netdev - Re: [RFC PATCH] net: ipv4: increase dhcp inter device timeout

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Date:	Fri, 07 Aug 2015 16:15:46 +0900
From:	YOSHIFUJI Hideaki <hideaki.yoshifuji@...aclelinux.com>
To:	Mugunthan V N <mugunthanvnm@...com>, netdev@...r.kernel.org
CC:	hideaki.yoshifuji@...aclelinux.com,
	"David S . Miller" <davem@...emloft.net>,
	Alexey Kuznetsov <kuznet@....inr.ac.ru>,
	James Morris <jmorris@...ei.org>,
	Hideaki YOSHIFUJI <yoshfuji@...ux-ipv6.org>,
	Patrick McHardy <kaber@...sh.net>
Subject: Re: [RFC PATCH] net: ipv4: increase dhcp inter device timeout

Hi,

Mugunthan V N wrote:
> When a system has multiple ethernet devices and during DHCP
> request (for using NFS), the system waits only for HZ/2 which is
> 500mS before switching to another interface for DHCP.
> 
> There are some routers (Ex: Trendnet routers) which responds to
> DHCP request at about 560mS. When the system has only one
> ethernet interface there is no issue as the timeout is 2S and the
> dev xid doesn't change and only retries.
> 
> But when the system has multiple Ethernet like DRA74x with CPSW
> in dual EMAC mode, the DHCP response is dropped as the dev xid
> changes while shifting to the next device. So changing inter
> device timeout to HZ (which is 1S).
> 
> Signed-off-by: Mugunthan V N <mugunthanvnm@...com>
> ---
>  net/ipv4/ipconfig.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/net/ipv4/ipconfig.c b/net/ipv4/ipconfig.c
> index 8e7328c..bdb8cb5 100644
> --- a/net/ipv4/ipconfig.c
> +++ b/net/ipv4/ipconfig.c
> @@ -94,7 +94,7 @@
>  /* Define the timeout for waiting for a DHCP/BOOTP/RARP reply */
>  #define CONF_OPEN_RETRIES 	2	/* (Re)open devices twice */
>  #define CONF_SEND_RETRIES 	6	/* Send six requests per open */
> -#define CONF_INTER_TIMEOUT	(HZ/2)	/* Inter-device timeout: 1/2 second */
> +#define CONF_INTER_TIMEOUT	(HZ)	/* Inter-device timeout: 1/2 second */

You should update comment as well at least.

--yoshfuji

>  #define CONF_BASE_TIMEOUT	(HZ*2)	/* Initial timeout: 2 seconds */
>  #define CONF_TIMEOUT_RANDOM	(HZ)	/* Maximum amount of randomization */
>  #define CONF_TIMEOUT_MULT	*7/4	/* Rate of timeout growth */
> 

-- 
Hideaki Yoshifuji <hideaki.yoshifuji@...aclelinux.com>
Technical Division, MIRACLE LINUX CORPORATION
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