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feat(client): re-resolve the server hostnames at the DNS TTL

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hbc, hbc_mini.py and hbc_mini.c resolved the server once at startup, so an
address change needed a client restart. They now re-resolve every TTL seconds
(smallest A/AAAA TTL, floor 30s, 300s when unknown) and re-point, add or drop
connections to follow the new addresses; a failed lookup keeps the current ones.

Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com>
This commit is contained in:
andreas
2026-10-28 04:23:55 -04:00
co-authored by Claude Sonnet 5.5
parent e8d9c4a958
commit 885d5dc937
9 changed files with 887 additions and 1 deletions
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scripts/c/test_probe.c
+51
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@@ -226,6 +226,55 @@ static int live_mode(void) {
return 0;
}
/* ---- server address re-resolution (dns_apply) ---- */
static void dns_conn(int i, int af, const char *addr) {
memset(&g_conns[i], 0, sizeof(conn_t));
g_conns[i].conn_id = i + 1; g_conns[i].af = af; g_conns[i].port = 5;
snprintf(g_conns[i].addr, sizeof(g_conns[i].addr), "%s", addr);
conn_open(&g_conns[i]);
}
static void dns_push(int n, const dns_addr_t *a) {
memcpy(g_dns.addrs, a, n * sizeof(*a)); g_dns.n = n; g_dns.ready = true;
}
static void test_dns_apply_follows_changes(void) {
int id = 3;
dns_conn(0, AF_INET, "1.1.1.1"); dns_conn(1, AF_INET6, "2001:db8::1"); g_nconns = 2;
dns_addr_t moved[2] = {{AF_INET, "9.9.9.9"}, {AF_INET6, "2001:db8::9"}};
dns_push(2, moved); dns_apply(&id, "me", 5);
CHECK(g_nconns == 2);
CHECK_STR(g_conns[0].addr, "9.9.9.9");
CHECK_STR(g_conns[1].addr, "2001:db8::9");
/* the first connection's address vanishes and nothing replaces it: it survives, the other goes */
dns_addr_t v6only[1] = {{AF_INET6, "2001:db8::9"}};
dns_push(1, v6only); dns_apply(&id, "me", 5);
CHECK(g_nconns == 1);
CHECK_STR(g_conns[0].addr, "2001:db8::9");
CHECK(g_conns[0].af == AF_INET6);
dns_addr_t grown[2] = {{AF_INET6, "2001:db8::9"}, {AF_INET, "5.5.5.5"}};
dns_push(2, grown); dns_apply(&id, "me", 5);
CHECK(g_nconns == 2);
CHECK_STR(g_conns[1].addr, "5.5.5.5");
CHECK(g_conns[1].conn_id == 3);
dns_push(2, grown); dns_apply(&id, "me", 5); /* unchanged: nothing happens */
CHECK(g_nconns == 2 && id == 4);
for (int i = 0; i < g_nconns; i++) conn_close(&g_conns[i]);
g_nconns = 0;
}
static void test_dns_ttl_unknown_for_ip_literals(void) {
CHECK(dns_host_ttl("192.0.2.1", 0) == -1);
CHECK(dns_host_ttl("2001:db8::1", 0) == -1);
const char *h[] = {"192.0.2.1"}; dns_ctx_t x = {h, 1, 5, 0};
CHECK(dns_refresh_delay(&x) == DNS_DEFAULT_TTL);
}
int main(int argc, char **argv) {
if (argc > 1 && !strcmp(argv[1], "--live")) return live_mode();
test_gateway_parsers();
@@ -238,6 +287,8 @@ int main(int argc, char **argv) {
test_route_loss_then_return_pings_immediately();
test_missing_ping_stays_unknown_even_after_route_loss();
test_unsupported_family_is_unknown();
test_dns_apply_follows_changes();
test_dns_ttl_unknown_for_ip_literals();
printf("%d checks, %d failed\n", g_run, g_fail);
return g_fail ? 1 : 0;
}