net: Allow ethtool to set interface in loopback mode. (eed2a12f) · Commits · 戴 / test

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>

drivers/net/loopback.c

+2 −1

Original line number	Diff line number	Diff line
		@@ -174,7 +174,8 @@ static void loopback_setup(struct net_device *dev)
		\| NETIF_F_HIGHDMA
		\| NETIF_F_LLTX
		\| NETIF_F_NETNS_LOCAL
		\| NETIF_F_VLAN_CHALLENGED;
		\| NETIF_F_VLAN_CHALLENGED
		\| NETIF_F_LOOPBACK;
		dev->ethtool_ops = &loopback_ethtool_ops;
		dev->header_ops = &eth_header_ops;
		dev->netdev_ops = &loopback_ops;

include/linux/netdevice.h

+2 −1

Original line number	Diff line number	Diff line
		@@ -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 \| \

net/core/ethtool.c

+1 −1

Original line number	Diff line number	Diff line
		@@ -362,7 +362,7 @@ static const char netdev_features_strings[ETHTOOL_DEV_FEATURE_WORDS * 32][ETH_GS
		/* NETIF_F_RXHASH */ "rx-hashing",
		/* NETIF_F_RXCSUM */ "rx-checksum",
		/* NETIF_F_NOCACHE_COPY */ "tx-nocache-copy"
		"",
		/* NETIF_F_LOOPBACK */ "loopback",
		};

		static int __ethtool_get_sset_count(struct net_device *dev, int sset)

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