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From 93249f1901cc3f1f08d5f8f66f7cd6f7bd918946 Mon Sep 17 00:00:00 2001
From: Dan Williams <dcbw@redhat.com>
Date: Thu, 16 Dec 2010 17:47:59 -0600
Subject: [PATCH] dns: direct IPv4 reverse DNS queries to split DNS servers
When split DNS is used for a local caching nameserver, make sure
that reverse DNS queries for hosts within the VPN tunnel are directed
to the VPN's nameservers, not to the public upstream nameservers.
---
src/dns-manager/Makefile.am | 4 +-
src/dns-manager/nm-dns-dnsmasq.c | 22 +++++++--
src/dns-manager/nm-dns-utils.c | 99 ++++++++++++++++++++++++++++++++++++++
src/dns-manager/nm-dns-utils.h | 28 +++++++++++
4 files changed, 148 insertions(+), 5 deletions(-)
create mode 100644 src/dns-manager/nm-dns-utils.c
create mode 100644 src/dns-manager/nm-dns-utils.h
diff --git a/src/dns-manager/Makefile.am b/src/dns-manager/Makefile.am
index 1ffe62d..7b5fc4f 100644
--- a/src/dns-manager/Makefile.am
+++ b/src/dns-manager/Makefile.am
@@ -14,7 +14,9 @@ libdns_manager_la_SOURCES = \
nm-dns-dnsmasq.h \
nm-dns-dnsmasq.c \
nm-dns-bind.h \
- nm-dns-bind.c
+ nm-dns-bind.c \
+ nm-dns-utils.h \
+ nm-dns-utils.c
libdns_manager_la_CPPFLAGS = \
$(DBUS_CFLAGS) \
diff --git a/src/dns-manager/nm-dns-dnsmasq.c b/src/dns-manager/nm-dns-dnsmasq.c
index 41c8e2a..9cc0197 100644
--- a/src/dns-manager/nm-dns-dnsmasq.c
+++ b/src/dns-manager/nm-dns-dnsmasq.c
@@ -33,6 +33,7 @@
#include "nm-logging.h"
#include "nm-ip4-config.h"
#include "nm-ip6-config.h"
+#include "nm-dns-utils.h"
G_DEFINE_TYPE (NMDnsDnsmasq, nm_dns_dnsmasq, NM_TYPE_DNS_PLUGIN)
@@ -75,9 +76,11 @@ add_ip4_config (GString *str, NMIP4Config *ip4, gboolean split)
gboolean added = FALSE;
if (split) {
+ char **domains, **iter;
+
/* FIXME: it appears that dnsmasq can only handle one nameserver
- * per domain (at the manpage seems to indicate that) so only use
- * the first nameserver here.
+ * per domain (and the manpage says this too) so only use the first
+ * nameserver here.
*/
addr.s_addr = nm_ip4_config_get_nameserver (ip4, 0);
memset (&buf[0], 0, sizeof (buf));
@@ -103,6 +106,17 @@ add_ip4_config (GString *str, NMIP4Config *ip4, gboolean split)
added = TRUE;
}
}
+
+ /* Ensure reverse-DNS works by directing queries for in-addr.arpa
+ * domains to the split domain's nameserver.
+ */
+ domains = nm_dns_utils_get_ip4_rdns_domains (ip4);
+ if (domains) {
+ for (iter = domains; iter && *iter; iter++)
+ g_string_append_printf (str, "server=/%s/%s\n", *iter, buf);
+ g_strfreev (domains);
+ added = TRUE;
+ }
}
/* If no searches or domains, just add the namservers */
@@ -216,7 +230,7 @@ update (NMDnsPlugin *plugin,
}
/* Now add interface configs without split DNS */
- for (iter = (GSList *) dev_configs; iter;iter = g_slist_next (iter)) {
+ for (iter = (GSList *) dev_configs; iter; iter = g_slist_next (iter)) {
if (NM_IS_IP4_CONFIG (iter->data))
add_ip4_config (conf, NM_IP4_CONFIG (iter->data), FALSE);
else if (NM_IS_IP6_CONFIG (iter->data))
@@ -224,7 +238,7 @@ update (NMDnsPlugin *plugin,
}
/* And any other random configs */
- for (iter = (GSList *) other_configs; iter;iter = g_slist_next (iter)) {
+ for (iter = (GSList *) other_configs; iter; iter = g_slist_next (iter)) {
if (NM_IS_IP4_CONFIG (iter->data))
add_ip4_config (conf, NM_IP4_CONFIG (iter->data), FALSE);
else if (NM_IS_IP6_CONFIG (iter->data))
diff --git a/src/dns-manager/nm-dns-utils.c b/src/dns-manager/nm-dns-utils.c
new file mode 100644
index 0000000..615adfd
--- /dev/null
+++ b/src/dns-manager/nm-dns-utils.c
@@ -0,0 +1,99 @@
+/* -*- Mode: C; tab-width: 4; indent-tabs-mode: t; c-basic-offset: 4 -*- */
+/* This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2, or (at your option)
+ * any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License along
+ * with this program; if not, write to the Free Software Foundation, Inc.,
+ * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
+ *
+ * Copyright (C) 2010 Red Hat, Inc.
+ *
+ */
+
+#include <arpa/inet.h>
+#include <string.h>
+
+#include "nm-dns-utils.h"
+#include "nm-utils.h"
+
+static void
+add_ip4_to_rdns_array (guint32 ip, GPtrArray *domains) /* network byte order */
+{
+ guint32 defprefix;
+ guchar *p;
+ char *str = NULL;
+ int i;
+
+ defprefix = nm_utils_ip4_get_default_prefix (ip);
+
+ /* Convert to host byte order, mask the host bits, and convert back */
+ ip = ntohl (ip);
+ ip &= 0xFFFFFFFF << (32 - defprefix);
+ ip = htonl (ip);
+ p = (guchar *) &ip;
+
+ if (defprefix == 8)
+ str = g_strdup_printf ("%u.in-addr.arpa", p[0] & 0xFF);
+ else if (defprefix == 16)
+ str = g_strdup_printf ("%u.%u.in-addr.arpa", p[1] & 0xFF, p[0] & 0xFF);
+ else if (defprefix == 24)
+ str = g_strdup_printf ("%u.%u.%u.in-addr.arpa", p[2] & 0xFF, p[1] & 0xFF, p[0] & 0xFF);
+
+ g_return_if_fail (str != NULL);
+
+ /* Suppress duplicates */
+ for (i = 0; i < domains->len; i++) {
+ if (strcmp (str, g_ptr_array_index (domains, i)) == 0)
+ break;
+ }
+
+ if (i == domains->len)
+ g_ptr_array_add (domains, str);
+ else
+ g_free (str);
+}
+
+char **
+nm_dns_utils_get_ip4_rdns_domains (NMIP4Config *ip4)
+{
+ GPtrArray *domains = NULL;
+ int i;
+
+ g_return_val_if_fail (ip4 != NULL, NULL);
+
+ domains = g_ptr_array_sized_new (5);
+
+ /* To calculate the reverse DNS domains for this IP4 config, we take
+ * all the IP addresses and routes in the config, calculate the network
+ * portion, and convert that to classful, and use the network bits for
+ * the final domain. FIXME: better handle classless routing, which might
+ * require us to add multiple domains for each actual network prefix to
+ * cover all the separate networks in that block.
+ */
+
+ for (i = 0; i < nm_ip4_config_get_num_addresses (ip4); i++) {
+ NMIP4Address *addr = nm_ip4_config_get_address (ip4, i);
+
+ add_ip4_to_rdns_array (nm_ip4_address_get_address (addr), domains);
+ }
+
+ for (i = 0; i < nm_ip4_config_get_num_routes (ip4); i++) {
+ NMIP4Route *route = nm_ip4_config_get_route (ip4, i);
+
+ add_ip4_to_rdns_array (nm_ip4_route_get_dest (route), domains);
+ }
+
+ /* Terminating NULL so we can use g_strfreev() to free it */
+ g_ptr_array_add (domains, NULL);
+
+ /* Free the array and return NULL if the only element was the ending NULL */
+ return (char **) g_ptr_array_free (domains, (domains->len == 1));
+}
+
diff --git a/src/dns-manager/nm-dns-utils.h b/src/dns-manager/nm-dns-utils.h
new file mode 100644
index 0000000..daa6711
--- /dev/null
+++ b/src/dns-manager/nm-dns-utils.h
@@ -0,0 +1,28 @@
+/* -*- Mode: C; tab-width: 4; indent-tabs-mode: t; c-basic-offset: 4 -*- */
+/* This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2, or (at your option)
+ * any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License along
+ * with this program; if not, write to the Free Software Foundation, Inc.,
+ * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
+ *
+ * Copyright (C) 2010 Red Hat, Inc.
+ *
+ */
+
+#ifndef NM_DNS_UTILS_H
+#define NM_DNS_UTILS_H
+
+#include "nm-ip4-config.h"
+
+char **nm_dns_utils_get_ip4_rdns_domains (NMIP4Config *ip4);
+
+#endif /* NM_DNS_UTILS_H */
+
--
1.7.3.4
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