event.c

adns for unix/linux, adns-1.3.tar.gz

/*
 * event.c
 * - event loop core
 * - TCP connection management
 * - user-visible check/wait and event-loop-related functions
 */
/*
 *  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 <errno.h>
#include <stdlib.h>
#include <unistd.h>

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

#include "internal.h"
#include "tvarith.h"

/* TCP connection management. */

static void tcp_close(adns_state ads) {
  int serv;
  
  serv= ads->tcpserver;
  close(ads->tcpsocket);
  ads->tcpsocket= -1;
  ads->tcprecv.used= ads->tcprecv_skip= ads->tcpsend.used= 0;
}

void adns__tcp_broken(adns_state ads, const char *what, const char *why) {
  int serv;
  adns_query qu;
  
  assert(ads->tcpstate == server_connecting || ads->tcpstate == server_ok);
  serv= ads->tcpserver;
  if (what) adns__warn(ads,serv,0,"TCP connection failed: %s: %s",what,why);

  if (ads->tcpstate == server_connecting) {
    /* Counts as a retry for all the queries waiting for TCP. */
    for (qu= ads->tcpw.head; qu; qu= qu->next)
      qu->retries++;
  }

  tcp_close(ads);
  ads->tcpstate= server_broken;
  ads->tcpserver= (serv+1)%ads->nservers;
}

static void tcp_connected(adns_state ads, struct timeval now) {
  adns_query qu, nqu;
  
  adns__debug(ads,ads->tcpserver,0,"TCP connected");
  ads->tcpstate= server_ok;
  for (qu= ads->tcpw.head; qu && ads->tcpstate == server_ok; qu= nqu) {
    nqu= qu->next;
    assert(qu->state == query_tcpw);
    adns__querysend_tcp(qu,now);
  }
}

static void tcp_broken_events(adns_state ads) {
  adns_query qu, nqu;
  
  assert(ads->tcpstate == server_broken);
  for (qu= ads->tcpw.head; qu; qu= nqu) {
    nqu= qu->next;
    assert(qu->state == query_tcpw);
    if (qu->retries > ads->nservers) {
      LIST_UNLINK(ads->tcpw,qu);
      adns__query_fail(qu,adns_s_allservfail);
    }
  }
  ads->tcpstate= server_disconnected;
}

void adns__tcp_tryconnect(adns_state ads, struct timeval now) {
  int r, fd, tries;
  struct sockaddr_in addr;
  struct protoent *proto;

  for (tries=0; tries<ads->nservers; tries++) {
    switch (ads->tcpstate) {
    case server_connecting:
    case server_ok:
    case server_broken:
      return;
    case server_disconnected:
      break;
    default:
      abort();
    }
    
    assert(!ads->tcpsend.used);
    assert(!ads->tcprecv.used);
    assert(!ads->tcprecv_skip);

    proto= getprotobyname("tcp");
    if (!proto) {
      adns__diag(ads,-1,0,"unable to find protocol no. for TCP !");
      return;
    }
    fd= socket(AF_INET,SOCK_STREAM,proto->p_proto);
    if (fd<0) {
      adns__diag(ads,-1,0,"cannot create TCP socket: %s",strerror(errno));
      return;
    }
    r= adns__setnonblock(ads,fd);
    if (r) {
      adns__diag(ads,-1,0,"cannot make TCP socket nonblocking:"
		 " %s",strerror(r));
      close(fd);
      return;
    }
    memset(&addr,0,sizeof(addr));
    addr.sin_family= AF_INET;
    addr.sin_port= htons(DNS_PORT);
    addr.sin_addr= ads->servers[ads->tcpserver].addr;
    r= connect(fd,(const struct sockaddr*)&addr,sizeof(addr));
    ads->tcpsocket= fd;
    ads->tcpstate= server_connecting;
    if (r==0) { tcp_connected(ads,now); return; }
    if (errno == EWOULDBLOCK || errno == EINPROGRESS) {
      ads->tcptimeout= now;
      timevaladd(&ads->tcptimeout,TCPCONNMS);
      return;
    }
    adns__tcp_broken(ads,"connect",strerror(errno));
    tcp_broken_events(ads);
  }
}

/* Timeout handling functions. */

void adns__must_gettimeofday(adns_state ads, const struct timeval **now_io,
			     struct timeval *tv_buf) {
  const struct timeval *now;
  int r;

  now= *now_io;
  if (now) return;
  r= gettimeofday(tv_buf,0); if (!r) { *now_io= tv_buf; return; }
  adns__diag(ads,-1,0,"gettimeofday failed: %s",strerror(errno));
  adns_globalsystemfailure(ads);
  return;
}

static void inter_immed(struct timeval **tv_io, struct timeval *tvbuf) {
  struct timeval *rbuf;

  if (!tv_io) return;

  rbuf= *tv_io;
  if (!rbuf) { *tv_io= rbuf= tvbuf; }

  timerclear(rbuf);
}
    
static void inter_maxto(struct timeval **tv_io, struct timeval *tvbuf,
			struct timeval maxto) {
  struct timeval *rbuf;

  if (!tv_io) return;
  rbuf= *tv_io;
  if (!rbuf) {
    *tvbuf= maxto; *tv_io= tvbuf;
  } else {
    if (timercmp(rbuf,&maxto,>)) *rbuf= maxto;
  }
/*fprintf(stderr,"inter_maxto maxto=%ld.%06ld result=%ld.%06ld\n",
	maxto.tv_sec,maxto.tv_usec,(**tv_io).tv_sec,(**tv_io).tv_usec);*/
}

static void inter_maxtoabs(struct timeval **tv_io, struct timeval *tvbuf,
			   struct timeval now, struct timeval maxtime) {
  /* tv_io may be 0 */
  ldiv_t dr;

/*fprintf(stderr,"inter_maxtoabs now=%ld.%06ld maxtime=%ld.%06ld\n",
	now.tv_sec,now.tv_usec,maxtime.tv_sec,maxtime.tv_usec);*/
  if (!tv_io) return;
  maxtime.tv_sec -= (now.tv_sec+2);
  maxtime.tv_usec -= (now.tv_usec-2000000);
  dr= ldiv(maxtime.tv_usec,1000000);
  maxtime.tv_sec += dr.quot;
  maxtime.tv_usec -= dr.quot*1000000;
  if (maxtime.tv_sec<0) timerclear(&maxtime);
  inter_maxto(tv_io,tvbuf,maxtime);
}

static void timeouts_queue(adns_state ads, int act,
			   struct timeval **tv_io, struct timeval *tvbuf,
			   struct timeval now, struct query_queue *queue) {
  adns_query qu, nqu;
  
  for (qu= queue->head; qu; qu= nqu) {
    nqu= qu->next;
    if (!timercmp(&now,&qu->timeout,>)) {
      inter_maxtoabs(tv_io,tvbuf,now,qu->timeout);
    } else {
      if (!act) { inter_immed(tv_io,tvbuf); return; }
      LIST_UNLINK(*queue,qu);
      if (qu->state != query_tosend) {
	adns__query_fail(qu,adns_s_timeout);
      } else {
	adns__query_send(qu,now);
      }
      nqu= queue->head;
    }
  }
}

static void tcp_events(adns_state ads, int act,
		       struct timeval **tv_io, struct timeval *tvbuf,
		       struct timeval now) {
  for (;;) {
    switch (ads->tcpstate) {
    case server_broken:
      if (!act) { inter_immed(tv_io,tvbuf); return; }
      tcp_broken_events(ads);
    case server_disconnected: /* fall through */
      if (!ads->tcpw.head) return;
      if (!act) { inter_immed(tv_io,tvbuf); return; }
      adns__tcp_tryconnect(ads,now);
      break;
    case server_ok:
      if (ads->tcpw.head) return;
      if (!ads->tcptimeout.tv_sec) {
	assert(!ads->tcptimeout.tv_usec);
	ads->tcptimeout= now;
	timevaladd(&ads->tcptimeout,TCPIDLEMS);
      }
    case server_connecting: /* fall through */
      if (!act || !timercmp(&now,&ads->tcptimeout,>)) {
	inter_maxtoabs(tv_io,tvbuf,now,ads->tcptimeout);
	return;
      } {
	/* TCP timeout has happened */
	switch (ads->tcpstate) {
	case server_connecting: /* failed to connect */
	  adns__tcp_broken(ads,"unable to make connection","timed out");
	  break;
	case server_ok: /* idle timeout */
	  tcp_close(ads);
	  ads->tcpstate= server_disconnected;
	  return;
	default:
	  abort();
	}
      }
      break;
    default:
      abort();
    }
  }
  return;
}

void adns__timeouts(adns_state ads, int act,
		    struct timeval **tv_io, struct timeval *tvbuf,
		    struct timeval now) {
  timeouts_queue(ads,act,tv_io,tvbuf,now, &ads->udpw);
  timeouts_queue(ads,act,tv_io,tvbuf,now, &ads->tcpw);
  tcp_events(ads,act,tv_io,tvbuf,now);
}

void adns_firsttimeout(adns_state ads,
		       struct timeval **tv_io, struct timeval *tvbuf,
		       struct timeval now) {
  adns__consistency(ads,0,cc_entex);
  adns__timeouts(ads, 0, tv_io,tvbuf, now);
  adns__consistency(ads,0,cc_entex);
}

void adns_processtimeouts(adns_state ads, const struct timeval *now) {
  struct timeval tv_buf;

  adns__consistency(ads,0,cc_entex);
  adns__must_gettimeofday(ads,&now,&tv_buf);
  if (now) adns__timeouts(ads, 1, 0,0, *now);
  adns__consistency(ads,0,cc_entex);
}

/* fd handling functions.  These are the top-level of the real work of
 * reception and often transmission.
 */

int adns__pollfds(adns_state ads, struct pollfd pollfds_buf[MAX_POLLFDS]) {
  /* Returns the number of entries filled in.  Always zeroes revents. */

  assert(MAX_POLLFDS==2);

  pollfds_buf[0].fd= ads->udpsocket;
  pollfds_buf[0].events= POLLIN;
  pollfds_buf[0].revents= 0;

  switch (ads->tcpstate) {
  case server_disconnected:
  case server_broken:
    return 1;
  case server_connecting:
    pollfds_buf[1].events= POLLOUT;
    break;
  case server_ok:
    pollfds_buf[1].events=
      ads->tcpsend.used ? POLLIN|POLLOUT|POLLPRI : POLLIN|POLLPRI;
    break;
  default:
    abort();
  }
  pollfds_buf[1].fd= ads->tcpsocket;
  return 2;
}

int adns_processreadable(adns_state ads, int fd, const struct timeval *now) {
  int want, dgramlen, r, udpaddrlen, serv, old_skip;
  byte udpbuf[DNS_MAXUDP];
  struct sockaddr_in udpaddr;
  
  adns__consistency(ads,0,cc_entex);

  switch (ads->tcpstate) {
  case server_disconnected:
  case server_broken:
  case server_connecting:
    break;
  case server_ok:
    if (fd != ads->tcpsocket) break;
    assert(!ads->tcprecv_skip);
    do {
      if (ads->tcprecv.used >= ads->tcprecv_skip+2) {
	dgramlen= ((ads->tcprecv.buf[ads->tcprecv_skip]<<8) |
	           ads->tcprecv.buf[ads->tcprecv_skip+1]);
	if (ads->tcprecv.used >= ads->tcprecv_skip+2+dgramlen) {
	  old_skip= ads->tcprecv_skip;
	  ads->tcprecv_skip += 2+dgramlen;
	  adns__procdgram(ads, ads->tcprecv.buf+old_skip+2,
			  dgramlen, ads->tcpserver, 1,*now);
	  continue;
	} else {
	  want= 2+dgramlen;
	}
      } else {
	want= 2;
      }
      ads->tcprecv.used -= ads->tcprecv_skip;
      memmove(ads->tcprecv.buf, ads->tcprecv.buf+ads->tcprecv_skip,
	      ads->tcprecv.used);