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net: Introduce NETIF_F_GRO_HW. 

Introduce NETIF_F_GRO_HW feature flag for NICs that support hardware
GRO.  With this flag, we can now independently turn on or off hardware
GRO when GRO is on.  Previously, drivers were using NETIF_F_GRO to
control hardware GRO and so it cannot be independently turned on or
off without affecting GRO.

Hardware GRO (just like GRO) guarantees that packets can be re-segmented
by TSO/GSO to reconstruct the original packet stream.  Logically,
GRO_HW should depend on GRO since it a subset, but we will let
individual drivers enforce this dependency as they see fit.

Since NETIF_F_GRO is not propagated between upper and lower devices,
NETIF_F_GRO_HW should follow suit since it is a subset of GRO.  In other
words, a lower device can independent have GRO/GRO_HW enabled or disabled
and no feature propagation is required.  This will preserve the current
GRO behavior.  This can be changed later if we decide to propagate GRO/
GRO_HW/RXCSUM from upper to lower devices.

Cc: Ariel Elior <Ariel.Elior@cavium.com>
Cc: everest-linux-l2@cavium.com
Signed-off-by: Michael Chan <michael.chan@broadcom.com>
Acked-by: Alexander Duyck <alexander.h.duyck@intel.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Michael Chan 2017-12-16 03:09:40 -05:00 committed by David S. Miller
parent 398b841e4a
commit fb1f5f79ae
4 changed files with 25 additions and 0 deletions
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9
Documentation/networking/netdev-features.txt
View File

@ -163,3 +163,12 @@ This requests that the NIC receive all possible frames, including errored
frames (such as bad FCS, etc). This can be helpful when sniffing a link with
bad packets on it. Some NICs may receive more packets if also put into normal
PROMISC mode.
* rx-gro-hw
This requests that the NIC enables Hardware GRO (generic receive offload).
Hardware GRO is basically the exact reverse of TSO, and is generally
stricter than Hardware LRO. A packet stream merged by Hardware GRO must
be re-segmentable by GSO or TSO back to the exact original packet stream.
Hardware GRO is dependent on RXCSUM since every packet successfully merged
by hardware must also have the checksum verified by hardware.

3
include/linux/netdev_features.h
View File

@ -78,6 +78,8 @@ enum {
NETIF_F_HW_ESP_TX_CSUM_BIT, /* ESP with TX checksum offload */
NETIF_F_RX_UDP_TUNNEL_PORT_BIT, /* Offload of RX port for UDP tunnels */
NETIF_F_GRO_HW_BIT, /* Hardware Generic receive offload */
/*
* Add your fresh new feature above and remember to update
* netdev_features_strings[] in net/core/ethtool.c and maybe
@ -97,6 +99,7 @@ enum {
#define NETIF_F_FRAGLIST __NETIF_F(FRAGLIST)
#define NETIF_F_FSO __NETIF_F(FSO)
#define NETIF_F_GRO __NETIF_F(GRO)
#define NETIF_F_GRO_HW __NETIF_F(GRO_HW)
#define NETIF_F_GSO __NETIF_F(GSO)
#define NETIF_F_GSO_ROBUST __NETIF_F(GSO_ROBUST)
#define NETIF_F_HIGHDMA __NETIF_F(HIGHDMA)

12
net/core/dev.c
View File

@ -7424,6 +7424,18 @@ static netdev_features_t netdev_fix_features(struct net_device *dev,
features &= ~dev->gso_partial_features;
}
if (!(features & NETIF_F_RXCSUM)) {
/* NETIF_F_GRO_HW implies doing RXCSUM since every packet
* successfully merged by hardware must also have the
* checksum verified by hardware. If the user does not
* want to enable RXCSUM, logically, we should disable GRO_HW.
*/
if (features & NETIF_F_GRO_HW) {
netdev_dbg(dev, "Dropping NETIF_F_GRO_HW since no RXCSUM feature.\n");
features &= ~NETIF_F_GRO_HW;
}
}
return features;
}

1
net/core/ethtool.c
View File

@ -73,6 +73,7 @@ static const char netdev_features_strings[NETDEV_FEATURE_COUNT][ETH_GSTRING_LEN]
[NETIF_F_LLTX_BIT] = "tx-lockless",
[NETIF_F_NETNS_LOCAL_BIT] = "netns-local",
[NETIF_F_GRO_BIT] = "rx-gro",
[NETIF_F_GRO_HW_BIT] = "rx-gro-hw",
[NETIF_F_LRO_BIT] = "rx-lro",
[NETIF_F_TSO_BIT] = "tx-tcp-segmentation",