res_send.c

DHCP服务器源码

				       (stdout, ";; undersized: %d\n", len));
				terrno = ISC_R_NOSPACE;
				badns |= (1 << ns);
				res_nclose(statp);
				goto next_ns;
			}
			cp = (u_char *)ans;
			while (len != 0 &&
			       (n = read(statp->_sock,
					 (char *)cp, (unsigned)len))
			       > 0) {
				cp += n;
				len -= n;
			}
			if (n <= 0) {
				terrno = uerr2isc (errno);
				Perror(statp, stderr, "read(vc)", errno);
				res_nclose(statp);
				goto next_ns;
			}
			if (truncated) {
				/*
				 * Flush rest of answer
				 * so connection stays in synch.
				 */
				anhp->tc = 1;
				len = resplen - anssiz;
				while (len != 0) {
					char junk[PACKETSZ];

					n = (len > sizeof(junk)
					     ? sizeof(junk)
					     : len);
					n = read(statp->_sock,
						 junk, (unsigned)n);
					if (n > 0)
						len -= n;
					else
						break;
				}
			}
			/*
			 * The calling applicating has bailed out of
			 * a previous call and failed to arrange to have
			 * the circuit closed or the server has got
			 * itself confused. Anyway drop the packet and
			 * wait for the correct one.
			 */
			if (hp->id != anhp->id) {
				DprintQ((statp->options & RES_DEBUG) ||
					(statp->pfcode & RES_PRF_REPLY),
					(stdout,
					 ";; old answer (unexpected):\n"),
					ans, (resplen>anssiz)?anssiz:resplen);
				goto read_len;
			}
		} else {
			/*
			 * Use datagrams.
			 */
			int start, timeout, finish;
			fd_set dsmask;
			struct sockaddr_in from;
			SOCKLEN_T fromlen;
			int seconds;

			if (statp->_sock < 0 ||
			    (statp->_flags & RES_F_VC) != 0) {
				if ((statp->_flags & RES_F_VC) != 0)
					res_nclose(statp);
				statp->_sock = socket(PF_INET, SOCK_DGRAM, 0);
				if (statp->_sock < 0 ||
				    statp->_sock > highestFD) {
#ifndef CAN_RECONNECT
 bad_dg_sock:
#endif
					terrno = uerr2isc (errno);
					Perror(statp, stderr,
					       "socket(dg)", errno);
					return terrno;
				}
				statp->_flags &= ~RES_F_CONN;
			}
#ifndef CANNOT_CONNECT_DGRAM
			/*
			 * On a 4.3BSD+ machine (client and server,
			 * actually), sending to a nameserver datagram
			 * port with no nameserver will cause an
			 * ICMP port unreachable message to be returned.
			 * If our datagram socket is "connected" to the
			 * server, we get an ECONNREFUSED error on the next
			 * socket operation, and select returns if the
			 * error message is received.  We can thus detect
			 * the absence of a nameserver without timing out.
			 * If we have sent queries to at least two servers,
			 * however, we don't want to remain connected,
			 * as we wish to receive answers from the first
			 * server to respond.
			 */
			if (statp->nscount == 1 || (try == 0 && ns == 0)) {
				/*
				 * Connect only if we are sure we won't
				 * receive a response from another server.
				 */
				if ((statp->_flags & RES_F_CONN) == 0) {
					if (connect(statp->_sock,
						    (struct sockaddr *)nsap,
						    sizeof *nsap) < 0) {
						Aerror(statp, stderr,
						       "connect(dg)",
						       errno, *nsap);
						badns |= (1 << ns);
						res_nclose(statp);
						goto next_ns;
					}
					statp->_flags |= RES_F_CONN;
				}
                              if (send(statp->_sock,
				       (const char*)buf, (unsigned)buflen, 0)
				  != buflen) {
					Perror(statp, stderr, "send", errno);
					badns |= (1 << ns);
					res_nclose(statp);
					goto next_ns;
				}
			} else {
				/*
				 * Disconnect if we want to listen
				 * for responses from more than one server.
				 */
				if ((statp->_flags & RES_F_CONN) != 0) {
#ifdef CAN_RECONNECT
					struct sockaddr_in no_addr;

					no_addr.sin_family = AF_INET;
					no_addr.sin_addr.s_addr = INADDR_ANY;
					no_addr.sin_port = 0;
					(void) connect(statp->_sock,
						       (struct sockaddr *)
						        &no_addr,
						       sizeof no_addr);
#else
					struct sockaddr_in local_addr;
					SOCKLEN_T len;
					int result, s1;

					len = sizeof(local_addr);
					s1 = socket(PF_INET, SOCK_DGRAM, 0);
					result = getsockname(statp->_sock,
						(struct sockaddr *)&local_addr,
							     &len);
					if (s1 < 0)
						goto bad_dg_sock;
					(void) dup2(s1, statp->_sock);
					(void) close(s1);
					if (result == 0) {
						/*
						 * Attempt to rebind to old
						 * port.  Note connected socket
						 * has an sin_addr set.
						 */
						local_addr.sin_addr.s_addr =
							htonl(0);
						(void)bind(statp->_sock,
							   (struct sockaddr *)
							   &local_addr,
							   (unsigned)len);
					}
					Dprint(statp->options & RES_DEBUG,
					       (stdout, ";; new DG socket\n"));
#endif /* CAN_RECONNECT */
					statp->_flags &= ~RES_F_CONN;
					errno = 0;
				}
#endif /* !CANNOT_CONNECT_DGRAM */
				if (sendto(statp->_sock,
					   (const char *)buf, buflen, 0,
					   (struct sockaddr *)nsap,
					   sizeof *nsap)
				    != buflen) {
					Aerror(statp, stderr, "sendto", errno, *nsap);
					badns |= (1 << ns);
					res_nclose(statp);
					goto next_ns;
				}
#ifndef CANNOT_CONNECT_DGRAM
			}
#endif /* !CANNOT_CONNECT_DGRAM */

			if (statp->_sock < 0 || statp->_sock > highestFD) {
				Perror(statp, stderr,
				       "fd out-of-bounds", EMFILE);
				res_nclose(statp);
				goto next_ns;
			}

			/*
			 * Wait for reply
			 */
			seconds = (statp->retrans << try);
			if (try > 0)
				seconds /= statp->nscount;
			if (seconds <= 0)
				seconds = 1;
			start = cur_time;
			timeout = seconds;
			finish = start + timeout;
 wait:
			FD_ZERO(&dsmask);
			FD_SET(statp->_sock, &dsmask);
			{
				struct timeval t;
				t.tv_sec = timeout;
				t.tv_usec = 0;
				n = select(statp->_sock + 1,
					   &dsmask, NULL, NULL, &t);
			}
			if (n == 0) {
				Dprint(statp->options & RES_DEBUG,
				       (stdout, ";; timeout\n"));
				gotsomewhere = 1;
				goto next_ns;
			}
			if (n < 0) {
				if (errno == EINTR) {
					if (finish >= cur_time) {
						timeout = finish - cur_time;
						goto wait;
					}
				}
				Perror(statp, stderr, "select", errno);
				res_nclose(statp);
				goto next_ns;
			}
			errno = 0;
			fromlen = sizeof(struct sockaddr_in);
			resplen = recvfrom(statp->_sock,
					   (char *)ans, anssiz, 0,
					   (struct sockaddr *)&from, &fromlen);
			if (resplen <= 0) {
				Perror(statp, stderr, "recvfrom", errno);
				res_nclose(statp);
				goto next_ns;
			}
			gotsomewhere = 1;
			if (resplen < HFIXEDSZ) {
				/*
				 * Undersized message.
				 */
				Dprint(statp->options & RES_DEBUG,
				       (stdout, ";; undersized: %d\n",
					resplen));
				terrno = ISC_R_NOSPACE;
				badns |= (1 << ns);
				res_nclose(statp);
				goto next_ns;
			}
			if (hp->id != anhp->id) {
				/*
				 * response from old query, ignore it.
				 * XXX - potential security hazard could
				 *	 be detected here.
				 */
				DprintQ((statp->options & RES_DEBUG) ||
					(statp->pfcode & RES_PRF_REPLY),
					(stdout, ";; old answer:\n"),
					ans, (resplen>anssiz)?anssiz:resplen);
				goto wait;
			}
#ifdef CHECK_SRVR_ADDR
			if (!(statp->options & RES_INSECURE1) &&
			    !res_ourserver_p(statp, &from)) {
				/*
				 * response from wrong server? ignore it.
				 * XXX - potential security hazard could
				 *	 be detected here.
				 */
				DprintQ((statp->options & RES_DEBUG) ||
					(statp->pfcode & RES_PRF_REPLY),
					(stdout, ";; not our server:\n"),
					ans, (resplen>anssiz)?anssiz:resplen);
				goto wait;
			}
#endif
			if (!(statp->options & RES_INSECURE2) &&
			    !res_queriesmatch((u_char *)buf,
					      ((u_char *)buf) + buflen,
					      (u_char *)ans,
					      ((u_char *)ans) + anssiz)) {
				/*
				 * response contains wrong query? ignore it.
				 * XXX - potential security hazard could
				 *	 be detected here.
				 */
				DprintQ((statp->options & RES_DEBUG) ||
					(statp->pfcode & RES_PRF_REPLY),
					(stdout, ";; wrong query name:\n"),
					ans, (resplen>anssiz)?anssiz:resplen);
				goto wait;
			}
			if (anhp->rcode == SERVFAIL ||
			    anhp->rcode == NOTIMP ||
			    anhp->rcode == REFUSED) {
				DprintQ(statp->options & RES_DEBUG,
					(stdout, "server rejected query:\n"),
					ans, (resplen>anssiz)?anssiz:resplen);
				badns |= (1 << ns);
				res_nclose(statp);
				/* don't retry if called from dig */
				if (!statp->pfcode)
					goto next_ns;
			}
			if (!(statp->options & RES_IGNTC) && anhp->tc) {
				/*
				 * get rest of answer;
				 * use TCP with same server.
				 */
				Dprint(statp->options & RES_DEBUG,
				       (stdout, ";; truncated answer\n"));
				v_circuit = 1;
				res_nclose(statp);
				goto same_ns;
			}
		} /*if vc/dg*/
		Dprint((statp->options & RES_DEBUG) ||
		       ((statp->pfcode & RES_PRF_REPLY) &&
			(statp->pfcode & RES_PRF_HEAD1)),
		       (stdout, ";; got answer:\n"));
		DprintQ((statp->options & RES_DEBUG) ||
			(statp->pfcode & RES_PRF_REPLY),
			(stdout, ""),
			ans, (resplen>anssiz)?anssiz:resplen);
		/*
		 * If using virtual circuits, we assume that the first server
		 * is preferred over the rest (i.e. it is on the local
		 * machine) and only keep that one open.
		 * If we have temporarily opened a virtual circuit,
		 * or if we haven't been asked to keep a socket open,
		 * close the socket.
		 */
		if ((v_circuit && (!(statp->options & RES_USEVC) || ns != 0)) ||
		    !(statp->options & RES_STAYOPEN)) {
			res_nclose(statp);
		}
		if (statp->rhook) {
			int done = 0, loops = 0;

			do {
				res_sendhookact act;

				act = (*statp->rhook)(nsap, buf, buflen,
						      ans, anssiz, &resplen);
				switch (act) {
				case res_goahead:
				case res_done:
					done = 1;
					break;
				case res_nextns:
					res_nclose(statp);
					goto next_ns;
				case res_modified:
					/* give the hook another try */
					if (++loops < 42) /*doug adams*/
						break;
					/*FALLTHROUGH*/
				case res_error:
					/*FALLTHROUGH*/
				default:
					return ISC_R_UNEXPECTED;
				}
			} while (!done);

		}
		*ansret = resplen;
		return ISC_R_SUCCESS;
 next_ns: ;
	   } /*foreach ns*/
	} /*foreach retry*/
	res_nclose(statp);
	if (!v_circuit) {
		if (!gotsomewhere)
			terrno = ISC_R_CONNREFUSED;  /* no nameservers found */
		else
			errno = ISC_R_TIMEDOUT;	/* no answer obtained */
	}
	return terrno;
}

/*
 * This routine is for closing the socket if a virtual circuit is used and
 * the program wants to close it.  This provides support for endhostent()
 * which expects to close the socket.
 *
 * This routine is not expected to be user visible.
 */
void
res_nclose(res_state statp) {
	if (statp->_sock >= 0) {
		(void) close(statp->_sock);
		statp->_sock = -1;
		statp->_flags &= ~(RES_F_VC | RES_F_CONN);
	}
}

/* Private */
static int
cmpsock(struct sockaddr_in *a1, struct sockaddr_in *a2) {
	return ((a1->sin_family == a2->sin_family) &&
		(a1->sin_port == a2->sin_port) &&
		(a1->sin_addr.s_addr == a2->sin_addr.s_addr));
}

#ifdef NEED_PSELECT
/* XXX needs to move to the porting library. */
static int
pselect(int nfds, void *rfds, void *wfds, void *efds,
	struct timespec *tsp,
	const sigset_t *sigmask)
{
	struct timeval tv, *tvp;
	sigset_t sigs;
	int n;

	if (tsp) {
		tvp = &tv;
		tv = evTimeVal(*tsp);
	} else
		tvp = NULL;
	if (sigmask)
		sigprocmask(SIG_SETMASK, sigmask, &sigs);
	n = select(nfds, rfds, wfds, efds, tvp);
	if (sigmask)
		sigprocmask(SIG_SETMASK, &sigs, NULL);
	if (tsp)
		*tsp = evTimeSpec(tv);
	return (n);
}
#endif