#include <stdio.h>
#include <errno.h>
#include <fcntl.h>
#include <stdlib.h>
#include <stdarg.h>
#include <unistd.h>
#include <signal.h>
#include <net/if.h>
#include <termios.h>
#include <strings.h>
#include <net/bpf.h>
#include <sys/wait.h>
#include <net/if_dl.h>
#include <sys/ioctl.h>
#include <sys/socket.h>
#include <net/if_ether.h>
#include <net/ethertypes.h>

extern const char *__progname;

#include "pppoe.h"

#define UNIQLEN 8
#define MAXPKTLEN 1514 /* forced by Ethernet */

#define PPP_FLAG 0x7e
#define PPP_ESC  0x7d
#define PPP_MOD  0x20
#define PPP_INITFCS 0xffff
#define PPP_GOODFCS 0xf0b8
#define PPP_FCSCHAR(fcs,c) (((fcs)>>8)^ppp_fcstab[((fcs)^(c))&0xff])

typedef struct tag TAG;

struct tag {
  unsigned short int type;
  unsigned short int length;
  const unsigned char *value;
  } ;

static const char *ifname;
static const char *pppname;
static int iis;
static int bpffd;
static int randfd;
static const char *bpfname;
static int bpfblen;
static char *bpfbuf;
static unsigned char mymac[6];
static int state;
#define S_INITIATE 1 /* sending PADI packets, looking for PADO */
#define S_REQUEST  2 /* sent PADR packet, looking for PADS */
#define S_SESSION  3 /* exchanging data packets */
static unsigned short int session_id;
static struct timeval timeout;
static char uniq[UNIQLEN];
static unsigned char peermac[6];
static int ntags;
static TAG *tags;
static int tagsalloc;
static unsigned char opkt[MAXPKTLEN];
static int pktoff;
static char ptymname[11];
static int ptymfd;
static char ptysname[11];
static int ptysfd;
static int devnull;
static sigset_t caught_sigs;
static int pppd_pid;
static int pppdeathpipe;
static unsigned char ppp_pty_frame[MAXPKTLEN+2];
static int ppp_pty_flen;
static int ppp_pty_fcs;
static int ppp_pty_esc;
static const unsigned short int ppp_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 };
static int plevel;
#define P_NONE  0
#define P_WARN  1
#define P_NOTE  2
#define P_INFO  3
#define P_DEBUG 4
static int pppdebug = 0;

static void p(int, const char *, ...)
	__attribute__((__format__(__printf__,2,3)));
static void p(int level, const char *fmt, ...)
{
 va_list ap;

 if (plevel >= level)
  { va_start(ap,fmt);
    vprintf(fmt,ap);
    va_end(ap);
  }
}

static void catch_signal(int sig, void (*handler)(int))
{
 struct sigaction sa;

 sigaddset(&caught_sigs,sig);
 sa.sa_handler = handler;
 sigemptyset(&sa.sa_mask);
 sa.sa_flags = SA_RESTART;
 sigaction(sig,&sa,0);
}

static void sig_to_pppd(int sig)
{
 if (pppd_pid > 1) kill(pppd_pid,sig);
}

static void sig_to_self(int sig, void (*handler)(int))
{
 struct sigaction sa;
 sigset_t m;

 sa.sa_handler = SIG_DFL;
 sigemptyset(&sa.sa_mask);
 sa.sa_flags = 0;
 sigaction(sig,&sa,0);
 sigemptyset(&m);
 sigaddset(&m,sig);
 sigprocmask(SIG_UNBLOCK,&m,0);
 kill(getpid(),sig);
 /* if we survived... */
 catch_signal(sig,handler);
}

static void sig_to_pppd_or_self(int sig)
{
 if (pppd_pid > 1) sig_to_pppd(sig);
 else              sig_to_self(sig,sig_to_pppd_or_self);
}

static void sig_to_pppd_and_self(int sig)
{
 sig_to_pppd(sig);
 sig_to_self(sig,sig_to_pppd_and_self);
}

static void setup(void)
{
 int i;
 char *n;
 char *d;
 struct ifreq ifr;
 struct bpf_version bpf_vers;
 static struct bpf_insn bpf_code[]
  = { BPF_STMT(BPF_LD+BPF_H+BPF_ABS,12),
      BPF_JUMP(BPF_JMP+BPF_JEQ+BPF_K,ETHERTYPE_PPPOE,1,0),
      BPF_JUMP(BPF_JMP+BPF_JEQ+BPF_K,ETHERTYPE_PPPOEDISC,0,5),
      BPF_STMT(BPF_LD+BPF_W+BPF_ABS,0),
      BPF_JUMP(BPF_JMP+BPF_JEQ+BPF_K,0/*runtime*/,0,3),
#define CODE_OFFSET_ETH_4_AT_0 4
      BPF_STMT(BPF_LD+BPF_H+BPF_ABS,4),
      BPF_JUMP(BPF_JMP+BPF_JEQ+BPF_K,0/*runtime*/,0,1),
#define CODE_OFFSET_ETH_2_AT_4 6
      BPF_STMT(BPF_RET+BPF_K,-1),
      BPF_STMT(BPF_RET+BPF_K,0) };
 struct bpf_program bpf_prog;
 struct termios tio;
 struct ifconf ifc;
 struct ifreq *ifcr;
 int l;
 struct sockaddr_dl *sdl;
 int havemac;
 char ifcbuf[8192] __attribute__((__aligned__));

 devnull = open("/dev/null",O_RDWR,0);
 if (devnull < 0)
  { fprintf(stderr,"%s: /dev/null: %s\n",__progname,strerror(errno));
    exit(1);
  }
 while ((devnull < 3) && (devnull >= 0)) devnull = dup(devnull);
 iis = socket(AF_LOCAL,SOCK_DGRAM,0);
 if (iis < 0)
  { fprintf(stderr,"%s: interface ioctl socket: %s\n",__progname,strerror(errno));
    exit(1);
  }
 randfd = open("/dev/urandom",O_RDONLY,0);
 if (randfd < 0)
  { fprintf(stderr,"%s: /dev/urandom: %s\n",__progname,strerror(errno));
    exit(1);
  }
 n = 0;
 d = 0;
 for (i=0;;i++)
  { free(n);
    asprintf(&n,"bpf%d",i);
    free(d);
    asprintf(&d,"/dev/%s",n);
    bpffd = open(d,O_RDWR,0);
    if (bpffd >= 0) break;
    if (errno == EBUSY) continue;
    fprintf(stderr,"%s: %s: %s\n",__progname,d,strerror(errno));
    exit(1);
  }
 bpfname = n;
 free(d);
 bpfblen = 65536;
 if (ioctl(bpffd,BIOCSBLEN,&bpfblen) < 0)
  { fprintf(stderr,"%s: BIOCSBLEN on %s: %s\n",__progname,bpfname,strerror(errno));
    exit(1);
  }
 strncpy(&ifr.ifr_name[0],ifname,sizeof(ifr.ifr_name));
 if (ioctl(bpffd,BIOCSETIF,&ifr) < 0)
  { fprintf(stderr,"%s: BIOCSETIF %s on %s: %s\n",__progname,ifname,bpfname,strerror(errno));
    exit(1);
  }
 i = 1;
 if (ioctl(bpffd,BIOCIMMEDIATE,&i) < 0)
  { fprintf(stderr,"%s: enable BIOCIMMEDIATE on %s: %s\n",__progname,bpfname,strerror(errno));
    exit(1);
  }
 if (ioctl(bpffd,BIOCVERSION,&bpf_vers) < 0)
  { fprintf(stderr,"%s: BIOCVERSION on %s: %s\n",__progname,bpfname,strerror(errno));
    exit(1);
  }
 if ( (bpf_vers.bv_major != BPF_MAJOR_VERSION) ||
      (bpf_vers.bv_minor < BPF_MINOR_VERSION) )
  { fprintf(stderr,"%s: incompatible BPF filter version: program %d.%d, kernel %d.%d\n",__progname,BPF_MAJOR_VERSION,BPF_MINOR_VERSION,bpf_vers.bv_major,bpf_vers.bv_minor);
    exit(1);
  }
 havemac = 0;
 ifc.ifc_buf = &ifcbuf[0];
 ifc.ifc_len = sizeof(ifcbuf);
 if (ioctl(iis,SIOCGIFCONF,&ifc) < 0)
  { fprintf(stderr,"%s: SIOCGIFCONF: %s\n",__progname,strerror(errno));
    exit(1);
  }
 i = 0;
 while (i < ifc.ifc_len)
  { ifcr = (void *) (i+(char *)ifc.ifc_req);
    l = ifcr->ifr_addr.sa_len;
    if (l < sizeof(struct sockaddr)) l = sizeof(struct sockaddr);
    l += sizeof(ifcr->ifr_name);
    if (i+l > ifc.ifc_len)
     { fprintf(stderr,"%s: SIOCGIFCONF partial ifreq (want %d, %d left)\n",__progname,l,ifc.ifc_len-i);
       break;
     }
    if (ifcr->ifr_addr.sa_family == AF_LINK)
     { if (i > 0) bcopy(ifcr,&ifcbuf[0],l);
       ifcr = (void *) &ifcbuf[0];
       sdl = (struct sockaddr_dl *) &ifcr->ifr_addr;
       if ( !bcmp(&sdl->sdl_data[0],ifname,sdl->sdl_nlen) &&
	    !ifname[sdl->sdl_nlen] )
	{ if (sdl->sdl_alen == 6)
	   { if (havemac)
	      { fprintf(stderr,"%s: warning: multiple MAC addresses found for %s, using last\n",__progname,ifname);
		if (havemac == 1) fprintf(stderr,"\t%02x:%02x:%02x:%02x:%02x:%02x\n",mymac[0],mymac[1],mymac[2],mymac[3],mymac[4],mymac[5]);
	      }
	     bcopy(LLADDR(sdl),&mymac[0],6);
	     if (havemac) fprintf(stderr,"\t%02x:%02x:%02x:%02x:%02x:%02x\n",mymac[0],mymac[1],mymac[2],mymac[3],mymac[4],mymac[5]);
	     havemac ++;
	   }
	}
     }
    i += l;
  }
 if (! havemac)
  { fprintf(stderr,"%s: no MAC address found for %s\n",__progname,ifname);
    exit(1);
  }
 p(P_INFO,"%s -> %02x:%02x:%02x:%02x:%02x:%02x\n",ifname,mymac[0],mymac[1],mymac[2],mymac[3],mymac[4],mymac[5]);
 /* Should these two be in network byte order? */
 bpf_code[CODE_OFFSET_ETH_4_AT_0].k =
	(mymac[0] << 24) | (mymac[1] << 16) | (mymac[2] << 8) | mymac[3];
 bpf_code[CODE_OFFSET_ETH_2_AT_4].k = (mymac[4] << 8) | mymac[5];
 bpf_prog.bf_len = sizeof(bpf_code) / sizeof(bpf_code[0]);
 bpf_prog.bf_insns = &bpf_code[0];
 if (ioctl(bpffd,BIOCSETF,&bpf_prog) < 0)
  { fprintf(stderr,"%s: BIOCSETF on %s: %s\n",__progname,bpfname,strerror(errno));
    exit(1);
  }
 bpfbuf = malloc(bpfblen);
 for (i=0;i<256;i++)
  { static const char ptychr[16] = "pqrstuvwxyzPQRST";
    sprintf(&ptymname[0],"/dev/pty%c%x",ptychr[i>>4],i&0xf);
    ptymfd = open(&ptymname[0],O_RDWR,0);
    if (ptymfd >= 0)
     { strcpy(&ptysname[0],&ptymname[0]);
       ptysname[5] = 't';
       ptysfd = open(&ptysname[0],O_RDWR,0);
       if (ptysfd >= 0) break;
       close(ptymfd);
       ptymfd = -1;
     }
    else
     { if (errno == ENOENT) break;
     }
  }
 if (ptymfd < 0)
  { fprintf(stderr,"%s: all ptys in use\n",__progname);
    exit(1);
  }
 tio.c_iflag = 0;
 tio.c_oflag = 0;
 tio.c_cflag = CS8 | CREAD | CLOCAL;
 tio.c_lflag = 0;
 tio.c_cc[VMIN] = 1;
 tio.c_cc[VTIME] = 0;
 tcsetattr(ptysfd,TCSANOW,&tio);
 tags = 0;
 ntags = 0;
 tagsalloc = 0;
 pppdeathpipe = -1;
 ppp_pty_flen = 0;
 ppp_pty_esc = 0;
 pppd_pid = -1;
 sigemptyset(&caught_sigs);
 catch_signal(SIGHUP,sig_to_pppd_or_self);
 catch_signal(SIGINT,sig_to_pppd_or_self);
 catch_signal(SIGTERM,sig_to_pppd_or_self);
 catch_signal(SIGTSTP,sig_to_pppd_and_self);
 catch_signal(SIGCONT,sig_to_pppd);
}

static void init_packet(void)
{
 pktoff = 0;
}

static int pktlenchk(int len)
{
 if (pktoff+len > MAXPKTLEN)
  { if (pktoff <= MAXPKTLEN) p(P_WARN,"output packet overflow\n");
    pktoff = MAXPKTLEN + 1;
    return(1);
  }
 return(0);
}

static void append_packet(const void *data, int len)
{
 if (pktlenchk(len)) return;
 bcopy(data,&opkt[pktoff],len);
 pktoff += len;
}

static void append_packet_8(unsigned char v)
{
 if (pktlenchk(1)) return;
 opkt[pktoff++] = v;
}

static void append_packet_16(unsigned short int v)
{
 if (pktlenchk(2)) return;
 opkt[pktoff++] = v >> 8;
 opkt[pktoff++] = v & 0xff;
}

static int skip_packet(int n)
{
 if (pktlenchk(n)) return(-1);
 pktoff += n;
 return(pktoff-n);
}

static void write_packet_16(int at, unsigned short int v)
{
 if ((at < 0) || (at+2 > pktoff))
  { fprintf(stderr,"write_packet_16 outside packet\n");
    abort();
  }
 opkt[at] = v >> 8;
 opkt[at+1] = v & 0xff;
}

static int packet_length(void)
{
 return(pktoff);
}

static void pad_packet(void)
{
 if (pktoff < ETHER_MIN_LEN-ETHER_CRC_LEN)
  { bzero(&opkt[pktoff],ETHER_MIN_LEN-ETHER_CRC_LEN-pktoff);
    pktoff = ETHER_MIN_LEN - ETHER_CRC_LEN;
  }
}

static void send_padi(void)
{
 int len;
 int lenat;
 int paybase;

 init_packet();
 /* Ethernet header */
 append_packet("\xff\xff\xff\xff\xff\xff",6);
 append_packet(&mymac[0],6);
 append_packet_16(ETHERTYPE_PPPOEDISC);
 /* PPPoE header */
 append_packet_8((PPPOE_VER<<4)|PPPOE_TYPE);
 append_packet_8(PPPOE_CODE_PADI);
 append_packet_16(0); /* SESSION_ID */
 lenat = skip_packet(2);
 /* PPPoE payload */
 paybase = skip_packet(0);
 /* Zero-length Service-Name */
 append_packet_16(PPPOE_TAG_SERV);
 append_packet_16(0);
 /* UNIQLEN-byte random Host-Uniq */
 append_packet_16(PPPOE_TAG_HUNIQ);
 append_packet_16(UNIQLEN);
 read(randfd,&uniq[0],UNIQLEN);
 append_packet(&uniq[0],UNIQLEN);
 /* Set length */
 write_packet_16(lenat,packet_length()-paybase);
 pad_packet();
 len = packet_length();
 write(bpffd,&opkt[0],len);
  { const unsigned char *pp;
    int i;
    p(P_DEBUG,"wrote PADI packet: [%d]",len);
    for (pp=&opkt[0],i=len;i>0;pp++,i--) p(P_DEBUG," %02x",*pp);
    p(P_DEBUG,"\n");
  }
}

static void process_timeout(void)
{
 switch (state)
  { case S_REQUEST:
       state = S_INITIATE;
       gettimeofday(&timeout,0);
       /* fall through */
    case S_INITIATE:
       send_padi();
       timeout.tv_sec += 5;
       break;
  }
}

static void scan_tags(const unsigned char *dp, int len)
{
 unsigned short int type;
 unsigned short int length;

 ntags = 0;
 while (len > 0)
  { if (len < 4)
     { p(P_WARN,"note: too-short tag header (length %d) ignored\n",len);
       break;
     }
    type = (dp[0] << 8) | dp[1];
    length = (dp[2] << 8) | dp[3];
    if (length > len-4)
     { p(P_WARN,"note: tag overruns packet (length %d, %d left) - ignored\n",length,len-4);
       break;
     }
    if (ntags >= tagsalloc)
     { tags = realloc(tags,sizeof(*tags)*++tagsalloc);
     }
    tags[ntags].type = type;
    tags[ntags].length = length;
    tags[ntags].value = dp + 4;
    ntags ++;
    dp += 4 + length;
    len -= 4 + length;
  }
}

static int find_next_tag(unsigned short int type, int i)
{
 for (i++;i<ntags;i++) if (tags[i].type == type) return(i);
 return(-1);
}

static int find_first_tag(unsigned short int type)
{
 return(find_next_tag(type,-1));
}

static void send_padr(void)
{
 int len;
 int lenat;
 int i;
 int paybase;

 init_packet();
 /* Ethernet header */
 append_packet(&peermac[0],6);
 append_packet(&mymac[0],6);
 append_packet_16(ETHERTYPE_PPPOEDISC);
 /* PPPoE header */
 append_packet_8((PPPOE_VER<<4)|PPPOE_TYPE);
 append_packet_8(PPPOE_CODE_PADR);
 append_packet_16(0); /* SESSION_ID */
 lenat = skip_packet(2);
 /* PPPoE payload */
 paybase = skip_packet(0);
 /* Zero-length Service-Name */
 append_packet_16(PPPOE_TAG_SERV);
 append_packet_16(0);
 /* UNIQLEN-byte random Host-Uniq */
 append_packet_16(PPPOE_TAG_HUNIQ);
 append_packet_16(UNIQLEN);
 read(randfd,&uniq[0],UNIQLEN);
 append_packet(&uniq[0],UNIQLEN);
 /* Copy of any AC-Cookies */
 i = find_first_tag(PPPOE_TAG_ACCOOK);
 while (i >= 0)
  { append_packet_16(PPPOE_TAG_ACCOOK);
    append_packet_16(tags[i].length);
    append_packet(tags[i].value,tags[i].length);
    i = find_next_tag(PPPOE_TAG_ACCOOK,i);
  }
 /* Copy of any Relay-Session-Ids */
 i = find_first_tag(PPPOE_TAG_RELAYID);
 while (i >= 0)
  { append_packet_16(PPPOE_TAG_RELAYID);
    append_packet_16(tags[i].length);
    append_packet(tags[i].value,tags[i].length);
    i = find_next_tag(PPPOE_TAG_RELAYID,i);
  }
 /* Set length */
 write_packet_16(lenat,packet_length()-paybase);
 pad_packet();
 len = packet_length();
 write(bpffd,&opkt[0],len);
  { const unsigned char *pp;
    int i;
    p(P_DEBUG,"wrote PADR packet: [%d]",len);
    for (pp=&opkt[0],i=len;i>0;pp++,i--) p(P_DEBUG," %02x",*pp);
    p(P_DEBUG,"\n");
  }
}

static void send_padt(void)
{
 int len;
 int lenat;
 int paybase;

 init_packet();
 /* Ethernet header */
 append_packet(&peermac[0],6);
 append_packet(&mymac[0],6);
 append_packet_16(ETHERTYPE_PPPOEDISC);
 /* PPPoE header */
 append_packet_8((PPPOE_VER<<4)|PPPOE_TYPE);
 append_packet_8(PPPOE_CODE_PADT);
 append_packet_16(session_id);
 lenat = skip_packet(2);
 /* PPPoE payload */
 paybase = skip_packet(0);
 /* Set length */
 write_packet_16(lenat,packet_length()-paybase);
 pad_packet();
 len = packet_length();
 write(bpffd,&opkt[0],len);
  { const unsigned char *pp;
    int i;
    p(P_DEBUG,"wrote PADT packet: [%d]",len);
    for (pp=&opkt[0],i=len;i>0;pp++,i--) p(P_DEBUG," %02x",*pp);
    p(P_DEBUG,"\n");
  }
}

static void fork_pppd(void)
{
 int kid;
 int i;
 int e;
 int deathpipe[2];
 int forkpipe[2];
 int pidpipe[2];
 sigset_t prevmask;

 sigprocmask(SIG_BLOCK,&caught_sigs,&prevmask);
 if ( (pipe(pidpipe) < 0) ||
      (pipe(forkpipe) < 0) ||
      (pipe(deathpipe) < 0) )
  { fprintf(stderr,"%s: pipe: %s\n",__progname,strerror(errno));
    exit(1);
  }
 kid = fork();
 if (kid < 0)
  { fprintf(stderr,"%s: fork: %s\n",__progname,strerror(errno));
    exit(1);
  }
 if (kid != 0)
  { char c;
    close(forkpipe[1]);
    if (read(forkpipe[0],&c,1) == 1)
     { for (i=0;i<sizeof(e);i++) read(forkpipe[0],((char *)&e)+i,1);
       fprintf(stderr,"%s: %s: %s\n",__progname,(c=='f')?"fork":"exec pppd",strerror(e));
       exit(1);
     }
    close(forkpipe[0]);
    close(deathpipe[1]);
    pppdeathpipe = deathpipe[0];
    for (i=0;i<sizeof(pppd_pid);i++) read(pidpipe[0],((char *)&pppd_pid)+i,1);
    close(pidpipe[0]);
    close(pidpipe[1]);
    sigprocmask(SIG_SETMASK,&prevmask,0);
    return;
  }
 kid = fork();
 if (kid < 0)
  { e = errno;
    write(forkpipe[1],"f",1);
    write(forkpipe[1],&e,sizeof(e));
    _exit(0);
  }
 if (kid != 0)
  { sigfillset(&prevmask);
    sigprocmask(SIG_BLOCK,&prevmask,0);
    pppd_pid = kid;
    write(pidpipe[1],&pppd_pid,sizeof(pppd_pid));
    for (i=getdtablesize()-1;i>2;i--) if (i != deathpipe[1]) close(i);
    wait(&i);
    _exit(0);
  }
 p(P_INFO,"forked pppd, pid %d\n",getpid());
 fflush(stdout);
 sigprocmask(SIG_SETMASK,&prevmask,0);
 fcntl(forkpipe[1],F_SETFD,1);
 dup2(ptysfd,0);
 dup2(0,1);
 for (i=getdtablesize()-1;i>2;i--) if (i != forkpipe[1]) close(i);
  { const char *args[1000]; /* hope 1000 is enough! */
    const char **ap;
    ap = &args[0];
    /* XXX there should be a way to configure things a user might
       reasonably want to tweak, like IPX support, at run time.... */
    *ap++ = "pppd";
    *ap++ = "115200"; /* XXX - pppd demands(!) a speed in some versions */
    *ap++ = "connect"; *ap++ = "/usr/bin/true";
    *ap++ = "ipcp-accept-local";
    *ap++ = "ipcp-accept-remote";
    *ap++ = "local";
    *ap++ = "mru"; *ap++ = "1400";
    *ap++ = "mtu"; *ap++ = "1400";
    *ap++ = "name"; *ap++ = pppname;
    *ap++ = "noaccomp";
    *ap++ = "noauth";
    *ap++ = "nobsdcomp";
    *ap++ = "noccp";
    *ap++ = "nodefaultroute";
    *ap++ = "nodeflate";
    *ap++ = "nodetach";
    *ap++ = "noipdefault";
    *ap++ = "noipx";
    *ap++ = "nopcomp";
    *ap++ = "nopersist";
    *ap++ = "nopredictor1";
    *ap++ = "noproxyarp";
    *ap++ = "novj";
    *ap++ = "novjccomp";
    if (pppdebug) *ap++ = "debug";
    *ap = 0;
    execv("/usr/sbin/pppd",(const void *)&args[0]);
  }
 e = errno;
 write(forkpipe[1],"e",1);
 write(forkpipe[1],&e,sizeof(e));
 _exit(0);
}

static void send_frame_to_pppd(const void *data, int len)
{
 unsigned char stuffup[3+(len*2)+4+1];
 unsigned char *sp;
 const unsigned char *dp;
 unsigned short int fcs;

 static void addchar(unsigned char ch)
  { switch (ch)
     { case PPP_FLAG: case PPP_ESC: case 0x00 ... 0x1f: case 0x7f ... 0x9f:
	  *sp++ = PPP_ESC;
	  *sp++ = ch ^ PPP_MOD;
	  break;
       default:
	  *sp++ = ch;
	  break;
     }
    fcs = PPP_FCSCHAR(fcs,ch);
  }

 sp = &stuffup[0];
 fcs = PPP_INITFCS;
 *sp++ = PPP_FLAG;
 addchar(0xff);
 addchar(0x03);
 for (dp=data;len>0;dp++,len--) addchar(*dp);
 fcs = 0xffff & ~fcs;
  { unsigned short int fcssave;
    fcssave = fcs;
    addchar(fcssave&0xff);
    addchar(fcssave>>8);
  }
 *sp++ = PPP_FLAG;
 write(ptymfd,&stuffup[0],sp-&stuffup[0]);
  { int i;
    int l;
    l = sp - &stuffup[0];
    p(P_DEBUG,"wrote to tty %d:",l);
    for (i=0;i<l;i++) p(P_DEBUG," %02x",stuffup[i]);
    p(P_DEBUG,"\n");
  }
}

static void process_packet(const void *data, int len)
{
 const unsigned char *dp;
 unsigned short int etype;
 unsigned char srcmac[6];

  { int i;
    p(P_DEBUG,"received packet: [%d]",len);
    for (dp=data,i=len;i>0;dp++,i--) p(P_DEBUG," %02x",*dp);
    p(P_DEBUG,"\n");
  }
 dp = data;
 if (len < 14)
  { p(P_WARN,"received runt packet (len %d)\n",len);
    return;
  }
 if (bcmp(dp,&mymac[0],6))
  { p(P_WARN,"received packet not for me(?) [for %02x:%02x:%02x:%02x:%02x:%02x]\n",dp[0],dp[1],dp[2],dp[3],dp[4],dp[5]);
    return;
  }
 etype = (dp[12] << 8) | dp[13];
 if ((etype != ETHERTYPE_PPPOEDISC) && (etype != ETHERTYPE_PPPOE))
  { p(P_WARN,"received packet of wrong ethertype (%04x)\n",etype);
    return;
  }
 bcopy(dp+6,&srcmac[0],6);
 dp += 14;
 len -= 14;
 if (len < 6)
  { p(P_WARN,"received packet too short to hold PPPoE header (%d)\n",len);
    return;
  }
 if ((dp[0] & 0xf0) != 0x10)
  { p(P_WARN,"received packet with wrong ver (%d)\n",dp[0]>>4);
    return;
  }
 if ((dp[0] & 0x0f) != 0x01)
  { p(P_WARN,"received packet with wrong ver (%d)\n",dp[0]&0xf);
    return;
  }
 if ((dp[4]<<8)+dp[5] > len-6)
  { p(P_WARN,"length PPPoE header too large (%d, only %d available)\n",(dp[4]<<8)+dp[5],len-6);
    return;
  }
 if ((dp[4]<<8)+dp[5] != len-6)
  { p(P_DEBUG,"[shrinking length from %d to %d]\n",len,(dp[4]<<8)+dp[5]+6);
    len = (dp[4]<<8) + dp[5] + 6;
  }
 switch (state)
  { case S_INITIATE:
	{ int acnx;
	  int i;
	  /* expecting PADO */
	  if (etype != ETHERTYPE_PPPOEDISC)
	   { p(P_WARN,"received Session-phase packet in Initate state\n");
	     return;
	   }
	  if (dp[1] != PPPOE_CODE_PADO)
	   { p(P_WARN,"received non-PADO (code %d) packet in Initate state\n",dp[1]);
	     return;
	   }
	  if (dp[2] || dp[3])
	   { p(P_WARN,"received PADO packet with session ID %02x%02x\n",dp[2],dp[3]);
	     return;
	   }
	  scan_tags(dp+6,len-6);
	  acnx = find_first_tag(PPPOE_TAG_ACNAME);
	  if (acnx < 0)
	   { p(P_WARN,"received PADO without an AC-Name tag\n");
	     return;
	   }
	  i = find_first_tag(PPPOE_TAG_SERV);
	  while (i >= 0)
	   { if (tags[i].length == 0) break;
	     i = find_next_tag(PPPOE_TAG_SERV,i);
	   }
	  if (i < 0)
	   { p(P_WARN,"received PADO without our Service-Name tag\n");
	     return;
	   }
	  i = find_first_tag(PPPOE_TAG_HUNIQ);
	  while (i >= 0)
	   { if ( (tags[i].length == UNIQLEN) &&
		  !bcmp(tags[i].value,&uniq[0],UNIQLEN) ) break;
	     i = find_next_tag(PPPOE_TAG_HUNIQ,i);
	   }
	  if (i < 0)
	   { p(P_WARN,"received PADO without our Host-Uniq tag\n");
	     return;
	   }
	  bcopy(&srcmac[0],&peermac[0],6);
	  p(P_INFO,"PADO from AC \"%.*s\" at %02x:%02x:%02x:%02x:%02x:%02x\n",tags[acnx].length,tags[acnx].value,peermac[0],peermac[1],peermac[2],peermac[3],peermac[4],peermac[5]);
	  send_padr();
	  state = S_REQUEST;
	}
       break;
    case S_REQUEST:
	{ int sid;
	  int i;
	  /* expecting PADS */
	  if (etype != ETHERTYPE_PPPOEDISC)
	   { p(P_WARN,"received Session-phase packet in Initate state\n");
	     return;
	   }
	  if (dp[1] != PPPOE_CODE_PADS)
	   { p(P_WARN,"received non-PADS (code %d) packet in Request state\n",dp[1]);
	     return;
	   }
	  if (bcmp(&srcmac[0],&peermac[0],6))
	   { p(P_WARN,"received PADS packet from someone (%02x:%02x:%02x:%02x:%02x:%02x) other than our peer (%02x:%02x:%02x:%02x:%02x:%02x)\n",srcmac[0],srcmac[1],srcmac[2],srcmac[3],srcmac[4],srcmac[5],peermac[0],peermac[1],peermac[2],peermac[3],peermac[4],peermac[5]);
	     return;
	   }
	  sid = (dp[2] << 8) | dp[3];
	  scan_tags(dp+6,len-6);
	  i = find_first_tag(PPPOE_TAG_HUNIQ);
	  while (i >= 0)
	   { if ( (tags[i].length == UNIQLEN) &&
		  !bcmp(tags[i].value,&uniq[0],UNIQLEN) ) break;
	     i = find_next_tag(PPPOE_TAG_HUNIQ,i);
	   }
	  if (i < 0)
	   { p(P_WARN,"received PADS without our Host-Uniq tag\n");
	     return;
	   }
	  i = find_first_tag(PPPOE_TAG_SNAMEERR);
	  if (i >= 0)
	   { p(P_WARN,"received PADS with Service-Name-Error tag\n");
	     return;
	   }
	  session_id = sid;
	  p(P_INFO,"PADS with session ID %04x\n",sid);
	  state = S_SESSION;
	  fork_pppd();
	}
       break;
    case S_SESSION:
	{ int sid;
	  /* expecting data or maybe a PADT */
	  switch (etype)
	   { case ETHERTYPE_PPPOEDISC:
		if (dp[1] != PPPOE_CODE_PADT)
		 { p(P_WARN,"received non-PADT (code %d) discover packet in Session state\n",dp[1]);
		   return;
		 }
		if (bcmp(&srcmac[0],&peermac[0],6))
		 { p(P_WARN,"received PADT packet from someone (%02x:%02x:%02x:%02x:%02x:%02x) other than our peer (%02x:%02x:%02x:%02x:%02x:%02x)\n",srcmac[0],srcmac[1],srcmac[2],srcmac[3],srcmac[4],srcmac[5],peermac[0],peermac[1],peermac[2],peermac[3],peermac[4],peermac[5]);
		   return;
		 }
		sid = (dp[2] << 8) | dp[3];
		if (sid != session_id)
		 { p(P_WARN,"received PADT packet for wrong session (packet %04x, current %04x)\n",sid,session_id);
		   return;
		 }
		p(P_INFO,"Exiting on PADT\n");
		exit(0);
		break;
	     case ETHERTYPE_PPPOE:
		if (dp[1] != PPPOE_CODE_DATA)
		 { p(P_WARN,"received non-DATA (code %d) session packet\n",dp[1]);
		   return;
		 }
		if (bcmp(&srcmac[0],&peermac[0],6))
		 { p(P_WARN,"received DATA packet from someone (%02x:%02x:%02x:%02x:%02x:%02x) other than our peer (%02x:%02x:%02x:%02x:%02x:%02x)\n",srcmac[0],srcmac[1],srcmac[2],srcmac[3],srcmac[4],srcmac[5],peermac[0],peermac[1],peermac[2],peermac[3],peermac[4],peermac[5]);
		   return;
		 }
		sid = (dp[2] << 8) | dp[3];
		if (sid != session_id)
		 { p(P_WARN,"received DATA packet for wrong session (packet %04x, current %04x)\n",sid,session_id);
		   return;
		 }
		send_frame_to_pppd(dp+6,len-6);
		break;
	   }
	}
       break;
  }
}

static void process_bpf_input(void)
{
 int n;
 struct bpf_hdr h;
 int l;
 char *bp;

 n = read(bpffd,bpfbuf,bpfblen);
 if (n < 0)
  { fprintf(stderr,"%s: bpf read: %s\n",__progname,strerror(errno));
    exit(1);
  }
 bp = bpfbuf;
 while (n > 0)
  { if (n < sizeof(h))
     { fprintf(stderr,"%s: partial header!\n",__progname);
       break;
     }
    bcopy(bp,&h,sizeof(h));
    if (h.bh_caplen != h.bh_datalen)
     { fprintf(stderr,"%s: truncated packet(?), ignored\n",__progname);
     }
    else
     { l = h.bh_hdrlen + h.bh_caplen;
       if (l > n)
	{ fprintf(stderr,"%s: partial packet(?) (l=%d n=%d)\n",__progname,l,n);
	  break;
	}
       process_packet(bp+h.bh_hdrlen,h.bh_caplen);
       l = BPF_WORDALIGN(l);
       if (l > n) l = n;
       bp += l;
       n -= l;
     }
  }
}

static void send_data(const void *pppframe, int ppplen)
{
 int len;
 int lenat;
 int paybase;

 if (state != S_SESSION) return;
 init_packet();
 /* Ethernet header */
 append_packet(&peermac[0],6);
 append_packet(&mymac[0],6);
 append_packet_16(ETHERTYPE_PPPOE);
 /* PPPoE header */
 append_packet_8((PPPOE_VER<<4)|PPPOE_TYPE);
 append_packet_8(PPPOE_CODE_DATA);
 append_packet_16(session_id);
 lenat = skip_packet(2);
 /* PPPoE payload */
 paybase = skip_packet(0);
 append_packet(pppframe,ppplen);
 /* Set length */
 write_packet_16(lenat,packet_length()-paybase);
 pad_packet();
 len = packet_length();
 write(bpffd,&opkt[0],len);
  { const unsigned char *pp;
    int i;
    p(P_DEBUG,"wrote DATA packet: [%d]",len);
    for (pp=&opkt[0],i=len;i>0;pp++,i--) p(P_DEBUG," %02x",*pp);
    p(P_DEBUG,"\n");
  }
}

static void process_pty_input(void)
{
 unsigned char ibuf[8192];
 int n;
 int i;
 int c;

 n = read(ptymfd,&ibuf[0],sizeof(ibuf));
 if (n < 0)
  { fprintf(stderr,"%s: pty read: %s\n",__progname,strerror(errno));
    exit(1);
  }
 p(P_DEBUG,"pty read: got %d:",n);
 for (i=0;i<n;i++) p(P_DEBUG," %02x",ibuf[i]);
 p(P_DEBUG,"\n");
 for (i=0;i<n;i++)
  { switch (ibuf[i])
     { case PPP_FLAG:
	  if ( (ppp_pty_flen > 0) &&
	       !ppp_pty_esc &&
	       (ppp_pty_fcs == PPP_GOODFCS) )
	   { if ( (ppp_pty_flen > 4) &&
		  (ppp_pty_frame[0] == 0xff) &&
		  (ppp_pty_frame[1] == 0x03) )
	      { send_data(&ppp_pty_frame[2],ppp_pty_flen-4);
	      }
	     else
	      { send_data(&ppp_pty_frame[0],ppp_pty_flen-2);
	      }
	   }
	  ppp_pty_flen = 0;
	  ppp_pty_fcs = 0xffff;
	  ppp_pty_esc = 0;
	  break;
       case PPP_ESC:
	  ppp_pty_esc = 1;
	  break;
       default:
	  if (ppp_pty_esc)
	   { c = ibuf[i] ^ PPP_MOD;
	     ppp_pty_esc = 0;
	   }
	  else
	   { c = ibuf[i];
	   }
	  if ((ppp_pty_flen >= 0) && (ppp_pty_flen < MAXPKTLEN+2))
	   { ppp_pty_frame[ppp_pty_flen++] = c;
	     ppp_pty_fcs = PPP_FCSCHAR(ppp_pty_fcs,c);
	   }
	  break;
     }
  }
}

static void process_ppp_death(void)
{
 while (wait3(0,WNOHANG,0) > 0) ;
 p(P_INFO,"exiting on ppp death\n");
 close(pppdeathpipe);
 send_padt();
 exit(0);
/*
 state = S_INITIATE;
 gettimeofday(&timeout,0);
 timeout.tv_sec = 1;
*/
}

static void handleargs(int ac, char **av)
{
 int skip;
 int errs;

 skip = 0;
 errs = 0;
 for (ac--,av++;ac;ac--,av++)
  { if (skip > 0)
     { skip --;
       continue;
     }
    if (**av != '-')
     { if (! ifname)
	{ ifname = *av;
	}
       else if (! pppname)
	{ pppname = *av;
	}
       else
	{ fprintf(stderr,"%s: extra argument `%s'\n",__progname,*av);
	  errs ++;
	}
       continue;
     }
    if (0)
     {
needarg:;
       fprintf(stderr,"%s: %s needs a following argument\n",__progname,*av);
       errs ++;
       continue;
     }
#define WANTARG() do { if (++skip >= ac) goto needarg; } while (0)
    if (!strcmp(*av,"-if"))
     { WANTARG();
       ifname = av[skip];
       continue;
     }
    else if (!strcmp(*av,"-name"))
     { WANTARG();
       pppname = av[skip];
       continue;
     }
    else if (!strcmp(*av,"-debug"))
     { WANTARG();
	    if (!strcasecmp(av[skip],"none"))  plevel = P_NONE;
       else if (!strcasecmp(av[skip],"warn"))  plevel = P_WARN;
       else if (!strcasecmp(av[skip],"note"))  plevel = P_NOTE;
       else if (!strcasecmp(av[skip],"info"))  plevel = P_INFO;
       else if (!strcasecmp(av[skip],"debug")) plevel = P_DEBUG;
       else
	{ fprintf(stderr,"%s: bad -debug arg `%s'\n",__progname,av[skip]);
	  fprintf(stderr,"%s:  valid args are: none warn note info debug\n",__progname);
	  errs ++;
	}
       continue;
     }
    else if (!strcmp(*av,"-pppdebug"))
     { pppdebug = 1;
       continue;
     }
#undef WANTARG
    fprintf(stderr,"%s: unrecognized option `%s'\n",__progname,*av);
    errs ++;
  }
 if (! ifname)
  { fprintf(stderr,"%s: must specify an interface name\n",__progname);
    errs ++;
  }
 if (! pppname)
  { fprintf(stderr,"%s: must specify PPP name\n",__progname);
    errs ++;
  }
 if (errs) exit(1);
}

int main(int, char **);
int main(int ac, char **av)
{
 handleargs(ac,av);
 setup();
 state = S_INITIATE;
 gettimeofday(&timeout,0);
 while (1)
  { struct timeval *seltimeout;
    struct timeval delta;
    fd_set rfds;
    int srv;
    seltimeout = 0;
    FD_ZERO(&rfds);
    FD_SET(bpffd,&rfds);
    switch (state)
     { case S_INITIATE:
       case S_REQUEST:
	   { struct timeval now;
	     gettimeofday(&now,0);
	     if ( (now.tv_sec > timeout.tv_sec) ||
		  ( (now.tv_sec == timeout.tv_sec) &&
		    (now.tv_usec >= timeout.tv_usec) ) )
	      { delta.tv_sec = 0;
		delta.tv_usec = 0;
	      }
	     else if (timeout.tv_usec >= now.tv_usec)
	      { delta.tv_sec = timeout.tv_sec - now.tv_sec;
		delta.tv_usec = timeout.tv_usec - now.tv_usec;
	      }
	     else
	      { delta.tv_sec = timeout.tv_sec - 1 - now.tv_sec;
		delta.tv_usec = timeout.tv_usec + 1000000 - now.tv_usec;
	      }
	     seltimeout = &delta;
	   }
	  break;
       case S_SESSION:
	  FD_SET(ptymfd,&rfds);
	  FD_SET(pppdeathpipe,&rfds);
	  break;
     }
    srv = select(FD_SETSIZE,&rfds,0,0,seltimeout);
    if (srv < 0)
     { if (errno == EINTR) continue;
       fprintf(stderr,"%s: select: %s\n",__progname,strerror(errno));
       exit(1);
     }
    if (srv == 0)
     { process_timeout();
     }
    else
     { if (FD_ISSET(bpffd,&rfds)) process_bpf_input();
       if (state == S_SESSION)
	{ if (FD_ISSET(ptymfd,&rfds)) process_pty_input();
	  if (FD_ISSET(pppdeathpipe,&rfds)) process_ppp_death();
	}
     }
  }
}