Cache network interface information

Whenever getaddrinfo needed network interface information it used the
netlink interface to read the information every single time.  The
problem is that this information can change at any time.

The patch implements monitoring of the network interfaces through
nscd.  If no change is detected the previously read information can
be reused (which is the norm).  This timestamp information is also
made available to other processes using the shared memory segment
between nscd and those processes.

10 files changed, 359 insertions, 46 deletions

diff --git a/ChangeLog b/ChangeLog
index b4e65a847c..005a1b7ff5 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,29 @@
+2011-10-31  Ulrich Drepper  <drepper@gmail.com>
+
+	* include/ifaddrs.h: Declare __free_in6ai and __bump_nl_timestamp.
+	* inet/check_pf.c: Provide dummy versions of __free_in6ai and
+	__bump_nl_timestamp.
+	* nscd/connections (nscd_init): When host database is served open
+	netlink socket and request notification about configuration changes.
+	(main_loop_poll): Track netlink file descriptor and bump timestamp
+	in case data becomes available.
+	(main_loop_epoll): Likewise.
+	* nscd/nscd-client.h (DB_VERSION): Bump to 2.
+	(database_pers_head): Add extra_data fileds.
+	Declare __nscd_get_mapping and __nscd_get_nl_timestamp.
+	* nscd/nscd_gethst_r.c (__nscd_get_nl_timestamp): New function.
+	* nscd/nscd_helper.c (__nscd_get_mapping): Renamed from get_mapping.
+	Adjust caller.
+	* sysdeps/posix/getaddrinfo.c (getaddrinfo): Don't call free on
+	in6ai data, call __free_in6ai.
+	* sysdeps/unix/sysv/linux/Makefile [subdir=nscd] (sysdep-CFLAGS):
+	Add -DHAVE_NETLINK.
+	* sysdeps/unix/sysv/linux/check_pf.c: Major rewrite.  Cache the
+	interface information.  Reuse previous data if netlink timestamp
+	is not changed.
+	(__bump_nl_timestamp): New function.
+	(__free_in6ai): New function.
+
 2011-10-30  Ulrich Drepper  <drepper@gmail.com>
 
 	* sysdeps/unix/sysv/linux/check_pf.c (make_request): Don't call
diff --git a/include/ifaddrs.h b/include/ifaddrs.h
index 50e4c48e82..e1c6cac114 100644
--- a/include/ifaddrs.h
+++ b/include/ifaddrs.h
@@ -21,8 +21,13 @@ struct in6addrinfo
 extern void __check_pf (bool *seen_ipv4, bool *seen_ipv6,
 			struct in6addrinfo **in6ai, size_t *in6ailen)
   attribute_hidden;
+extern void __free_in6ai (struct in6addrinfo *in6ai) attribute_hidden;
 extern void __check_native (uint32_t a1_index, int *a1_native,
 			    uint32_t a2_index, int *a2_native)
   attribute_hidden;
 
+#ifdef IS_IN_nscd
+extern uint32_t __bump_nl_timestamp (void) attribute_hidden;
+#endif
+
 #endif	/* ifaddrs.h */
diff --git a/inet/check_pf.c b/inet/check_pf.c
index b015432659..0fa34ccbbd 100644
--- a/inet/check_pf.c
+++ b/inet/check_pf.c
@@ -1,5 +1,5 @@
 /* Determine protocol families for which interfaces exist.  Generic version.
-   Copyright (C) 2003, 2006 Free Software Foundation, Inc.
+   Copyright (C) 2003, 2006, 2011 Free Software Foundation, Inc.
    This file is part of the GNU C Library.
 
    The GNU C Library is free software; you can redistribute it and/or
@@ -54,3 +54,19 @@ __check_pf (bool *seen_ipv4, bool *seen_ipv6,
 
   (void) freeifaddrs (ifa);
 }
+
+
+void
+__free_in6ai (struct in6addrinfo *in6ai)
+{
+  /* Nothing to do.  */
+}
+
+
+#ifdef IS_IN_nscd
+uint32_t
+__bump_nl_timestamp (void)
+{
+  return 0;
+}
+#endif
diff --git a/nscd/connections.c b/nscd/connections.c
index 2b5c7ef53c..1b8a9bdba7 100644
--- a/nscd/connections.c
+++ b/nscd/connections.c
@@ -24,6 +24,7 @@
 #include <errno.h>
 #include <fcntl.h>
 #include <grp.h>
+#include <ifaddrs.h>
 #include <libintl.h>
 #include <pthread.h>
 #include <pwd.h>
@@ -32,6 +33,9 @@
 #include <stdlib.h>
 #include <unistd.h>
 #include <arpa/inet.h>
+#ifdef HAVE_NETLINK
+# include <netlink/netlink.h>
+#endif
 #ifdef HAVE_EPOLL
 # include <sys/epoll.h>
 #endif
@@ -247,6 +251,11 @@ static int sock;
 int inotify_fd = -1;
 #endif
 
+#ifdef HAVE_NETLINK
+/* Descriptor for netlink status updates.  */
+static int nl_status_fd = -1;
+#endif
+
 #ifndef __ASSUME_SOCK_CLOEXEC
 /* Negative if SOCK_CLOEXEC is not supported, positive if it is, zero
    before be know the result.  */
@@ -903,6 +912,65 @@ cannot set socket to close on exec: %s; disabling paranoia mode"),
       exit (1);
     }
 
+#ifdef HAVE_NETLINK
+  if (dbs[hstdb].enabled)
+    {
+      /* Try to open netlink socket to monitor network setting changes.  */
+      nl_status_fd = socket (AF_NETLINK,
+			     SOCK_RAW | SOCK_CLOEXEC | SOCK_NONBLOCK,
+			     NETLINK_ROUTE);
+      if (nl_status_fd != -1)
+	{
+	  struct sockaddr_nl snl;
+	  memset (&snl, '\0', sizeof (snl));
+	  snl.nl_family = AF_NETLINK;
+	  /* XXX Is this the best set to use?  */
+	  snl.nl_groups = (RTMGRP_IPV4_IFADDR | RTMGRP_TC | RTMGRP_IPV4_MROUTE
+			   | RTMGRP_IPV4_ROUTE | RTMGRP_IPV4_RULE
+			   | RTMGRP_IPV6_IFADDR | RTMGRP_IPV6_MROUTE
+			   | RTMGRP_IPV6_ROUTE | RTMGRP_IPV6_IFINFO
+			   | RTMGRP_IPV6_PREFIX);
+
+	  if (bind (nl_status_fd, (struct sockaddr *) &snl, sizeof (snl)) != 0)
+	    {
+	      close (nl_status_fd);
+	      nl_status_fd = -1;
+	    }
+	  else
+	    {
+	      /* Start the timestamp process.  */
+	      dbs[hstdb].head->extra_data[NSCD_HST_IDX_CONF_TIMESTAMP]
+		= __bump_nl_timestamp ();
+
+# ifndef __ASSUME_SOCK_CLOEXEC
+	      if (have_sock_cloexec < 0)
+		{
+		  /* We don't want to get stuck on accept.  */
+		  int fl = fcntl (nl_status_fd, F_GETFL);
+		  if (fl == -1
+		      || fcntl (nl_status_fd, F_SETFL, fl | O_NONBLOCK) == -1)
+		    {
+		      dbg_log (_("\
+cannot change socket to nonblocking mode: %s"),
+			       strerror (errno));
+		      exit (1);
+		    }
+
+		  /* The descriptor needs to be closed on exec.  */
+		  if (paranoia
+		      && fcntl (nl_status_fd, F_SETFD, FD_CLOEXEC) == -1)
+		    {
+		      dbg_log (_("cannot set socket to close on exec: %s"),
+			       strerror (errno));
+		      exit (1);
+		    }
+		}
+# endif
+	    }
+	}
+    }
+#endif
+
   /* Change to unprivileged uid/gid/groups if specified in config file */
   if (server_user != NULL)
     finish_drop_privileges ();
@@ -1826,6 +1894,18 @@ main_loop_poll (void)
     }
 #endif
 
+#ifdef HAVE_NETLINK
+  size_t idx_nl_status_fd = 0;
+  if (nl_status_fd != -1)
+    {
+      idx_nl_status_fd = nused;
+      conns[nused].fd = nl_status_fd;
+      conns[nused].events = POLLRDNORM;
+      ++nused;
+      firstfree = nused;
+    }
+#endif
+
   while (1)
     {
       /* Wait for any event.  We wait at most a couple of seconds so
@@ -1968,6 +2048,20 @@ disabled inotify after read error %d"),
 	    }
 #endif
 
+#ifdef HAVE_NETLINK
+	  if (idx_nl_status_fd != 0 && conns[idx_nl_status_fd].revents != 0)
+	    {
+	      char buf[4096];
+	      /* Read all the data.  We do not interpret it here.  */
+	      while (TEMP_FAILURE_RETRY (read (nl_status_fd, buf,
+					       sizeof (buf))) != -1)
+		;
+
+	      dbs[hstdb].head->extra_data[NSCD_HST_IDX_CONF_TIMESTAMP]
+		= __bump_nl_timestamp ();
+	    }
+#endif
+
 	  for (size_t cnt = first; cnt < nused && n > 0; ++cnt)
 	    if (conns[cnt].revents != 0)
 	      {
@@ -2046,6 +2140,17 @@ main_loop_epoll (int efd)
     }
 # endif
 
+# ifdef HAVE_NETLINK
+  if (nl_status_fd != -1)
+    {
+      ev.events = EPOLLRDNORM;
+      ev.data.fd = nl_status_fd;
+      if (epoll_ctl (efd, EPOLL_CTL_ADD, nl_status_fd, &ev) == -1)
+	/* We cannot use epoll.  */
+	return;
+    }
+# endif
+
   while (1)
     {
       struct epoll_event revs[100];
@@ -2162,6 +2267,18 @@ main_loop_epoll (int efd)
 		}
 	  }
 # endif
+# ifdef HAVE_NETLINK
+	else if (revs[cnt].data.fd == nl_status_fd)
+	  {
+	    char buf[4096];
+	    /* Read all the data.  We do not interpret it here.  */
+	    while (TEMP_FAILURE_RETRY (read (nl_status_fd, buf,
+					     sizeof (buf))) != -1)
+	      ;
+
+	    __bump_nl_timestamp ();
+	  }
+# endif
 	else
 	  {
 	    /* Remove the descriptor from the epoll descriptor.  */
@@ -2185,6 +2302,7 @@ main_loop_epoll (int efd)
       time_t laststart = now - ACCEPT_TIMEOUT;
       assert (starttime[sock] == 0);
       assert (inotify_fd == -1 || starttime[inotify_fd] == 0);
+      assert (nl_status_fd == -1 || starttime[nl_status_fd] == 0);
       for (int cnt = highest; cnt > STDERR_FILENO; --cnt)
 	if (starttime[cnt] != 0 && starttime[cnt] < laststart)
 	  {
diff --git a/nscd/nscd-client.h b/nscd/nscd-client.h
index caad26a9cc..b5cd2d2c1e 100644
--- a/nscd/nscd-client.h
+++ b/nscd/nscd-client.h
@@ -260,12 +260,17 @@ struct hashentry
 
 
 /* Current persistent database version.  */
-#define DB_VERSION	1
+#define DB_VERSION	2
 
 /* Maximum time allowed between updates of the timestamp.  */
 #define MAPPING_TIMEOUT (5 * 60)
 
 
+/* Used indices for the EXTRA_DATA element of 'database_pers_head'.
+   Each database has its own indices.  */
+#define NSCD_HST_IDX_CONF_TIMESTAMP	0
+
+
 /* Header of persistent database file.  */
 struct database_pers_head
 {
@@ -274,6 +279,8 @@ struct database_pers_head
   volatile int32_t gc_cycle;
   volatile int32_t nscd_certainly_running;
   volatile nscd_time_t timestamp;
+  /* Room for extensions.  */
+  volatile uint32_t extra_data[4];
 
   nscd_ssize_t module;
   nscd_ssize_t data_size;
@@ -322,6 +329,12 @@ extern int __nscd_open_socket (const char *key, size_t keylen,
 			       request_type type, void *response,
 			       size_t responselen) attribute_hidden;
 
+/* Try to get a file descriptor for the shared meory segment
+   containing the database.  */
+extern struct mapped_database *__nscd_get_mapping (request_type type,
+						   const char *key,
+						   struct mapped_database **mappedp) attribute_hidden;
+
 /* Get reference of mapping.  */
 extern struct mapped_database *__nscd_get_map_ref (request_type type,
 						   const char *name,
@@ -371,4 +384,7 @@ extern ssize_t writeall (int fd, const void *buf, size_t len)
 extern ssize_t sendfileall (int tofd, int fromfd, off_t off, size_t len)
   attribute_hidden;
 
+/* Get netlink timestamp counter from mapped area or zero.  */
+extern uint32_t __nscd_get_nl_timestamp (void);
+
 #endif /* nscd.h */
diff --git a/nscd/nscd_gethst_r.c b/nscd/nscd_gethst_r.c
index 70631fa961..6ee142d71b 100644
--- a/nscd/nscd_gethst_r.c
+++ b/nscd/nscd_gethst_r.c
@@ -1,4 +1,4 @@
-/* Copyright (C) 1998-2005, 2006, 2007, 2008, 2009
+/* Copyright (C) 1998-2005, 2006, 2007, 2008, 2009, 2011
    Free Software Foundation, Inc.
    This file is part of the GNU C Library.
    Contributed by Ulrich Drepper <drepper@cygnus.com>, 1998.
@@ -98,6 +98,27 @@ libc_freeres_fn (hst_map_free)
 }
 
 
+uint32_t
+__nscd_get_nl_timestamp (void)
+{
+  if (__nss_not_use_nscd_hosts != 0)
+    return 0;
+
+  struct mapped_database *map = __hst_map_handle.mapped;
+
+  if (map == NULL
+      || (map != NO_MAPPING
+	  && map->head->nscd_certainly_running == 0
+	  && map->head->timestamp + MAPPING_TIMEOUT < time (NULL)))
+    map = __nscd_get_mapping (GETFDHST, "hosts", &__hst_map_handle.mapped);
+
+  if (map == NO_MAPPING)
+    return 0;
+
+  return map->head->extra_data[NSCD_HST_IDX_CONF_TIMESTAMP];
+}
+
+
 int __nss_have_localdomain attribute_hidden;
 
 static int
diff --git a/nscd/nscd_helper.c b/nscd/nscd_helper.c
index fe63f9a7fe..365b599892 100644
--- a/nscd/nscd_helper.c
+++ b/nscd/nscd_helper.c
@@ -277,9 +277,9 @@ __nscd_unmap (struct mapped_database *mapped)
 
 /* Try to get a file descriptor for the shared meory segment
    containing the database.  */
-static struct mapped_database *
-get_mapping (request_type type, const char *key,
-	     struct mapped_database **mappedp)
+struct mapped_database *
+__nscd_get_mapping (request_type type, const char *key,
+		    struct mapped_database **mappedp)
 {
   struct mapped_database *result = NO_MAPPING;
 #ifdef SCM_RIGHTS
@@ -449,8 +449,8 @@ __nscd_get_map_ref (request_type type, const char *name,
 	  || (cur->head->nscd_certainly_running == 0
 	      && cur->head->timestamp + MAPPING_TIMEOUT < time (NULL))
 	  || cur->head->data_size > cur->datasize)
-	cur = get_mapping (type, name,
-			   (struct mapped_database **) &mapptr->mapped);
+	cur = __nscd_get_mapping (type, name,
+				  (struct mapped_database **) &mapptr->mapped);
 
       if (__builtin_expect (cur != NO_MAPPING, 1))
 	{
diff --git a/sysdeps/posix/getaddrinfo.c b/sysdeps/posix/getaddrinfo.c
index a5aafe93ac..216c9cce5f 100644
--- a/sysdeps/posix/getaddrinfo.c
+++ b/sysdeps/posix/getaddrinfo.c
@@ -2386,7 +2386,7 @@ getaddrinfo (const char *name, const char *service,
 	       || (hints->ai_family == PF_INET6 && ! seen_ipv6))
 	{
 	  /* We cannot possibly return a valid answer.  */
-	  free (in6ai);
+	  __free_in6ai (in6ai);
 	  return EAI_NONAME;
 	}
     }
@@ -2400,7 +2400,7 @@ getaddrinfo (const char *name, const char *service,
 	{
 	  if (hints->ai_flags & AI_NUMERICSERV)
 	    {
-	      free (in6ai);
+	      __free_in6ai (in6ai);
 	      return EAI_NONAME;
 	    }
 
@@ -2422,7 +2422,7 @@ getaddrinfo (const char *name, const char *service,
       if (last_i != 0)
 	{
 	  freeaddrinfo (p);
-	  free (in6ai);
+	  __free_in6ai (in6ai);
 
 	  return -(last_i & GAIH_EAI);
 	}
@@ -2434,7 +2434,7 @@ getaddrinfo (const char *name, const char *service,
     }
   else
     {
-      free (in6ai);
+      __free_in6ai (in6ai);
       return EAI_FAMILY;
     }
 
@@ -2622,7 +2622,7 @@ getaddrinfo (const char *name, const char *service,
       p->ai_canonname = canonname;
     }
 
-  free (in6ai);
+  __free_in6ai (in6ai);
 
   if (p)
     {
diff --git a/sysdeps/unix/sysv/linux/Makefile b/sysdeps/unix/sysv/linux/Makefile
index af53f70c51..30320269c5 100644
--- a/sysdeps/unix/sysv/linux/Makefile
+++ b/sysdeps/unix/sysv/linux/Makefile
@@ -161,6 +161,6 @@ CFLAGS-mq_receive.c += -fexceptions
 endif
 
 ifeq ($(subdir),nscd)
-sysdep-CFLAGS += -DHAVE_EPOLL -DHAVE_SENDFILE -DHAVE_INOTIFY
+sysdep-CFLAGS += -DHAVE_EPOLL -DHAVE_SENDFILE -DHAVE_INOTIFY -DHAVE_NETLINK
 CFLAGS-gai.c += -DNEED_NETLINK
 endif
diff --git a/sysdeps/unix/sysv/linux/check_pf.c b/sysdeps/unix/sysv/linux/check_pf.c
index d5ad7ea2e5..1f66684e4f 100644
--- a/sysdeps/unix/sysv/linux/check_pf.c
+++ b/sysdeps/unix/sysv/linux/check_pf.c
@@ -1,5 +1,5 @@
 /* Determine protocol families for which interfaces exist.  Linux version.
-   Copyright (C) 2003, 2006, 2007, 2008, 2010, 2011 Free Software Foundation, Inc.
+   Copyright (C) 2003, 2006-2008, 2010, 2011 Free Software Foundation, Inc.
    This file is part of the GNU C Library.
 
    The GNU C Library is free software; you can redistribute it and/or
@@ -33,6 +33,9 @@
 
 #include <not-cancel.h>
 #include <kernel-features.h>
+#include <bits/libc-lock.h>
+#include <atomic.h>
+#include <nscd/nscd-client.h>
 
 
 #ifndef IFA_F_HOMEADDRESS
@@ -43,9 +46,42 @@
 #endif
 
 
-static int
-make_request (int fd, pid_t pid, bool *seen_ipv4, bool *seen_ipv6,
-	      struct in6addrinfo **in6ai, size_t *in6ailen)
+struct cached_data
+{
+  uint32_t timestamp;
+  uint32_t usecnt;
+  bool seen_ipv4;
+  bool seen_ipv6;
+  size_t in6ailen;
+  struct in6addrinfo in6ai[0];
+};
+
+static struct cached_data noai6ai_cached =
+  {
+    .usecnt = 3,	/* Make sure we never try to delete this entry.  */
+    .in6ailen = 0
+  };
+
+static struct cached_data *cache;
+__libc_lock_define_initialized (static, lock);
+
+
+#ifdef IS_IN_nscd
+static uint32_t nl_timestamp;
+
+uint32_t
+__bump_nl_timestamp (void)
+{
+  if (atomic_increment_val (&nl_timestamp) == 0)
+    atomic_increment (&nl_timestamp);
+
+  return nl_timestamp;
+}
+#endif
+
+
+static struct cached_data *
+make_request (int fd, pid_t pid)
 {
   struct req
   {
@@ -99,9 +135,6 @@ make_request (int fd, pid_t pid, bool *seen_ipv4, bool *seen_ipv6,
 				    sizeof (nladdr))) < 0)
     goto out_fail;
 
-  *seen_ipv4 = false;
-  *seen_ipv6 = false;
-
   bool done = false;
   struct in6ailist
   {
@@ -109,6 +142,8 @@ make_request (int fd, pid_t pid, bool *seen_ipv4, bool *seen_ipv6,
     struct in6ailist *next;
   } *in6ailist = NULL;
   size_t in6ailistlen = 0;
+  bool seen_ipv4 = false;
+  bool seen_ipv6 = false;
 
   do
     {
@@ -172,12 +207,12 @@ make_request (int fd, pid_t pid, bool *seen_ipv4, bool *seen_ipv6,
 		    {
 		      if (*(const in_addr_t *) address
 			  != htonl (INADDR_LOOPBACK))
-			*seen_ipv4 = true;
+			seen_ipv4 = true;
 		    }
 		  else
 		    {
 		      if (!IN6_IS_ADDR_LOOPBACK (address))
-			*seen_ipv6 = true;
+			seen_ipv6 = true;
 		    }
 		}
 
@@ -211,30 +246,46 @@ make_request (int fd, pid_t pid, bool *seen_ipv4, bool *seen_ipv6,
     }
   while (! done);
 
-  if (*seen_ipv6 && in6ailist != NULL)
+  struct cached_data *result;
+  if (seen_ipv6 && in6ailist != NULL)
     {
-      *in6ai = malloc (in6ailistlen * sizeof (**in6ai));
-      if (*in6ai == NULL)
+      result = malloc (sizeof (*result)
+		       + in6ailistlen * sizeof (struct in6addrinfo));
+      if (result == NULL)
 	goto out_fail;
 
-      *in6ailen = in6ailistlen;
+#ifdef IS_IN_nscd
+      result->timestamp = nl_timestamp;
+#else
+      result->timestamp = __nscd_get_nl_timestamp ();
+#endif
+      result->usecnt = 2;
+      result->seen_ipv4 = seen_ipv4;
+      result->seen_ipv6 = true;
+      result->in6ailen = in6ailistlen;
 
       do
 	{
-	  (*in6ai)[--in6ailistlen] = in6ailist->info;
+	  result->in6ai[--in6ailistlen] = in6ailist->info;
 	  in6ailist = in6ailist->next;
 	}
       while (in6ailist != NULL);
     }
+  else
+    {
+      noai6ai_cached.seen_ipv4 = seen_ipv4;
+      noai6ai_cached.seen_ipv6 = seen_ipv6;
+      result = &noai6ai_cached;
+    }
 
   if (use_malloc)
     free (buf);
-  return 0;
+  return result;
 
 out_fail:
   if (use_malloc)
     free (buf);
-  return -1;
+  return NULL;
 }
 
 
@@ -258,28 +309,65 @@ __check_pf (bool *seen_ipv4, bool *seen_ipv6,
 
   if (! __no_netlink_support)
     {
-      int fd = __socket (PF_NETLINK, SOCK_RAW, NETLINK_ROUTE);
+      struct cached_data *olddata = NULL;
+      struct cached_data *data = NULL;
 
-      if (__builtin_expect (fd >= 0, 1))
+      __libc_lock_lock (lock);
+
+#ifdef IS_IN_nscd
+# define cache_valid() nl_timestamp != 0 && cache->timestamp == nl_timestamp
+#else
+# define cache_valid() \
+      ({ uint32_t val = __nscd_get_nl_timestamp ();			      \
+	 val != 0 && cache->timestamp == val; })
+#endif
+      if (cache != NULL && cache_valid ())
+	{
+	  data = cache;
+	  atomic_increment (&cache->usecnt);
+	}
+      else
 	{
-	  struct sockaddr_nl nladdr;
-	  memset (&nladdr, '\0', sizeof (nladdr));
-	  nladdr.nl_family = AF_NETLINK;
+	  int fd = __socket (PF_NETLINK, SOCK_RAW, NETLINK_ROUTE);
 
-	  socklen_t addr_len = sizeof (nladdr);
+	  if (__builtin_expect (fd >= 0, 1))
+	    {
+	      struct sockaddr_nl nladdr;
+	      memset (&nladdr, '\0', sizeof (nladdr));
+	      nladdr.nl_family = AF_NETLINK;
+
+	      socklen_t addr_len = sizeof (nladdr);
+
+	      if(__bind (fd, (struct sockaddr *) &nladdr, sizeof (nladdr)) == 0
+		 && __getsockname (fd, (struct sockaddr *) &nladdr,
+				   &addr_len) == 0)
+		data = make_request (fd, nladdr.nl_pid);
+
+	      close_not_cancel_no_status (fd);
+	    }
+
+	  if (data != NULL)
+	    {
+	      olddata = cache;
+	      cache = data;
+	    }
+	}
 
-	  bool success
-	    = (__bind (fd, (struct sockaddr *) &nladdr, sizeof (nladdr)) == 0
-	       && __getsockname (fd, (struct sockaddr *) &nladdr,
-				 &addr_len) == 0
-	       && make_request (fd, nladdr.nl_pid, seen_ipv4, seen_ipv6,
-				in6ai, in6ailen) == 0);
+      __libc_lock_unlock (lock);
 
-	  close_not_cancel_no_status (fd);
+      if (data != NULL)
+	{
+	  /* It worked.  */
+	  *seen_ipv4 = data->seen_ipv4;
+	  *seen_ipv6 = data->seen_ipv6;
+	  *in6ailen = data->in6ailen;
+	  *in6ai = data->in6ai;
+
+	  if (olddata != NULL && olddata->usecnt > 0
+	      && atomic_add_zero (&olddata->usecnt, -1))
+	    free (olddata);
 
-	  if (success)
-	    /* It worked.  */
-	    return;
+	  return;
 	}
 
 #if __ASSUME_NETLINK_SUPPORT == 0
@@ -318,3 +406,26 @@ __check_pf (bool *seen_ipv4, bool *seen_ipv6,
   (void) freeifaddrs (ifa);
 #endif
 }
+
+
+void
+__free_in6ai (struct in6addrinfo *ai)
+{
+  if (ai != NULL)
+    {
+      struct cached_data *data =
+	(struct cached_data *) ((char *) ai
+				- offsetof (struct cached_data, in6ai));
+
+      if (atomic_add_zero (&data->usecnt, -1))
+	{
+	  __libc_lock_lock (lock);
+
+	  if (data->usecnt == 0)
+	    /* Still unused.  */
+	    free (data);
+
+	  __libc_lock_unlock (lock);
+	}
+    }
+}