overhaul the dns farm: cut its size in half

i've eliminated the master dns process, so now the workers just
act like regular connections and are handled by the normal pollarray.

everything seems to still work. ;)


svn:r327

4 files changed, 217 insertions, 434 deletions

diff --git a/src/or/connection.c b/src/or/connection.c
index 26ee19527..bb7f5e8ec 100644
--- a/src/or/connection.c
+++ b/src/or/connection.c
@@ -545,7 +545,7 @@ int connection_process_inbuf(connection_t *conn) {
       return connection_edge_process_inbuf(conn);
     case CONN_TYPE_DIR:
       return connection_dir_process_inbuf(conn);
-    case CONN_TYPE_DNSMASTER:
+    case CONN_TYPE_DNSWORKER:
       return connection_dns_process_inbuf(conn); 
     default:
       log(LOG_DEBUG,"connection_process_inbuf() got unexpected conn->type.");
@@ -686,7 +686,7 @@ int connection_finished_flushing(connection_t *conn) {
       return connection_edge_finished_flushing(conn);
     case CONN_TYPE_DIR:
       return connection_dir_finished_flushing(conn);
-    case CONN_TYPE_DNSMASTER:
+    case CONN_TYPE_DNSWORKER:
       return connection_dns_finished_flushing(conn);
     default:
       log(LOG_DEBUG,"connection_finished_flushing() got unexpected conn->type.");
diff --git a/src/or/dns.c b/src/or/dns.c
index c9668f096..562eb1cab 100644
--- a/src/or/dns.c
+++ b/src/or/dns.c
@@ -3,407 +3,21 @@
 /* $Id$ */
 
 #include "or.h"
+#include "tree.h"
 
 #define MAX_ADDRESSLEN 256
 
-#define MAX_DNSSLAVES 50
-#define MIN_DNSSLAVES 3 /* 1 for the tor process, 3 slaves */
-
-struct slave_data_t {
-  int fd; /* socket to talk on */
-  int num_processed; /* number of times we've used this slave */
-  char busy; /* whether this slave currently has a task */
-  char question[MAX_ADDRESSLEN]; /* the hostname that we're resolving */
-  unsigned char question_len; /* how many bytes in question */
-  char answer[MAX_ADDRESSLEN]; /* the answer to the question */
-  unsigned char answer_len; /* how many bytes in answer */
-};
-
-struct slave_data_t slave_data[MAX_DNSSLAVES+1];
-struct pollfd poll_data[MAX_DNSSLAVES+1];
-
-static int dns_spawn_slave(void);
-static int dns_read_block(int fd, char *string, unsigned char *len);
-static int dns_write_block(int fd, char *string, unsigned char len);
-static int dns_read_tor_question(int index);
-static int dns_read_slave_response(int index);
-static int dns_find_idle_slave(int max);
-static int dns_assign_to_slave(int from, int to);
-static int dns_master_to_tor(int from, int to);
-static void dns_master_main(int fd);
-static int dns_tor_to_master(connection_t *exitconn);
-static int dns_found_answer(char *question, uint32_t answer, uint32_t valid);
-
-int connection_dns_finished_flushing(connection_t *conn) {
-
-  assert(conn && conn->type == CONN_TYPE_DNSMASTER);
-
-  connection_stop_writing(conn);
-
-  return 0;
-}
-
-int connection_dns_process_inbuf(connection_t *conn) {
-  unsigned char length;
-  char buf[MAX_ADDRESSLEN];
-  char *question;
-  uint32_t answer;
-
-  assert(conn && conn->type == CONN_TYPE_DNSMASTER);
-  assert(conn->state == DNSMASTER_STATE_OPEN);
-
-  if(conn->inbuf_reached_eof) {
-    log(LOG_ERR,"connection_dns_process_inbuf(): Read eof. No more dnsmaster!");
-    return -1;
-  }
-
-  assert(conn->inbuf);
-
-  if(conn->inbuf_datalen <= 0)
-    return 0;
-
-  /* peek into the inbuf, so we can check if it's all here */
-  length = *conn->inbuf; /* warning: abstraction violation :( */
-  assert(length < 240);
-
-  if(conn->inbuf_datalen < 1+length) { /* entire answer available? */
-    log(LOG_INFO,"connection_dns_process_inbuf(): %d available, waiting for %d.", conn->inbuf_datalen, length+1);
-    return 0; /* not yet */
-  }
-
-  if(connection_fetch_from_buf(buf,1+length,conn) < 0) {
-    log(LOG_ERR,"connection_dns_process_inbuf(): Broken inbuf. No more dnsmaster!");
-    return -1;
-  }
- 
-  question = buf+1;
-  log(LOG_DEBUG,"connection_dns_process_inbuf(): length %d, question '%s', strlen question %d", length, question, strlen(question));
-  assert(length == 4 + strlen(question) + 1);
-
-  answer = *(uint32_t *)(buf+1+length-4);
-  dns_found_answer(question, answer, (answer != 0));
-  return connection_process_inbuf(conn); /* process the remainder of the buffer */
-}
-
-/* return -1 if error, else the fd that can talk to the dns master */
-int dns_master_start(void) {
-  connection_t *conn;
-  pid_t pid;
-  int fd[2];
-
-  if(socketpair(AF_UNIX, SOCK_STREAM, 0, fd) < 0) {
-    log(LOG_ERR,"dns_master_start(): socketpair failed.");
-    return -1;
-  }
-
-  pid = fork();
-  if(pid < 0) {
-    log(LOG_ERR,"dns_master_start(): fork failed.");
-    return -1;
-  }
-  if(pid == 0) { /* i'm the child */
-    log(LOG_DEBUG,"dns_master_start(): child says fd0 %d, fd1 %d.", fd[0], fd[1]);
-    close(fd[0]);
-    dns_master_main(fd[1]);
-    assert(0); /* never gets here */
-  }
-
-  /* i'm the parent */
-
-  close(fd[1]);
-
-  fcntl(fd[0], F_SETFL, O_NONBLOCK); /* set s to non-blocking */
-
-  conn = connection_new(CONN_TYPE_DNSMASTER);
-  if(!conn) {
-    log(LOG_INFO,"dns_master_start(): connection_new failed. Giving up.");
-    /* XXX tell the dnsmaster to die */
-    return -1;
-  }
-
-  conn->s = fd[0];
-  conn->address = strdup("localhost");
-  conn->receiver_bucket = -1; /* edge connections don't do receiver buckets */
-  conn->bandwidth = -1;
-
-  if(connection_add(conn) < 0) { /* no space, forget it */
-    log(LOG_INFO,"dns_master_start(): connection_add failed. Giving up.");
-    connection_free(conn);
-    /* XXX tell the dnsmaster to die */    
-    return -1;
-  }
-
-  conn->state = DNSMASTER_STATE_OPEN;
-  connection_start_reading(conn);
-  log(LOG_INFO,"dns_master_start(): dns handler is spawned.");
-  return fd[0];
-}
-
-static void dns_slave_main(int fd) {
-  char question[MAX_ADDRESSLEN];
-  unsigned char question_len;
-  struct hostent *rent;
-
-  for(;;) {
-    if(dns_read_block(fd, question, &question_len) < 0) { /* the master wants us to die */
-      log(LOG_INFO,"dns_slave_main(): eof on read from master. Exiting.");
-      exit(0);
-    }
-
-    rent = gethostbyname(question);
-    if (!rent) { 
-      log(LOG_INFO,"dns_slave_main(): Could not resolve dest addr %s. Returning nulls.",question);
-      if(dns_write_block(fd, "\0\0\0\0", 4) < 0) {
-        log(LOG_INFO,"dns_slave_main(): writing to master failed. Exiting.");
-        exit(0);
-      }
-    } else {
-      if(dns_write_block(fd, rent->h_addr, rent->h_length) < 0) {
-        log(LOG_INFO,"dns_slave_main(): writing to master failed. Exiting.");
-        exit(0);
-      }
-      log(LOG_INFO,"dns_slave_main(): Answered question '%s'.",question);
-    }
-  }
-}
-
-static int dns_spawn_slave(void) {
-  pid_t pid;
-  int fd[2];
-
-  if(socketpair(AF_UNIX, SOCK_STREAM, 0, fd) < 0) {
-    perror("socketpair");
-    exit(1);
-  }
-
-  pid = fork();
-  if(pid < 0) {
-    perror("fork");
-    exit(1);
-  }
-  if(pid == 0) { /* i'm the child */
-    close(fd[0]);
-    dns_slave_main(fd[1]);
-    assert(0); /* never gets here */  
-  }
-
-  /* i'm the parent */
-  log(LOG_INFO,"dns_spawn_slave(): just spawned a slave."); // XXX change to debug
-  close(fd[1]);
-  return fd[0];
-}
-
-/* read a first byte from fd, put it into *len. Then read *len
- * bytes from fd and put it into string.
- * Return -1 if eof or read error or bad len, else return 0.
- */
-int dns_read_block(int fd, char *string, unsigned char *len) {
-  int read_result;
-
-  log(LOG_DEBUG,"dns_read_block(): Calling read to learn length (fd %d).", fd);
-  read_result = read(fd, len, 1);
-  log(LOG_DEBUG,"dns_read_block(): read finished, returned %d", read_result);
-  if (read_result < 0) {
-    log(LOG_INFO,"dns_read_block(): read len returned error");
-    return -1;
-  } else if (read_result == 0) {
-    log(LOG_INFO,"dns_read_block(): Encountered eof reading len");
-    return -1;
-  } else if (*len <= 0) {
-    log(LOG_INFO,"dns_read_block(): len not >0");
-    return -1;
-  }
-
-  log(LOG_DEBUG,"dns_read_block(): Calling read to get string, length %u.", *len);
-  read_result = read(fd, string, *len);
-  if (read_result < 0) {
-    log(LOG_INFO,"dns_read_block(): read string returned error");
-    return -1;
-  } else if (read_result == 0) {
-    log(LOG_INFO,"dns_read_block(): Encountered eof reading string");
-    return -1;
-  }
-
-  string[*len] = 0; /* null terminate it, just in case */
-//  log(LOG_INFO,"dns_read_block(): Read '%s', len %u.",string,*len);
-  return 0;
-}
-
-/* write ("%c%s", string, len) onto fd */
-static int dns_write_block(int fd, char *string, unsigned char len) {
-  int write_result;
-  int written=0;
-  char tmp[257];
-
-  assert(len <= 250);
-  tmp[0] = len;
-  memcpy(tmp+1, string, len);
-  log(LOG_DEBUG,"dns_write_block(): writing length %u, fd %d.", len, fd);
-
-  while(written < len+1) {
-    write_result = write(fd, tmp, len+1-written);
-    if (write_result < 0) {
-      return -1;
-    }
-    written += write_result;
-  }
-
-  return 0;
-}
-
-/* pull in question. block until we've read everything. 
- * return -1 if eof. */
-static int dns_read_tor_question(int index) {
-
-  log(LOG_DEBUG,"dns_read_tor_question(): Pulling question from tor");
-  if(dns_read_block(slave_data[index].fd,
-                    slave_data[index].question,
-                    &slave_data[index].question_len) < 0)
-    return -1;
-
-//  log(LOG_INFO,"dns_read_tor_question(): Read question '%s'",slave_data[index].question);
-  return 0;
-}
-
-/* pull in answer. block until we've read it. return -1 if eof. */
-static int dns_read_slave_response(int index) {
-
-  if(dns_read_block(slave_data[index].fd,
-                    slave_data[index].answer,
-                    &slave_data[index].answer_len) < 0)
-    return -1;
-
-  return 0;
-}
-
-static int dns_find_idle_slave(int max) {
-  int i;
-
-  for(i=1;i<max;i++)
-    if(slave_data[i].busy == 0) {
-      log(LOG_DEBUG,"dns_find_idle_slave(): slave %d is chosen.",i);
-      return i;
-    }
-
-  assert(0); /* should never get here */
-  return 0;
-}
-
-static int dns_assign_to_slave(int from, int to) {
-
-  slave_data[to].question_len = slave_data[from].question_len;
-  memcpy(slave_data[to].question, slave_data[from].question, slave_data[from].question_len);
-
-//  slave_data[from].question_len = 0;
-
-  log(LOG_DEBUG,"dns_assign_to_slave(): from index %d to %d (writing fd %d)",from,to,slave_data[to].fd);
-  if(dns_write_block(slave_data[to].fd,
-                     slave_data[to].question,
-                     slave_data[to].question_len) < 0) {
-    log(LOG_INFO,"dns_assign_to_slave(): writing to slave failed.");
-    return -1;
-  }
-
-  return 0;
-}
-
-static int dns_master_to_tor(int from, int to) {
-  char tmp[MAX_ADDRESSLEN*2];
-  unsigned char len;
-
-  len = slave_data[from].question_len+1+slave_data[from].answer_len;
-  memcpy(tmp, slave_data[from].question, slave_data[from].question_len);
-  tmp[slave_data[from].question_len] = 0; /* null terminate it */
-  memcpy(tmp+1+slave_data[from].question_len, slave_data[from].answer, slave_data[from].answer_len);
-
-  log(LOG_DEBUG,"dns_master_to_tor(): question is '%s', length %d",slave_data[from].question,slave_data[from].question_len);
-  log(LOG_DEBUG,"dns_master_to_tor(): answer is %d %d %d %d",
-    slave_data[from].answer[0],
-    slave_data[from].answer[1],
-    slave_data[from].answer[2],
-    slave_data[from].answer[3]);
-  assert(slave_data[from].answer_len == 4);
-  if(dns_write_block(slave_data[to].fd, tmp, len) < 0) {
-    log(LOG_INFO,"dns_master_to_tor(): writing to tor failed.");
-    return -1;
-  }
-
-  return 0;
-}
-
-static void dns_master_main(int fd) {
-  int nfds=1; /* the 0th index is the tor process, the rest are slaves */
-  int num_slaves_busy=0;
-  int num_slaves_needed = MIN_DNSSLAVES;
-  int poll_result, idle, i;
-
-  poll_data[0].fd = slave_data[0].fd = fd;
-  poll_data[0].events = POLLIN;
-
-  for(;;) { /* loop forever */
-
-    assert(num_slaves_needed < MAX_DNSSLAVES);
-    while(nfds-1 < num_slaves_needed) {
-      /* add another slave. */
-
-      i = nfds;
-      memset(&slave_data[i], 0, sizeof(struct slave_data_t));
-      memset(&poll_data[i], 0, sizeof(struct pollfd));
-      slave_data[i].fd = poll_data[i].fd = dns_spawn_slave();
-      poll_data[i].events = POLLIN; /* listen always, to prevent accidental deadlock */      
-      nfds++;
-    }
-
-    /* XXX later, decide on a timeout value, to catch wedged slaves */
-
-    poll_result = poll(poll_data, nfds, -1);
-    log(LOG_DEBUG,"dns_master_main(): Poll returned -- activity!");
-    for(i=0;i<nfds;i++) {
-      if(poll_data[i].revents & POLLIN) {
-        if(i==0) { /* note that we read only one question per poll loop */
-          if(dns_read_tor_question(i) >= 0) {
-            while(1) {
-              idle = dns_find_idle_slave(nfds);
-              if(dns_assign_to_slave(i, idle) >= 0)
-                break; /* successfully assigned to one */
-              /* XXX slave must die, recalc num slaves and num busy */
-            }
-            num_slaves_busy++; 
-          } else { /* error */
-            log(LOG_INFO,"dns_master_main(): dns_read_tor_question failed. Master dying.");
-            exit(1);
-          }
-        } else {
-          if(dns_read_slave_response(i) >= 0) {
-            if(dns_master_to_tor(i, 0) < 0) {
-              log(LOG_INFO,"dns_master_main(): dns_master_to_tor failed. Master dying.");
-              exit(1);
-            }
-            slave_data[i].busy = 0;
-            num_slaves_busy--;
-            poll_data[0].events = POLLIN; /* resume reading from tor if we'd stopped */
-          } else { /* error */
-            log(LOG_INFO,"dns_master_main(): dns_read_slave_response failed. Leaving slave stranded (FIXME)");
-          }
-        }
-      }
-    }
-    log(LOG_DEBUG,"dns_master_main(): Finished looping over fd's.");
-
-    if(num_slaves_busy >= num_slaves_needed) {
-      if(num_slaves_needed == MAX_DNSSLAVES-1)
-        poll_data[0].events = 0; /* stop reading from tor */
-      else
-        num_slaves_needed++;
-    }
-
-  }
-  assert(0); /* should never get here */
-}
+#define MAX_DNSWORKERS 50
+#define MIN_DNSWORKERS 3
 
+int num_workers=0;
+int num_workers_busy=0;
 
-
-#include "tree.h"
+static int dns_assign_to_worker(connection_t *exitconn);
+static int dns_found_answer(char *question, uint32_t answer);
+static void dnsworker_main(int fd);
+static int dns_spawn_worker(void);
+static void spawn_enough_workers(void);
 
 struct pending_connection_t {
   struct connection_t *conn;
@@ -433,14 +47,18 @@ static int compare_cached_resolves(struct cached_resolve *a, struct cached_resol
 SPLAY_PROTOTYPE(cache_tree, cached_resolve, node, compare_cached_resolves);
 SPLAY_GENERATE(cache_tree, cached_resolve, node, compare_cached_resolves);
 
-void init_cache_tree(void) {
+static void init_cache_tree(void) {
   SPLAY_INIT(&cache_root);
 }
 
+void dns_init(void) {
+  init_cache_tree();
+  spawn_enough_workers();
+}
 
-/* see if the question 'exitconn->address' has been answered. if so,
- * if resolve valid, put it into exitconn->addr and call
- * connection_exit_connect directly. If resolve failed, return -1.
+/* See if the question 'exitconn->address' has been answered. if so,
+ * if resolve valid, put it into exitconn->addr and exec to
+ * connection_exit_connect. If resolve failed, return -1.
  *
  * Else, if seen before and pending, add conn to the pending list,
  * and return 0.
@@ -485,50 +103,51 @@ int dns_resolve(connection_t *exitconn) {
     resolve->pending_connections = pending_connection;
 
     SPLAY_INSERT(cache_tree, &cache_root, resolve);
-    return dns_tor_to_master(exitconn);
+    return dns_assign_to_worker(exitconn);
   }
 
   assert(0);
   return 0; /* not reached; keep gcc happy */
 }
 
-static int dns_tor_to_master(connection_t *exitconn) {
+static int dns_assign_to_worker(connection_t *exitconn) {
   connection_t *dnsconn;
   unsigned char len;
-  int do_dns_directly=0;
+  struct hostent *rent;
+
+  spawn_enough_workers(); /* respawn here, to be sure there are enough */
 
-  dnsconn = connection_get_by_type(CONN_TYPE_DNSMASTER);
+  dnsconn = connection_get_by_type_state(CONN_TYPE_DNSWORKER, DNSWORKER_STATE_IDLE);
 
   if(!dnsconn) {
-    log(LOG_ERR,"dns_tor_to_master(): dns master nowhere to be found!");
-  }
+    log(LOG_INFO,"dns_assign_to_worker(): no idle dns workers. Doing it myself.");
 
-  if(!dnsconn || do_dns_directly) {
-    /* new version which does it all right here */
-    struct hostent *rent;
+    /* short version which does it all right here */
     rent = gethostbyname(exitconn->address);
     if (!rent) {
-      return dns_found_answer(exitconn->address, 0, 0);
+      return dns_found_answer(exitconn->address, 0);
     }
-    return dns_found_answer(exitconn->address, *(uint32_t *)rent->h_addr, 1);
+    return dns_found_answer(exitconn->address, *(uint32_t *)rent->h_addr);
   }
 
-  len = strlen(exitconn->address);
-  if(connection_write_to_buf(&len, 1, dnsconn) < 0) {
-    log(LOG_DEBUG,"dns_tor_to_master(): Couldn't write length.");
-    return -1;
-  }
+  dnsconn->address = strdup(exitconn->address);
+  dnsconn->state = DNSWORKER_STATE_BUSY;
+  num_workers_busy++;
 
-  if(connection_write_to_buf(exitconn->address, len, dnsconn) < 0) {
-    log(LOG_DEBUG,"dns_tor_to_master(): Couldn't write address.");
+  len = strlen(dnsconn->address);
+  /* FFFF we should have it retry if the first worker bombs out */
+  if(connection_write_to_buf(&len, 1, dnsconn) < 0 ||
+     connection_write_to_buf(dnsconn->address, len, dnsconn) < 0) {
+    log(LOG_NOTICE,"dns_assign_to_worker(): Write failed. Closing worker and failing resolve.");
+    dnsconn->marked_for_close = 1;
     return -1;
   }
 
-//  log(LOG_DEBUG,"dns_tor_to_master(): submitted '%s'", address);
+//  log(LOG_DEBUG,"dns_assign_to_worker(): submitted '%s'", exitconn->address);
   return 0;
 }
 
-static int dns_found_answer(char *question, uint32_t answer, uint32_t valid) {
+static int dns_found_answer(char *question, uint32_t answer) {
   struct pending_connection_t *pend;
   struct cached_resolve search;
   struct cached_resolve *resolve;
@@ -541,7 +160,7 @@ static int dns_found_answer(char *question, uint32_t answer, uint32_t valid) {
     return 0;
   }
 
-//  assert(resolve->state == CACHE_STATE_PENDING);
+  assert(resolve->state == CACHE_STATE_PENDING);
   /* XXX this is a bug which hasn't been found yet. Probably something
    * about slaves answering questions when they're not supposed to, and
    * reusing the old question.
@@ -552,7 +171,7 @@ static int dns_found_answer(char *question, uint32_t answer, uint32_t valid) {
   }
 
   resolve->answer = ntohl(answer);
-  if(valid)
+  if(resolve->answer)
     resolve->state = CACHE_STATE_VALID;
   else
     resolve->state = CACHE_STATE_FAILED;
@@ -569,6 +188,157 @@ static int dns_found_answer(char *question, uint32_t answer, uint32_t valid) {
   return 0;
 }
 
+/******************************************************************/
+
+int connection_dns_finished_flushing(connection_t *conn) {
+  assert(conn && conn->type == CONN_TYPE_DNSWORKER);
+  connection_stop_writing(conn);
+  return 0;
+}
+
+int connection_dns_process_inbuf(connection_t *conn) {
+  uint32_t answer;
+
+  assert(conn && conn->type == CONN_TYPE_DNSWORKER);
+
+  if(conn->inbuf_reached_eof) {
+    log(LOG_ERR,"connection_dnsworker_process_inbuf(): Read eof. Worker dying.");
+    /* XXX if the dns request is pending, go through and either repeat or mark it failed */
+    return -1;
+  }
+
+  assert(conn->state == DNSWORKER_STATE_BUSY);
+  if(conn->inbuf_datalen < 4) /* entire answer available? */
+    return 0; /* not yet */
+  assert(conn->inbuf_datalen == 4);
+
+  if(connection_fetch_from_buf((char*)&answer,sizeof(answer),conn) < 0) {
+    log(LOG_ERR,"connection_dnsworker_process_inbuf(): Broken inbuf. Worker dying.");
+    /* XXX exitconn's never going to get his answer :( */
+    return -1;
+  }
+
+  dns_found_answer(conn->address, answer);
+
+  free(conn->address);
+  conn->address = NULL;
+  conn->state = DNSWORKER_STATE_IDLE;
+  num_workers_busy--;
+
+  return 0;
+}
+
+static void dnsworker_main(int fd) {
+  char question[MAX_ADDRESSLEN];
+  unsigned char question_len;
+  struct hostent *rent;
+
+  for(;;) {
+
+    if(read(fd, &question_len, 1) != 1) {
+      log(LOG_INFO,"dnsworker_main(): read length failed. Exiting.");
+      exit(0);
+    }
+    assert(question_len > 0);
+
+    if(read(fd, question, question_len) != question_len) {
+      log(LOG_INFO,"dnsworker_main(): read hostname failed. Exiting.");
+      exit(0);
+    }
+    question[question_len] = 0; /* null terminate it */
+
+    rent = gethostbyname(question);
+    if (!rent) {
+      log(LOG_INFO,"dnsworker_main(): Could not resolve dest addr %s. Returning nulls.",question);
+      /* XXX it's conceivable write could return 1 through 3. but that's never gonna happen, right? */
+      if(write(fd, "\0\0\0\0", 4) != 4) {
+        log(LOG_INFO,"dnsworker_main(): writing nulls failed. Exiting.");
+        exit(0);
+      }
+    } else {
+      assert(rent->h_length == 4); /* break to remind us if we move away from ipv4 */
+      if(write(fd, rent->h_addr, 4) != 4) {
+        log(LOG_INFO,"dnsworker_main(): writing answer failed. Exiting.");
+        exit(0);
+      }
+      log(LOG_INFO,"dnsworker_main(): Answered question '%s'.",question);
+    }
+  }
+}
+
+static int dns_spawn_worker(void) {
+  pid_t pid;
+  int fd[2];
+  connection_t *conn;
+
+  if(socketpair(AF_UNIX, SOCK_STREAM, 0, fd) < 0) {
+    perror("socketpair");
+    exit(1);
+  }
+
+  pid = fork();
+  if(pid < 0) {
+    perror("fork");
+    exit(1);
+  }
+  if(pid == 0) { /* i'm the child */
+    close(fd[0]);
+    dnsworker_main(fd[1]);
+    assert(0); /* never gets here */
+  }
+
+  /* i'm the parent */
+  log(LOG_DEBUG,"dns_spawn_worker(): just spawned a worker.");
+  close(fd[1]);
+
+  conn = connection_new(CONN_TYPE_DNSWORKER);
+  if(!conn) {
+    close(fd[0]);
+    return -1;
+  }
+
+  fcntl(fd[0], F_SETFL, O_NONBLOCK); /* set it to non-blocking */
+
+  /* set up conn so it's got all the data we need to remember */
+  conn->receiver_bucket = -1; /* non-cell connections don't do receiver buckets */
+  conn->bandwidth = -1;
+  conn->s = fd[0];
+
+  if(connection_add(conn) < 0) { /* no space, forget it */
+    log(LOG_INFO,"dns_spawn_worker(): connection_add failed. Giving up.");
+    connection_free(conn); /* this closes fd[0] */
+    return -1;
+  }
+
+  conn->state = DNSWORKER_STATE_IDLE;
+  connection_start_reading(conn);
+
+  return 0; /* success */
+}
+
+static void spawn_enough_workers(void) {
+  int num_workers_needed; /* aim to have 1 more than needed,
+                           * but no less than min and no more than max */
+
+  if(num_workers_busy >= MIN_DNSWORKERS)
+    num_workers_needed = num_workers_busy+1;
+  else
+    num_workers_needed = MIN_DNSWORKERS;
+
+  if(num_workers_needed >= MAX_DNSWORKERS)
+    num_workers_needed = MAX_DNSWORKERS;
+
+  while(num_workers < num_workers_needed) {
+    if(dns_spawn_worker() < 0) {
+      log(LOG_ERR,"spawn_enough_workers(): spawn failed!");
+      return;
+    }
+    num_workers++;
+  }
+
+  /* FFFF this is where we will cull extra workers */
+}
+
 /*
   Local Variables:
   mode:c
diff --git a/src/or/main.c b/src/or/main.c
index 99d827675..c231d57d6 100644
--- a/src/or/main.c
+++ b/src/or/main.c
@@ -168,6 +168,18 @@ connection_t *connection_get_by_type(int type) {
   return NULL;
 }
 
+connection_t *connection_get_by_type_state(int type, int state) {
+  int i;
+  connection_t *conn;
+
+  for(i=0;i<nfds;i++) {
+    conn = connection_array[i];
+    if(conn->type == type && conn->state == state)
+       return conn;
+  }
+  return NULL;
+}
+
 void connection_watch_events(connection_t *conn, short events) {
 
   assert(conn && conn->poll_index < nfds);
@@ -782,17 +794,13 @@ int tor_main(int argc, char *argv[]) {
     exit(1);
   log(options.loglevel,NULL);         /* assign logging severity level from options */
 
-  if (options.Daemon)
+  if(options.Daemon)
     daemonize();
 
   if(options.OnionRouter) { /* only spawn dns handlers if we're a router */
-    if(dns_master_start() < 0) {
-      log(LOG_ERR,"main(): We're running without a dns handler. Bad news.");
-    }
+    dns_init(); /* initialize the dns resolve tree, and spawn workers */
   }
 
-  init_cache_tree(); /* initialize the dns resolve tree */
-
   signal (SIGINT,  catch); /* catch kills so we can exit cleanly */
   signal (SIGTERM, catch);
   signal (SIGUSR1, catch); /* to dump stats to stdout */
diff --git a/src/or/or.h b/src/or/or.h
index 80392bcf1..3a75f29ea 100644
--- a/src/or/or.h
+++ b/src/or/or.h
@@ -62,11 +62,12 @@
 #define CONN_TYPE_AP 7
 #define CONN_TYPE_DIR_LISTENER 8
 #define CONN_TYPE_DIR 9
-#define CONN_TYPE_DNSMASTER 10
+#define CONN_TYPE_DNSWORKER 10
 
 #define LISTENER_STATE_READY 0
 
-#define DNSMASTER_STATE_OPEN 0
+#define DNSWORKER_STATE_IDLE 0
+#define DNSWORKER_STATE_BUSY 1
 
 /* how to read these states:
  * foo_CONN_STATE_bar_baz:
@@ -83,7 +84,7 @@
 #define OR_CONN_STATE_SERVER_NONCE_WAIT 8 /* waiting for confirmation of nonce */
 #define OR_CONN_STATE_OPEN 9 /* ready to send/receive cells. */
 
-#define EXIT_CONN_STATE_RESOLVING 0 /* waiting for response from dnsmaster */
+#define EXIT_CONN_STATE_RESOLVING 0 /* waiting for response from dns farm */
 #define EXIT_CONN_STATE_CONNECTING 1 /* waiting for connect() to finish */
 #define EXIT_CONN_STATE_OPEN 2
 #if 0
@@ -267,6 +268,9 @@ struct connection_t {
 
 /* Used while negotiating OR/OR connections */
   char nonce[8];
+
+/* Used by worker connections */
+  int num_processed;
  
 };
 
@@ -646,7 +650,7 @@ int connection_dir_handle_listener_read(connection_t *conn);
 
 int connection_dns_finished_flushing(connection_t *conn);
 int connection_dns_process_inbuf(connection_t *conn);
-void init_cache_tree(void);
+void dns_init(void);
 int dns_resolve(connection_t *exitconn);
 int dns_master_start(void);
 
@@ -664,6 +668,7 @@ connection_t *connection_twin_get_by_addr_port(uint32_t addr, uint16_t port);
 connection_t *connection_exact_get_by_addr_port(uint32_t addr, uint16_t port);
 
 connection_t *connection_get_by_type(int type);
+connection_t *connection_get_by_type_state(int type, int state);
 
 void connection_watch_events(connection_t *conn, short events);
 void connection_stop_reading(connection_t *conn);