Use /proc/net/sockstat6 to detect IPv6 support

The file /sys/module/ipv6 does not exist in all container
implementations (e.g. Virtuozzo). Using /proc/net/sockstat6
detects IPv6 support reliably in these environments, too.

This file does not exist when the kernel is not compiled with
IPv6 support, or if IPv6 support is disabled, so simply checking
for existence should be a suitable check.

Fixes #2059

diff --git a/src/basic/socket-util.c b/src/basic/socket-util.c
index 79901a6..be144e1 100644 (file)
--- a/src/basic/socket-util.c
+++ b/src/basic/socket-util.c
@@ -440,17 +440,10 @@ const char* socket_address_get_path(const SocketAddress *a) {
 }
 
 bool socket_ipv6_is_supported(void) {
-        _cleanup_free_ char *l = NULL;
-
-        if (access("/sys/module/ipv6", F_OK) != 0)
+        if (access("/proc/net/sockstat6", F_OK) != 0)
                 return false;
 
-        /* If we can't check "disable" parameter, assume enabled */
-        if (read_one_line_file("/sys/module/ipv6/parameters/disable", &l) < 0)
-                return true;
-
-        /* If module was loaded with disable=1 no IPv6 available */
-        return l[0] == '0';
+        return true;
 }
 
 bool socket_address_matches_fd(const SocketAddress *a, int fd) {