resolv: Do not copy IPv4 addresses to IPv6 address array
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Message ID 9d15b097-23d1-1aac-f037-7d3a5a21c538@redhat.com
State New
Headers show

Commit Message

Florian Weimer June 30, 2017, 6:05 p.m. UTC
On 06/29/2017 08:35 PM, Florian Weimer wrote:
> While working on the resolver code, I discovered some address copying
> which appears to be unnecessary.  The attached patch removes that.
> 
> The comments refer to timing data, but we currently do not have that.
> 
> Andreas, if I recall correctly, you wrote get_nsaddr.  What do you think
> about this change?

This is the patch rebased to current master.

Thanks,
Florian

Patch
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resolv: Do not copy IPv4 addresses to IPv6 address array

get_nsaddr already prefers IPv4 addresses if they are present
(af_family != 0).  If we ensure that nssocks is initialized to -1
and sockets are closed even without an allocated server address,
there is no need to make these copies anymore.

2017-06-29  Florian Weimer  <fweimer@redhat.com>

	* resolv/bits/types/res_state.h (struct __res_state): Rename
	_u._ext.nscount to _u._ext.__glibc_unused_nscount.
	* resolv/res_init.c (res_vinit): Adjust.  Initialize nssocks
	member.
	* resolv/res_send.c (__libc_res_nsend): Do not copy IPv4
	nameserver addresses.
	* resolv/res-close.c (__res_iclose): Close sockets even if the
	name server address has not been allocated.
	* support/resolv_test.c (resolv_test_start): Do not clear
	_res._u._ext.nscount because it is unused.

diff --git a/resolv/bits/types/res_state.h b/resolv/bits/types/res_state.h
index cee4b6d..d274cf3 100644
--- a/resolv/bits/types/res_state.h
+++ b/resolv/bits/types/res_state.h
@@ -40,7 +40,7 @@  struct __res_state {
 	union {
 		char	pad[52];	/* On an i386 this means 512b total. */
 		struct {
-			uint16_t		nscount;
+			uint16_t		__glibc_unused_nscount;
 			uint16_t		nsmap[MAXNS];
 			int			nssocks[MAXNS];
 			uint16_t		nscount6;
diff --git a/resolv/res-close.c b/resolv/res-close.c
index 73f18d1..3195298 100644
--- a/resolv/res-close.c
+++ b/resolv/res-close.c
@@ -97,19 +97,18 @@  __res_iclose (res_state statp, bool free_addr)
       statp->_flags &= ~(RES_F_VC | RES_F_CONN);
     }
   for (int ns = 0; ns < statp->nscount; ns++)
-    if (statp->_u._ext.nsaddrs[ns] != NULL)
-      {
-        if (statp->_u._ext.nssocks[ns] != -1)
-          {
-            close_not_cancel_no_status (statp->_u._ext.nssocks[ns]);
-            statp->_u._ext.nssocks[ns] = -1;
-          }
-        if (free_addr)
-          {
-            free (statp->_u._ext.nsaddrs[ns]);
-            statp->_u._ext.nsaddrs[ns] = NULL;
-          }
-      }
+    {
+      if (statp->_u._ext.nssocks[ns] != -1)
+        {
+          close_not_cancel_no_status (statp->_u._ext.nssocks[ns]);
+          statp->_u._ext.nssocks[ns] = -1;
+        }
+      if (free_addr)
+        {
+          free (statp->_u._ext.nsaddrs[ns]);
+          statp->_u._ext.nsaddrs[ns] = NULL;
+        }
+    }
 }
 libc_hidden_def (__res_iclose)
 
diff --git a/resolv/res_init.c b/resolv/res_init.c
index 5d8b2c9..8f7b8dc 100644
--- a/resolv/res_init.c
+++ b/resolv/res_init.c
@@ -155,9 +155,12 @@  res_vinit_1 (res_state statp, bool preinit, FILE *fp, char **buffer)
   statp->_flags = 0;
   statp->__glibc_unused_qhook = NULL;
   statp->__glibc_unused_rhook = NULL;
-  statp->_u._ext.nscount = 0;
+  statp->_u._ext.__glibc_unused_nscount = 0;
   for (int n = 0; n < MAXNS; n++)
-    statp->_u._ext.nsaddrs[n] = NULL;
+    {
+      statp->_u._ext.nsaddrs[n] = NULL;
+      statp->_u._ext.nssocks[n] = -1;
+    }
 
   /* Allow user to override the local domain definition.  */
   if ((cp = getenv ("LOCALDOMAIN")) != NULL)
@@ -328,7 +331,6 @@  res_vinit_1 (res_state statp, bool preinit, FILE *fp, char **buffer)
 
                       statp->nsaddr_list[nserv].sin_family = 0;
                       statp->_u._ext.nsaddrs[nserv] = sa6;
-                      statp->_u._ext.nssocks[nserv] = -1;
                       have_serv6 = true;
                       nserv++;
                     }
diff --git a/resolv/res_send.c b/resolv/res_send.c
index a7daae8..6ec957f 100644
--- a/resolv/res_send.c
+++ b/resolv/res_send.c
@@ -423,54 +423,6 @@  __libc_res_nsend(res_state statp, const u_char *buf, int buflen,
 	gotsomewhere = 0;
 	terrno = ETIMEDOUT;
 
-	/*
-	 * If the ns_addr_list in the resolver context has changed, then
-	 * invalidate our cached copy and the associated timing data.
-	 */
-	if (EXT(statp).nscount != 0) {
-		int needclose = 0;
-
-		if (EXT(statp).nscount != statp->nscount)
-			needclose++;
-		else
-			for (unsigned int ns = 0; ns < statp->nscount; ns++) {
-				if (statp->nsaddr_list[ns].sin_family != 0
-				    && !sock_eq((struct sockaddr_in6 *)
-						&statp->nsaddr_list[ns],
-						EXT(statp).nsaddrs[ns]))
-				{
-					needclose++;
-					break;
-				}
-			}
-		if (needclose) {
-			__res_iclose(statp, false);
-			EXT(statp).nscount = 0;
-		}
-	}
-
-	/*
-	 * Maybe initialize our private copy of the ns_addr_list.
-	 */
-	if (EXT(statp).nscount == 0) {
-		for (unsigned int ns = 0; ns < statp->nscount; ns++) {
-			EXT(statp).nssocks[ns] = -1;
-			if (statp->nsaddr_list[ns].sin_family == 0)
-				continue;
-			if (EXT(statp).nsaddrs[ns] == NULL)
-				EXT(statp).nsaddrs[ns] =
-				    malloc(sizeof (struct sockaddr_in6));
-			if (EXT(statp).nsaddrs[ns] != NULL)
-				memset (mempcpy(EXT(statp).nsaddrs[ns],
-						&statp->nsaddr_list[ns],
-						sizeof (struct sockaddr_in)),
-					'\0',
-					sizeof (struct sockaddr_in6)
-					- sizeof (struct sockaddr_in));
-		}
-		EXT(statp).nscount = statp->nscount;
-	}
-
 	/* Name server index offset.  Used to implement
 	   RES_ROTATE.  */
 	unsigned int ns_offset = nameserver_offset (statp);
diff --git a/support/resolv_test.c b/support/resolv_test.c
index 050cd71..b5df5ff 100644
--- a/support/resolv_test.c
+++ b/support/resolv_test.c
@@ -1103,7 +1103,6 @@  resolv_test_start (struct resolv_redirect_config config)
   /* Disable IPv6 name server addresses.  The code below only
      overrides the IPv4 addresses.  */
   __res_iclose (&_res, true);
-  _res._u._ext.nscount = 0;
 
   /* Redirect queries to the server socket.  */
   if (test_verbose)