linux-kernel - Re: [PATCH nf-next v5] netfilter: ipvs: Fix reuse connection if RS weight is 0

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Date:   Wed, 3 Nov 2021 10:55:16 +0100
From:   Simon Horman <horms@...ge.net.au>
To:     yangxingwu <xingwu.yang@...il.com>
Cc:     ja@....bg, pablo@...filter.org, kadlec@...filter.org, fw@...len.de,
        davem@...emloft.net, kuba@...nel.org, netdev@...r.kernel.org,
        lvs-devel@...r.kernel.org, netfilter-devel@...r.kernel.org,
        coreteam@...filter.org, linux-kernel@...r.kernel.org,
        linux-doc@...r.kernel.org, corbet@....net,
        Chuanqi Liu <legend050709@...com>
Subject: Re: [PATCH nf-next v5] netfilter: ipvs: Fix reuse connection if RS
 weight is 0

On Mon, Nov 01, 2021 at 10:04:16AM +0800, yangxingwu wrote:
> We are changing expire_nodest_conn to work even for reused connections when
> conn_reuse_mode=0, just as what was done with commit dc7b3eb900aa ("ipvs:
> Fix reuse connection if real server is dead").
> 
> For controlled and persistent connections, the new connection will get the
> needed real server depending on the rules in ip_vs_check_template().
> 
> Fixes: d752c3645717 ("ipvs: allow rescheduling of new connections when port reuse is detected")
> Co-developed-by: Chuanqi Liu <legend050709@...com>
> Signed-off-by: Chuanqi Liu <legend050709@...com>
> Signed-off-by: yangxingwu <xingwu.yang@...il.com>

Thanks, and sorry but I have a few nits.

> ---
>  Documentation/networking/ipvs-sysctl.rst | 3 +--
>  net/netfilter/ipvs/ip_vs_core.c          | 8 ++++----
>  2 files changed, 5 insertions(+), 6 deletions(-)
> 
> diff --git a/Documentation/networking/ipvs-sysctl.rst b/Documentation/networking/ipvs-sysctl.rst
> index 2afccc63856e..1cfbf1add2fc 100644
> --- a/Documentation/networking/ipvs-sysctl.rst
> +++ b/Documentation/networking/ipvs-sysctl.rst
> @@ -37,8 +37,7 @@ conn_reuse_mode - INTEGER
>  
>  	0: disable any special handling on port reuse. The new
>  	connection will be delivered to the same real server that was
> -	servicing the previous connection. This will effectively
> -	disable expire_nodest_conn.
> +	servicing the previous connection.

nit: s/servicing/service/

>  
>  	bit 1: enable rescheduling of new connections when it is safe.
>  	That is, whenever expire_nodest_conn and for TCP sockets, when
> diff --git a/net/netfilter/ipvs/ip_vs_core.c b/net/netfilter/ipvs/ip_vs_core.c
> index 128690c512df..f9d65d2c8da8 100644
> --- a/net/netfilter/ipvs/ip_vs_core.c
> +++ b/net/netfilter/ipvs/ip_vs_core.c
> @@ -1964,7 +1964,6 @@ ip_vs_in(struct netns_ipvs *ipvs, unsigned int hooknum, struct sk_buff *skb, int
>  	struct ip_vs_proto_data *pd;
>  	struct ip_vs_conn *cp;
>  	int ret, pkts;
> -	int conn_reuse_mode;
>  	struct sock *sk;
>  
>  	/* Already marked as IPVS request or reply? */
> @@ -2041,15 +2040,16 @@ ip_vs_in(struct netns_ipvs *ipvs, unsigned int hooknum, struct sk_buff *skb, int
>  	cp = INDIRECT_CALL_1(pp->conn_in_get, ip_vs_conn_in_get_proto,
>  			     ipvs, af, skb, &iph);
>  
> -	conn_reuse_mode = sysctl_conn_reuse_mode(ipvs);
> -	if (conn_reuse_mode && !iph.fragoffs && is_new_conn(skb, &iph) && cp) {
> +	if (!iph.fragoffs && is_new_conn(skb, &iph) && cp) {
>  		bool old_ct = false, resched = false;
> +		int conn_reuse_mode = sysctl_conn_reuse_mode(ipvs);

We should probably try to move towards reverse xmas tree, which
is preferred for Linux network code these days.

So could you move the conn_reuse_mode line above the bool line?

>  
>  		if (unlikely(sysctl_expire_nodest_conn(ipvs)) && cp->dest &&
>  		    unlikely(!atomic_read(&cp->dest->weight))) {
>  			resched = true;
>  			old_ct = ip_vs_conn_uses_old_conntrack(cp, skb);
> -		} else if (is_new_conn_expected(cp, conn_reuse_mode)) {
> +		} else if (conn_reuse_mode &&
> +			   is_new_conn_expected(cp, conn_reuse_mode)) {
>  			old_ct = ip_vs_conn_uses_old_conntrack(cp, skb);
>  			if (!atomic_read(&cp->n_control)) {
>  				resched = true;
> -- 
> 2.30.2
>