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Date: Wed, 4 May 2011 13:15:27 +0200 From: Michał Mirosław <mirq-linux@...e.qmqm.pl> To: Mahesh Bandewar <maheshb@...gle.com> Cc: Matt Carlson <mcarlson@...adcom.com>, David Miller <davem@...emloft.net>, netdev <netdev@...r.kernel.org>, Michael Chan <mchan@...adcom.com>, Ben Hutchings <bhutchings@...arflare.com>, Tom Herbert <therbert@...gle.com> Subject: Re: [PATCH 1/2] net: Allow ethtool to set interface in loopback mode. On Tue, May 03, 2011 at 06:18:54PM -0700, Mahesh Bandewar wrote: > This patch enables ethtool to set the loopback mode on a given interface. > By configuring the interface in loopback mode in conjunction with a policy > route / rule, a userland application can stress the egress / ingress path > exposing the flows of the change in progress and potentially help developer(s) > understand the impact of those changes without even sending a packet out > on the network. > > Following set of commands illustrates one such example - > a) ip -4 addr add 192.168.1.1/24 dev eth1 > b) ip -4 rule add from all iif eth1 lookup 250 > c) ip -4 route add local 0/0 dev lo proto kernel scope host table 250 > d) arp -Ds 192.168.1.100 eth1 > e) arp -Ds 192.168.1.200 eth1 > f) sysctl -w net.ipv4.ip_nonlocal_bind=1 > g) sysctl -w net.ipv4.conf.all.accept_local=1 > # Assuming that the machine has 8 cores > h) taskset 000f netserver -L 192.168.1.200 > i) taskset 00f0 netperf -t TCP_CRR -L 192.168.1.100 -H 192.168.1.200 -l 30 > > Signed-off-by: Mahesh Bandewar <maheshb@...gle.com> > --- > include/linux/netdevice.h | 3 ++- > net/core/ethtool.c | 2 +- > 2 files changed, 3 insertions(+), 2 deletions(-) > > diff --git a/include/linux/netdevice.h b/include/linux/netdevice.h > index d5de66a..e7244ed 100644 > --- a/include/linux/netdevice.h > +++ b/include/linux/netdevice.h > @@ -1067,6 +1067,7 @@ struct net_device { > #define NETIF_F_RXHASH (1 << 28) /* Receive hashing offload */ > #define NETIF_F_RXCSUM (1 << 29) /* Receive checksumming offload */ > #define NETIF_F_NOCACHE_COPY (1 << 30) /* Use no-cache copyfromuser */ > +#define NETIF_F_LOOPBACK (1 << 31) /* Enable loopback */ [...] Just for correctness: you could add this flag to loopback's dev->features. It's just an aesthetics point, though. Best Regards, Michał Mirosław -- To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
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