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.

1 files changed, 118 insertions, 0 deletions

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)
 	  {