1 files changed, 26 insertions, 13 deletions

diff --git a/src/libsystemd/sd-bus/sd-bus.c b/src/libsystemd/sd-bus/sd-bus.c
index 31cdcb4e5b..5285278d92 100644
--- a/src/libsystemd/sd-bus/sd-bus.c
+++ b/src/libsystemd/sd-bus/sd-bus.c
@@ -44,6 +44,7 @@
 #include "bus-kernel.h"
 #include "bus-control.h"
 #include "bus-objects.h"
+#include "bus-util.h"
 #include "bus-container.h"
 #include "bus-protocol.h"
 #include "bus-track.h"
@@ -1001,6 +1002,8 @@ static int bus_parse_next_address(sd_bus *b) {
 }
 
 static int bus_start_address(sd_bus *b) {
+        bool container_kdbus_available = false;
+        bool kdbus_available = false;
         int r;
 
         assert(b);
@@ -1010,15 +1013,29 @@ static int bus_start_address(sd_bus *b) {
 
                 bus_close_fds(b);
 
+                /*
+                 * Usually, if you provide multiple different bus-addresses, we
+                 * try all of them in order. We use the first one that
+                 * succeeds. However, if you mix kernel and unix addresses, we
+                 * never try unix-addresses if a previous kernel address was
+                 * tried and kdbus was available. This is required to prevent
+                 * clients to fallback to the bus-proxy if kdbus is available
+                 * but failed (eg., too many connections).
+                 */
+
                 if (b->exec_path)
                         r = bus_socket_exec(b);
-                else if ((b->nspid > 0 || b->machine) && b->kernel)
+                else if ((b->nspid > 0 || b->machine) && b->kernel) {
                         r = bus_container_connect_kernel(b);
-                else if ((b->nspid > 0 || b->machine) && b->sockaddr.sa.sa_family != AF_UNSPEC)
+                        if (r < 0 && !IN_SET(r, -ENOENT, -ESOCKTNOSUPPORT))
+                                container_kdbus_available = true;
+                } else if (!container_kdbus_available && (b->nspid > 0 || b->machine) && b->sockaddr.sa.sa_family != AF_UNSPEC)
                         r = bus_container_connect_socket(b);
-                else if (b->kernel)
+                else if (b->kernel) {
                         r = bus_kernel_connect(b);
-                else if (b->sockaddr.sa.sa_family != AF_UNSPEC)
+                        if (r < 0 && !IN_SET(r, -ENOENT, -ESOCKTNOSUPPORT))
+                                kdbus_available = true;
+                } else if (!kdbus_available && b->sockaddr.sa.sa_family != AF_UNSPEC)
                         r = bus_socket_connect(b);
                 else
                         skipped = true;
@@ -1173,10 +1190,7 @@ int bus_set_address_system(sd_bus *b) {
         if (e)
                 return sd_bus_set_address(b, e);
 
-        if (is_kdbus_available())
-                return sd_bus_set_address(b, KERNEL_SYSTEM_BUS_ADDRESS);
-
-        return sd_bus_set_address(b, UNIX_SYSTEM_BUS_ADDRESS);
+        return sd_bus_set_address(b, DEFAULT_SYSTEM_BUS_ADDRESS);
 }
 
 _public_ int sd_bus_open_system(sd_bus **ret) {
@@ -1224,17 +1238,16 @@ int bus_set_address_user(sd_bus *b) {
                 return sd_bus_set_address(b, e);
 
         e = secure_getenv("XDG_RUNTIME_DIR");
-        if (is_kdbus_available())
-                (void) asprintf(&b->address, KERNEL_USER_BUS_ADDRESS_FMT, getuid());
-        else if (e) {
+        if (e) {
                 _cleanup_free_ char *ee = NULL;
 
                 ee = bus_address_escape(e);
                 if (!ee)
                         return -ENOMEM;
 
-                (void) asprintf(&b->address, UNIX_USER_BUS_ADDRESS_FMT, ee);
-        }
+                (void) asprintf(&b->address, KERNEL_USER_BUS_ADDRESS_FMT ";" UNIX_USER_BUS_ADDRESS_FMT, getuid(), ee);
+        } else
+                (void) asprintf(&b->address, KERNEL_USER_BUS_ADDRESS_FMT, getuid());
 
         if (!b->address)
                 return -ENOMEM;