networkd: propagate DNS/NTP server from uplink to dhcp server

When handing out DHCP leases, try to propagate DNS/NTP server
information from "uplink". The "uplink" is automatically determined as
the network interface with the highest priority default route on it.

1 files changed, 38 insertions, 0 deletions

diff --git a/src/network/networkd-manager.c b/src/network/networkd-manager.c
index ab89c1bc47..46bcdff1cf 100644
--- a/src/network/networkd-manager.c
+++ b/src/network/networkd-manager.c
@@ -34,6 +34,7 @@
 #include "def.h"
 #include "virt.h"
 #include "set.h"
+#include "local-addresses.h"
 
 #include "networkd.h"
 
@@ -845,3 +846,40 @@ int manager_address_pool_acquire(Manager *m, int family, unsigned prefixlen, uni
 
         return 0;
 }
+
+Link* manager_find_uplink(Manager *m, Link *exclude) {
+        _cleanup_free_ struct local_address *gateways = NULL;
+        int n, i;
+
+        assert(m);
+
+        /* Looks for a suitable "uplink", via black magic: an
+         * interface that is up and where the default route with the
+         * highest priority points to. */
+
+        n = local_gateways(m->rtnl, 0, AF_UNSPEC, &gateways);
+        if (n < 0) {
+                log_warning_errno(n, "Failed to determine list of default gateways: %m");
+                return NULL;
+        }
+
+        for (i = 0; i < n; i++) {
+                Link *link;
+
+                link = hashmap_get(m->links, INT_TO_PTR(gateways[i].ifindex));
+                if (!link) {
+                        log_debug("Weird, found a gateway for a link we don't now. Ignoring.");
+                        continue;
+                }
+
+                if (link == exclude)
+                        continue;
+
+                if (link->operstate < LINK_OPERSTATE_ROUTABLE)
+                        continue;
+
+                return link;
+        }
+
+        return NULL;
+}