sd-netlink: append instead of prepend multipart message

Previously, e.g., networkd enumerated network interfaces with ifindex
in a decreasing order, as sd-netlink inverses the order of the received
multipart messages.
Let's keep the order of the multipart messages. Hopefully this changes
no behavior, as our code do not depend on the order of the received
multipart messages.

Before:
===
Nov 26 09:35:10 systemd[1]: Starting Network Configuration...
Nov 26 09:35:11 systemd-networkd[36185]: wlp59s0: Saved new link: ifindex=3, iftype=ETHER(1), kind=n/a
Nov 26 09:35:12 systemd-networkd[36185]: enp0s31f6: Saved new link: ifindex=2, iftype=ETHER(1), kind=n/a
Nov 26 09:35:12 systemd-networkd[36185]: lo: Saved new link: ifindex=1, iftype=LOOPBACK(772), kind=n/a

After:
===
Nov 26 09:45:18 systemd[1]: Starting Network Configuration...
Nov 26 09:45:19 systemd-networkd[38372]: lo: Saved new link: ifindex=1, iftype=LOOPBACK(772), kind=n/a
Nov 26 09:45:19 systemd-networkd[38372]: enp0s31f6: Saved new link: ifindex=2, iftype=ETHER(1), kind=n/a
Nov 26 09:45:19 systemd-networkd[38372]: wlp59s0: Saved new link: ifindex=3, iftype=ETHER(1), kind=n/a

diff --git a/src/libsystemd/sd-netlink/netlink-socket.c b/src/libsystemd/sd-netlink/netlink-socket.c
index 2a9f64141903c1052d9f7d6e072fad59ee94f847..96162963a75b222e80dd272b115278bc20fc28c2 100644 (file)
--- a/src/libsystemd/sd-netlink/netlink-socket.c
+++ b/src/libsystemd/sd-netlink/netlink-socket.c
@@ -429,15 +429,20 @@ int socket_read_message(sd_netlink *nl) {
                         } else {
                                 sd_netlink_message *existing;
 
-                                existing = hashmap_remove(nl->rqueue_partial_by_serial, UINT32_TO_PTR(hdr->nlmsg_seq));
-                                if (existing)
-                                        /* push the message onto the multi-part message stack */
-                                        m->next = existing;
-
-                                /* put it into the queue for partially received messages. */
-                                r = netlink_queue_partially_received_message(nl, m);
-                                if (r < 0)
-                                        return r;
+                                existing = hashmap_get(nl->rqueue_partial_by_serial, UINT32_TO_PTR(hdr->nlmsg_seq));
+                                if (existing) {
+                                        /* This is the continuation of the previously read messages.
+                                         * Let's append this message at the end. */
+                                        while (existing->next)
+                                                existing = existing->next;
+                                        existing->next = TAKE_PTR(m);
+                                } else {
+                                        /* This is the first message. Put it into the queue for partially
+                                         * received messages. */
+                                        r = netlink_queue_partially_received_message(nl, m);
+                                        if (r < 0)
+                                                return r;
+                                }
                         }
 
                 } else {