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net: Allow ethtool to set interface in loopback mode.

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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@google.com>
Acked-by: Ben Hutchings <bhutchings@solarflare.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Mahesh Bandewar
2011-05-04 15:30:11 +00:00
committed by David S. Miller
parent 47a0200d53
commit eed2a12f1e
3 changed files with 5 additions and 3 deletions
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3
include/linux/netdevice.h
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@@ -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 */
/* Segmentation offload features */
#define NETIF_F_GSO_SHIFT 16
@@ -1082,7 +1083,7 @@ struct net_device {
/* = all defined minus driver/device-class-related */
#define NETIF_F_NEVER_CHANGE (NETIF_F_VLAN_CHALLENGED | \
NETIF_F_LLTX | NETIF_F_NETNS_LOCAL)
#define NETIF_F_ETHTOOL_BITS (0x7f3fffff & ~NETIF_F_NEVER_CHANGE)
#define NETIF_F_ETHTOOL_BITS (0xff3fffff & ~NETIF_F_NEVER_CHANGE)
/* List of features with software fallbacks. */
#define NETIF_F_GSO_SOFTWARE (NETIF_F_TSO | NETIF_F_TSO_ECN | \