dns: add CIDR reverse DNS IPv4 entries to dnsmasq

When a reverse DNS entry must be added to dnsmasq, instead of
considering IP addresses as classful use the prefix to compute one or
more "in-addr.arpa" according to CIDR rules.

https://bugzilla.gnome.org/show_bug.cgi?id=767174

4 files changed, 126 insertions, 52 deletions

diff --git a/src/dns-manager/nm-dns-utils.c b/src/dns-manager/nm-dns-utils.c
index e920611acc..d864aa9619 100644
--- a/src/dns-manager/nm-dns-utils.c
+++ b/src/dns-manager/nm-dns-utils.c
@@ -23,52 +23,14 @@
 #include <string.h>
 
 #include "nm-dns-utils.h"
+#include "nm-core-internal.h"
 #include "nm-platform.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);
-
-	if (!str) {
-		g_return_if_fail (str != NULL);
-		return;
-	}
-
-	/* 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)
 {
+	char **strv;
 	GPtrArray *domains = NULL;
 	int i;
 
@@ -76,30 +38,24 @@ nm_dns_utils_get_ip4_rdns_domains (NMIP4Config *ip4)
 
 	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++) {
 		const NMPlatformIP4Address *address = nm_ip4_config_get_address (ip4, i);
 
-		add_ip4_to_rdns_array (address->address, domains);
+		nm_utils_get_reverse_dns_domains_ip4 (address->address, address->plen, domains);
 	}
 
 	for (i = 0; i < nm_ip4_config_get_num_routes (ip4); i++) {
 		const NMPlatformIP4Route *route = nm_ip4_config_get_route (ip4, i);
 
-		add_ip4_to_rdns_array (route->network, domains);
+		nm_utils_get_reverse_dns_domains_ip4 (route->network, route->plen, 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));
-}
+	strv = (char **) g_ptr_array_free (domains, (domains->len == 1));
 
+	return _nm_utils_strv_cleanup (strv, FALSE, FALSE, TRUE);
+
+}
diff --git a/src/nm-core-utils.c b/src/nm-core-utils.c
index 12b537713e..1258a75f1e 100644
--- a/src/nm-core-utils.c
+++ b/src/nm-core-utils.c
@@ -3270,3 +3270,51 @@ nm_utils_dnsmasq_status_to_string (int status, char *dest, gsize size)
 	g_snprintf (dest, size, "%s (%d)", msg, status);
 	return dest;
 }
+
+/**
+ * nm_utils_get_reverse_dns_domains_ip4:
+ * @addr: IP address in network order
+ * @plen: prefix length
+ * @domains: array for results
+ *
+ * Creates reverse DNS domains for the given address and prefix length, and
+ * append them to @domains.
+ */
+void
+nm_utils_get_reverse_dns_domains_ip4 (guint32 addr, guint8 plen, GPtrArray *domains)
+{
+	guint32 ip, ip2, mask;
+	guchar *p;
+	guint octets;
+	guint i;
+	gsize len0, len;
+	char *str, *s;
+
+	g_return_if_fail (domains);
+	g_return_if_fail (plen <= 32);
+
+	if (!plen)
+		return;
+
+	octets = (plen - 1) / 8 + 1;
+	ip = ntohl (addr);
+	mask = 0xFFFFFFFF << (32 - plen);
+	ip &= mask;
+	ip2 = ip;
+
+	len0 = NM_STRLEN ("in-addr.arpa") + (4 * octets) + 1;
+	while ((ip2 & mask) == ip) {
+		addr = htonl (ip2);
+		p = (guchar *) &addr;
+
+		len = len0;
+		str = s = g_malloc (len);
+		for (i = octets; i > 0; i--)
+			nm_utils_strbuf_append (&s, &len, "%u.", p[i - 1] & 0xff);
+		nm_utils_strbuf_append_str (&s, &len, "in-addr.arpa");
+
+		g_ptr_array_add (domains, str);
+
+		ip2 += 1 << ((32 - plen) & ~7);
+	}
+}
diff --git a/src/nm-core-utils.h b/src/nm-core-utils.h
index db7794f615..8b278f725b 100644
--- a/src/nm-core-utils.h
+++ b/src/nm-core-utils.h
@@ -406,4 +406,6 @@ gboolean nm_utils_ip4_address_is_link_local (in_addr_t addr);
 
 const char *nm_utils_dnsmasq_status_to_string (int status, char *dest, gsize size);
 
+void nm_utils_get_reverse_dns_domains_ip4 (guint32 ip, guint8 plen, GPtrArray *domains);
+
 #endif /* __NM_CORE_UTILS_H__ */
diff --git a/src/tests/test-general.c b/src/tests/test-general.c
index d29cdc0eed..34e928811d 100644
--- a/src/tests/test-general.c
+++ b/src/tests/test-general.c
@@ -1363,6 +1363,72 @@ test_duplicate_decl_specifier (void)
 
 /*****************************************************************************/
 
+static void
+test_reverse_dns_ip4 (void)
+{
+	guint32 addr;
+	GPtrArray *domains = g_ptr_array_new_full (8, g_free);
+
+	inet_pton (AF_INET, "7.2.3.0", &addr);
+	nm_utils_get_reverse_dns_domains_ip4 (addr, 27, domains);
+	g_assert_cmpuint (domains->len, ==, 32);
+	g_assert_cmpstr (domains->pdata[0], ==, "0.3.2.7.in-addr.arpa");
+	g_assert_cmpstr (domains->pdata[31], ==, "31.3.2.7.in-addr.arpa");
+
+	g_ptr_array_set_size (domains, 0);
+
+	inet_pton (AF_INET, "10.155.16.0", &addr);
+	nm_utils_get_reverse_dns_domains_ip4 (addr, 22, domains);
+	g_assert_cmpuint (domains->len, ==, 4);
+	g_assert_cmpstr (domains->pdata[0], ==, "16.155.10.in-addr.arpa");
+	g_assert_cmpstr (domains->pdata[1], ==, "17.155.10.in-addr.arpa");
+	g_assert_cmpstr (domains->pdata[2], ==, "18.155.10.in-addr.arpa");
+	g_assert_cmpstr (domains->pdata[3], ==, "19.155.10.in-addr.arpa");
+
+	g_ptr_array_set_size (domains, 0);
+
+	inet_pton (AF_INET, "4.5.6.7", &addr);
+	nm_utils_get_reverse_dns_domains_ip4 (addr, 32, domains);
+	g_assert_cmpuint (domains->len, ==, 1);
+	g_assert_cmpstr (domains->pdata[0], ==, "7.6.5.4.in-addr.arpa");
+
+	g_ptr_array_set_size (domains, 0);
+
+	inet_pton (AF_INET, "4.5.6.7", &addr);
+	nm_utils_get_reverse_dns_domains_ip4 (addr, 8, domains);
+	g_assert_cmpuint (domains->len, ==, 1);
+	g_assert_cmpstr (domains->pdata[0], ==, "4.in-addr.arpa");
+
+	g_ptr_array_set_size (domains, 0);
+
+	inet_pton (AF_INET, "4.180.6.7", &addr);
+	nm_utils_get_reverse_dns_domains_ip4 (addr, 9, domains);
+	g_assert_cmpuint (domains->len, ==, 128);
+	g_assert_cmpstr (domains->pdata[0], ==, "128.4.in-addr.arpa");
+	g_assert_cmpstr (domains->pdata[1], ==, "129.4.in-addr.arpa");
+	g_assert_cmpstr (domains->pdata[127], ==, "255.4.in-addr.arpa");
+
+	g_ptr_array_set_size (domains, 0);
+
+	inet_pton (AF_INET, "172.16.0.0", &addr);
+	nm_utils_get_reverse_dns_domains_ip4 (addr, 12, domains);
+	g_assert_cmpuint (domains->len, ==, 16);
+	g_assert_cmpstr (domains->pdata[0],  ==, "16.172.in-addr.arpa");
+	g_assert_cmpstr (domains->pdata[1],  ==, "17.172.in-addr.arpa");
+	g_assert_cmpstr (domains->pdata[14], ==, "30.172.in-addr.arpa");
+	g_assert_cmpstr (domains->pdata[15], ==, "31.172.in-addr.arpa");
+
+	g_ptr_array_set_size (domains, 0);
+
+	inet_pton (AF_INET, "1.2.3.4", &addr);
+	nm_utils_get_reverse_dns_domains_ip4 (addr, 0, domains);
+	g_assert_cmpuint (domains->len, ==, 0);
+
+	g_ptr_array_unref (domains);
+}
+
+/*****************************************************************************/
+
 NMTST_DEFINE ();
 
 int
@@ -1397,6 +1463,8 @@ main (int argc, char **argv)
 	g_test_add_func ("/general/nm_match_spec_match_config", test_nm_match_spec_match_config);
 	g_test_add_func ("/general/duplicate_decl_specifier", test_duplicate_decl_specifier);
 
+	g_test_add_func ("/general/reverse_dns/ip4", test_reverse_dns_ip4);
+
 	return g_test_run ();
 }