YangYuxi is reporting that connection reuse is causing one-second delay when SYN hits existing connection in TIME_WAIT state. Such delay was added to give time to expire both the IPVS connection and the corresponding conntrack. This was considered a rare case at that time but it is causing problem for some environments such as Kubernetes. As nf_conntrack_tcp_packet() can decide to release the conntrack in TIME_WAIT state and to replace it with a fresh NEW conntrack, we can use this to allow rescheduling just by tuning our check: if the conntrack is confirmed we can not schedule it to different real server and the one-second delay still applies but if new conntrack was created, we are free to select new real server without any delays. YangYuxi lists some of the problem reports: - One second connection delay in masquerading mode: https://marc.info/?t=151683118100004&r=1&w=2 - IPVS low throughput #70747 https://github.com/kubernetes/kubernetes/issues/70747 - Apache Bench can fill up ipvs service proxy in seconds #544 https://github.com/cloudnativelabs/kube-router/issues/544 - Additional 1s latency in `host -> service IP -> pod` https://github.com/kubernetes/kubernetes/issues/90854 Fixes: f719e3754ee2 ("ipvs: drop first packet to redirect conntrack") Co-developed-by: YangYuxi <yx.atom1@xxxxxxxxx> Signed-off-by: YangYuxi <yx.atom1@xxxxxxxxx> Signed-off-by: Julian Anastasov <ja@xxxxxx> --- include/net/ip_vs.h | 10 ++++------ net/netfilter/ipvs/ip_vs_core.c | 12 +++++++----- 2 files changed, 11 insertions(+), 11 deletions(-) diff --git a/include/net/ip_vs.h b/include/net/ip_vs.h index 83be2d93b407..fe96aa462d05 100644 --- a/include/net/ip_vs.h +++ b/include/net/ip_vs.h @@ -1624,18 +1624,16 @@ static inline void ip_vs_conn_drop_conntrack(struct ip_vs_conn *cp) } #endif /* CONFIG_IP_VS_NFCT */ -/* Really using conntrack? */ -static inline bool ip_vs_conn_uses_conntrack(struct ip_vs_conn *cp, - struct sk_buff *skb) +/* Using old conntrack that can not be redirected to another real server? */ +static inline bool ip_vs_conn_uses_old_conntrack(struct ip_vs_conn *cp, + struct sk_buff *skb) { #ifdef CONFIG_IP_VS_NFCT enum ip_conntrack_info ctinfo; struct nf_conn *ct; - if (!(cp->flags & IP_VS_CONN_F_NFCT)) - return false; ct = nf_ct_get(skb, &ctinfo); - if (ct) + if (ct && nf_ct_is_confirmed(ct)) return true; #endif return false; diff --git a/net/netfilter/ipvs/ip_vs_core.c b/net/netfilter/ipvs/ip_vs_core.c index aa6a603a2425..517f6a2ac15a 100644 --- a/net/netfilter/ipvs/ip_vs_core.c +++ b/net/netfilter/ipvs/ip_vs_core.c @@ -2066,14 +2066,14 @@ ip_vs_in(struct netns_ipvs *ipvs, unsigned int hooknum, struct sk_buff *skb, int conn_reuse_mode = sysctl_conn_reuse_mode(ipvs); if (conn_reuse_mode && !iph.fragoffs && is_new_conn(skb, &iph) && cp) { - bool uses_ct = false, resched = false; + bool old_ct = false, resched = false; if (unlikely(sysctl_expire_nodest_conn(ipvs)) && cp->dest && unlikely(!atomic_read(&cp->dest->weight))) { resched = true; - uses_ct = ip_vs_conn_uses_conntrack(cp, skb); + old_ct = ip_vs_conn_uses_old_conntrack(cp, skb); } else if (is_new_conn_expected(cp, conn_reuse_mode)) { - uses_ct = ip_vs_conn_uses_conntrack(cp, skb); + old_ct = ip_vs_conn_uses_old_conntrack(cp, skb); if (!atomic_read(&cp->n_control)) { resched = true; } else { @@ -2081,15 +2081,17 @@ ip_vs_in(struct netns_ipvs *ipvs, unsigned int hooknum, struct sk_buff *skb, int * that uses conntrack while it is still * referenced by controlled connection(s). */ - resched = !uses_ct; + resched = !old_ct; } } if (resched) { + if (!old_ct) + cp->flags &= ~IP_VS_CONN_F_NFCT; if (!atomic_read(&cp->n_control)) ip_vs_conn_expire_now(cp); __ip_vs_conn_put(cp); - if (uses_ct) + if (old_ct) return NF_DROP; cp = NULL; } -- 2.26.2
