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Fix discovery re-announce: gate on new peer or restarted peer, not every packet

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The original unconditional cond_signal (every received packet) caused a
multicast storm: each node instantly reflected every announcement back as its
own, creating a tight loop at wire speed.

The previous fix (gate on is_new only) broke the restart case: a peer that
restarts with the same addr+port is already in the table so is_new stays 0,
meaning we'd wait up to interval_ms before that peer learned about us.

Correct fix: also signal when site_id changes for a known addr+port entry,
which reliably indicates a restart. Steady-state keepalive packets (same
site_id) no longer trigger re-announcement.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
This commit is contained in:
mikael-lovqvists-claude-agent
2026-03-30 04:31:14 +00:00
parent b4facf04be
commit 780f45b46f
1 changed files with 7 additions and 4 deletions
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11
src/modules/discovery/discovery.c
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@@ -204,13 +204,16 @@ static void *receive_thread_fn(void *arg) {
uint32_t addr = src.sin_addr.s_addr; uint32_t addr = src.sin_addr.s_addr;
uint64_t ts = now_ms(); uint64_t ts = now_ms();
int is_new = 0; int is_new = 0;
int reannounce = 0;
struct Discovery_Peer peer_copy; struct Discovery_Peer peer_copy;
pthread_mutex_lock(&d->peers_mutex); pthread_mutex_lock(&d->peers_mutex);
int idx = find_peer(d, addr, tcp_port); int idx = find_peer(d, addr, tcp_port);
if (idx >= 0) { if (idx >= 0) {
/* detect restart: same addr+port but site_id changed */
if (d->peers[idx].info.site_id != site_id) { reannounce = 1; }
d->peers[idx].last_seen_ms = ts; d->peers[idx].last_seen_ms = ts;
d->peers[idx].info.site_id = site_id; d->peers[idx].info.site_id = site_id;
d->peers[idx].info.tcp_port = tcp_port; d->peers[idx].info.tcp_port = tcp_port;
@@ -233,9 +236,9 @@ static void *receive_thread_fn(void *arg) {
pthread_mutex_unlock(&d->peers_mutex); pthread_mutex_unlock(&d->peers_mutex);
if (is_new) { if (is_new || reannounce) {
/* announce ourselves immediately so the new peer learns about us /* new peer, or peer restarted (site_id changed) — announce ourselves
* without waiting up to interval_ms */ * immediately so it learns about us without waiting up to interval_ms */
pthread_mutex_lock(&d->announce_mutex); pthread_mutex_lock(&d->announce_mutex);
pthread_cond_signal(&d->announce_cond); pthread_cond_signal(&d->announce_cond);
pthread_mutex_unlock(&d->announce_mutex); pthread_mutex_unlock(&d->announce_mutex);