pppoe.c

This a free PPPoE redirector for Linux.基于LINUX环境下的PPPOE协议源代码

    struct ifnet_head ifhead;
    struct ifnet intf;
    unsigned long v;
    char ifn[IFNAMSIZ+1];
    struct arpcom arp;

    k = kvm_open(NULL,NULL,NULL,O_RDONLY,"pppoe");
    if (k == NULL) {
      fprintf(stderr, "pppoe: failed to open kvm\n");
      return -1;
    }
    n[0].n_name = "_ifnet";
    n[1].n_name = NULL;
    if (kvm_nlist(k,n) != 0) {
      fprintf(stderr, "pppoe: could not find interface list\n");
      kvm_close(k);
      return -1;
    }
    if (kvm_read(k,n[0].n_value,(void *)&ifhead,sizeof(ifhead)) != 
	sizeof(ifhead)) {
      fprintf(stderr, "pppoe: could not read ifnet_head structure\n");
      kvm_close(k);
      return -1;
    }
    v = (unsigned long)(ifhead.tqh_first);
    while(v != 0) {
      if (kvm_read(k,v,(void *)&intf,sizeof(intf)) != sizeof(intf)) {
	fprintf(stderr, "pppoe: could not read ifnet structure\n");
	kvm_close(k);
	return -1;
      }
      strncpy(ifn,intf.if_xname,IFNAMSIZ);
      ifn[IFNAMSIZ] = '\0';
      if (strcmp(ifn,if_name) == 0) 
	/* found our interface */
	break;
      else 
	/* walk the chain */
	v = (unsigned long)(intf.if_list.tqe_next);
    }
    if (v == 0) {
      fprintf(stderr, "pppoe: cannot find interface %s in kernel\n",if_name);
      kvm_close(k);
      return -1;
    }
    /* since we have the right interface, and we determined previously
       that it is an ethernet interface, reread from the same address into
       a "struct arpcom" structure (which begins with a struct ifnet).
       The ethernet address is located past the end of the ifnet structure */
    if (kvm_read(k,v,(void *)&arp,sizeof(arp)) != sizeof(arp)) {
      fprintf(stderr, "could not read arpcom structure\n");
      kvm_close(k);
      return -1;
    }
    /* whew! */
    /* save a copy of this for ourselves */
    memcpy(local_ether,arp.ac_enaddr,ETH_ALEN);
    if (hw_addr)
      memcpy(hw_addr,arp.ac_enaddr,ETH_ALEN); /* also copy if requested */
    kvm_close(k);
  }

  /* setup BPF filter */
  {
    union { unsigned int i; unsigned char b[4]; } x;
    union { unsigned short i; unsigned char b[2]; } y;

    filt[1].k = type; /* set type of packet we are looking for */
#ifndef SIMPLE_BPF
    /* now setup our source address so it gets filtered out */
    for(i = 0; i < 4; i++)
      x.b[i] = local_ether[i];
    for(i = 0; i < 2; i++)
      y.b[i] = local_ether[i+4];
    filt[3].k = x.i;
    filt[5].k = y.i;
#endif /* SIMPLE_BPF */
  }
  prog.bf_insns = filt;
  prog.bf_len = sizeof(filt)/sizeof(struct bpf_insn);
  if (ioctl(fd, BIOCSETF, &prog) < 0) {
    perror("pppoe: bpf(BIOCSETF)");
    return -1;
  }

  return fd;
#else /* do regular linux stuff */
  int optval = 1, rv;
  struct ifreq ifr;

  if ((rv = socket(PF_INET, SOCK_PACKET, htons(type))) < 0)
  {
      perror("pppoe: socket");
      return -1;
  }

  if (setsockopt(rv, SOL_SOCKET, SO_BROADCAST, &optval, sizeof(optval)) < 0)
  {
      perror("pppoe: setsockopt");
      return -1;
  }

  if (hw_addr != NULL) {
      strncpy(ifr.ifr_name, if_name, sizeof(ifr.ifr_name));
      
      if (ioctl(rv, SIOCGIFHWADDR, &ifr) < 0)
      {
	  perror("pppoe: ioctl(SIOCGIFHWADDR)");
	  return -1;
      }
      
      if (ifr.ifr_hwaddr.sa_family != ARPHRD_ETHER)
      {
	  fprintf(error_file, "pppoe: interface %s is not Ethernet!\n", if_name);
	  return -1;
      }
      
      memcpy(hw_addr, ifr.ifr_hwaddr.sa_data, sizeof(ifr.ifr_hwaddr.sa_data));
      
  }
  return rv;
#endif /* USE_BPF / linux */
}

int 
create_padi(struct pppoe_packet *packet, const char *src, const char *name)
{
    int size;

    if (packet == NULL)
	return 0;

    size = sizeof(struct pppoe_packet) + sizeof(struct pppoe_tag);
    if (name != NULL)
	size += strlen(name);

#ifdef __linux__
    memcpy(packet->ethhdr.h_dest, MAC_BCAST_ADDR, 6);
    memcpy(packet->ethhdr.h_source, src, 6);
    packet->ethhdr.h_proto = htons(ETH_P_PPPOE_DISC);
#else
    memcpy(packet->ethhdr.ether_dhost, MAC_BCAST_ADDR, 6);
    memcpy(packet->ethhdr.ether_shost, src, 6);
    packet->ethhdr.ether_type = htons(ETH_P_PPPOE_DISC);
#endif
    packet->ver = 1;
    packet->type = 1;
    packet->code = CODE_PADI;
    packet->session = 0;
    packet->length = htons(size - sizeof(struct pppoe_packet));
    
    /* fill out a blank service-name tag */
    (*(struct pppoe_tag *)(packet+1)).type = htons(TAG_SERVICE_NAME);
    (*(struct pppoe_tag *)(packet+1)).length = name ? htons(strlen(name)) : 0;
    if (name != NULL)
	memcpy((char *)(packet + 1) + sizeof(struct pppoe_tag), name,
	       strlen(name));

    return size;
}

int 
create_padr(struct pppoe_packet *packet, const char *src, const char *dst,
	    char *name)
{
    int size;

    if (packet == NULL)
	return 0;

    size = sizeof(struct pppoe_packet) + sizeof(struct pppoe_tag);
    if (name != NULL)
	size += strlen(name);

#ifdef __linux__
    memcpy(packet->ethhdr.h_dest, dst, 6);
    memcpy(packet->ethhdr.h_source, src, 6);
    packet->ethhdr.h_proto = htons(ETH_P_PPPOE_DISC);
#else
    memcpy(packet->ethhdr.ether_dhost, dst, 6);
    memcpy(packet->ethhdr.ether_shost, src, 6);
    packet->ethhdr.ether_type = htons(ETH_P_PPPOE_DISC);
#endif
    packet->ver = 1;
    packet->type = 1;
    packet->code = CODE_PADR;
    packet->session = 0;
    packet->length = htons(size - sizeof(struct pppoe_packet));
    
    /* fill out a blank service-name tag */
    (*(struct pppoe_tag *)(packet+1)).type = htons(TAG_SERVICE_NAME);
    (*(struct pppoe_tag *)(packet+1)).length = name ? htons(strlen(name)) : 0;
    if (name != NULL)
	memcpy((char *)(packet + 1) + sizeof(struct pppoe_tag), name,
	       strlen(name));
    memset(((char *)packet) + size, 0, 14);
    return size;
}

unsigned short fcstab[256] = {
    0x0000, 0x1189, 0x2312, 0x329b, 0x4624, 0x57ad, 0x6536, 0x74bf,
    0x8c48, 0x9dc1, 0xaf5a, 0xbed3, 0xca6c, 0xdbe5, 0xe97e, 0xf8f7,
    0x1081, 0x0108, 0x3393, 0x221a, 0x56a5, 0x472c, 0x75b7, 0x643e,
    0x9cc9, 0x8d40, 0xbfdb, 0xae52, 0xdaed, 0xcb64, 0xf9ff, 0xe876,
    0x2102, 0x308b, 0x0210, 0x1399, 0x6726, 0x76af, 0x4434, 0x55bd,
    0xad4a, 0xbcc3, 0x8e58, 0x9fd1, 0xeb6e, 0xfae7, 0xc87c, 0xd9f5,
    0x3183, 0x200a, 0x1291, 0x0318, 0x77a7, 0x662e, 0x54b5, 0x453c,
    0xbdcb, 0xac42, 0x9ed9, 0x8f50, 0xfbef, 0xea66, 0xd8fd, 0xc974,
    0x4204, 0x538d, 0x6116, 0x709f, 0x0420, 0x15a9, 0x2732, 0x36bb,
    0xce4c, 0xdfc5, 0xed5e, 0xfcd7, 0x8868, 0x99e1, 0xab7a, 0xbaf3,
    0x5285, 0x430c, 0x7197, 0x601e, 0x14a1, 0x0528, 0x37b3, 0x263a,
    0xdecd, 0xcf44, 0xfddf, 0xec56, 0x98e9, 0x8960, 0xbbfb, 0xaa72,
    0x6306, 0x728f, 0x4014, 0x519d, 0x2522, 0x34ab, 0x0630, 0x17b9,
    0xef4e, 0xfec7, 0xcc5c, 0xddd5, 0xa96a, 0xb8e3, 0x8a78, 0x9bf1,
    0x7387, 0x620e, 0x5095, 0x411c, 0x35a3, 0x242a, 0x16b1, 0x0738,
    0xffcf, 0xee46, 0xdcdd, 0xcd54, 0xb9eb, 0xa862, 0x9af9, 0x8b70,
    0x8408, 0x9581, 0xa71a, 0xb693, 0xc22c, 0xd3a5, 0xe13e, 0xf0b7,
    0x0840, 0x19c9, 0x2b52, 0x3adb, 0x4e64, 0x5fed, 0x6d76, 0x7cff,
    0x9489, 0x8500, 0xb79b, 0xa612, 0xd2ad, 0xc324, 0xf1bf, 0xe036,
    0x18c1, 0x0948, 0x3bd3, 0x2a5a, 0x5ee5, 0x4f6c, 0x7df7, 0x6c7e,
    0xa50a, 0xb483, 0x8618, 0x9791, 0xe32e, 0xf2a7, 0xc03c, 0xd1b5,
    0x2942, 0x38cb, 0x0a50, 0x1bd9, 0x6f66, 0x7eef, 0x4c74, 0x5dfd,
    0xb58b, 0xa402, 0x9699, 0x8710, 0xf3af, 0xe226, 0xd0bd, 0xc134,
    0x39c3, 0x284a, 0x1ad1, 0x0b58, 0x7fe7, 0x6e6e, 0x5cf5, 0x4d7c,
    0xc60c, 0xd785, 0xe51e, 0xf497, 0x8028, 0x91a1, 0xa33a, 0xb2b3,
    0x4a44, 0x5bcd, 0x6956, 0x78df, 0x0c60, 0x1de9, 0x2f72, 0x3efb,
    0xd68d, 0xc704, 0xf59f, 0xe416, 0x90a9, 0x8120, 0xb3bb, 0xa232,
    0x5ac5, 0x4b4c, 0x79d7, 0x685e, 0x1ce1, 0x0d68, 0x3ff3, 0x2e7a,
    0xe70e, 0xf687, 0xc41c, 0xd595, 0xa12a, 0xb0a3, 0x8238, 0x93b1,
    0x6b46, 0x7acf, 0x4854, 0x59dd, 0x2d62, 0x3ceb, 0x0e70, 0x1ff9,
    0xf78f, 0xe606, 0xd49d, 0xc514, 0xb1ab, 0xa022, 0x92b9, 0x8330,
    0x7bc7, 0x6a4e, 0x58d5, 0x495c, 0x3de3, 0x2c6a, 0x1ef1, 0x0f78
};

#define PPPINITFCS16    0xffff  /* Initial FCS value */
#define PPPGOODFCS16    0xf0b8  /* Good final FCS value */
/*
 * Calculate a new fcs given the current fcs and the new data.
 */
unsigned short pppfcs16(register unsigned short fcs, 
			register unsigned char * cp, 
			register int len)
{
/*    assert(sizeof (unsigned short) == 2);
    assert(((unsigned short) -1) > 0); */

    while (len--)
	fcs = (fcs >> 8) ^ fcstab[(fcs ^ *cp++) & 0xff];
    
    return (fcs);
}

#define FRAME_ESC 0x7d
#define FRAME_FLAG 0x7e
#define FRAME_ADDR 0xff
#define FRAME_CTL 0x03
#define FRAME_ENC 0x20

#define ADD_OUT(c) { *out++ = (c); n++; if (opt_verbose) fprintf(log_file, "%x ", (c)); }

void encode_ppp(int fd, unsigned char *buf, int len)
{
    static int first = 0;
    unsigned char out_buf[PACKETBUF];
    unsigned char *out = out_buf;
    unsigned char header[2], tail[2];
    int i,n;
    unsigned short fcs;
    time_t tm;

    header[0] = FRAME_ADDR;
    header[1] = FRAME_CTL;
    fcs = pppfcs16(PPPINITFCS16, header, 2);
    fcs = pppfcs16(fcs, buf, len) ^ 0xffff;
    tail[0] = fcs & 0x00ff;
    tail[1] = (fcs >> 8) & 0x00ff;

    if (opt_verbose)
    {
	time(&tm);
	fprintf(log_file, "%sWriting to pppd: \n", ctime(&tm));
    }

    n = 0;
    if (!first) {
	ADD_OUT(FRAME_FLAG);
	first = 1;
    }
    ADD_OUT(FRAME_ADDR); /* the header - which is constant */
    ADD_OUT(FRAME_ESC);
    ADD_OUT(FRAME_CTL ^ FRAME_ENC);

    for (i = 0; i < len; i++)
	if (buf[i] == FRAME_FLAG || buf[i] == FRAME_ESC || buf[i] < 0x20)
	{
	    ADD_OUT(FRAME_ESC);
	    ADD_OUT(buf[i] ^ FRAME_ENC);
	}
	else
	    ADD_OUT(buf[i]);
    
    for (i = 0; i < 2; i++) {
	if (tail[i] == FRAME_FLAG || tail[i] == FRAME_ESC || tail[i] < 0x20) {
	    ADD_OUT(FRAME_ESC);
	    ADD_OUT(tail[i] ^ FRAME_ENC);
	} else 
	    ADD_OUT(tail[i]);
    }
    ADD_OUT(FRAME_FLAG);

    write(fd, out_buf, n);

    if (opt_verbose)
	fprintf(log_file, "\n");
}

int 
create_sess(struct pppoe_packet *packet, const char *src, const char *dst, 
	    unsigned char *buf, int bufsize, int sess)
{
    int size;
    int i, o = 0;

    if (opt_fwd || !((buf[0] == FRAME_FLAG) || (buf[0] == FRAME_ADDR)))
    {
	if (opt_fwd_search) /* search for a valid packet */
	{
	    while (*buf++ != FRAME_FLAG && bufsize != 0)
		bufsize--;
	    if (bufsize == 0)
		return 0;
	}
	else
	{
	    fprintf(error_file, "create_sess: invalid data\n");
	    return 0;
	}
    }

    for (i = (buf[0] == FRAME_FLAG ? 4 : 3); i < bufsize - 1; i++) 
	if (buf[i] == FRAME_ESC)
	    buf[o++] = buf[++i] ^ FRAME_ENC;
	else
	    buf[o++] = buf[i];

    bufsize = o - 2; /* ignore fcs */

    if (packet == NULL)
	return 0;

    size = sizeof(struct pppoe_packet) + bufsize;

#ifdef __linux__
    memcpy(packet->ethhdr.h_dest, dst, 6);
    memcpy(packet->ethhdr.h_source, src, 6);
    packet->ethhdr.h_proto = htons(ETH_P_PPPOE_SESS);
#else
    memcpy(packet->ethhdr.ether_dhost, dst, 6);
    memcpy(packet->ethhdr.ether_shost, src, 6);
    packet->ethhdr.ether_type = htons(ETH_P_PPPOE_SESS);
#endif
    packet->ver = 1;
    packet->type = 1;
    packet->code = CODE_SESS;
    packet->session = sess;
    packet->length = htons(size - sizeof(struct pppoe_packet));
    
    /* fill out payload */
    memcpy(packet + 1, buf, bufsize);
    
    return size;
}

int 
send_packet(int sock, struct pppoe_packet *packet, int len, const char *ifn)
{
#ifdef USE_BPF
  int c;
  if ((c = write(sock,packet,len)) != len)
    perror("pppoe: write (send_packet)");
  return c;
#else /* regular linux stuff */
    struct sockaddr addr;
    int c;
    time_t tm;

    memset(&addr, 0, sizeof(addr));
    strcpy(addr.sa_data, ifn);

    if (opt_verbose == 1)
    {
	time(&tm);
	fprintf(log_file, "%sSending ", ctime(&tm));
	print_packet(packet);
	fputc('\n', log_file);
    }


    if ((c = sendto(sock, packet, len, 0, &addr, sizeof(addr))) < 0)
	perror("pppoe: sendto (send_packet)");
    
    return c;
#endif /* USE_BPF */
}

#ifdef USE_BPF
/* return:  -1 == error, 0 == okay, 1 == ignore this packet */
int read_bpf_packet(int fd, struct pppoe_packet *packet) {
    /* Nastiness - BPF may return multiple packets in one fell swoop */
    /* This makes select() difficult to use - you need to be ready to
       clear out packets as they arrive */
    static char *buf = NULL;
    static int lastdrop = 0;
    static int n = 0, off = 0;
    struct bpf_hdr *h;

    if (buf == NULL) {
	if ((buf = malloc(bpf_buf_size)) == NULL) {
	    perror("pppoe:malloc");
	    return -1;
	}
    }

    if (off < n) {
	/* read out of previously grabbed buffer */
	if (n-off < sizeof(struct bpf_hdr)) {
	    fprintf(stderr, "BPF: not enough left for header:  %d\n", n-off);
	    off = n = 0; /* force reread from BPF next time */
	    return 1; /* try again */