slirp.c

一个Windows下的Linux专用虚拟机

		}
	}
        *pnfds = nfds;
}	

void slirp_select_poll(fd_set *readfds, fd_set *writefds, fd_set *xfds)
{
    struct socket *so, *so_next;
    int ret;

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

	/* Update time */
	updtime();
	
	/*
	 * See if anything has timed out 
	 */
	if (link_up) {
		if (time_fasttimo && ((curtime - time_fasttimo) >= 2)) {
			tcp_fasttimo();
			time_fasttimo = 0;
		}
		if (do_slowtimo && ((curtime - last_slowtimo) >= 499)) {
			ip_slowtimo();
			tcp_slowtimo();
			last_slowtimo = curtime;
		}
	}
	
	/*
	 * Check sockets
	 */
	if (link_up) {
		/*
		 * Check TCP sockets
		 */
		for (so = tcb.so_next; so != &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, (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_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_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_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 = udb.so_next; so != &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 (if_queued && link_up)
	   if_start();

	/* 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	*/
	unsigned char		ar_sip[4];		/* sender IP address		*/
	unsigned char		ar_tha[ETH_ALEN];	/* target hardware address	*/
	unsigned char		ar_tip[4];		/* target IP address		*/
};

void arp_input(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 (!memcmp(ah->ar_tip, &special_addr, 3)) {
            if (ah->ar_tip[3] == CTL_DNS || ah->ar_tip[3] == CTL_ALIAS) 
                goto arp_ok;
            for (ex_ptr = exec_list; ex_ptr; ex_ptr = ex_ptr->ex_next) {
                if (ex_ptr->ex_addr == ah->ar_tip[3])
                    goto arp_ok;
            }
            return;
        arp_ok:
            /* ARP request for alias/dns mac address */
            memcpy(reh->h_dest, pkt + ETH_ALEN, ETH_ALEN);
            memcpy(reh->h_source, special_ethaddr, ETH_ALEN - 1);
            reh->h_source[5] = ah->ar_tip[3];
            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);
            memcpy(rah->ar_sip, ah->ar_tip, 4);
            memcpy(rah->ar_tha, ah->ar_sha, ETH_ALEN);
            memcpy(rah->ar_tip, ah->ar_sip, 4);
            slirp_output(arp_reply, sizeof(arp_reply));
        }
        break;
    case ARPOP_REPLY:
        if (!memcmp(ah->ar_sip, &client_addr, 4)) {
            memcpy(client_ethaddr, eh->h_source, ETH_ALEN);
        }
        break;
    default:
        break;
    }
}

void slirp_input(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(pkt, pkt_len);
        break;
    case ETH_P_IP:
        m = m_get();
        if (!m)
            return;
        /* Note: we add to align the IP header */
        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(const uint8_t *ip_data, int ip_data_len)
{
    uint8_t buf[1600];
    struct ethhdr *eh = (struct ethhdr *)buf;
    struct arphdr *rah = (struct arphdr *)(buf + ETH_HLEN);

    if (ip_data_len + ETH_HLEN > sizeof(buf))
        return;

    if(!memcmp(client_ethaddr,bcast_ethaddr,6))
    {
	/* make an ARP request to have the client address */
	memcpy(eh->h_dest, bcast_ethaddr, ETH_ALEN);
	memcpy(eh->h_source, special_ethaddr, ETH_ALEN - 1);
	eh->h_source[5] = CTL_ALIAS;
	eh->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);
	memcpy(rah->ar_sha, eh->h_source, ETH_ALEN);
	memcpy(rah->ar_sip, &special_addr, 4);
	rah->ar_sip[3]=CTL_ALIAS;
	memcpy(rah->ar_tha, bcast_ethaddr, ETH_ALEN);
	memcpy(rah->ar_tip, &client_addr, 4); 

	slirp_output(buf, sizeof(struct arphdr)+ ETH_HLEN);
/* XXX: We loose the first packet here, cause client_ethaddr 
   is bcast_ethaddr. */
    }

    memcpy(eh->h_dest, client_ethaddr, ETH_ALEN);
    memcpy(eh->h_source, special_ethaddr, ETH_ALEN - 1);
    /* XXX: not correct */
    eh->h_source[5] = CTL_ALIAS;
    eh->h_proto = htons(ETH_P_IP);
    memcpy(buf + sizeof(struct ethhdr), ip_data, ip_data_len);
    slirp_output(buf, ip_data_len + ETH_HLEN);
}

int slirp_redir(int is_udp, int host_port, 
                struct in_addr guest_addr, int guest_port)
{
    if (is_udp) {
        if (!udp_listen(htons(host_port), guest_addr.s_addr, 
                        htons(guest_port), 0))
            return -1;
    } else {
        if (!solisten(htons(host_port), guest_addr.s_addr, 
                      htons(guest_port), 0))
            return -1;
    }
    return 0;
}

int slirp_add_exec(int do_pty, const char *args, int addr_low_byte, 
                  int guest_port)
{
    return add_exec(&exec_list, do_pty, (char *)args, 
                    addr_low_byte, htons(guest_port));
}