resolv: Deprecate legacy interfaces in libresolv

Debugging interfaces: p_*, fp_*, and sym_* could conceivably be
used to produce debug out, but these functions have not been
updated to parse more resource records, so they are not very useful
today.  Likewise for ns_sprintrr and ns_sprintrrf.  ns_format_ttl and
ns_parse_ttl are related to these.

Internal implementation details: res_isourserver is probably only
useful in the implementation of a stub resolver, and so is
res_nameinquery.

Unclear semantics and bad performance: ns_samedomain, ns_subdomain,
ns_makecanon, ns_samename do textual converions & copies instead of
checking equivalence of the wire format.

inet_neta cannot handle IPv6 addresses.

res_hostalias has been superseded by getaddrinfo with AI_CANONNAME.
hostalias is not thread-safe.

Some functions have int as size arguments instead of size_t, so they
do not follow current coding practices.  However, dn_expand and
b64_ntop are somewhat widely used (to name just two examples), so
deprecating them seems problematic.

Reviewed-by: Carlos O'Donell <carlos@systemhalted.org>

4 files changed, 95 insertions, 41 deletions

diff --git a/NEWS b/NEWS
index 13ffe627da..4df348cce5 100644
--- a/NEWS
+++ b/NEWS
@@ -93,6 +93,20 @@ Deprecated and removed features, and other changes affecting compatibility:
 * The function pthread_yield has been deprecated; programs should use
   the equivalent standard function sched_yield instead.
 
+* The function inet_neta declared in <arpa/inet.h> has been deprecated.
+
+* Various rarely-used functions declared in <resolv.h> and
+  <arpa/nameser.h> have been deprecated.  Applications are encouraged to
+  use dedicated DNS processing libraries if applicable.  For <resolv.h>,
+  this affects the functions dn_count_labels, fp_nquery, fp_query,
+  fp_resstat, hostalias, loc_aton, loc_ntoa, p_cdname, p_cdnname,
+  p_class, p_fqname, p_fqnname, p_option, p_query, p_rcode, p_time,
+  p_type, putlong, putshort, res_hostalias, res_isourserver,
+  res_nameinquery, res_queriesmatch, res_randomid, sym_ntop, sym_ntos,
+  sym_ston.  For <arpa/nameser.h>, the functions ns_datetosecs,
+  ns_format_ttl, ns_makecanon, ns_parse_ttl, ns_samedomain, ns_samename,
+  ns_sprintrr, ns_sprintrrf, ns_subdomain have been deprecated.
+
 * The pthread cancellation handler is now installed with SA_RESTART and
   pthread_cancel will always send the internal SIGCANCEL on a cancellation
   request.  It should not be visible to application since the cancellation
diff --git a/inet/arpa/inet.h b/inet/arpa/inet.h
index 3a99dbfa5a..54c9c6d468 100644
--- a/inet/arpa/inet.h
+++ b/inet/arpa/inet.h
@@ -74,7 +74,8 @@ extern int inet_aton (const char *__cp, struct in_addr *__inp) __THROW;
 
 /* Format a network number NET into presentation format and place result
    in buffer starting at BUF with length of LEN bytes.  */
-extern char *inet_neta (in_addr_t __net, char *__buf, size_t __len) __THROW;
+extern char *inet_neta (in_addr_t __net, char *__buf, size_t __len) __THROW
+  __attribute_deprecated_msg__ ("Use inet_ntop instead");
 
 /* Convert network number for interface type AF in buffer starting at
    CP to presentation format.  The result will specifiy BITS bits of
diff --git a/resolv/arpa/nameser.h b/resolv/arpa/nameser.h
index a99d5ec508..017d7b194a 100644
--- a/resolv/arpa/nameser.h
+++ b/resolv/arpa/nameser.h
@@ -52,6 +52,12 @@
 #include <sys/types.h>
 #include <stdint.h>
 
+#ifdef _LIBC
+# define __NAMESER_DEPRECATED
+#else
+# define __NAMESER_DEPRECATED __attribute_deprecated__
+#endif
+
 /*
  * Define constants based on RFC 883, RFC 1034, RFC 1035
  */
@@ -401,14 +407,18 @@ int		ns_skiprr (const unsigned char *, const unsigned char *,
 int		ns_parserr (ns_msg *, ns_sect, int, ns_rr *) __THROW;
 int		ns_sprintrr (const ns_msg *, const ns_rr *,
 			     const char *, const char *, char *, size_t)
-     __THROW;
+  __THROW __NAMESER_DEPRECATED;
 int		ns_sprintrrf (const unsigned char *, size_t, const char *,
 			      ns_class, ns_type, unsigned long,
 			      const unsigned char *, size_t, const char *,
-			      const char *, char *, size_t) __THROW;
-int		ns_format_ttl (unsigned long, char *, size_t) __THROW;
-int		ns_parse_ttl (const char *, unsigned long *) __THROW;
-uint32_t	ns_datetosecs (const char *, int *) __THROW;
+			      const char *, char *, size_t)
+  __THROW __NAMESER_DEPRECATED;
+int		ns_format_ttl (unsigned long, char *, size_t)
+  __THROW __NAMESER_DEPRECATED;
+int		ns_parse_ttl (const char *, unsigned long *)
+  __THROW __NAMESER_DEPRECATED;
+uint32_t	ns_datetosecs (const char *, int *)
+  __THROW __NAMESER_DEPRECATED;
 int		ns_name_ntol (const unsigned char *, unsigned char *, size_t)
      __THROW;
 int		ns_name_ntop (const unsigned char *, char *, size_t) __THROW;
@@ -431,10 +441,15 @@ int		ns_name_skip (const unsigned char **, const unsigned char *)
 void		ns_name_rollback (const unsigned char *,
 				  const unsigned char **,
 				  const unsigned char **) __THROW;
-int		ns_samedomain (const char *, const char *) __THROW;
-int		ns_subdomain (const char *, const char *) __THROW;
-int		ns_makecanon (const char *, char *, size_t) __THROW;
-int		ns_samename (const char *, const char *) __THROW;
+
+int		ns_samedomain (const char *, const char *) __THROW
+  __NAMESER_DEPRECATED;
+int		ns_subdomain (const char *, const char *) __THROW
+  __NAMESER_DEPRECATED;
+int		ns_makecanon (const char *, char *, size_t) __THROW
+  __NAMESER_DEPRECATED;
+int		ns_samename (const char *, const char *) __THROW
+  __NAMESER_DEPRECATED;
 __END_DECLS
 
 #include <arpa/nameser_compat.h>
diff --git a/resolv/resolv.h b/resolv/resolv.h
index a039a9e636..02a35173e9 100644
--- a/resolv/resolv.h
+++ b/resolv/resolv.h
@@ -174,14 +174,27 @@ __END_DECLS
 #define res_search		__res_search
 #define res_send		__res_send
 
+#ifdef _LIBC
+# define __RESOLV_DEPRECATED
+# define __RESOLV_DEPRECATED_MSG(msg)
+#else
+# define __RESOLV_DEPRECATED __attribute_deprecated__
+# define __RESOLV_DEPRECATED_MSG(msg) __attribute_deprecated_msg__ (msg)
+#endif
+
 __BEGIN_DECLS
-void		fp_nquery (const unsigned char *, int, FILE *) __THROW;
-void		fp_query (const unsigned char *, FILE *) __THROW;
-const char *	hostalias (const char *) __THROW;
-void		p_query (const unsigned char *) __THROW;
+void		fp_nquery (const unsigned char *, int, FILE *) __THROW
+  __RESOLV_DEPRECATED;
+void		fp_query (const unsigned char *, FILE *) __THROW
+  __RESOLV_DEPRECATED;
+const char *	hostalias (const char *) __THROW
+  __RESOLV_DEPRECATED_MSG ("use getaddrinfo instead");
+void		p_query (const unsigned char *) __THROW
+  __RESOLV_DEPRECATED;
 void		res_close (void) __THROW;
 int		res_init (void) __THROW;
-int		res_isourserver (const struct sockaddr_in *) __THROW;
+int		res_isourserver (const struct sockaddr_in *) __THROW
+  __RESOLV_DEPRECATED;
 int		res_mkquery (int, const char *, int, int,
 			     const unsigned char *, int, const unsigned char *,
 			     unsigned char *, int) __THROW;
@@ -238,50 +251,61 @@ int		res_hnok (const char *) __THROW;
 int		res_ownok (const char *) __THROW;
 int		res_mailok (const char *) __THROW;
 int		res_dnok (const char *) __THROW;
-int		sym_ston (const struct res_sym *, const char *, int *) __THROW;
-const char *	sym_ntos (const struct res_sym *, int, int *) __THROW;
-const char *	sym_ntop (const struct res_sym *, int, int *) __THROW;
+int		sym_ston (const struct res_sym *, const char *, int *) __THROW
+  __RESOLV_DEPRECATED;
+const char *	sym_ntos (const struct res_sym *, int, int *) __THROW
+  __RESOLV_DEPRECATED;
+const char *	sym_ntop (const struct res_sym *, int, int *) __THROW
+  __RESOLV_DEPRECATED;
 int		b64_ntop (const unsigned char *, size_t, char *, size_t)
-     __THROW;
+  __THROW;
 int		b64_pton (char const *, unsigned char *, size_t) __THROW;
-int		loc_aton (const char *__ascii, unsigned char *__binary) __THROW;
-const char *	loc_ntoa (const unsigned char *__binary, char *__ascii) __THROW;
+int		loc_aton (const char *__ascii, unsigned char *__binary) __THROW
+  __RESOLV_DEPRECATED;
+const char *	loc_ntoa (const unsigned char *__binary, char *__ascii) __THROW
+  __RESOLV_DEPRECATED;
 int		dn_skipname (const unsigned char *, const unsigned char *)
-     __THROW;
-void		putlong (uint32_t, unsigned char *) __THROW;
-void		putshort (uint16_t, unsigned char *) __THROW;
-const char *	p_class (int) __THROW;
-const char *	p_time (uint32_t) __THROW;
-const char *	p_type (int) __THROW;
-const char *	p_rcode (int) __THROW;
-const unsigned char * p_cdnname (const unsigned char *,
-				 const unsigned char *, int, FILE *) __THROW;
+  __THROW;
+void		putlong (uint32_t, unsigned char *) __THROW
+  __RESOLV_DEPRECATED_MSG ("use NS_PUT16 instead");
+void		putshort (uint16_t, unsigned char *) __THROW
+  __RESOLV_DEPRECATED_MSG ("use NS_PUT32 instead");
+const char *	p_class (int) __THROW __RESOLV_DEPRECATED;
+const char *	p_time (uint32_t) __THROW __RESOLV_DEPRECATED;
+const char *	p_type (int) __THROW __RESOLV_DEPRECATED;
+const char *	p_rcode (int) __THROW __RESOLV_DEPRECATED;
+const unsigned char * p_cdnname (const unsigned char *, const unsigned char *,
+				 int, FILE *) __THROW __RESOLV_DEPRECATED;
 const unsigned char * p_cdname (const unsigned char *, const unsigned char *,
-				FILE *) __THROW;
+				FILE *) __THROW __RESOLV_DEPRECATED;
 const unsigned char * p_fqnname (const unsigned char *__cp,
 				 const unsigned char *__msg,
-				 int, char *, int) __THROW;
-const unsigned char * p_fqname (const unsigned char *,
-				const unsigned char *, FILE *) __THROW;
-const char *	p_option (unsigned long __option) __THROW;
-int		dn_count_labels (const char *) __THROW;
+				 int, char *, int) __THROW __RESOLV_DEPRECATED;
+const unsigned char * p_fqname (const unsigned char *, const unsigned char *,
+				FILE *) __THROW __RESOLV_DEPRECATED;
+const char *	p_option (unsigned long __option) __THROW __RESOLV_DEPRECATED;
+int		dn_count_labels (const char *) __THROW __RESOLV_DEPRECATED;
 int		dn_comp (const char *, unsigned char *, int, unsigned char **,
 			 unsigned char **) __THROW;
 int		dn_expand (const unsigned char *, const unsigned char *,
 			   const unsigned char *, char *, int) __THROW;
-unsigned int	res_randomid (void) __THROW;
+unsigned int	res_randomid (void) __THROW
+  __RESOLV_DEPRECATED_MSG ("use getentropy instead");
 int		res_nameinquery (const char *, int, int,
 				 const unsigned char *,
-				 const unsigned char *) __THROW;
+				 const unsigned char *) __THROW
+  __RESOLV_DEPRECATED;
 int		res_queriesmatch (const unsigned char *,
 				  const unsigned char *,
 				  const unsigned char *,
-				  const unsigned char *) __THROW;
+				  const unsigned char *) __THROW
+  __RESOLV_DEPRECATED;
 /* Things involving a resolver context. */
 int		res_ninit (res_state) __THROW;
-void		fp_resstat (const res_state, FILE *) __THROW;
+void		fp_resstat (const res_state, FILE *) __THROW
+  __RESOLV_DEPRECATED;
 const char *	res_hostalias (const res_state, const char *, char *, size_t)
-     __THROW;
+     __THROW __RESOLV_DEPRECATED_MSG ("use getaddrinfo instead");
 int		res_nquery (res_state, const char *, int, int,
 			    unsigned char *, int) __THROW;
 int		res_nsearch (res_state, const char *, int, int,