Patch from Tony J. White:

I've created a patch for adding dn_expand() to uClibc 0.9.21.

dn_expand() is used by at least ipsec-tools and also openldap I think.

libc/inet/Makefile

@@ -42,7 +42,8 @@ MOBJ2=encodeh.o decodeh.o encoded.o decoded.o lengthd.o encodeq.o \
 	closenameservers.o resolvename.o gethostbyname.o res_init.o \
 	res_query.o gethostbyaddr.o read_etc_hosts_r.o get_hosts_byname_r.o \
 	get_hosts_byaddr_r.o gethostbyname2.o getnameinfo.o gethostent.o \
-	gethostbyname_r.o gethostbyname2_r.o gethostbyaddr_r.o
+	gethostbyname_r.o gethostbyname2_r.o gethostbyaddr_r.o \
+	res_comp.o ns_name.o
 
 MSRC3=socketcalls.c
 MOBJ3= accept.o bind.o connect.o getpeername.o getsockname.o getsockopt.o \

libc/inet/resolv.c

@@ -7,6 +7,75 @@
  * modify it under the terms of the GNU Library General Public
  * License as published by the Free Software Foundation; either
  * version 2 of the License, or (at your option) any later version.
+*/
+
+/*
+ * Portions Copyright (c) 1985, 1993
+ *    The Regents of the University of California.  All rights reserved.
+ * 
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ * 4. Neither the name of the University nor the names of its contributors
+ *    may be used to endorse or promote products derived from this software
+ *    without specific prior written permission.
+ * 
+ * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
+ * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
+ * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
+ * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
+ * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+ * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
+ * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+ * SUCH DAMAGE.
+ */
+
+/*
+ * Portions Copyright (c) 1993 by Digital Equipment Corporation.
+ * 
+ * Permission to use, copy, modify, and distribute this software for any
+ * purpose with or without fee is hereby granted, provided that the above
+ * copyright notice and this permission notice appear in all copies, and that
+ * the name of Digital Equipment Corporation not be used in advertising or
+ * publicity pertaining to distribution of the document or software without
+ * specific, written prior permission.
+ * 
+ * THE SOFTWARE IS PROVIDED "AS IS" AND DIGITAL EQUIPMENT CORP. DISCLAIMS ALL
+ * WARRANTIES WITH REGARD TO THIS SOFTWARE, INCLUDING ALL IMPLIED WARRANTIES
+ * OF MERCHANTABILITY AND FITNESS.   IN NO EVENT SHALL DIGITAL EQUIPMENT
+ * CORPORATION BE LIABLE FOR ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL
+ * DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR
+ * PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS
+ * ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS
+ * SOFTWARE.
+ */
+
+/*
+ * Portions Copyright (c) 1996-1999 by Internet Software Consortium.
+ *
+ * Permission to use, copy, modify, and distribute this software for any
+ * purpose with or without fee is hereby granted, provided that the above
+ * copyright notice and this permission notice appear in all copies.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS" AND INTERNET SOFTWARE CONSORTIUM DISCLAIMS
+ * ALL WARRANTIES WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES
+ * OF MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL INTERNET SOFTWARE
+ * CONSORTIUM BE LIABLE FOR ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL
+ * DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR
+ * PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS
+ * ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS
+ * SOFTWARE.
+ */
+
+/*
  *
  *  5-Oct-2000 W. Greathouse  wgreathouse@smva.com
  *                              Fix memory leak and memory corruption.
@@ -54,6 +123,10 @@
  *   Fixed __decode_dotted to count the terminating null character
  *   in a host name.
  *
+ * 02-Oct-2003 Tony J. White <tjw@tjw.org>
+ *   Lifted dn_expand() and dependent ns_name_uncompress(), ns_name_unpack(),
+ *   and ns_name_ntop() from glibc 2.3.2 for compatibility with ipsec-tools 
+ *   and openldap.
  *
  */
 
@@ -186,6 +259,13 @@ extern int __decode_answer(unsigned char * message, int offset,
 extern int __length_question(unsigned char * message, int offset);
 extern int __open_nameservers(void);
 extern void __close_nameservers(void);
+extern int __dn_expand(const u_char *, const u_char *, const u_char *,
+	char *, int);
+extern int __ns_name_uncompress(const u_char *, const u_char *, 
+		const u_char *, char *, size_t);
+extern int __ns_name_ntop(const u_char *, char *, size_t);
+extern int __ns_name_unpack(const u_char *, const u_char *, const u_char *,
+               u_char *, size_t);
 
 
 #ifdef L_encodeh
@@ -1987,3 +2067,234 @@ int gethostbyaddr_r (const void *addr, socklen_t len, int type,
 	return NETDB_SUCCESS;
 }
 #endif
+
+#ifdef L_res_comp
+/*
+ * Expand compressed domain name 'comp_dn' to full domain name.
+ * 'msg' is a pointer to the begining of the message,
+ * 'eomorig' points to the first location after the message,
+ * 'exp_dn' is a pointer to a buffer of size 'length' for the result.
+ * Return size of compressed name or -1 if there was an error.
+ */
+int __dn_expand(const u_char *msg, const u_char *eom, const u_char *src,
+          char *dst, int dstsiz)
+{
+	int n = ns_name_uncompress(msg, eom, src, dst, (size_t)dstsiz);
+
+	if (n > 0 && dst[0] == '.')
+		dst[0] = '\0';
+	return (n);
+}
+#endif /* L_res_comp */
+
+#ifdef L_ns_name
+/*
+ * printable(ch)
+ *      Thinking in noninternationalized USASCII (per the DNS spec),
+ *      is this character visible and not a space when printed ?
+ * return:
+ *      boolean.
+ */
+static int printable(int ch) 
+{
+        return (ch > 0x20 && ch < 0x7f);
+}
+
+/*
+ * special(ch)
+ *      Thinking in noninternationalized USASCII (per the DNS spec),
+ *      is this characted special ("in need of quoting") ?
+ * return:
+ *      boolean.
+ */
+static int special(int ch) 
+{
+        switch (ch) {
+        case 0x22: /* '"' */
+        case 0x2E: /* '.' */
+        case 0x3B: /* ';' */
+        case 0x5C: /* '\\' */
+        /* Special modifiers in zone files. */
+        case 0x40: /* '@' */
+        case 0x24: /* '$' */
+                return (1);
+        default:
+                return (0);
+        }
+}
+
+/*
+ * ns_name_uncompress(msg, eom, src, dst, dstsiz)
+ *      Expand compressed domain name to presentation format.
+ * return:
+ *      Number of bytes read out of `src', or -1 (with errno set).
+ * note:
+ *      Root domain returns as "." not "".
+ */
+int __ns_name_uncompress(const u_char *msg, const u_char *eom, 
+		const u_char *src, char *dst, size_t dstsiz)
+{
+	u_char tmp[NS_MAXCDNAME];
+	int n;
+
+	if ((n = ns_name_unpack(msg, eom, src, tmp, sizeof tmp)) == -1)
+		return (-1);
+	if (ns_name_ntop(tmp, dst, dstsiz) == -1)
+		return (-1);
+	return (n);
+}
+
+
+/*
+ * ns_name_ntop(src, dst, dstsiz)
+ *      Convert an encoded domain name to printable ascii as per RFC1035.
+ * return:
+ *      Number of bytes written to buffer, or -1 (with errno set)
+ * notes:
+ *      The root is returned as "."
+ *      All other domains are returned in non absolute form
+ */
+int __ns_name_ntop(const u_char *src, char *dst, size_t dstsiz) {
+	const u_char *cp;
+	char *dn, *eom;
+	u_char c;
+	u_int n;
+	const char digits[] = "0123456789";
+
+	cp = src;
+	dn = dst;
+	eom = dst + dstsiz;
+
+	while ((n = *cp++) != 0) {
+		if ((n & NS_CMPRSFLGS) != 0) {
+			/* Some kind of compression pointer. */
+			__set_errno (EMSGSIZE);
+			return (-1);
+		}
+		if (dn != dst) {
+			if (dn >= eom) {
+				__set_errno (EMSGSIZE);
+				return (-1);
+			}
+			*dn++ = '.';
+		}
+		if (dn + n >= eom) {
+			__set_errno (EMSGSIZE);
+			return (-1);
+		}
+		for ((void)NULL; n > 0; n--) {
+			c = *cp++;
+			if (special(c)) {
+				if (dn + 1 >= eom) {
+					__set_errno (EMSGSIZE);
+					return (-1);
+				}
+				*dn++ = '\\';
+				*dn++ = (char)c;
+			} else if (!printable(c)) {
+				if (dn + 3 >= eom) {
+					__set_errno (EMSGSIZE);
+					return (-1);
+				}
+				*dn++ = '\\';
+				*dn++ = digits[c / 100];
+				*dn++ = digits[(c % 100) / 10];
+				*dn++ = digits[c % 10];
+			} else {
+				if (dn >= eom) {
+					__set_errno (EMSGSIZE);
+					return (-1);
+				}
+				*dn++ = (char)c;
+			}
+		}
+	}
+	if (dn == dst) {
+		if (dn >= eom) {
+			__set_errno (EMSGSIZE);
+			return (-1);
+		}
+		*dn++ = '.';
+	}
+	if (dn >= eom) {
+		__set_errno (EMSGSIZE);
+		return (-1);
+	}
+	*dn++ = '\0';
+        return (dn - dst);
+}
+
+/*
+ * ns_name_unpack(msg, eom, src, dst, dstsiz)
+ *      Unpack a domain name from a message, source may be compressed.
+ * return:
+ *      -1 if it fails, or consumed octets if it succeeds.
+ */
+int __ns_name_unpack(const u_char *msg, const u_char *eom, const u_char *src,
+               u_char *dst, size_t dstsiz)
+{
+	const u_char *srcp, *dstlim;
+	u_char *dstp;
+	int n, len, checked;
+
+	len = -1;
+	checked = 0;
+	dstp = dst;
+	srcp = src;
+	dstlim = dst + dstsiz;
+	if (srcp < msg || srcp >= eom) {
+		__set_errno (EMSGSIZE);
+		return (-1);
+	}
+	/* Fetch next label in domain name. */
+	while ((n = *srcp++) != 0) {
+		/* Check for indirection. */
+		switch (n & NS_CMPRSFLGS) {
+		case 0:
+			/* Limit checks. */
+			if (dstp + n + 1 >= dstlim || srcp + n >= eom) {
+				__set_errno (EMSGSIZE);
+				return (-1);
+			}
+			checked += n + 1;
+			*dstp++ = n;
+			memcpy(dstp, srcp, n);
+			dstp += n;
+			srcp += n;
+			break;
+
+		case NS_CMPRSFLGS:
+			if (srcp >= eom) {
+				__set_errno (EMSGSIZE);
+				return (-1);
+			}
+			if (len < 0)
+				len = srcp - src + 1;
+			srcp = msg + (((n & 0x3f) << 8) | (*srcp & 0xff));
+			if (srcp < msg || srcp >= eom) {  /* Out of range. */
+				__set_errno (EMSGSIZE);
+				return (-1);
+			}
+			checked += 2;
+			/*
+			 * Check for loops in the compressed name;
+			 * if we've looked at the whole message,
+			 * there must be a loop.
+			 */
+			if (checked >= eom - msg) {
+				__set_errno (EMSGSIZE);
+				return (-1);
+			}
+			break;
+
+		default:
+			__set_errno (EMSGSIZE);
+			return (-1);                    /* flag error */
+		}
+	}
+	*dstp = '\0';
+	if (len < 0)
+		len = srcp - src;
+	return (len);
+}
+#endif /* L_ns_name */