core: loopback - simplify check_loopback()

We no longer configure the addresses on the loopback interface, but simply bring it up
and let the kernel do the rest. Also change the check to only check if the interface
is up, rather than checking for the IPv4 loopback address.

1 files changed, 18 insertions, 24 deletions

diff --git a/src/core/loopback-setup.c b/src/core/loopback-setup.c
index ab6335c0c..0d7d00cfc 100644
--- a/src/core/loopback-setup.c
+++ b/src/core/loopback-setup.c
@@ -56,30 +56,24 @@ static int start_loopback(sd_rtnl *rtnl) {
         return 0;
 }
 
-static int check_loopback(void) {
+static bool check_loopback(sd_rtnl *rtnl) {
+        _cleanup_rtnl_message_unref_ sd_rtnl_message *req = NULL, *reply = NULL;
+        unsigned flags;
         int r;
-        _cleanup_close_ int fd = -1;
-        union {
-                struct sockaddr sa;
-                struct sockaddr_in in;
-        } sa = {
-                .in.sin_family = AF_INET,
-                .in.sin_addr.s_addr = htonl(INADDR_LOOPBACK),
-        };
-
-        /* If we failed to set up the loop back device, check whether
-         * it might already be set up */
-
-        fd = socket(AF_INET, SOCK_DGRAM|SOCK_NONBLOCK|SOCK_CLOEXEC, 0);
-        if (fd < 0)
-                return -errno;
-
-        if (bind(fd, &sa.sa, sizeof(sa.in)) >= 0)
-                r = 1;
-        else
-                r = errno == EADDRNOTAVAIL ? 0 : -errno;
-
-        return r;
+
+        r = sd_rtnl_message_new_link(rtnl, &req, RTM_GETLINK, LOOPBACK_IFINDEX);
+        if (r < 0)
+                return r;
+
+        r = sd_rtnl_call(rtnl, req, 0, &reply);
+        if (r < 0)
+                return r;
+
+        r = sd_rtnl_message_link_get_flags(reply, &flags);
+        if (r < 0)
+                return r;
+
+        return flags & IFF_UP;
 }
 
 int loopback_setup(void) {
@@ -92,7 +86,7 @@ int loopback_setup(void) {
 
         r = start_loopback(rtnl);
         if (r == -EPERM) {
-                if (check_loopback() < 0)
+                if (!check_loopback(rtnl))
                         return log_warning_errno(EPERM, "Failed to configure loopback device: %m");
         } else if (r < 0)
                 return log_warning_errno(r, "Failed to configure loopback device: %m");