network: radv: Send RA on newly-added dynamic prefix

When a prefix is delegated to an interface that is already sending
RAs, send an RA immediately to inform clients of the new prefix.
This allows them to start using it immediately instead of waiting
up to nearly 10 minutes (depending on when the last timed RA was
sent).  This type of situation might occur if, for example, an
outage of the WAN connection caused the addresses and prefixes to
be lost and later regained after service was restored.  The
condition for the number of RAs sent being above 0 simultaneously
ensures that RADV is already running and that this code doesn't
send any RAs before the timed RAs have started when the interface
first comes up.

diff --git a/src/libsystemd-network/sd-radv.c b/src/libsystemd-network/sd-radv.c
index 7383c84724a06a9abe183e563b65a871acd2c702..6163cf169143467713c6b64213f840f20e872a59 100644 (file)
--- a/src/libsystemd-network/sd-radv.c
+++ b/src/libsystemd-network/sd-radv.c
@@ -578,6 +578,15 @@ _public_ int sd_radv_add_prefix(sd_radv *ra, sd_radv_prefix *p, int dynamic) {
 
         cur = p;
 
+        /* If RAs have already been sent, send an RA immediately to announce the newly-added prefix */
+        if (ra->ra_sent > 0) {
+            r = radv_send(ra, NULL, ra->lifetime);
+            if (r < 0)
+                    log_radv_errno(r, "Unable to send Router Advertisement for added prefix: %m");
+            else
+                    log_radv("Sent Router Advertisement for added prefix");
+        }
+
  update:
         r = sd_event_now(ra->event, clock_boottime_or_monotonic(), &time_now);
         if (r < 0)
@@ -686,6 +695,15 @@ _public_ int sd_radv_add_route_prefix(sd_radv *ra, sd_radv_route_prefix *p, int
                 return 0;
         }
 
+        /* If RAs have already been sent, send an RA immediately to announce the newly-added route prefix */
+        if (ra->ra_sent > 0) {
+            r = radv_send(ra, NULL, ra->lifetime);
+            if (r < 0)
+                    log_radv_errno(r, "Unable to send Router Advertisement for added route prefix: %m");
+            else
+                    log_radv("Sent Router Advertisement for added route prefix");
+        }
+
  update:
         r = sd_event_now(ra->event, clock_boottime_or_monotonic(), &time_now);
         if (r < 0)