Reentrancy: Avoid reentrant callbacks

[adns] / src / setup.c

/*
 * setup.c
 * - configuration file parsing
 * - management of global state
 */
/*
 *  This file is part of adns, which is
 *    Copyright (C) 1997-2000,2003,2006  Ian Jackson
 *    Copyright (C) 1999-2000,2003,2006  Tony Finch
 *    Copyright (C) 1991 Massachusetts Institute of Technology
 *  (See the file INSTALL for full details.)
 *  
 *  This program is free software; you can redistribute it and/or modify
 *  it under the terms of the GNU General Public License as published by
 *  the Free Software Foundation; either version 2, or (at your option)
 *  any later version.
 *  
 *  This program is distributed in the hope that it will be useful,
 *  but WITHOUT ANY WARRANTY; without even the implied warranty of
 *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 *  GNU General Public License for more details.
 *  
 *  You should have received a copy of the GNU General Public License
 *  along with this program; if not, write to the Free Software Foundation,
 *  Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA. 
 */

#include <stdlib.h>
#include <errno.h>
#include <limits.h>
#include <unistd.h>
#include <fcntl.h>

#include <sys/types.h>
#include <netdb.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/inet.h>

#include "internal.h"

static void readconfig(adns_state ads, const char *filename, int warnmissing);

static void addserver(adns_state ads, const struct sockaddr *sa, int n) {
  int i;
  adns_rr_addr *ss;
  char buf[ADNS_ADDR2TEXT_BUFLEN];
  
  for (i=0; i<ads->nservers; i++) {
    if (adns__sockaddr_equal_p(sa, &ads->servers[i].addr.sa)) {
      adns__debug(ads,-1,0,"duplicate nameserver %s ignored",
		  adns__sockaddr_ntoa(sa, buf));
      return;
    }
  }
  
  if (ads->nservers>=MAXSERVERS) {
    adns__diag(ads,-1,0,"too many nameservers, ignoring %s",
	       adns__sockaddr_ntoa(sa, buf));
    return;
  }

  ss= ads->servers+ads->nservers;
  assert(n <= sizeof(ss->addr));
  ss->len = n;
  memcpy(&ss->addr, sa, n);
  ads->nservers++;
}

static void freesearchlist(adns_state ads) {
  if (ads->nsearchlist) free(*ads->searchlist);
  free(ads->searchlist);
}

static void saveerr(adns_state ads, int en) {
  if (!ads->configerrno) ads->configerrno= en;
}

static void configparseerr(adns_state ads, const char *fn, int lno,
			   const char *fmt, ...) {
  va_list al;

  saveerr(ads,EINVAL);
  if (!ads->logfn || (ads->iflags & adns_if_noerrprint)) return;

  if (lno==-1) adns__lprintf(ads,"adns: %s: ",fn);
  else adns__lprintf(ads,"adns: %s:%d: ",fn,lno);
  va_start(al,fmt);
  adns__vlprintf(ads,fmt,al);
  va_end(al);
  adns__lprintf(ads,"\n");
}

static int nextword(const char **bufp_io, const char **word_r, int *l_r) {
  const char *p, *q;

  p= *bufp_io;
  while (ctype_whitespace(*p)) p++;
  if (!*p) return 0;

  q= p;
  while (*q && !ctype_whitespace(*q)) q++;

  *l_r= q-p;
  *word_r= p;
  *bufp_io= q;

  return 1;
}

static void ccf_nameserver(adns_state ads, const char *fn,
			   int lno, const char *buf) {
  adns_rr_addr a;
  char addrbuf[ADNS_ADDR2TEXT_BUFLEN];
  int err;

  a.len= sizeof(a.addr);
  err= adns_text2addr(buf,DNS_PORT, 0, &a.addr.sa,&a.len);
  switch (err) {
  case 0:
    break;
  case EINVAL:
    configparseerr(ads,fn,lno,"invalid nameserver address `%s'",buf);
    return;
  default:
    configparseerr(ads,fn,lno,"failed to parse nameserver address `%s': %s",
		   buf,strerror(err));
    return;
  }
  adns__debug(ads,-1,0,"using nameserver %s",
	      adns__sockaddr_ntoa(&a.addr.sa, addrbuf));
  addserver(ads,&a.addr.sa,a.len);
}

static void ccf_search(adns_state ads, const char *fn,
		       int lno, const char *buf) {
  const char *bufp, *word;
  char *newchars, **newptrs, **pp;
  int count, tl, l;

  if (!buf) return;

  bufp= buf;
  count= 0;
  tl= 0;
  while (nextword(&bufp,&word,&l)) { count++; tl += l+1; }

  newptrs= malloc(sizeof(char*)*count);
  if (!newptrs) { saveerr(ads,errno); return; }

  newchars= malloc(tl);
  if (!newchars) { saveerr(ads,errno); free(newptrs); return; }

  bufp= buf;
  pp= newptrs;
  while (nextword(&bufp,&word,&l)) {
    *pp++= newchars;
    memcpy(newchars,word,l);
    newchars += l;
    *newchars++ = 0;
  }

  freesearchlist(ads);
  ads->nsearchlist= count;
  ads->searchlist= newptrs;
}

static int gen_pton(const char *text, int *af_io, union gen_addr *a) {
  adns_rr_addr addr;
  int err;

  addr.len= sizeof(addr.addr);
  err= adns_text2addr(text,0, adns_qf_addrlit_scope_forbid,
		      &addr.addr.sa, &addr.len);
  if (err) { assert(err == EINVAL); return 0; }
  if (*af_io == AF_UNSPEC) *af_io= addr.addr.sa.sa_family;
  else if (*af_io != addr.addr.sa.sa_family) return 0;
  adns__sockaddr_extract(&addr.addr.sa, a, 0);
  return 1;
}

static void ccf_sortlist(adns_state ads, const char *fn,
			 int lno, const char *buf) {
  const char *word;
  char tbuf[200], *slash, *ep;
  const char *maskwhat;
  struct sortlist *sl;
  int l;
  int af;
  int initial= -1;

  if (!buf) return;
  
  ads->nsortlist= 0;
  while (nextword(&buf,&word,&l)) {
    if (ads->nsortlist >= MAXSORTLIST) {
      adns__diag(ads,-1,0,"too many sortlist entries,"
		 " ignoring %.*s onwards",l,word);
      return;
    }

    if (l >= sizeof(tbuf)) {
      configparseerr(ads,fn,lno,"sortlist entry `%.*s' too long",l,word);
      continue;
    }
    
    memcpy(tbuf,word,l); tbuf[l]= 0;
    slash= strchr(tbuf,'/');
    if (slash) *slash++= 0;

    sl= &ads->sortlist[ads->nsortlist];
    af= AF_UNSPEC;
    if (!gen_pton(tbuf, &af, &sl->base)) {
      configparseerr(ads,fn,lno,"invalid address `%s' in sortlist",tbuf);
      continue;
    }

    if (slash) {
      if (slash[strspn(slash, "0123456789")]) {
	maskwhat = "mask";
	if (!gen_pton(slash,&af,&sl->mask)) {
	  configparseerr(ads,fn,lno,"invalid mask `%s' in sortlist",slash);
	  continue;
	}
      } else {
	maskwhat = "prefix length";
	initial= strtoul(slash,&ep,10);
	if (*ep || initial>adns__addr_width(af)) {
	  configparseerr(ads,fn,lno,"mask length `%s' invalid",slash);
	  continue;
	}
	adns__prefix_mask(af, initial, &sl->mask);
      }
    } else {
      maskwhat = "implied prefix length";
      initial= adns__guess_prefix_length(af, &sl->base);
      if (initial < 0) {
	configparseerr(ads,fn,lno, "network address `%s'"
		       " in sortlist is not in classed ranges,"
		       " must specify mask explicitly", tbuf);
	continue;
      }
      adns__prefix_mask(af, initial, &sl->mask);
    }

    if (!adns__addr_match_p(af,&sl->base, af,&sl->base,&sl->mask)) {
      if (initial >= 0) {
	configparseerr(ads,fn,lno, "%s %d in sortlist"
		       " overlaps address `%s'",maskwhat,initial,tbuf);
      } else {
	configparseerr(ads,fn,lno, "%s `%s' in sortlist"
		       " overlaps address `%s'",maskwhat,slash,tbuf);
      }
      continue;
    }

    sl->af= af;
    ads->nsortlist++;
  }
}

static void ccf_options(adns_state ads, const char *fn,
			int lno, const char *buf) {
  const char *word;
  char *ep;
  unsigned long v;
  int l;

  if (!buf) return;

  while (nextword(&buf,&word,&l)) {
    if (l==5 && !memcmp(word,"debug",5)) {
      ads->iflags |= adns_if_debug;
      continue;
    }
    if (l>=6 && !memcmp(word,"ndots:",6)) {
      v= strtoul(word+6,&ep,10);
      if (l==6 || ep != word+l || v > INT_MAX) {
	configparseerr(ads,fn,lno,"option `%.*s' malformed"
		       " or has bad value",l,word);
	continue;
      }
      ads->searchndots= v;
      continue;
    }
    if (l>=12 && !memcmp(word,"adns_checkc:",12)) {
      if (!strcmp(word+12,"none")) {
	ads->iflags &= ~adns_if_checkc_freq;
	ads->iflags |= adns_if_checkc_entex;
      } else if (!strcmp(word+12,"entex")) {
	ads->iflags &= ~adns_if_checkc_freq;
	ads->iflags |= adns_if_checkc_entex;
      } else if (!strcmp(word+12,"freq")) {
	ads->iflags |= adns_if_checkc_freq;
      } else {
	configparseerr(ads,fn,lno, "option adns_checkc has bad value `%s' "
		       "(must be none, entex or freq", word+12);
      }
      continue;
    }
    adns__diag(ads,-1,0,"%s:%d: unknown option `%.*s'", fn,lno, l,word);
  }
}

static void ccf_clearnss(adns_state ads, const char *fn,
			 int lno, const char *buf) {
  ads->nservers= 0;
}

static void ccf_include(adns_state ads, const char *fn,
			int lno, const char *buf) {
  if (!*buf) {
    configparseerr(ads,fn,lno,"`include' directive with no filename");
    return;
  }
  readconfig(ads,buf,1);
}

static void ccf_lookup(adns_state ads, const char *fn, int lno,
		       const char *buf) {
  int found_bind=0;
  const char *word;
  int l;

  if (!*buf) {
    configparseerr(ads,fn,lno,"`lookup' directive with no databases");
    return;
  }

  while (nextword(&buf,&word,&l)) {
    if (l==4 && !memcmp(word,"bind",4)) {
      found_bind=1;
    } else if (l==4 && !memcmp(word,"file",4)) {
      /* ignore this and hope /etc/hosts is not essential */
    } else if (l==2 && !memcmp(word,"yp",2)) {
      adns__diag(ads,-1,0,"%s:%d: yp lookups not supported by adns", fn,lno);
      found_bind=-1;
    } else {
      adns__diag(ads,-1,0,"%s:%d: unknown `lookup' database `%.*s'",
		 fn,lno, l,word);
      found_bind=-1;
    }
  }
  if (!found_bind)
    adns__diag(ads,-1,0,"%s:%d: `lookup' specified, but not `bind'", fn,lno);
}

static const struct configcommandinfo {
  const char *name;
  void (*fn)(adns_state ads, const char *fn, int lno, const char *buf);
} configcommandinfos[]= {
  { "nameserver",        ccf_nameserver  },
  { "domain",            ccf_search      },
  { "search",            ccf_search      },
  { "sortlist",          ccf_sortlist    },
  { "options",           ccf_options     },
  { "clearnameservers",  ccf_clearnss    },
  { "include",           ccf_include     },
  { "lookup",            ccf_lookup      }, /* OpenBSD */
  {  0                                   }
};

typedef union {
  FILE *file;
  const char *text;
} getline_ctx;

static int gl_file(adns_state ads, getline_ctx *src_io, const char *filename,
		   int lno, char *buf, int buflen) {
  FILE *file= src_io->file;
  int c, i;
  char *p;

  p= buf;
  buflen--;
  i= 0;
    
  for (;;) { /* loop over chars */
    if (i == buflen) {
      adns__diag(ads,-1,0,"%s:%d: line too long, ignored",filename,lno);
      goto x_badline;
    }
    c= getc(file);
    if (!c) {
      adns__diag(ads,-1,0,"%s:%d: line contains nul, ignored",filename,lno);
      goto x_badline;
    } else if (c == '\n') {
      break;
    } else if (c == EOF) {
      if (ferror(file)) {
	saveerr(ads,errno);
	adns__diag(ads,-1,0,"%s:%d: read error: %s",
		   filename,lno,strerror(errno));
	return -1;
      }
      if (!i) return -1;
      break;
    } else {
      *p++= c;
      i++;
    }
  }

  *p++= 0;
  return i;

 x_badline:
  saveerr(ads,EINVAL);
  while ((c= getc(file)) != EOF && c != '\n');
  return -2;
}

static int gl_text(adns_state ads, getline_ctx *src_io, const char *filename,
		   int lno, char *buf, int buflen) {
  const char *cp= src_io->text;
  int l;

  if (!cp || !*cp) return -1;

  if (*cp == ';' || *cp == '\n') cp++;
  l= strcspn(cp,";\n");
  src_io->text = cp+l;

  if (l >= buflen) {
    adns__diag(ads,-1,0,"%s:%d: line too long, ignored",filename,lno);
    saveerr(ads,EINVAL);
    return -2;
  }
    
  memcpy(buf,cp,l);
  buf[l]= 0;
  return l;
}

static void readconfiggeneric(adns_state ads, const char *filename,
			      int (*getline)(adns_state ads, getline_ctx*,
					     const char *filename, int lno,
					     char *buf, int buflen),
			      /* Returns >=0 for success, -1 for EOF or error
			       * (error will have been reported), or -2 for
			       * bad line was encountered, try again.
			       */
			      getline_ctx gl_ctx) {
  char linebuf[2000], *p, *q;
  int lno, l, dirl;
  const struct configcommandinfo *ccip;

  for (lno=1;
       (l= getline(ads,&gl_ctx, filename,lno, linebuf,sizeof(linebuf))) != -1;
       lno++) {
    if (l == -2) continue;
    while (l>0 && ctype_whitespace(linebuf[l-1])) l--;
    linebuf[l]= 0;
    p= linebuf;
    while (ctype_whitespace(*p)) p++;
    if (*p == '#' || *p == ';' || !*p) continue;
    q= p;
    while (*q && !ctype_whitespace(*q)) q++;
    dirl= q-p;
    for (ccip=configcommandinfos;
	 ccip->name &&
	   !(strlen(ccip->name)==dirl && !memcmp(ccip->name,p,q-p));
	 ccip++);
    if (!ccip->name) {
      adns__diag(ads,-1,0,"%s:%d: unknown configuration directive `%.*s'",
		 filename,lno,(int)(q-p),p);
      continue;
    }
    while (ctype_whitespace(*q)) q++;
    ccip->fn(ads,filename,lno,q);
  }
}

static const char *instrum_getenv(adns_state ads, const char *envvar) {
  const char *value;

  value= getenv(envvar);
  if (!value) adns__debug(ads,-1,0,"environment variable %s not set",envvar);
  else adns__debug(ads,-1,0,"environment variable %s"
		   " set to `%s'",envvar,value);
  return value;
}

static void readconfig(adns_state ads, const char *filename, int warnmissing) {
  getline_ctx gl_ctx;
  
  gl_ctx.file= fopen(filename,"r");
  if (!gl_ctx.file) {
    if (errno == ENOENT) {
      if (warnmissing)
	adns__debug(ads,-1,0, "configuration file"
		    " `%s' does not exist",filename);
      return;
    }
    saveerr(ads,errno);
    adns__diag(ads,-1,0,"cannot open configuration file `%s': %s",
	       filename,strerror(errno));
    return;
  }

  readconfiggeneric(ads,filename,gl_file,gl_ctx);
  
  fclose(gl_ctx.file);
}

static void readconfigtext(adns_state ads, const char *text,
			   const char *showname) {
  getline_ctx gl_ctx;
  
  gl_ctx.text= text;
  readconfiggeneric(ads,showname,gl_text,gl_ctx);
}
  
static void readconfigenv(adns_state ads, const char *envvar) {
  const char *filename;

  if (ads->iflags & adns_if_noenv) {
    adns__debug(ads,-1,0,"not checking environment variable `%s'",envvar);
    return;
  }
  filename= instrum_getenv(ads,envvar);
  if (filename) readconfig(ads,filename,1);
}

static void readconfigenvtext(adns_state ads, const char *envvar) {
  const char *textdata;

  if (ads->iflags & adns_if_noenv) {
    adns__debug(ads,-1,0,"not checking environment variable `%s'",envvar);
    return;
  }
  textdata= instrum_getenv(ads,envvar);
  if (textdata) readconfigtext(ads,textdata,envvar);
}


int adns__setnonblock(adns_state ads, int fd) {
  int r;
  
  r= fcntl(fd,F_GETFL,0); if (r<0) return errno;
  r |= O_NONBLOCK;
  r= fcntl(fd,F_SETFL,r); if (r<0) return errno;
  return 0;
}

static int init_begin(adns_state *ads_r, adns_initflags flags,
		      adns_logcallbackfn *logfn, void *logfndata) {
  adns_state ads;
  pid_t pid;
  
  ads= malloc(sizeof(*ads)); if (!ads) return errno;

  ads->iflags= flags;
  ads->logfn= logfn;
  ads->logfndata= logfndata;
  ads->configerrno= 0;
  LIST_INIT(ads->udpw);
  LIST_INIT(ads->tcpw);
  LIST_INIT(ads->childw);
  LIST_INIT(ads->output);
  LIST_INIT(ads->intdone);
  ads->forallnext= 0;
  ads->nextid= 0x311f;
  ads->nudp= 0;
  ads->tcpsocket= -1;
  adns__vbuf_init(&ads->tcpsend);
  adns__vbuf_init(&ads->tcprecv);
  ads->tcprecv_skip= 0;
  ads->nservers= ads->nsortlist= ads->nsearchlist= ads->tcpserver= 0;
  ads->searchndots= 1;
  ads->tcpstate= server_disconnected;
  timerclear(&ads->tcptimeout);
  ads->searchlist= 0;

  pid= getpid();
  ads->rand48xsubi[0]= pid;
  ads->rand48xsubi[1]= (unsigned long)pid >> 16;
  ads->rand48xsubi[2]= pid ^ ((unsigned long)pid >> 16);

  *ads_r= ads;
  return 0;
}

static int init_finish(adns_state ads) {
  struct sockaddr_in sin;
  struct protoent *proto;
  struct udpsocket *udp;
  int i, j;
  int r;
  
  if (!ads->nservers) {
    if (ads->logfn && ads->iflags & adns_if_debug)
      adns__lprintf(ads,"adns: no nameservers, using IPv4 localhost\n");
    memset(&sin, 0, sizeof(sin));
    sin.sin_family = AF_INET;
    sin.sin_port = htons(DNS_PORT);
    sin.sin_addr.s_addr = htonl(INADDR_LOOPBACK);
    addserver(ads,(struct sockaddr *)&sin, sizeof(sin));
  }

  proto= getprotobyname("udp"); if (!proto) { r= ENOPROTOOPT; goto x_free; }
  ads->nudp= 0;
  for (i=0; i<ads->nservers; i++) {
    if (adns__udpsocket_by_af(ads, ads->servers[i].addr.sa.sa_family))
      continue;
    assert(ads->nudp < MAXUDP);
    udp= &ads->udpsocket[ads->nudp];
    udp->af= ads->servers[i].addr.sa.sa_family;
    udp->fd= socket(udp->af,SOCK_DGRAM,proto->p_proto);
    if (udp->fd < 0) { r= errno; goto x_free; }
    ads->nudp++;
    r= adns__setnonblock(ads,udp->fd);
    if (r) { r= errno; goto x_closeudp; }
  }
  
  return 0;

 x_closeudp:
  for (j=0; j<ads->nudp; j++) close(ads->udpsocket[j].fd);
 x_free:
  free(ads);
  return r;
}

static void init_abort(adns_state ads) {
  if (ads->nsearchlist) {
    free(ads->searchlist[0]);
    free(ads->searchlist);
  }
  free(ads);
}

static void logfn_file(adns_state ads, void *logfndata,
		       const char *fmt, va_list al) {
  vfprintf(logfndata,fmt,al);
}

static int init_files(adns_state *ads_r, adns_initflags flags,
		      adns_logcallbackfn *logfn, void *logfndata) {
  adns_state ads;
  const char *res_options, *adns_res_options;
  int r;
  
  r= init_begin(&ads, flags, logfn, logfndata);
  if (r) return r;
  
  res_options= instrum_getenv(ads,"RES_OPTIONS");
  adns_res_options= instrum_getenv(ads,"ADNS_RES_OPTIONS");
  ccf_options(ads,"RES_OPTIONS",-1,res_options);
  ccf_options(ads,"ADNS_RES_OPTIONS",-1,adns_res_options);

  readconfig(ads,"/etc/resolv.conf",1);
  readconfig(ads,"/etc/resolv-adns.conf",0);
  readconfigenv(ads,"RES_CONF");
  readconfigenv(ads,"ADNS_RES_CONF");

  readconfigenvtext(ads,"RES_CONF_TEXT");
  readconfigenvtext(ads,"ADNS_RES_CONF_TEXT");

  ccf_options(ads,"RES_OPTIONS",-1,res_options);
  ccf_options(ads,"ADNS_RES_OPTIONS",-1,adns_res_options);

  ccf_search(ads,"LOCALDOMAIN",-1,instrum_getenv(ads,"LOCALDOMAIN"));
  ccf_search(ads,"ADNS_LOCALDOMAIN",-1,instrum_getenv(ads,"ADNS_LOCALDOMAIN"));

  if (ads->configerrno && ads->configerrno != EINVAL) {
    r= ads->configerrno;
    init_abort(ads);
    return r;
  }

  r= init_finish(ads);
  if (r) return r;

  adns__consistency(ads,0,cc_entex);
  *ads_r= ads;
  return 0;
}

int adns_init(adns_state *ads_r, adns_initflags flags, FILE *diagfile) {
  return init_files(ads_r, flags, logfn_file, diagfile ? diagfile : stderr);
}

static int init_strcfg(adns_state *ads_r, adns_initflags flags,
		       adns_logcallbackfn *logfn, void *logfndata,
		       const char *configtext) {
  adns_state ads;
  int r;

  r= init_begin(&ads, flags, logfn, logfndata);
  if (r) return r;

  readconfigtext(ads,configtext,"<supplied configuration text>");
  if (ads->configerrno) {
    r= ads->configerrno;
    init_abort(ads);
    return r;
  }

  r= init_finish(ads);  if (r) return r;
  adns__consistency(ads,0,cc_entex);
  *ads_r= ads;
  return 0;
}

int adns_init_strcfg(adns_state *ads_r, adns_initflags flags,
		     FILE *diagfile, const char *configtext) {
  return init_strcfg(ads_r, flags,
		     diagfile ? logfn_file : 0, diagfile,
		     configtext);
}

int adns_init_logfn(adns_state *newstate_r, adns_initflags flags,
		    const char *configtext /*0=>use default config files*/,
		    adns_logcallbackfn *logfn /*0=>logfndata is a FILE* */,
		    void *logfndata /*0 with logfn==0 => discard*/) {
  if (!logfn && logfndata)
    logfn= logfn_file;
  if (configtext)
    return init_strcfg(newstate_r, flags, logfn, logfndata, configtext);
  else
    return init_files(newstate_r, flags, logfn, logfndata);
}

void adns_finish(adns_state ads) {
  int i;
  adns__consistency(ads,0,cc_entex);
  for (;;) {
    if (ads->udpw.head) adns__cancel(ads->udpw.head);
    else if (ads->tcpw.head) adns__cancel(ads->tcpw.head);
    else if (ads->childw.head) adns__cancel(ads->childw.head);
    else if (ads->output.head) adns__cancel(ads->output.head);
    else if (ads->intdone.head) adns__cancel(ads->output.head);
    else break;
  }
  for (i=0; i<ads->nudp; i++) close(ads->udpsocket[i].fd);
  if (ads->tcpsocket >= 0) close(ads->tcpsocket);
  adns__vbuf_free(&ads->tcpsend);
  adns__vbuf_free(&ads->tcprecv);
  freesearchlist(ads);
  free(ads);
}

void adns_forallqueries_begin(adns_state ads) {
  adns__consistency(ads,0,cc_entex);
  ads->forallnext=
    ads->udpw.head ? ads->udpw.head :
    ads->tcpw.head ? ads->tcpw.head :
    ads->childw.head ? ads->childw.head :
    ads->output.head;
}
  
adns_query adns_forallqueries_next(adns_state ads, void **context_r) {
  adns_query qu, nqu;

  adns__consistency(ads,0,cc_entex);
  nqu= ads->forallnext;
  for (;;) {
    qu= nqu;
    if (!qu) return 0;
    if (qu->next) {
      nqu= qu->next;
    } else if (qu == ads->udpw.tail) {
      nqu=
	ads->tcpw.head ? ads->tcpw.head :
	ads->childw.head ? ads->childw.head :
	ads->output.head;
    } else if (qu == ads->tcpw.tail) {
      nqu=
	ads->childw.head ? ads->childw.head :
	ads->output.head;
    } else if (qu == ads->childw.tail) {
      nqu= ads->output.head;
    } else {
      nqu= 0;
    }
    if (!qu->parent) break;
  }
  ads->forallnext= nqu;
  if (context_r) *context_r= qu->ctx.ext;
  return qu;
}