/* This file is in the public domain. */

#include <stdio.h>
#include <errno.h>
#include <netdb.h>
#include <fcntl.h>
#include <ctype.h>
#include <unistd.h>
#include <stdarg.h>
#include <stdlib.h>
#include <strings.h>
#include <sys/stat.h>
#include <arpa/inet.h>
#include <netinet/in.h>
#include <sys/timersock.h>

extern const char *__progname;

#include "protocol.h"
#include "pollloop.h"

typedef struct ipaddr IPADDR;
typedef struct peer PEER;
typedef struct uplink UPLINK;
typedef struct listen LISTEN;
typedef struct public PUBLIC;
typedef struct isource ISOURCE;
typedef struct apstate APSTATE;

/*
 * State for parsing ADDR/PORT stuff.  This exists so that specific
 *  uses of the parser can tweak it in a failure callback.
 */
struct apstate {
  char *addr;
  char *port;
  struct addrinfo hints;
  } ;

/*
 * An item on the stack of includes for config files.
 */
struct isource {
  ISOURCE *link;
  char *file;
  FILE *f;
  int lno;
  } ;

/*
 * A listen-at point.
 */
struct listen {
  LISTEN *link;
  struct sockaddr *sa;
  int salen;
  char *txt;
  int fd;
  } ;

/*
 * An uplink point.  Each of these is somewhere we want to maintain a
 *  connection to.
 */
struct uplink {
  UPLINK *link;
  struct sockaddr *sa;
  int salen;
  char *txt;
  time_t stamp;
  PEER *peer;
  } ;

/*
 * A connection to a peer.
 *
 * These include connections which we have initiated but which have not
 *  yet completed at the socket layer and connections which have come
 *  up at the socket layer but have not passed crypto verification;
 *  they are just like other PEERs except that the callbacks for their
 *  poll IDs are unusual.
 */
struct peer {
  struct sockaddr *lclsa;
  int lclsalen;
  struct sockaddr *remsa;
  int remsalen;
  char *txt;
  int fd;
  int id;
  } ;

/*
 * An IP address, without a port number.
 */
struct ipaddr {
  int af;
  union {
    struct in_addr v4;
    struct in6_addr v6;
    } ;
  } ;

/*
 * The shared-cloudwide secret key, pointer and length.
 */
static unsigned char *ck;
static int cklen;

/*
 * This host's cloud ID.
 */
static unsigned char cid;

/*
 * This host's list of cloud IP addresses.
 */
static int ncipaddrs;
static IPADDR **cipaddrs;

/*
 * Boolean saying whether this host ignores PUBLIC packets.
 */
static int ignore_public;

/*
 * Stack of input sources.  Used when reading the config.
 */
static ISOURCE *isrc;

/*
 * Listening points.  The difference between types 1 and 2, and between
 *  types 4 and 3, is whether this list is empty or not.
 */
static LISTEN *listens;

/*
 * Uplink points.  Initially, these come from uplink declarations in
 *  the configuration; if ignore_public is false, the list is mutated
 *  as PUBLIC packets come in and timers expire.
 */
static UPLINK *uplinks;

/*
 * The list of PEERs.
 */
static int npeers;
static int apeers;
static PEER **peers;

/*
 * The fd and poll ID for the timer socket driving attempts to
 *  (re)connect to uplinks.
 */
static int pcfd;
static int pcid;

/*
 * The block ID for cleaning up dead PEERs, and a boolean indicating
 *  whether it might have work to do.
 */
static int peercleanup_id;
static int peercleanup_needed;

#define Cisspace(c) isspace((unsigned char)(c))

static void config_err(const char *, ...)
	__attribute__((__format__(__printf__,1,2),__noreturn__));
static void config_err(const char *fmt, ...)
{
 va_list ap;
 char *s;

 void dump_isrc_chain(ISOURCE *i)
  { if (i->link) dump_isrc_chain(i->link);
    fprintf(stderr," \"%s\", line %d:",i->file,i->lno);
  }

 va_start(ap,fmt);
 vasprintf(&s,fmt,ap);
 va_end(ap);
 fprintf(stderr,"%s:",__progname);
 dump_isrc_chain(isrc);
 fprintf(stderr," %s\n",s);
 free(s);
 exit(1);
}

static void config_err_cleanup(void (*)(void), const char *, ...)
	__attribute__((__format__(__printf__,2,3),__noreturn__));
static void config_err_cleanup(void (*cleanup)(void), const char *fmt, ...)
{
 va_list ap;
 char *s;

 void dump_isrc_chain(ISOURCE *i)
  { if (i->link) dump_isrc_chain(i->link);
    fprintf(stderr," \"%s\", line %d:",i->file,i->lno);
  }

 va_start(ap,fmt);
 vasprintf(&s,fmt,ap);
 va_end(ap);
 fprintf(stderr,"%s:",__progname);
 dump_isrc_chain(isrc);
 fprintf(stderr," %s\n",s);
 free(s);
 (*cleanup)();
 exit(1);
}

static void push_isrc(const char *s)
{
 FILE *f;
 ISOURCE *i;

 f = fopen(s,"r");
 if (f == 0) config_err("can't open config file %s: %s",s,strerror(errno));
 i = malloc(sizeof(ISOURCE));
 i->file = strdup(s);
 i->f = f;
 i->lno = 0;
 i->link = isrc;
 isrc = i;
}

static void pop_isrc(void)
{
 ISOURCE *i;

 i = isrc;
 isrc = i->link;
 free(i->file);
 fclose(i->f);
 free(i);
}

static struct addrinfo *crack_addr_port(const char *s, int flags, void (*custom)(APSTATE *))
{
 APSTATE st;
 const char *slash;
 int i;
 struct addrinfo *rv;

 slash = index(s,'/');
 if (! slash) config_err("no slash in ADDR/PORT");
 i = slash - s;
 st.addr = malloc(i+1);
 bcopy(s,st.addr,i);
 st.addr[i] = '\0';
 st.port = strdup(slash+1);
 st.hints.ai_flags = flags;
 st.hints.ai_family = PF_UNSPEC;
 st.hints.ai_socktype = SOCK_STREAM;
 st.hints.ai_protocol = 0;
 st.hints.ai_addrlen = 0;
 st.hints.ai_addr = 0;
 st.hints.ai_canonname = 0;
 st.hints.ai_next = 0;
 if (custom) (*custom)(&st);
 i = getaddrinfo(st.addr,st.port,&st.hints,&rv);
 if (i == 0) return(rv);
 config_err("lookup %s: %s",s,gai_strerror(i));
}

static void confline__at(const char *s)
{
 push_isrc(s);
}

static void confline_key(const char *s)
{
 free(ck);
 cklen = strlen(s);
 ck = malloc(cklen);
 bcopy(s,ck,cklen);
}

static void confline_keyfile(const char *s)
{
 int fd;
 struct stat stb;
 int r;
 int l;
 unsigned char *b;

 fd = open(s,O_RDONLY,0);
 if (fd < 0) config_err("open %s: %s",s,strerror(errno));
 if (fstat(fd,&stb) < 0) config_err("fstat %s: %s",s,strerror(errno));
 if (stb.st_size < 1) config_err("%s: empty",s);
 else if (stb.st_size > 65536)
  { fprintf(stderr,"%s: %s: too large, using only first 64K\n",__progname,s);
    l = 65536;
  }
 else
  { l = stb.st_size;
  }
 b = malloc(l);
 r = read(fd,b,l);
 if (r < 0) config_err("read from %s: %s",s,strerror(errno));
 if (r != l) config_err("read from %s: wanted %d, got %d",s,l,r);
 close(fd);
 free(ck);
 ck = b;
 cklen = l;
}

static void confline_id(const char *s)
{
 long int id;
 char *ep;

 id = strtol(s,&ep,0);
 if (ep != s) while (*ep && Cisspace(*ep)) ep ++;
 if (ep == s) config_err("bad/missing ID number");
 if  (* ep) config_err("junk after ID number");
 if ((id < 0) || (id > 255)) config_err("ID %ld is out of range",id);
 cid = id;
}

static void confline_ip(const char *s)
{
 IPADDR *a;

 a = malloc(sizeof(IPADDR));
 if (inet_pton(AF_INET,s,&a->v4) > 0)
  { a->af = AF_INET;
  }
 else if (inet_pton(AF_INET6,s,&a->v6) > 0)
  { a->af = AF_INET6;
  }
 else
  { config_err("unparseable IP `%s'",s);
  }
 cipaddrs = realloc(cipaddrs,(ncipaddrs+1)*sizeof(IPADDR *));
 cipaddrs[ncipaddrs++] = a;
}

static void confline_type(const char *s)
{
 if (! strcmp(s,"public"))
  { ignore_public = 0;
  }
 else if (! strcmp(s,"private"))
  { ignore_public = 1;
  }
 else
  { config_err("bad `type' value `%s'",s);
  }
}

static void capcustom_listen(APSTATE *s)
{
 if (! strcmp(s->addr,"*"))
  {
  }
 else if (! strcmp(s->addr,"*4"))
  { s->hints.ai_family = AF_INET;
  }
 else if (! strcmp(s->addr,"*6"))
  { s->hints.ai_family = AF_INET6;
  }
 else
  { return;
  }
 free(s->addr);
 s->addr = 0;
}

static void confline_listen(const char *s)
{
 struct addrinfo *ai0;
 struct addrinfo *ai;
 LISTEN *l;
 char *txt;
 int fd;
 int e;

 void errcleanup(void)
  { if (fd >= 0) close(fd);
    if (txt) free(txt);
    freeaddrinfo(ai0);
  }

 ai0 = crack_addr_port(s,AI_PASSIVE,&capcustom_listen);
 for (ai=ai0;ai;ai=ai->ai_next)
  { char hstr[NI_MAXHOST];
    char sstr[NI_MAXSERV];
    fd = -1;
    txt = 0;
    e = getnameinfo(ai->ai_addr,ai->ai_addrlen,&hstr[0],NI_MAXHOST,&sstr[0],NI_MAXSERV,NI_NUMERICHOST|NI_NUMERICSERV);
    if (e) config_err_cleanup(&errcleanup,"getnameinfo [for %s]: %s",s,gai_strerror(e));
    asprintf(&txt,"%s/%s",&hstr[0],&sstr[0]);
    fd = socket(ai->ai_family,ai->ai_socktype,ai->ai_protocol);
    if (fd < 0) continue;
    if (bind(fd,ai->ai_addr,ai->ai_addrlen) < 0)
     { config_err_cleanup(&errcleanup,"bind %s [for %s]: %s",txt,s,strerror(errno));
     }
    if (listen(fd,10) < 0)
     { config_err_cleanup(&errcleanup,"bind %s [for %s]: %s",txt,s,strerror(errno));
     }
    l = malloc(sizeof(LISTEN));
    l->sa = malloc(ai->ai_addrlen);
    bcopy(ai->ai_addr,l->sa,ai->ai_addrlen);
    l->salen = ai->ai_addrlen;
    l->txt = txt;
    l->fd = fd;
    l->link = listens;
    listens = l;
  }
}

static void confline_uplink(const char *s)
{
 struct addrinfo *ai0;
 struct addrinfo *ai;
 UPLINK *u;
 char *txt;
 int fd;
 int e;
 time_t now;

 void errcleanup(void)
  { if (fd >= 0) close(fd);
    if (txt) free(txt);
    freeaddrinfo(ai0);
  }

 time(&now);
 ai0 = crack_addr_port(s,0,0);
 for (ai=ai0;ai;ai=ai->ai_next)
  { char hstr[NI_MAXHOST];
    char sstr[NI_MAXSERV];
    fd = -1;
    txt = 0;
    e = getnameinfo(ai->ai_addr,ai->ai_addrlen,&hstr[0],NI_MAXHOST,&sstr[0],NI_MAXSERV,NI_NUMERICHOST|NI_NUMERICSERV);
    if (e) config_err_cleanup(&errcleanup,"getnameinfo [for %s]: %s",s,gai_strerror(e));
    asprintf(&txt,"%s/%s",&hstr[0],&sstr[0]);
    u = malloc(sizeof(UPLINK));
    u->sa = malloc(ai->ai_addrlen);
    bcopy(ai->ai_addr,u->sa,ai->ai_addrlen);
    u->salen = ai->ai_addrlen;
    u->txt = txt;
    u->stamp = now;
    u->peer = 0;
    u->link = uplinks;
    uplinks = u;
  }
}

static void config_line(const char *s)
{
 const char *k0;
 int kl;
 static struct {
	  const char *key;
	  void (*handler)(const char *);
	  int keylen;
	  } keys[] = { { "@", &confline__at },
		       { "key", &confline_key },
		       { "keyfile", &confline_keyfile },
		       { "id", &confline_id },
		       { "ip", &confline_ip },
		       { "type", &confline_type },
		       { "listen", &confline_listen },
		       { "uplink", &confline_uplink },
		       { 0 } };
 int i;

 if (keys[0].keylen == 0) for (i=0;keys[i].key;i++) keys[i].keylen = strlen(keys[i].key);
 while (*s && Cisspace(*s)) s ++;
 if (! *s) return;
 if (*s == '#') return;
 k0 = s;
 while (*s && !Cisspace(*s)) s ++;
 kl = s - k0;
 while (*s && Cisspace(*s)) s ++;
 for (i=0;keys[i].key;i++)
  { if ((kl == keys[i].keylen) && !bcmp(k0,keys[i].key,kl))
     { (*keys[i].handler)(s);
       return;
     }
  }
 config_err("unrecognized config key `%.*s'",kl,k0);
}

static void config_read(void)
{
 char *lb;
 int la;
 int ln;
 int c;

 void savec(char ch)
  { if (ln >= la) lb = realloc(lb,la=ln+16);
    lb[ln++] = ch;
  }

 void cl(void)
  { savec('\0');
    config_line(lb);
  }

 lb = 0;
 la = 0;
 ln = 0;
 while <"read"> (1)
  { c = getc(isrc->f);
    switch (c)
     { case EOF:
	  if (ln > 0) cl();
	  ln = 0;
	  pop_isrc();
	  if (! isrc) break <"read">;
	  break;
       case '\n':
	  cl();
	  ln = 0;
	  break;
       default:
	  if (ln == 0) isrc->lno ++;
	  savec(c);
	  break;
     }
  }
 free(lb);
}


static void readconf(const char *fn)
{
 isrc = 0;
 push_isrc(fn);
 config_read();
}

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 != '-')
     { fprintf(stderr,"%s: stray 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,"-config"))
     { WANTARG();
       readconf(av[skip]);
       continue;
     }
#undef WANTARG
    fprintf(stderr,"%s: unrecognized option `%s'\n",__progname,*av);
    errs ++;
  }
 if (errs) exit(1);
}

static void init(void)
{
 ck = 0;
 ncipaddrs = 0;
 cipaddrs = 0;
 ignore_public = -1;
 listens = 0;
 uplinks = 0;
 npeers = 0;
 apeers = 0;
 peers = 0;
}

static void set_defaults(void)
{
 if (ignore_public < 0)
  { fprintf(stderr,"%s: no `type' line configured\n",__progname);
    exit(1);
  }
 if (uplinks == 0)
  { fprintf(stderr,"%s: no uplinks configured\n",__progname);
    exit(1);
  }
}

static PEER *new_peer(void)
{
 PEER *p;

 if (npeers >= apeers) peers = realloc(peers,(apeers=npeers+1)*sizeof(PEER *));
 p = malloc(sizeof(PEER));
 p->lclsa = 0;
 p->remsa = 0;
 p->txt = 0;
 p->fd = -1;
 p->id = PL_NOID;
 peers[npeers++] = p;
 return(p);
}

static int peercleanup(void *arg __attribute__((__unused__)))
{
 int i;
 PEER *p;

 if (! peercleanup_needed) return(BLOCK_NIL);
 peercleanup_needed = 0;
 for (i=npeers;i>=0;i--)
  { p = peers[i];
    if (p->fd >= 0) continue;
    free(p->lclsa);
    free(p->remsa);
    free(p->txt);
    free(p);
    npeers --;
    if (i < npeers) peers[i] = peers[npeers];
  }
 return(BLOCK_LOOP);
}

static void peer_check_connect(void *pv)
{
 PEER *p;
 int e;
 socklen_t el;

 p = pv;
 remove_poll_id(p->id);
 p->id = PL_NOID;
 el = sizeof(e);
 if ( (getsockopt(p->fd,SOL_SOCKET,SO_ERROR,&e,&el) < 0) ||
      (el != sizeof(e)) ||
      e )
  { close(p->fd);
    p->fd = -1;
    peercleanup_needed = 1;
    return;
  }
 peer_connect_ok(p);
}

static void pcfd_rd(void *arg __attribute__((__unused__)))
{
 struct timersock_event ev;
 UPLINK *ul;
 PEER *p;
 int s;

 while (read(pcfd,&ev,sizeof(ev)) > 0) ;
 for (ul=uplinks;ul;ul=ul->link)
  { if (ul->peer) continue;
    s = socket(ul->sa->sa_family,SOCK_STREAM,0);
    if (s < 0) continue;
    fcntl(s,F_SETFL,fcntl(s,F_GETFL,0)|O_NONBLOCK);
    p = new_peer();
    p->fd = s;
    p->id = PL_NOID;
    p->remsa = malloc(ul->salen);
    bcopy(ul->sa,p->remsa,ul->salen);
    p->remsalen = ul->salen;
    if (connect(s,p->remsa,p->remsalen) < 0)
     { if (errno == EINPROGRESS)
	{ p->id = add_poll_fd(s,&rwtest_always,&rwtest_never,0,&peer_check_connect,p);
	}
       else
	{ close(s);
	  p->fd = -1;
	  peercleanup_needed = 1;
	  continue;
	}
     }
    else
     { peer_connect_ok(p);
     }
  }
}

static void startup(void)
{
 struct itimerval itv;

 init_polling();
 pcfd = socket(AF_TIMER,SOCK_STREAM,0);
 itv.it_value.tv_sec = 1;
 itv.it_value.tv_usec = 0;
 itv.it_interval.tv_sec = 60;
 itv.it_interval.tv_usec = 0;
 write(pcfd,&itv,sizeof(itv));
 pcid = add_poll_fd(pcfd,&rwtest_always,&rwtest_never,&pcfd_rd,0,0);
 peercleanup_id = add_block_fn(&peercleanup,0);
 peercleanup_needed = 0;
}

int main(int, char **);
int main(int ac, char **av)
{
 init();
 handleargs(ac,av);
 set_defaults();
 startup();
 return(0);
}