
    tp->t_force = qemu_get_sbyte(f);
    tp->t_flags = qemu_get_be16(f);
    tp->snd_una = qemu_get_be32(f);
    tp->snd_nxt = qemu_get_be32(f);
    tp->snd_up = qemu_get_be32(f);
    tp->snd_wl1 = qemu_get_be32(f);
    tp->snd_wl2 = qemu_get_be32(f);
    tp->iss = qemu_get_be32(f);
    tp->snd_wnd = qemu_get_be32(f);
    tp->rcv_wnd = qemu_get_be32(f);
    tp->rcv_nxt = qemu_get_be32(f);
    tp->rcv_up = qemu_get_be32(f);
    tp->irs = qemu_get_be32(f);
    tp->rcv_adv = qemu_get_be32(f);
    tp->snd_max = qemu_get_be32(f);
    tp->snd_cwnd = qemu_get_be32(f);
    tp->snd_ssthresh = qemu_get_be32(f);
    tp->t_idle = qemu_get_sbe16(f);
    tp->t_rtt = qemu_get_sbe16(f);
    tp->t_rtseq = qemu_get_be32(f);
    tp->t_srtt = qemu_get_sbe16(f);
    tp->t_rttvar = qemu_get_sbe16(f);
    tp->t_rttmin = qemu_get_be16(f);
    tp->max_sndwnd = qemu_get_be32(f);
    tp->t_oobflags = qemu_get_byte(f);
    tp->t_iobc = qemu_get_byte(f);
    tp->t_softerror = qemu_get_sbe16(f);
    tp->snd_scale = qemu_get_byte(f);
    tp->rcv_scale = qemu_get_byte(f);
    tp->request_r_scale = qemu_get_byte(f);
    tp->requested_s_scale = qemu_get_byte(f);
    tp->ts_recent = qemu_get_be32(f);
    tp->ts_recent_age = qemu_get_be32(f);
    tp->last_ack_sent = qemu_get_be32(f);
    tcp_template(tp);
}

static int slirp_sbuf_load(QEMUFile *f, struct sbuf *sbuf)
{
    uint32_t off, sb_cc, sb_datalen;

    sb_cc = qemu_get_be32(f);
    sb_datalen = qemu_get_be32(f);

    sbreserve(sbuf, sb_datalen);

    if (sbuf->sb_datalen != sb_datalen)
        return -ENOMEM;

    sbuf->sb_cc = sb_cc;

    off = qemu_get_sbe32(f);
    sbuf->sb_wptr = sbuf->sb_data + off;
    off = qemu_get_sbe32(f);
    sbuf->sb_rptr = sbuf->sb_data + off;
    qemu_get_buffer(f, (unsigned char*)sbuf->sb_data, sbuf->sb_datalen);

    return 0;
}

static int slirp_socket_load(QEMUFile *f, struct socket *so)
{
    if (tcp_attach(so) < 0)
        return -ENOMEM;

    so->so_urgc = qemu_get_be32(f);
    so->so_faddr.s_addr = qemu_get_be32(f);
    so->so_laddr.s_addr = qemu_get_be32(f);
    so->so_fport = qemu_get_be16(f);
    so->so_lport = qemu_get_be16(f);
    so->so_iptos = qemu_get_byte(f);
    so->so_emu = qemu_get_byte(f);
    so->so_type = qemu_get_byte(f);
    so->so_state = qemu_get_be32(f);
    if (slirp_sbuf_load(f, &so->so_rcv) < 0)
        return -ENOMEM;
    if (slirp_sbuf_load(f, &so->so_snd) < 0)
        return -ENOMEM;
    slirp_tcp_load(f, so->so_tcpcb);

    return 0;
}

static void slirp_bootp_load(QEMUFile *f, Slirp *slirp)
{
    int i;

    for (i = 0; i < NB_BOOTP_CLIENTS; i++) {
        slirp->bootp_clients[i].allocated = qemu_get_be16(f);
        qemu_get_buffer(f, slirp->bootp_clients[i].macaddr, 6);
    }
}

static int slirp_state_load(QEMUFile *f, void *opaque, int version_id)
{
    Slirp *slirp = opaque;
    struct ex_list *ex_ptr;
    int r;

    while ((r = qemu_get_byte(f))) {
        int ret;
        struct socket *so = socreate(slirp);

        if (!so)
            return -ENOMEM;

        ret = slirp_socket_load(f, so);

        if (ret < 0)
            return ret;

        if ((so->so_faddr.s_addr & slirp->vnetwork_mask.s_addr) !=
            slirp->vnetwork_addr.s_addr) {
            return -EINVAL;
        }
        for (ex_ptr = slirp->exec_list; ex_ptr; ex_ptr = ex_ptr->ex_next) {
            if (ex_ptr->ex_pty == 3 &&
                so->so_faddr.s_addr == ex_ptr->ex_addr.s_addr &&
                so->so_fport == ex_ptr->ex_fport) {
                break;
            }
        }
        if (!ex_ptr)
            return -EINVAL;

        so->extra = (void *)ex_ptr->ex_exec;
    }

    if (version_id >= 2) {
        slirp->ip_id = qemu_get_be16(f);
    }

    if (version_id >= 3) {
        slirp_bootp_load(f, slirp);
    }

    return 0;
}