svn commit: trunk/uClibc/libc/inet

[vda at uclibc.org]

Author: vda
Date: 2008-10-27 17:12:25 -0700 (Mon, 27 Oct 2008)
New Revision: 23825

Log:
make getaddrinfo to NOT query DNS for IPv6 address if host is in
/etc/hosts and it has IPv4 address there.
The most common example is "127.0.0.1 localhost".
We don't want "ping localhost" to stall and time out on IPv6
queries to, say, inaccessible DNS server, right?

-    655              0       0     655     28f libc/inet/gethostbyname2_r.o
+    685              0       0     685     2ad libc/inet/gethostbyname2_r.o



Modified:
   trunk/uClibc/libc/inet/resolv.c


Changeset:
Modified: trunk/uClibc/libc/inet/resolv.c
===================================================================
--- trunk/uClibc/libc/inet/resolv.c	2008-10-27 22:02:54 UTC (rev 23824)
+++ trunk/uClibc/libc/inet/resolv.c	2008-10-28 00:12:25 UTC (rev 23825)
@@ -1551,7 +1551,7 @@
 	struct in_addr **addr_list = NULL;
 #ifdef __UCLIBC_HAS_IPV6__
 	struct in6_addr *in6 = NULL;
-	struct in6_addr **addr_list6 =NULL;
+	struct in6_addr **addr_list6 = NULL;
 #endif /* __UCLIBC_HAS_IPV6__ */
 	char *cp, **alias;
 	int aliases, i, ret = HOST_NOT_FOUND;
@@ -1613,14 +1613,15 @@
 
 		fp = __open_etc_hosts();
 		if (fp == NULL) {
-			result = NULL;
+			*result = NULL;
 			return errno;
 		}
 	}
 
 	*h_errnop = HOST_NOT_FOUND;
 	while (fgets(buf, buflen, fp)) {
-		if ((cp = strchr(buf, '#')))
+		cp = strchr(buf, '#');
+		if (cp)
 			*cp = '\0';
 		DPRINTF("Looking at: %s\n", buf);
 		aliases = 0;
@@ -1630,7 +1631,7 @@
 			while (*cp && isspace(*cp))
 				*cp++ = '\0';
 			if (!*cp)
-				continue;
+				break;
 			if (aliases < (2+MAX_ALIASES))
 				alias[aliases++] = cp;
 			while (*cp && !isspace(*cp))
@@ -1644,7 +1645,8 @@
 		if (action == GETHOSTENT) {
 			/* Return whatever the next entry happens to be. */
 			break;
-		} else if (action == GET_HOSTS_BYADDR) {
+		}
+		if (action == GET_HOSTS_BYADDR) {
 			if (strcmp(name, alias[0]) != 0)
 				continue;
 		} else {
@@ -1688,13 +1690,12 @@
 			 * If looking for an IPv6 addr, don't bail when we got the IPv4
 			 */
 			DPRINTF("Error: Found host but diff network type\n");
+			/* NB: gethostbyname2_r depends on this feature
+			 * to avoid looking for IPv6 addr of "localhost" etc */
 			ret = TRY_AGAIN;
 			continue;
 		}
-
-		if (action != GETHOSTENT)
-			fclose(fp);
-		return ret;
+		break;
 	}
 	if (action != GETHOSTENT)
 		fclose(fp);
@@ -2206,6 +2207,7 @@
 	int nest = 0;
 	int __nameserversXX;
 	char ** __nameserverXX;
+	int wrong_af = 0;
 
 	if (family == AF_INET)
 		return gethostbyname_r(name, result_buf, buf, buflen, result, h_errnop);
@@ -2223,11 +2225,15 @@
 		int old_errno = errno;	/* Save the old errno and reset errno */
 		__set_errno(0);			/* to check for missing /etc/hosts. */
 
-		if ((i = __get_hosts_byname_r(name, family, result_buf,
-									  buf, buflen, result, h_errnop)) == 0)
+		i = __get_hosts_byname_r(name, family, result_buf,
+				buf, buflen, result, h_errnop);
+		if (i == NETDB_SUCCESS) {
+//FIXME: restore errno?
 			return i;
+		}
 		switch (*h_errnop) {
 			case HOST_NOT_FOUND:
+				wrong_af = (i == TRY_AGAIN);
 			case NO_ADDRESS:
 				break;
 			case NETDB_INTERNAL:
@@ -2274,8 +2280,16 @@
 		return NETDB_SUCCESS;
 	}
 
-	memset((char *) &a, '\0', sizeof(a));
+	/* What if /etc/hosts has it but it's not IPv6?
+	 * F.e. "127.0.0.1 localhost". We don't do DNS query for such hosts -
+	 * "ping localhost" should be fast even if DNS server is down! */
+	if (wrong_af) {
+		*h_errnop = HOST_NOT_FOUND;
+		return TRY_AGAIN;
+	}
 
+	memset(&a, '\0', sizeof(a));
+
 	for (;;) {
 		__UCLIBC_MUTEX_LOCK(__resolv_lock);
 		__nameserversXX = __nameservers;
@@ -2306,7 +2320,8 @@
 				return -1;
 			}
 			continue;
-		} else if (a.atype == T_AAAA) {	/* ADDRESS */
+		}
+		if (a.atype == T_AAAA) {	/* ADDRESS */
 			memcpy(in, a.rdata, sizeof(*in));
 			result_buf->h_name = buf;
 			result_buf->h_addrtype = AF_INET6;
@@ -2314,11 +2329,10 @@
 			result_buf->h_addr_list = (char **) addr_list;
 			free(packet);
 			break;
-		} else {
-			free(packet);
-			*h_errnop = HOST_NOT_FOUND;
-			return TRY_AGAIN;
 		}
+		free(packet);
+		*h_errnop = HOST_NOT_FOUND;
+		return TRY_AGAIN;
 	}
 
 	*result = result_buf;