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sd-radv: do not stop on transient send errors

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When the periodic RA timer fires, any error returned by sendmsg()
currently propagates up through sd_radv_send() into radv_timeout(),
which then calls sd_radv_stop(). The RA engine is never started again
until the next carrier transition.

On an 802.3ad bond there is a window right after carrier-up where the
link is administratively up but no aggregator has been selected yet, so
sendmsg() returns ENOBUFS. If the very first RA after a flap lands in
that window, radv stops permanently and all clients lose their SLAAC
addresses, on-link/PD prefixes, and default router once the previously
advertised lifetimes expire, while IPv4 keeps working, leading to a very
confusing situation with v4 up and v6 down.

Handle this the same way solicited RAs already do (see
radv_process_packet()): log the failure and reschedule the timer instead
of giving up. ra_sent is left untouched on failure so we stay in the
fast initial-advertisement regime until a send actually succeeds.
This commit is contained in:
r-vdp
2026-05-15 03:34:52 +09:00
committed by Yu Watanabe
parent 39f4185c69
commit 62feba20aa
1 changed files with 13 additions and 5 deletions
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src/libsystemd-network/sd-radv.c
+13 -5
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@@ -254,9 +254,13 @@ int sd_radv_send(sd_radv *ra) {
r = radv_send_router(ra, NULL);
if (r < 0)
return log_radv_errno(ra, r, "Unable to send Router Advertisement: %m");
ra->ra_sent++;
/* Do not treat transient send failures (e.g. ENOBUFS while a bond is still selecting an
* aggregator after a carrier flap, or ENETDOWN/EADDRNOTAVAIL during a short link bounce) as
* fatal: log and reschedule so we try again instead of stopping the RA engine for good.
* Solicited RAs already behave this way, see radv_process_packet(). */
log_radv_errno(ra, r, "Unable to send Router Advertisement, will retry later: %m");
else
ra->ra_sent++;
/* RFC 4861, Section 6.2.4, sending initial Router Advertisements */
if (ra->ra_sent <= RADV_MAX_INITIAL_RTR_ADVERTISEMENTS)
@@ -283,8 +287,12 @@ int sd_radv_send(sd_radv *ra) {
assert(min_timeout <= max_timeout * 3 / 4);
timeout = min_timeout + random_u64_range(max_timeout - min_timeout);
log_radv(ra, "Sent unsolicited Router Advertisement. Next advertisement will be in %s.",
FORMAT_TIMESPAN(timeout, USEC_PER_SEC));
if (r >= 0)
log_radv(ra, "Sent unsolicited Router Advertisement. Next advertisement will be in %s.",
FORMAT_TIMESPAN(timeout, USEC_PER_SEC));
else
log_radv(ra, "Next Router Advertisement attempt in %s.",
FORMAT_TIMESPAN(timeout, USEC_PER_SEC));
return event_reset_time(
ra->event, &ra->timeout_event_source,