Re: [PATCH ipvs-next] ipvs: count pre-established TCP states as active

[Julian Anastasov]

	Hello,

On Fri, 3 Jun 2016, Michal Kubecek wrote:

> Some users observed that "least connection" distribution algorithm doesn't
> handle well bursts of TCP connections from reconnecting clients after
> a node or network failure.
> 
> This is because the algorithm counts active connection as worth 256
> inactive ones where for TCP, "active" only means TCP connections in
> ESTABLISHED state. In case of a connection burst, new connections are
> handled before previous ones have finished the three way handshaking so
> that all are still counted as "inactive", i.e. cheap ones. The become
> "active" quickly but at that time, all of them are already assigned to one
> real server (or few), resulting in highly unbalanced distribution.
> 
> Address this by counting the "pre-established" states as "active".
> 
> Signed-off-by: Michal Kubecek <mkubecek@xxxxxxx>

Acked-by: Julian Anastasov <ja@xxxxxx>

	Simon, please apply!

> ---
>  net/netfilter/ipvs/ip_vs_proto_tcp.c | 25 +++++++++++++++++++++++--
>  1 file changed, 23 insertions(+), 2 deletions(-)
> 
> diff --git a/net/netfilter/ipvs/ip_vs_proto_tcp.c b/net/netfilter/ipvs/ip_vs_proto_tcp.c
> index d7024b2ed769..5117bcb7d2f0 100644
> --- a/net/netfilter/ipvs/ip_vs_proto_tcp.c
> +++ b/net/netfilter/ipvs/ip_vs_proto_tcp.c
> @@ -395,6 +395,20 @@ static const char *const tcp_state_name_table[IP_VS_TCP_S_LAST+1] = {
>  	[IP_VS_TCP_S_LAST]		=	"BUG!",
>  };
>  
> +static const bool tcp_state_active_table[IP_VS_TCP_S_LAST] = {
> +	[IP_VS_TCP_S_NONE]		=	false,
> +	[IP_VS_TCP_S_ESTABLISHED]	=	true,
> +	[IP_VS_TCP_S_SYN_SENT]		=	true,
> +	[IP_VS_TCP_S_SYN_RECV]		=	true,
> +	[IP_VS_TCP_S_FIN_WAIT]		=	false,
> +	[IP_VS_TCP_S_TIME_WAIT]		=	false,
> +	[IP_VS_TCP_S_CLOSE]		=	false,
> +	[IP_VS_TCP_S_CLOSE_WAIT]	=	false,
> +	[IP_VS_TCP_S_LAST_ACK]		=	false,
> +	[IP_VS_TCP_S_LISTEN]		=	false,
> +	[IP_VS_TCP_S_SYNACK]		=	true,
> +};
> +
>  #define sNO IP_VS_TCP_S_NONE
>  #define sES IP_VS_TCP_S_ESTABLISHED
>  #define sSS IP_VS_TCP_S_SYN_SENT
> @@ -418,6 +432,13 @@ static const char * tcp_state_name(int state)
>  	return tcp_state_name_table[state] ? tcp_state_name_table[state] : "?";
>  }
>  
> +static bool tcp_state_active(int state)
> +{
> +	if (state >= IP_VS_TCP_S_LAST)
> +		return false;
> +	return tcp_state_active_table[state];
> +}
> +
>  static struct tcp_states_t tcp_states [] = {
>  /*	INPUT */
>  /*        sNO, sES, sSS, sSR, sFW, sTW, sCL, sCW, sLA, sLI, sSA	*/
> @@ -540,12 +561,12 @@ set_tcp_state(struct ip_vs_proto_data *pd, struct ip_vs_conn *cp,
>  
>  		if (dest) {
>  			if (!(cp->flags & IP_VS_CONN_F_INACTIVE) &&
> -			    (new_state != IP_VS_TCP_S_ESTABLISHED)) {
> +			    !tcp_state_active(new_state)) {
>  				atomic_dec(&dest->activeconns);
>  				atomic_inc(&dest->inactconns);
>  				cp->flags |= IP_VS_CONN_F_INACTIVE;
>  			} else if ((cp->flags & IP_VS_CONN_F_INACTIVE) &&
> -				   (new_state == IP_VS_TCP_S_ESTABLISHED)) {
> +				   tcp_state_active(new_state)) {
>  				atomic_inc(&dest->activeconns);
>  				atomic_dec(&dest->inactconns);
>  				cp->flags &= ~IP_VS_CONN_F_INACTIVE;
> -- 
> 2.8.3

Regards

--
Julian Anastasov <ja@xxxxxx>