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[PATCH,v2] ipvs: fix the connection sync failed in some cases

To: <wensong@xxxxxxxxxxxx>
Subject: [PATCH,v2] ipvs: fix the connection sync failed in some cases
Cc: <horms@xxxxxxxxxxxx>, <ja@xxxxxx>, <pablo@xxxxxxxxxxxxx>, <kadlec@xxxxxxxxxxxxx>, <fw@xxxxxxxxx>, <davem@xxxxxxxxxxxxx>, <kuba@xxxxxxxxxx>, <netdev@xxxxxxxxxxxxxxx>, <lvs-devel@xxxxxxxxxxxxxxx>, <netfilter-devel@xxxxxxxxxxxxxxx>, <geffrey.guo@xxxxxxxxxx>
From: guodeqing <geffrey.guo@xxxxxxxxxx>
Date: Thu, 16 Jul 2020 16:12:08 +0800
The sync_thread_backup only checks sk_receive_queue is empty or not,
there is a situation which cannot sync the connection entries when
sk_receive_queue is empty and sk_rmem_alloc is larger than sk_rcvbuf,
the sync packets are dropped in __udp_enqueue_schedule_skb, this is
because the packets in reader_queue is not read, so the rmem is
not reclaimed.

Here I add the check of whether the reader_queue of the udp sock is
empty or not to solve this problem.

Fixes: 2276f58ac589 ("udp: use a separate rx queue for packet reception")
Reported-by: zhouxudong <zhouxudong8@xxxxxxxxxx>
Signed-off-by: guodeqing <geffrey.guo@xxxxxxxxxx>
---
 net/netfilter/ipvs/ip_vs_sync.c | 12 ++++++++----
 1 file changed, 8 insertions(+), 4 deletions(-)

diff --git a/net/netfilter/ipvs/ip_vs_sync.c b/net/netfilter/ipvs/ip_vs_sync.c
index 605e0f6..2b8abbf 100644
--- a/net/netfilter/ipvs/ip_vs_sync.c
+++ b/net/netfilter/ipvs/ip_vs_sync.c
@@ -1717,6 +1717,8 @@ static int sync_thread_backup(void *data)
 {
        struct ip_vs_sync_thread_data *tinfo = data;
        struct netns_ipvs *ipvs = tinfo->ipvs;
+       struct sock *sk = tinfo->sock->sk;
+       struct udp_sock *up = udp_sk(sk);
        int len;
 
        pr_info("sync thread started: state = BACKUP, mcast_ifn = %s, "
@@ -1724,12 +1726,14 @@ static int sync_thread_backup(void *data)
                ipvs->bcfg.mcast_ifn, ipvs->bcfg.syncid, tinfo->id);
 
        while (!kthread_should_stop()) {
-               wait_event_interruptible(*sk_sleep(tinfo->sock->sk),
-                        !skb_queue_empty(&tinfo->sock->sk->sk_receive_queue)
-                        || kthread_should_stop());
+               wait_event_interruptible(*sk_sleep(sk),
+                                        
!skb_queue_empty_lockless(&sk->sk_receive_queue) ||
+                                        
!skb_queue_empty_lockless(&up->reader_queue) ||
+                                        kthread_should_stop());
 
                /* do we have data now? */
-               while (!skb_queue_empty(&(tinfo->sock->sk->sk_receive_queue))) {
+               while (!skb_queue_empty_lockless(&sk->sk_receive_queue) ||
+                      !skb_queue_empty_lockless(&up->reader_queue)) {
                        len = ip_vs_receive(tinfo->sock, tinfo->buf,
                                        ipvs->bcfg.sync_maxlen);
                        if (len <= 0) {
-- 
2.7.4


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