netdev - Re: [RFC PATCH net-next v2 02/10] ipv4: Add a sysctl to control multipath hash fields

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Date:   Tue, 11 May 2021 09:49:30 -0600
From:   David Ahern <dsahern@...il.com>
To:     Ido Schimmel <idosch@...sch.org>, netdev@...r.kernel.org
Cc:     davem@...emloft.net, kuba@...nel.org, petrm@...dia.com,
        roopa@...dia.com, nikolay@...dia.com, ssuryaextr@...il.com,
        mlxsw@...dia.com, Ido Schimmel <idosch@...dia.com>
Subject: Re: [RFC PATCH net-next v2 02/10] ipv4: Add a sysctl to control
 multipath hash fields

On 5/9/21 9:16 AM, Ido Schimmel wrote:
> diff --git a/net/ipv4/sysctl_net_ipv4.c b/net/ipv4/sysctl_net_ipv4.c
> index a62934b9f15a..da627c4d633a 100644
> --- a/net/ipv4/sysctl_net_ipv4.c
> +++ b/net/ipv4/sysctl_net_ipv4.c
> @@ -19,6 +19,7 @@
>  #include <net/snmp.h>
>  #include <net/icmp.h>
>  #include <net/ip.h>
> +#include <net/ip_fib.h>
>  #include <net/route.h>
>  #include <net/tcp.h>
>  #include <net/udp.h>
> @@ -48,6 +49,8 @@ static int ip_ping_group_range_min[] = { 0, 0 };
>  static int ip_ping_group_range_max[] = { GID_T_MAX, GID_T_MAX };
>  static u32 u32_max_div_HZ = UINT_MAX / HZ;
>  static int one_day_secs = 24 * 3600;
> +static u32 fib_multipath_hash_fields_all_mask __maybe_unused =
> +	FIB_MULTIPATH_HASH_FIELD_ALL_MASK;
>  
>  /* obsolete */
>  static int sysctl_tcp_low_latency __read_mostly;
> @@ -1052,6 +1055,14 @@ static struct ctl_table ipv4_net_table[] = {
>  		.extra1		= SYSCTL_ZERO,
>  		.extra2		= &two,
>  	},
> +	{
> +		.procname	= "fib_multipath_hash_fields",
> +		.data		= &init_net.ipv4.sysctl_fib_multipath_hash_fields,
> +		.maxlen		= sizeof(u32),
> +		.mode		= 0644,
> +		.proc_handler	= proc_douintvec_minmax,
> +		.extra2		= &fib_multipath_hash_fields_all_mask,

no .extra1 means 0 is allowed which effectively disables hashing and
multipath selection; only the first leg will be used. Is that intended?



> +	},
>  #endif
>  	{
>  		.procname	= "ip_unprivileged_port_start",
>