policy: preserve custom hostnames on local-mapping lines (rh #627269)

Try to preserve custom hostnames (ie, anything not a localhost* variant,
the current hostname, or the previous hostname) when rewriting the
127.0.0.1/::1 localhost mapping lines.

src/nm-policy-hostname.c

@@ -217,7 +217,7 @@ nm_policy_set_system_hostname (const char *new_hostname,
 	char old_hostname[HOST_NAME_MAX + 1];
 	int ret = 0;
 	const char *name;
-	gboolean set_hostname = TRUE, changed = FALSE;
+	gboolean set_hostname = TRUE, changed = FALSE, old_valid = TRUE;
 
 	if (new_hostname)
 		g_warn_if_fail (strlen (new_hostname));
@@ -230,11 +230,15 @@ nm_policy_set_system_hostname (const char *new_hostname,
 	if (ret != 0) {
 		nm_log_warn (LOGD_DNS, "couldn't get the system hostname: (%d) %s",
 		             errno, strerror (errno));
+		old_valid = FALSE;
 	} else {
 		/* Don't set the hostname if it isn't actually changing */
 		if (   (new_hostname && !strcmp (old_hostname, new_hostname))
 		    || (!new_hostname && !strcmp (old_hostname, FALLBACK_HOSTNAME4)))
 			set_hostname = FALSE;
+
+		if (old_hostname[0] == '\0')
+			old_valid = FALSE;
 	}
 
 	if (set_hostname) {
@@ -255,6 +259,7 @@ nm_policy_set_system_hostname (const char *new_hostname,
 	 * /etc/hosts at all.
 	 */
 	if (!nm_policy_hosts_update_etc_hosts (name,
+	                                       old_valid ? old_hostname : NULL,
 	                                       FALLBACK_HOSTNAME4,
 	                                       FALLBACK_HOSTNAME6,
 	                                       ip4_addr,

src/nm-policy-hosts.c

@@ -28,6 +28,9 @@
 #include "nm-policy-hosts.h"
 #include "nm-logging.h"
 
+#define IP4_LH "127.0.0.1"
+#define IP6_LH "::1"
+
 gboolean
 nm_policy_hosts_find_token (const char *line, const char *token)
 {
@@ -56,7 +59,7 @@ nm_policy_hosts_find_token (const char *line, const char *token)
 static gboolean
 is_local_mapping (const char *str, gboolean ip6, const char *hostname)
 {
-	const char *addr = ip6 ? "::1" : "127.0.0.1";
+	const char *addr = ip6 ? IP6_LH : IP4_LH;
 	const char *fallback = ip6 ? "localhost6" : "localhost";
 
 	return (   !strncmp (str, addr, strlen (addr))
@@ -137,12 +140,71 @@ ip6_addr_matches (const char *str, const char *ip6_addr)
 	return memcmp (&found, &given, sizeof (found)) == 0;
 }
 
+static char *
+get_custom_hostnames (const char *line,
+                      const char *hostname,
+                      const char *old_hostname)
+{
+	char **items = NULL, **iter;
+	guint start = 0;
+	GString *str = NULL;
+	char *custom = NULL;
+
+	g_return_val_if_fail (line != NULL, NULL);
+
+	if (!strncmp (line, IP4_LH, strlen (IP4_LH)))
+		start = strlen (IP4_LH);
+	else if (!strncmp (line, IP6_LH, strlen (IP6_LH)))
+		start = strlen (IP6_LH);
+
+	g_return_val_if_fail (start > 0, NULL);
+
+	/* Split the line into tokens */
+	items = g_strsplit_set (line + start, " \t", -1);
+	if (!items)
+		return NULL;
+
+	str = g_string_sized_new (50);
+	/* Ignore current & old hostnames, and localhost-anything */
+	for (iter = items; iter && *iter; iter++) {
+		if (*iter[0] == '\0')
+			continue;
+		if (hostname && !strcmp (*iter, hostname))
+			continue;
+		if (old_hostname && !strcmp (*iter, old_hostname))
+			continue;
+		if (!strcmp (*iter, "localhost"))
+			continue;
+		if (!strcmp (*iter, "localhost6"))
+			continue;
+		if (!strcmp (*iter, "localhost.localdomain"))
+			continue;
+		if (!strcmp (*iter, "localhost4.localdomain4"))
+			continue;
+		if (!strcmp (*iter, "localhost6.localdomain6"))
+			continue;
+
+		/* Found a custom hostname */
+		g_string_append_c (str, '\t');
+		g_string_append (str, *iter);
+	}
+
+	if (str->len)
+		custom = g_string_free (str, FALSE);
+	else
+		g_string_free (str, TRUE);
+
+	g_strfreev (items);
+	return custom;
+}
+
 #define ADDED_TAG "# Added by NetworkManager"
 
 GString *
 nm_policy_get_etc_hosts (const char **lines,
                          gsize existing_len,
                          const char *hostname,
+                         const char *old_hostname,
                          const char *fallback_hostname4,
                          const char *fallback_hostname6,
                          const char *ip4_addr,
@@ -163,7 +225,10 @@ nm_policy_get_etc_hosts (const char **lines,
 	gboolean hostname6_is_fallback;
 	gboolean host4_before = FALSE;
 	gboolean host6_before = FALSE;
+	gboolean no_stale = TRUE;
 	char *short_hostname = NULL;
+	char *custom4 = NULL;
+	char *custom6 = NULL;
 
 	g_return_val_if_fail (lines != NULL, FALSE);
 	g_return_val_if_fail (hostname != NULL, FALSE);
@@ -181,21 +246,20 @@ nm_policy_get_etc_hosts (const char **lines,
 	 * If all these things exist we don't need to bother updating the file.
 	 */
 
-	if (!ip4_addr) {
-		found_host4 = TRUE;
+	if (!ip4_addr)
 		host4_before = TRUE;
-	}
-	if (!ip6_addr) {
-		found_host6 = TRUE;
+	if (!ip6_addr)
 		host6_before = TRUE;
-	}
 
 	/* Look for the four cases from above */
 	for (line = lines; lines && *line; line++) {
-		if (!strlen (*line) || (*line[0] == '#'))
+		gboolean found_hostname = FALSE;
+
+		if ((*line[0] == '\0') || (*line[0] == '#'))
 			continue;
 
-		if (nm_policy_hosts_find_token (*line, hostname)) {
+		found_hostname = nm_policy_hosts_find_token (*line, hostname);
+		if (found_hostname) {
 			/* Found the current hostname on this line */
 			if (ip4_addr && ip4_addr_matches (*line, ip4_addr)) {
 				found_host4 = TRUE;
@@ -211,7 +275,7 @@ nm_policy_get_etc_hosts (const char **lines,
 				 * so make sure we update /etc/hosts.
 				 */
 				if (is_ip4_addr (*line))
-					found_host4 = FALSE;
+					no_stale = FALSE;
 			}
 
 			if (ip6_addr && ip6_addr_matches (*line, ip6_addr)) {
@@ -228,26 +292,54 @@ nm_policy_get_etc_hosts (const char **lines,
 				 * so make sure we update /etc/hosts.
 				 */
 				if (is_ip6_addr (*line))
-					found_host6 = FALSE;
+					no_stale = FALSE;
 			}
 		}
 
 		if (is_local_mapping (*line, FALSE, "localhost")) {
 			/* a 127.0.0.1 line containing 'localhost' */
 			found_localhost4 = TRUE;
+			custom4 = get_custom_hostnames (*line, hostname, old_hostname);
+			if (!ip4_addr) {
+				/* If there's no IP-specific mapping for the current hostname
+				 * but that hostname is present on in the local mapping line,
+				 * we've found our IPv4 hostname mapping.  If the hostname is
+				 * the fallback *IPv6* hostname it's not going to show up in
+				 * the IPv4 local mapping though, so fake it.
+				 */
+				if (hostname6_is_fallback || found_hostname)
+					found_host4 = TRUE;
+			}
 		} else if (is_local_mapping (*line, TRUE, "localhost6")) {
 			/* a ::1 line containing 'localhost6' */
 			found_localhost6 = TRUE;
+			custom6 = get_custom_hostnames (*line, hostname, old_hostname);
+			if (!ip6_addr) {
+				/* If there's no IP-specific mapping for the current hostname
+				 * but that hostname is present on in the local mapping line,
+				 * we've found our IPv6 hostname mapping.  If the hostname is
+				 * the fallback *IPv4* hostname it's not going to show up in
+				 * the IPv6 local mapping though, so fake it.
+				 */
+				if (hostname4_is_fallback || found_hostname)
+					found_host6 = TRUE;
+			}
 		}
 
-		if (found_localhost4 && found_host4 && found_localhost6 && found_host6 && host4_before && host6_before)
-			return NULL;  /* No update required */
+		if (   found_localhost4
+		    && found_host4
+		    && found_localhost6
+		    && found_host6
+		    && host4_before
+		    && host6_before
+		    && no_stale)
+			goto out;  /* No update required */
 	}
 
 	contents = g_string_sized_new (existing_len ? existing_len + 100 : 200);
 	if (!contents) {
 		g_set_error_literal (error, 0, 0, "not enough memory");
-		return NULL;
+		goto out;
 	}
 
 	/* Find the short hostname, like 'foo' from 'foo.bar.baz'; we want to
@@ -277,8 +369,6 @@ nm_policy_get_etc_hosts (const char **lines,
 	 * 'localhost6'.
 	 */
 	for (line = lines, initial_comments = TRUE; lines && *line; line++) {
-		gboolean add_line = TRUE;
-
 		/* This is the first line after the initial comments */
 		if (strlen (*line) && initial_comments && (*line[0] != '#')) {
 			initial_comments = FALSE;
@@ -311,7 +401,10 @@ nm_policy_get_etc_hosts (const char **lines,
 				if (short_hostname)
 					g_string_append_printf (contents, "\t%s", short_hostname);
 			}
-			g_string_append_printf (contents, "\t%s\tlocalhost\n", fallback_hostname4);
+			g_string_append_printf (contents, "\t%s\tlocalhost", fallback_hostname4);
+			if (custom4)
+				g_string_append (contents, custom4);
+			g_string_append_c (contents, '\n');
 
 			/* IPv6 localhost line */
 			g_string_append (contents, "::1");
@@ -320,26 +413,23 @@ nm_policy_get_etc_hosts (const char **lines,
 				if (short_hostname)
 					g_string_append_printf (contents, "\t%s", short_hostname);
 			}
-			g_string_append_printf (contents, "\t%s\tlocalhost6\n", fallback_hostname6);
+			g_string_append_printf (contents, "\t%s\tlocalhost6", fallback_hostname6);
+			if (custom6)
+				g_string_append (contents, custom6);
+			g_string_append_c (contents, '\n');
 
 			added = TRUE;
 		}
 
 		/* Don't add the original line if it is a localhost mapping */
-		if (is_local_mapping (*line, FALSE, "localhost"))
-			add_line = FALSE;
-		else if (is_local_mapping (*line, FALSE, fallback_hostname4))
-			add_line = FALSE;
-		else if (is_local_mapping (*line, FALSE, hostname))
-			add_line = FALSE;
-		else if (is_local_mapping (*line, TRUE, "localhost6"))
-			add_line = FALSE;
-		else if (is_local_mapping (*line, TRUE, fallback_hostname6))
-			add_line = FALSE;
-		else if (is_local_mapping (*line, TRUE, hostname))
-			add_line = FALSE;
-
-		if (add_line && !strstr (*line, ADDED_TAG)) {
+		if (   !is_local_mapping (*line, FALSE, "localhost")
+		    && !is_local_mapping (*line, FALSE, fallback_hostname4)
+		    && !is_local_mapping (*line, FALSE, hostname)
+		    && !is_local_mapping (*line, TRUE, "localhost6")
+		    && !is_local_mapping (*line, TRUE, fallback_hostname6)
+		    && !is_local_mapping (*line, TRUE, hostname)
+			&& !strstr (*line, ADDED_TAG)) {
+
 			g_string_append (contents, *line);
 			/* Only append the new line if this isn't the last line in the file */
 			if (*(line+1))
@@ -370,12 +460,16 @@ nm_policy_get_etc_hosts (const char **lines,
 		g_string_append_printf (contents, "::1\t%s\tlocalhost6\n", fallback_hostname6);
 	}
 
+out:
+	g_free (custom4);
+	g_free (custom6);
 	g_free (short_hostname);
 	return contents;
 }
 
 gboolean
 nm_policy_hosts_update_etc_hosts (const char *hostname,
+                                  const char *old_hostname,
                                   const char *fallback_hostname4,
                                   const char *fallback_hostname6,
                                   const char *ip4_addr,
@@ -405,6 +499,7 @@ nm_policy_hosts_update_etc_hosts (const char *hostname,
 	new_contents = nm_policy_get_etc_hosts ((const char **) lines,
 	                                        contents_len,
 	                                        hostname,
+	                                        old_hostname,
 	                                        fallback_hostname4,
 	                                        fallback_hostname6,
 	                                        ip4_addr,

src/nm-policy-hosts.h

@@ -24,6 +24,7 @@
 #include <glib.h>
 
 gboolean nm_policy_hosts_update_etc_hosts (const char *hostname,
+                                           const char *old_hostname,
                                            const char *fallback_hostname4,
                                            const char *fallback_hostname6,
                                            const char *ip4_addr,
@@ -36,6 +37,7 @@ gboolean nm_policy_hosts_find_token (const char *line, const char *token);
 GString *nm_policy_get_etc_hosts (const char **lines,
                                   gsize existing_len,
                                   const char *hostname,
+                                  const char *old_hostname,
                                   const char *fallback_hostname4,
                                   const char *fallback_hostname6,
                                   const char *ip4_addr,

src/tests/test-policy-hosts.c

@@ -26,6 +26,8 @@
 #define FALLBACK_HOSTNAME4 "localhost.localdomain"
 #define FALLBACK_HOSTNAME6 "localhost6.localdomain6"
 
+#define DEBUG 0
+
 static void
 test_generic (const char *before,
               const char *after,
@@ -43,6 +45,7 @@ test_generic (const char *before,
 	newc = nm_policy_get_etc_hosts ((const char **) lines,
 	                                strlen (before),
 	                                hostname,
+	                                NULL,
 	                                FALLBACK_HOSTNAME4,
 	                                FALLBACK_HOSTNAME6,
 	                                ip4_addr,
@@ -56,11 +59,11 @@ test_generic (const char *before,
 		g_clear_error (&error);
 	} else if (after == NULL) {
 		/* No change to /etc/hosts required */
-#if 0
+#if DEBUG
 		if (newc != NULL) {
 			g_message ("\n- NEW ---------------------------------\n"
 			           "%s"
-			           "- EXPECTED NONE -------------------------\n",
+			           "+ EXPECTED NONE +++++++++++++++++++++++++\n",
 			           newc->str);
 		}
 #endif
@@ -70,10 +73,10 @@ test_generic (const char *before,
 		g_assert (newc != NULL);
 		g_assert (error == NULL);
 
-#if 0
+#if DEBUG
 		g_message ("\n- NEW ---------------------------------\n"
 		           "%s"
-		           "- EXPECTED ------------------------------\n"
+		           "+ EXPECTED ++++++++++++++++++++++++++++++\n"
 		           "%s"
 		           "^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^\n",
 		           newc->str, after);
@@ -167,10 +170,17 @@ static const char *named_generic_before = \
 	"::1		localhost6.localdomain6 localhost6\n"
 	"127.0.0.1	lcmd.us.intellitxt.com\n";
 
+static const char *named_generic_after = \
+	"# Do not remove the following line, or various programs\n"
+	"# that require network functionality will fail.\n"
+	"127.0.0.1	playboy	localhost.localdomain	localhost\n"
+	"::1	playboy	localhost6.localdomain6	localhost6\n"
+	"127.0.0.1	lcmd.us.intellitxt.com\n";
+
 static void
 test_hosts_named_generic (void)
 {
-	test_generic (named_generic_before, NULL, "playboy", NULL, NULL, FALSE);
+	test_generic (named_generic_before, named_generic_after, "playboy", NULL, NULL, FALSE);
 }
 
 /*******************************************/
@@ -609,24 +619,114 @@ static const char *long_before = \
 	"127.0.0.1	ad.doubleclick.net\n"
 	"127.0.0.1	oascentral.movietickets.com\n"
 	"127.0.0.1	view.atdmt.com\n"
-	"127.0.0.1	ads.chumcity.com\n"
-	"127.0.0.1	ads.as4x.tmcs.net\n"
-	"127.0.0.1	n4403ad.doubleclick.net\n"
-	"127.0.0.1	www.assoc-amazon.com\n"
-	"127.0.0.1	s25.sitemeter.com\n"
-	"127.0.0.1	adlog.com.com\n"
-	"127.0.0.1	ahs.laptopmag.com\n"
-	"127.0.0.1	altfarm.mediaplex.com\n"
-	"127.0.0.1	ads.addynamix.com\n"
-	"127.0.0.1	srx.main.ebayrtm.com\n"
-	"127.0.0.1	cdn5.tribalfusion.com\n"
-	"127.0.0.1	a.tribalfusion.com\n";
+	"127.0.0.1	ads.chumcity.com\n";
 
+static const char *long_after = \
+	"# Do not remove the following line, or various programs\n"
+	"# that require network functionality will fail.\n"
+	"127.0.0.1	comet	localhost.localdomain	localhost\n"
+	"::1	comet	localhost6.localdomain6	localhost6\n"
+	"\n"
+	"127.0.0.1	lcmd.us.intellitxt.com\n"
+	"127.0.0.1	adserver.adtech.de\n"
+	"127.0.0.1	a.as-us.falkag.net\n"
+	"127.0.0.1	a.as-eu.falkag.net\n"
+	"127.0.0.1	ads.doubleclick.com\n"
+	"\n"
+	"# random comment\n"
+	"127.0.0.1	m1.2mdn.net\n"
+	"127.0.0.1	ds.serving-sys.com\n"
+	"127.0.0.1	pagead2.googlesyndication.com\n"
+	"127.0.0.1	ad.doubleclick.com\n"
+	"127.0.0.1	ad.doubleclick.net\n"
+	"127.0.0.1	oascentral.movietickets.com\n"
+	"127.0.0.1	view.atdmt.com\n"
+	"127.0.0.1	ads.chumcity.com\n";
 
 static void
 test_hosts_long (void)
 {
-	test_generic (long_before, NULL, "comet", NULL, NULL, FALSE);
+	test_generic (long_before, long_after, "comet", NULL, NULL, FALSE);
+}
+
+/*******************************************/
+
+static const char *custom4_before = \
+	"# Do not remove the following line, or various programs\n"
+	"# that require network functionality will fail.\n"
+	"127.0.0.1	localhost.localdomain localhost pintglass\n"
+	"::1	localhost6.localdomain6	localhost6\n";
+
+static const char *custom4_after = \
+	"# Do not remove the following line, or various programs\n"
+	"# that require network functionality will fail.\n"
+	"127.0.0.1	comet	localhost.localdomain	localhost	pintglass\n"
+	"::1	comet	localhost6.localdomain6	localhost6\n";
+
+static void
+test_hosts_custom4 (void)
+{
+	test_generic (custom4_before, custom4_after, "comet", NULL, NULL, FALSE);
+}
+
+/*******************************************/
+
+static const char *custom6_before = \
+	"# Do not remove the following line, or various programs\n"
+	"# that require network functionality will fail.\n"
+	"127.0.0.1	localhost.localdomain localhost\n"
+	"::1	localhost6.localdomain6	localhost6	pintglass\n";
+
+static const char *custom6_after = \
+	"# Do not remove the following line, or various programs\n"
+	"# that require network functionality will fail.\n"
+	"127.0.0.1	comet	localhost.localdomain	localhost\n"
+	"::1	comet	localhost6.localdomain6	localhost6	pintglass\n";
+
+static void
+test_hosts_custom6 (void)
+{
+	test_generic (custom6_before, custom6_after, "comet", NULL, NULL, FALSE);
+}
+
+/*******************************************/
+
+static const char *custom46_before = \
+	"# Do not remove the following line, or various programs\n"
+	"# that require network functionality will fail.\n"
+	"127.0.0.1	localhost.localdomain localhost shotglass\n"
+	"::1	localhost6.localdomain6	localhost6 pintglass\n";
+
+static const char *custom46_after = \
+	"# Do not remove the following line, or various programs\n"
+	"# that require network functionality will fail.\n"
+	"127.0.0.1	comet	localhost.localdomain	localhost	shotglass\n"
+	"::1	comet	localhost6.localdomain6	localhost6	pintglass\n";
+
+static void
+test_hosts_custom46 (void)
+{
+	test_generic (custom46_before, custom46_after, "comet", NULL, NULL, FALSE);
+}
+
+/*******************************************/
+
+static const char *custom46_mixed_before = \
+	"# Do not remove the following line, or various programs\n"
+	"# that require network functionality will fail.\n"
+	"127.0.0.1	localhost.localdomain localhost shotglass\n"
+	"::1	localhost6.localdomain6	localhost6 pintglass\n";
+
+static const char *custom46_mixed_after = \
+	"# Do not remove the following line, or various programs\n"
+	"# that require network functionality will fail.\n"
+	"127.0.0.1	comet	localhost.localdomain	localhost	shotglass\n"
+	"::1	comet	localhost6.localdomain6	localhost6	pintglass\n";
+
+static void
+test_hosts_custom46_mixed (void)
+{
+	test_generic (custom46_mixed_before, custom46_mixed_after, "comet", NULL, NULL, FALSE);
 }
 
 /*******************************************/
@@ -712,6 +812,10 @@ int main (int argc, char **argv)
 	g_test_suite_add (suite, TESTCASE (test_hosts_no_host4, NULL));
 	g_test_suite_add (suite, TESTCASE (test_hosts_no_host6, NULL));
 	g_test_suite_add (suite, TESTCASE (test_hosts_long, NULL));
+	g_test_suite_add (suite, TESTCASE (test_hosts_custom4, NULL));
+	g_test_suite_add (suite, TESTCASE (test_hosts_custom6, NULL));
+	g_test_suite_add (suite, TESTCASE (test_hosts_custom46, NULL));
+	g_test_suite_add (suite, TESTCASE (test_hosts_custom46_mixed, NULL));
 
 	return g_test_run ();
 }