X-Git-Url: https://git.subgeniuskitty.com/unix-history/.git/blobdiff_plain/7a8f7802612b5be9e7caa39b125448f8a349b77b..f7d00d5e72962c65438ba8b6e34237429386a0b9:/usr/src/lib/libc/net/res_send.c

diff --git a/usr/src/lib/libc/net/res_send.c b/usr/src/lib/libc/net/res_send.c
index b45595d912..4d447fed8d 100644
--- a/usr/src/lib/libc/net/res_send.c
+++ b/usr/src/lib/libc/net/res_send.c
@@ -1,13 +1,23 @@
-
 /*
- * Copyright (c) 1985 Regents of the University of California.
- * All rights reserved.  The Berkeley software License Agreement
- * specifies the terms and conditions for redistribution.
+ * Copyright (c) 1985, 1989 Regents of the University of California.
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms are permitted
+ * provided that the above copyright notice and this paragraph are
+ * duplicated in all such forms and that any documentation,
+ * advertising materials, and other materials related to such
+ * distribution and use acknowledge that the software was developed
+ * by the University of California, Berkeley.  The name of the
+ * University may not be used to endorse or promote products derived
+ * from this software without specific prior written permission.
+ * THIS SOFTWARE IS PROVIDED ``AS IS'' AND WITHOUT ANY EXPRESS OR
+ * IMPLIED WARRANTIES, INCLUDING, WITHOUT LIMITATION, THE IMPLIED
+ * WARRANTIES OF MERCHANTIBILITY AND FITNESS FOR A PARTICULAR PURPOSE.
  */
 
 #if defined(LIBC_SCCS) && !defined(lint)
-static char sccsid[] = "@(#)res_send.c	6.16 (Berkeley) %G%";
-#endif LIBC_SCCS and not lint
+static char sccsid[] = "@(#)res_send.c	6.24 (Berkeley) %G%";
+#endif /* LIBC_SCCS and not lint */
 
 /*
  * Send query to name server and wait for reply.
@@ -26,6 +36,7 @@ static char sccsid[] = "@(#)res_send.c	6.16 (Berkeley) %G%";
 extern int errno;
 
 static int s = -1;	/* socket used for communications */
+static struct sockaddr no_addr;
   
 
 #ifndef FD_SET
@@ -37,8 +48,6 @@ static int s = -1;	/* socket used for communications */
 #define FD_ZERO(p)	bzero((char *)(p), sizeof(*(p)))
 #endif
 
-#define KEEPOPEN (RES_USEVC|RES_STAYOPEN)
-
 res_send(buf, buflen, answer, anslen)
 	char *buf;
 	int buflen;
@@ -46,8 +55,9 @@ res_send(buf, buflen, answer, anslen)
 	int anslen;
 {
 	register int n;
-	int retry, v_circuit, resplen, ns;
-	int gotsomewhere = 0;
+	int try, v_circuit, resplen, ns;
+	int gotsomewhere = 0, connected = 0;
+	int connreset = 0;
 	u_short id, len;
 	char *cp;
 	fd_set dsmask;
@@ -56,6 +66,7 @@ res_send(buf, buflen, answer, anslen)
 	HEADER *anhp = (HEADER *) answer;
 	struct iovec iov[2];
 	int terrno = ETIMEDOUT;
+	char junk[512];
 
 #ifdef DEBUG
 	if (_res.options & RES_DEBUG) {
@@ -72,24 +83,29 @@ res_send(buf, buflen, answer, anslen)
 	/*
 	 * Send request, RETRY times, or until successful
 	 */
-	for (retry = _res.retry; retry > 0; retry--) {
+	for (try = 0; try < _res.retry; try++) {
 	   for (ns = 0; ns < _res.nscount; ns++) {
 #ifdef DEBUG
 		if (_res.options & RES_DEBUG)
 			printf("Querying server (# %d) address = %s\n", ns+1,
-			      inet_ntoa(_res.nsaddr_list[ns].sin_addr.s_addr));
+			      inet_ntoa(_res.nsaddr_list[ns].sin_addr));
 #endif DEBUG
+	usevc:
 		if (v_circuit) {
+			int truncated = 0;
+
 			/*
-			 * Use virtual circuit.
+			 * Use virtual circuit;
+			 * at most one attempt per server.
 			 */
+			try = _res.retry;
 			if (s < 0) {
 				s = socket(AF_INET, SOCK_STREAM, 0);
 				if (s < 0) {
 					terrno = errno;
 #ifdef DEBUG
 					if (_res.options & RES_DEBUG)
-					    perror("socket failed");
+					    perror("socket (vc) failed");
 #endif DEBUG
 					continue;
 				}
@@ -141,10 +157,31 @@ res_send(buf, buflen, answer, anslen)
 #endif DEBUG
 				(void) close(s);
 				s = -1;
+				/*
+				 * A long running process might get its TCP
+				 * connection reset if the remote server was
+				 * restarted.  Requery the server instead of
+				 * trying a new one.  When there is only one
+				 * server, this means that a query might work
+				 * instead of failing.  We only allow one reset
+				 * per query to prevent looping.
+				 */
+				if (terrno == ECONNRESET && !connreset) {
+					connreset = 1;
+					ns--;
+				}
 				continue;
 			}
 			cp = answer;
-			resplen = len = ntohs(*(u_short *)cp);
+			if ((resplen = ntohs(*(u_short *)cp)) > anslen) {
+#ifdef DEBUG
+				if (_res.options & RES_DEBUG)
+					fprintf(stderr, "response truncated\n");
+#endif DEBUG
+				len = anslen;
+				truncated = 1;
+			} else
+				len = resplen;
 			while (len != 0 &&
 			   (n = read(s, (char *)cp, (int)len)) > 0) {
 				cp += n;
@@ -160,43 +197,108 @@ res_send(buf, buflen, answer, anslen)
 				s = -1;
 				continue;
 			}
+			if (truncated) {
+				/*
+				 * Flush rest of answer
+				 * so connection stays in synch.
+				 */
+				anhp->tc = 1;
+				len = resplen - anslen;
+				while (len != 0) {
+					n = (len > sizeof(junk) ?
+					    sizeof(junk) : len);
+					if ((n = read(s, junk, n)) > 0)
+						len -= n;
+					else
+						break;
+				}
+			}
 		} else {
 			/*
 			 * Use datagrams.
 			 */
-			if (s < 0)
+			if (s < 0) {
 				s = socket(AF_INET, SOCK_DGRAM, 0);
+				if (s < 0) {
+					terrno = errno;
+#ifdef DEBUG
+					if (_res.options & RES_DEBUG)
+					    perror("socket (dg) failed");
+#endif DEBUG
+					continue;
+				}
+			}
 #if	BSD >= 43
-			if (_res.nscount == 1) {
+			/*
+			 * I'm tired of answering this question, so:
+			 * 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 (_res.nscount == 1 || (try == 0 && ns == 0)) {
 				/*
-				 * Connect/Send is detrimental if you
-				 * are going to poll more than one server
+				 * Don't use connect if we might
+				 * still receive a response
+				 * from another server.
 				 */
-				if (connect(s, &_res.nsaddr_list[ns],
-				    sizeof(struct sockaddr)) < 0 ||
-				    send(s, buf, buflen, 0) != buflen) {
+				if (connected == 0) {
+					if (connect(s, &_res.nsaddr_list[ns],
+					    sizeof(struct sockaddr)) < 0) {
+#ifdef DEBUG
+						if (_res.options & RES_DEBUG)
+							perror("connect");
+#endif DEBUG
+						continue;
+					}
+					connected = 1;
+				}
+				if (send(s, buf, buflen, 0) != buflen) {
 #ifdef DEBUG
 					if (_res.options & RES_DEBUG)
-						perror("connect");
+						perror("send");
 #endif DEBUG
 					continue;
 				}
-			} else
+			} else {
+				/*
+				 * Disconnect if we want to listen
+				 * for responses from more than one server.
+				 */
+				if (connected) {
+					(void) connect(s, &no_addr,
+					    sizeof(no_addr));
+					connected = 0;
+				}
 #endif BSD
-			if (sendto(s, buf, buflen, 0, &_res.nsaddr_list[ns],
-			    sizeof(struct sockaddr)) != buflen) {
+				if (sendto(s, buf, buflen, 0,
+				    &_res.nsaddr_list[ns],
+				    sizeof(struct sockaddr)) != buflen) {
 #ifdef DEBUG
-				if (_res.options & RES_DEBUG)
-					perror("sendto");
+					if (_res.options & RES_DEBUG)
+						perror("sendto");
 #endif DEBUG
-				continue;
+					continue;
+				}
+#if	BSD >= 43
 			}
+#endif
 
 			/*
 			 * Wait for reply
 			 */
-			timeout.tv_sec = (_res.retrans << (_res.retry - retry))
-				/ _res.nscount;
+			timeout.tv_sec = (_res.retrans << try);
+			if (try > 0)
+				timeout.tv_sec /= _res.nscount;
 			if (timeout.tv_sec <= 0)
 				timeout.tv_sec = 1;
 			timeout.tv_usec = 0;
@@ -220,7 +322,9 @@ wait:
 				if (_res.options & RES_DEBUG)
 					printf("timeout\n");
 #endif DEBUG
+#if BSD >= 43
 				gotsomewhere = 1;
+#endif
 				continue;
 			}
 			if ((resplen = recv(s, answer, anslen, 0)) <= 0) {
@@ -245,7 +349,8 @@ wait:
 			}
 			if (!(_res.options & RES_IGNTC) && anhp->tc) {
 				/*
-				 * get rest of answer
+				 * get rest of answer;
+				 * use TCP with same server.
 				 */
 #ifdef DEBUG
 				if (_res.options & RES_DEBUG)
@@ -253,13 +358,8 @@ wait:
 #endif DEBUG
 				(void) close(s);
 				s = -1;
-				/*
-				 * retry decremented on continue
-				 * to desired starting value
-				 */
-				retry = _res.retry + 1;
 				v_circuit = 1;
-				continue;
+				goto usevc;
 			}
 		}
 #ifdef DEBUG
@@ -269,17 +369,20 @@ wait:
 		}
 #endif DEBUG
 		/*
-		 * We are going to 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 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 ((_res.options & KEEPOPEN) == KEEPOPEN && ns == 0) {
-			return (resplen);
-		} else {
+		if ((v_circuit &&
+		    ((_res.options & RES_USEVC) == 0 || ns != 0)) ||
+		    (_res.options & RES_STAYOPEN) == 0) {
 			(void) close(s);
 			s = -1;
-			return (resplen);
 		}
+		return (resplen);
 	   }
 	}
 	if (s >= 0) {
@@ -288,9 +391,9 @@ wait:
 	}
 	if (v_circuit == 0)
 		if (gotsomewhere == 0)
-			errno = ECONNREFUSED;
+			errno = ECONNREFUSED;	/* no nameservers found */
 		else
-			errno = ETIMEDOUT;
+			errno = ETIMEDOUT;	/* no answer obtained */
 	else
 		errno = terrno;
 	return (-1);