+/* Check if conn should be synced.
+ * pkts: conn packets, use sysctl_sync_threshold to avoid packet check
+ * - (1) sync_refresh_period: reduce sync rate. Additionally, retry
+ * sync_retries times with period of sync_refresh_period/8
+ * - (2) if both sync_refresh_period and sync_period are 0 send sync only
+ * for state changes or only once when pkts matches sync_threshold
+ * - (3) templates: rate can be reduced only with sync_refresh_period or
+ * with (2)
+ */
+static int ip_vs_sync_conn_needed(struct netns_ipvs *ipvs,
+ struct ip_vs_conn *cp, int pkts)
+{
+ unsigned long orig = ACCESS_ONCE(cp->sync_endtime);
+ unsigned long now = jiffies;
+ unsigned long n = (now + cp->timeout) & ~3UL;
+ unsigned int sync_refresh_period;
+ int sync_period;
+ int force;
+
+ /* Check if we sync in current state */
+ if (unlikely(cp->flags & IP_VS_CONN_F_TEMPLATE))
+ force = 0;
+ else if (likely(cp->protocol == IPPROTO_TCP)) {
+ if (!((1 << cp->state) &
+ ((1 << IP_VS_TCP_S_ESTABLISHED) |
+ (1 << IP_VS_TCP_S_FIN_WAIT) |
+ (1 << IP_VS_TCP_S_CLOSE) |
+ (1 << IP_VS_TCP_S_CLOSE_WAIT) |
+ (1 << IP_VS_TCP_S_TIME_WAIT))))
+ return 0;
+ force = cp->state != cp->old_state;
+ if (force && cp->state != IP_VS_TCP_S_ESTABLISHED)
+ goto set;
+ } else if (unlikely(cp->protocol == IPPROTO_SCTP)) {
+ if (!((1 << cp->state) &
+ ((1 << IP_VS_SCTP_S_ESTABLISHED) |
+ (1 << IP_VS_SCTP_S_CLOSED) |
+ (1 << IP_VS_SCTP_S_SHUT_ACK_CLI) |
+ (1 << IP_VS_SCTP_S_SHUT_ACK_SER))))
+ return 0;
+ force = cp->state != cp->old_state;
+ if (force && cp->state != IP_VS_SCTP_S_ESTABLISHED)
+ goto set;
+ } else {
+ /* UDP or another protocol with single state */
+ force = 0;
+ }
+
+ sync_refresh_period = sysctl_sync_refresh_period(ipvs);
+ if (sync_refresh_period > 0) {
+ long diff = n - orig;
+ long min_diff = max(cp->timeout >> 1, 10UL * HZ);
+
+ /* Avoid sync if difference is below sync_refresh_period
+ * and below the half timeout.
+ */
+ if (abs(diff) < min_t(long, sync_refresh_period, min_diff)) {
+ int retries = orig & 3;
+
+ if (retries >= sysctl_sync_retries(ipvs))
+ return 0;
+ if (time_before(now, orig - cp->timeout +
+ (sync_refresh_period >> 3)))
+ return 0;
+ n |= retries + 1;
+ }
+ }
+ sync_period = sysctl_sync_period(ipvs);
+ if (sync_period > 0) {
+ if (!(cp->flags & IP_VS_CONN_F_TEMPLATE) &&
+ pkts % sync_period != sysctl_sync_threshold(ipvs))
+ return 0;
+ } else if (sync_refresh_period <= 0 &&
+ pkts != sysctl_sync_threshold(ipvs))
+ return 0;
+
+set:
+ cp->old_state = cp->state;
+ n = cmpxchg(&cp->sync_endtime, orig, n);
+ return n == orig || force;
+}
+