1 files changed, 89 insertions, 0 deletions
diff --git a/src/grp-system/libcore/src/loopback-setup.c b/src/grp-system/libcore/src/loopback-setup.c
new file mode 100644
index 0000000000..8eb6251bd7
--- /dev/null
+++ b/src/grp-system/libcore/src/loopback-setup.c
@@ -0,0 +1,89 @@
+/***
+  This file is part of systemd.
+
+  Copyright 2010 Lennart Poettering
+
+  systemd is free software; you can redistribute it and/or modify it
+  under the terms of the GNU Lesser General Public License as published by
+  the Free Software Foundation; either version 2.1 of the License, or
+  (at your option) any later version.
+
+  systemd 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
+  Lesser General Public License for more details.
+
+  You should have received a copy of the GNU Lesser General Public License
+  along with systemd; If not, see <http://www.gnu.org/licenses/>.
+***/
+
+#include <net/if.h>
+#include <stdlib.h>
+
+#include "core/loopback-setup.h"
+#include "sd-netlink/netlink-util.h"
+#include "systemd-basic/missing.h"
+#include "systemd-staging/sd-netlink.h"
+
+static int start_loopback(sd_netlink *rtnl) {
+        _cleanup_(sd_netlink_message_unrefp) sd_netlink_message *req = NULL;
+        int r;
+
+        r = sd_rtnl_message_new_link(rtnl, &req, RTM_SETLINK, LOOPBACK_IFINDEX);
+        if (r < 0)
+                return r;
+
+        r = sd_rtnl_message_link_set_flags(req, IFF_UP, IFF_UP);
+        if (r < 0)
+                return r;
+
+        r = sd_netlink_call(rtnl, req, 0, NULL);
+        if (r < 0)
+                return r;
+
+        return 0;
+}
+
+static bool check_loopback(sd_netlink *rtnl) {
+        _cleanup_(sd_netlink_message_unrefp) sd_netlink_message *req = NULL, *reply = NULL;
+        unsigned flags;
+        int r;
+
+        r = sd_rtnl_message_new_link(rtnl, &req, RTM_GETLINK, LOOPBACK_IFINDEX);
+        if (r < 0)
+                return false;
+
+        r = sd_netlink_call(rtnl, req, 0, &reply);
+        if (r < 0)
+                return false;
+
+        r = sd_rtnl_message_link_get_flags(reply, &flags);
+        if (r < 0)
+                return false;
+
+        return flags & IFF_UP;
+}
+
+int loopback_setup(void) {
+        _cleanup_(sd_netlink_unrefp) sd_netlink *rtnl = NULL;
+        int r;
+
+        r = sd_netlink_open(&rtnl);
+        if (r < 0)
+                return r;
+
+        r = start_loopback(rtnl);
+        if (r < 0) {
+
+                /* If we lack the permissions to configure the
+                 * loopback device, but we find it to be already
+                 * configured, let's exit cleanly, in order to
+                 * supported unprivileged containers. */
+                if (r == -EPERM && check_loopback(rtnl))
+                        return 0;
+
+                return log_warning_errno(r, "Failed to configure loopback device: %m");
+        }
+
+        return 0;
+}