Merge branch 'gro-fixed-id-gso-partial' (edd93cd7) · Commits · e / devices / android_kernel_xiaomi_nabu

Documentation/networking/segmentation-offloads.txt

0 → 100644

+130 −0

Original line number	Original line	Diff line number	Diff line
			Segmentation Offloads in the Linux Networking Stack

			Introduction
			============

			This document describes a set of techniques in the Linux networking stack
			to take advantage of segmentation offload capabilities of various NICs.

			The following technologies are described:
			* TCP Segmentation Offload - TSO
			* UDP Fragmentation Offload - UFO
			* IPIP, SIT, GRE, and UDP Tunnel Offloads
			* Generic Segmentation Offload - GSO
			* Generic Receive Offload - GRO
			* Partial Generic Segmentation Offload - GSO_PARTIAL

			TCP Segmentation Offload
			========================

			TCP segmentation allows a device to segment a single frame into multiple
			frames with a data payload size specified in skb_shinfo()->gso_size.
			When TCP segmentation requested the bit for either SKB_GSO_TCP or
			SKB_GSO_TCP6 should be set in skb_shinfo()->gso_type and
			skb_shinfo()->gso_size should be set to a non-zero value.

			TCP segmentation is dependent on support for the use of partial checksum
			offload. For this reason TSO is normally disabled if the Tx checksum
			offload for a given device is disabled.

			In order to support TCP segmentation offload it is necessary to populate
			the network and transport header offsets of the skbuff so that the device
			drivers will be able determine the offsets of the IP or IPv6 header and the
			TCP header. In addition as CHECKSUM_PARTIAL is required csum_start should
			also point to the TCP header of the packet.

			For IPv4 segmentation we support one of two types in terms of the IP ID.
			The default behavior is to increment the IP ID with every segment. If the
			GSO type SKB_GSO_TCP_FIXEDID is specified then we will not increment the IP
			ID and all segments will use the same IP ID. If a device has
			NETIF_F_TSO_MANGLEID set then the IP ID can be ignored when performing TSO
			and we will either increment the IP ID for all frames, or leave it at a
			static value based on driver preference.

			UDP Fragmentation Offload
			=========================

			UDP fragmentation offload allows a device to fragment an oversized UDP
			datagram into multiple IPv4 fragments. Many of the requirements for UDP
			fragmentation offload are the same as TSO. However the IPv4 ID for
			fragments should not increment as a single IPv4 datagram is fragmented.

			IPIP, SIT, GRE, UDP Tunnel, and Remote Checksum Offloads
			========================================================

			In addition to the offloads described above it is possible for a frame to
			contain additional headers such as an outer tunnel. In order to account
			for such instances an additional set of segmentation offload types were
			introduced including SKB_GSO_IPIP, SKB_GSO_SIT, SKB_GSO_GRE, and
			SKB_GSO_UDP_TUNNEL. These extra segmentation types are used to identify
			cases where there are more than just 1 set of headers. For example in the
			case of IPIP and SIT we should have the network and transport headers moved
			from the standard list of headers to "inner" header offsets.

			Currently only two levels of headers are supported. The convention is to
			refer to the tunnel headers as the outer headers, while the encapsulated
			data is normally referred to as the inner headers. Below is the list of
			calls to access the given headers:

			IPIP/SIT Tunnel:
			Outer Inner
			MAC skb_mac_header
			Network skb_network_header skb_inner_network_header
			Transport skb_transport_header

			UDP/GRE Tunnel:
			Outer Inner
			MAC skb_mac_header skb_inner_mac_header
			Network skb_network_header skb_inner_network_header
			Transport skb_transport_header skb_inner_transport_header

			In addition to the above tunnel types there are also SKB_GSO_GRE_CSUM and
			SKB_GSO_UDP_TUNNEL_CSUM. These two additional tunnel types reflect the
			fact that the outer header also requests to have a non-zero checksum
			included in the outer header.

			Finally there is SKB_GSO_REMCSUM which indicates that a given tunnel header
			has requested a remote checksum offload. In this case the inner headers
			will be left with a partial checksum and only the outer header checksum
			will be computed.

			Generic Segmentation Offload
			============================

			Generic segmentation offload is a pure software offload that is meant to
			deal with cases where device drivers cannot perform the offloads described
			above. What occurs in GSO is that a given skbuff will have its data broken
			out over multiple skbuffs that have been resized to match the MSS provided
			via skb_shinfo()->gso_size.

			Before enabling any hardware segmentation offload a corresponding software
			offload is required in GSO. Otherwise it becomes possible for a frame to
			be re-routed between devices and end up being unable to be transmitted.

			Generic Receive Offload
			=======================

			Generic receive offload is the complement to GSO. Ideally any frame
			assembled by GRO should be segmented to create an identical sequence of
			frames using GSO, and any sequence of frames segmented by GSO should be
			able to be reassembled back to the original by GRO. The only exception to
			this is IPv4 ID in the case that the DF bit is set for a given IP header.
			If the value of the IPv4 ID is not sequentially incrementing it will be
			altered so that it is when a frame assembled via GRO is segmented via GSO.

			Partial Generic Segmentation Offload
			====================================

			Partial generic segmentation offload is a hybrid between TSO and GSO. What
			it effectively does is take advantage of certain traits of TCP and tunnels
			so that instead of having to rewrite the packet headers for each segment
			only the inner-most transport header and possibly the outer-most network
			header need to be updated. This allows devices that do not support tunnel
			offloads or tunnel offloads with checksum to still make use of segmentation.

			With the partial offload what occurs is that all headers excluding the
			inner transport header are updated such that they will contain the correct
			values for if the header was simply duplicated. The one exception to this
			is the outer IPv4 ID field. It is up to the device drivers to guarantee
			that the IPv4 ID field is incremented in the case that a given header does
			not have the DF bit set.

include/linux/netdev_features.h

+8 −0

include/linux/netdevice.h

+7 −1

Original line number	Original line	Diff line number	Diff line
	@@ -1654,6 +1654,7 @@ struct net_device {
	netdev_features_t vlan_features;		netdev_features_t vlan_features;
	netdev_features_t hw_enc_features;		netdev_features_t hw_enc_features;
	netdev_features_t mpls_features;		netdev_features_t mpls_features;
			netdev_features_t gso_partial_features;

	int ifindex;		int ifindex;
	int group;		int group;
	@@ -2121,7 +2122,10 @@ struct napi_gro_cb {
	/* Used in GRE, set in fou/gue_gro_receive */		/* Used in GRE, set in fou/gue_gro_receive */
	u8 is_fou:1;		u8 is_fou:1;

	/* 6 bit hole */		/* Used to determine if flush_id can be ignored */
			u8 is_atomic:1;

			/* 5 bit hole */

	/* used to support CHECKSUM_COMPLETE for tunneling protocols */		/* used to support CHECKSUM_COMPLETE for tunneling protocols */
	__wsum csum;		__wsum csum;
	@@ -3992,6 +3996,7 @@ static inline bool net_gso_ok(netdev_features_t features, int gso_type)
	BUILD_BUG_ON(SKB_GSO_UDP != (NETIF_F_UFO >> NETIF_F_GSO_SHIFT));		BUILD_BUG_ON(SKB_GSO_UDP != (NETIF_F_UFO >> NETIF_F_GSO_SHIFT));
	BUILD_BUG_ON(SKB_GSO_DODGY != (NETIF_F_GSO_ROBUST >> NETIF_F_GSO_SHIFT));		BUILD_BUG_ON(SKB_GSO_DODGY != (NETIF_F_GSO_ROBUST >> NETIF_F_GSO_SHIFT));
	BUILD_BUG_ON(SKB_GSO_TCP_ECN != (NETIF_F_TSO_ECN >> NETIF_F_GSO_SHIFT));		BUILD_BUG_ON(SKB_GSO_TCP_ECN != (NETIF_F_TSO_ECN >> NETIF_F_GSO_SHIFT));
			BUILD_BUG_ON(SKB_GSO_TCP_FIXEDID != (NETIF_F_TSO_MANGLEID >> NETIF_F_GSO_SHIFT));
	BUILD_BUG_ON(SKB_GSO_TCPV6 != (NETIF_F_TSO6 >> NETIF_F_GSO_SHIFT));		BUILD_BUG_ON(SKB_GSO_TCPV6 != (NETIF_F_TSO6 >> NETIF_F_GSO_SHIFT));
	BUILD_BUG_ON(SKB_GSO_FCOE != (NETIF_F_FSO >> NETIF_F_GSO_SHIFT));		BUILD_BUG_ON(SKB_GSO_FCOE != (NETIF_F_FSO >> NETIF_F_GSO_SHIFT));
	BUILD_BUG_ON(SKB_GSO_GRE != (NETIF_F_GSO_GRE >> NETIF_F_GSO_SHIFT));		BUILD_BUG_ON(SKB_GSO_GRE != (NETIF_F_GSO_GRE >> NETIF_F_GSO_SHIFT));
	@@ -4000,6 +4005,7 @@ static inline bool net_gso_ok(netdev_features_t features, int gso_type)
	BUILD_BUG_ON(SKB_GSO_SIT != (NETIF_F_GSO_SIT >> NETIF_F_GSO_SHIFT));		BUILD_BUG_ON(SKB_GSO_SIT != (NETIF_F_GSO_SIT >> NETIF_F_GSO_SHIFT));
	BUILD_BUG_ON(SKB_GSO_UDP_TUNNEL != (NETIF_F_GSO_UDP_TUNNEL >> NETIF_F_GSO_SHIFT));		BUILD_BUG_ON(SKB_GSO_UDP_TUNNEL != (NETIF_F_GSO_UDP_TUNNEL >> NETIF_F_GSO_SHIFT));
	BUILD_BUG_ON(SKB_GSO_UDP_TUNNEL_CSUM != (NETIF_F_GSO_UDP_TUNNEL_CSUM >> NETIF_F_GSO_SHIFT));		BUILD_BUG_ON(SKB_GSO_UDP_TUNNEL_CSUM != (NETIF_F_GSO_UDP_TUNNEL_CSUM >> NETIF_F_GSO_SHIFT));
			BUILD_BUG_ON(SKB_GSO_PARTIAL != (NETIF_F_GSO_PARTIAL >> NETIF_F_GSO_SHIFT));
	BUILD_BUG_ON(SKB_GSO_TUNNEL_REMCSUM != (NETIF_F_GSO_TUNNEL_REMCSUM >> NETIF_F_GSO_SHIFT));		BUILD_BUG_ON(SKB_GSO_TUNNEL_REMCSUM != (NETIF_F_GSO_TUNNEL_REMCSUM >> NETIF_F_GSO_SHIFT));

	return (features & feature) == feature;		return (features & feature) == feature;

include/linux/skbuff.h

+17 −10

Original line number	Original line	Diff line number	Diff line
	@@ -465,23 +465,27 @@ enum {
	/* This indicates the tcp segment has CWR set. */		/* This indicates the tcp segment has CWR set. */
	SKB_GSO_TCP_ECN = 1 << 3,		SKB_GSO_TCP_ECN = 1 << 3,

	SKB_GSO_TCPV6 = 1 << 4,		SKB_GSO_TCP_FIXEDID = 1 << 4,

	SKB_GSO_FCOE = 1 << 5,		SKB_GSO_TCPV6 = 1 << 5,

	SKB_GSO_GRE = 1 << 6,		SKB_GSO_FCOE = 1 << 6,

	SKB_GSO_GRE_CSUM = 1 << 7,		SKB_GSO_GRE = 1 << 7,

	SKB_GSO_IPIP = 1 << 8,		SKB_GSO_GRE_CSUM = 1 << 8,

	SKB_GSO_SIT = 1 << 9,		SKB_GSO_IPIP = 1 << 9,

	SKB_GSO_UDP_TUNNEL = 1 << 10,		SKB_GSO_SIT = 1 << 10,

	SKB_GSO_UDP_TUNNEL_CSUM = 1 << 11,		SKB_GSO_UDP_TUNNEL = 1 << 11,

	SKB_GSO_TUNNEL_REMCSUM = 1 << 12,		SKB_GSO_UDP_TUNNEL_CSUM = 1 << 12,

			SKB_GSO_PARTIAL = 1 << 13,

			SKB_GSO_TUNNEL_REMCSUM = 1 << 14,
	};		};

	#if BITS_PER_LONG > 32		#if BITS_PER_LONG > 32
	@@ -3589,7 +3593,10 @@ static inline struct sec_path skb_sec_path(struct sk_buff skb)
	* Keeps track of level of encapsulation of network headers.		* Keeps track of level of encapsulation of network headers.
	*/		*/
	struct skb_gso_cb {		struct skb_gso_cb {
			union {
	int mac_offset;		int mac_offset;
			int data_offset;
			};
	int encap_level;		int encap_level;
	__wsum csum;		__wsum csum;
	__u16 csum_start;		__u16 csum_start;

net/core/dev.c

+61 −6

Original line number	Original line	Diff line number	Diff line
	@@ -2711,6 +2711,19 @@ struct sk_buff __skb_gso_segment(struct sk_buff skb,
	return ERR_PTR(err);		return ERR_PTR(err);
	}		}

			/* Only report GSO partial support if it will enable us to
			* support segmentation on this frame without needing additional
			* work.
			*/
			if (features & NETIF_F_GSO_PARTIAL) {
			netdev_features_t partial_features = NETIF_F_GSO_ROBUST;
			struct net_device *dev = skb->dev;

			partial_features \|= dev->features & dev->gso_partial_features;
			if (!skb_gso_ok(skb, features \| partial_features))
			features &= ~NETIF_F_GSO_PARTIAL;
			}

	BUILD_BUG_ON(SKB_SGO_CB_OFFSET +		BUILD_BUG_ON(SKB_SGO_CB_OFFSET +
	sizeof(*SKB_GSO_CB(skb)) > sizeof(skb->cb));		sizeof(*SKB_GSO_CB(skb)) > sizeof(skb->cb));

	@@ -2825,14 +2838,45 @@ static netdev_features_t dflt_features_check(const struct sk_buff *skb,
	return vlan_features_check(skb, features);		return vlan_features_check(skb, features);
	}		}

			static netdev_features_t gso_features_check(const struct sk_buff *skb,
			struct net_device *dev,
			netdev_features_t features)
			{
			u16 gso_segs = skb_shinfo(skb)->gso_segs;

			if (gso_segs > dev->gso_max_segs)
			return features & ~NETIF_F_GSO_MASK;

			/* Support for GSO partial features requires software
			* intervention before we can actually process the packets
			* so we need to strip support for any partial features now
			* and we can pull them back in after we have partially
			* segmented the frame.
			*/
			if (!(skb_shinfo(skb)->gso_type & SKB_GSO_PARTIAL))
			features &= ~dev->gso_partial_features;

			/* Make sure to clear the IPv4 ID mangling feature if the
			* IPv4 header has the potential to be fragmented.
			*/
			if (skb_shinfo(skb)->gso_type & SKB_GSO_TCPV4) {
			struct iphdr *iph = skb->encapsulation ?
			inner_ip_hdr(skb) : ip_hdr(skb);

			if (!(iph->frag_off & htons(IP_DF)))
			features &= ~NETIF_F_TSO_MANGLEID;
			}

			return features;
			}

	netdev_features_t netif_skb_features(struct sk_buff *skb)		netdev_features_t netif_skb_features(struct sk_buff *skb)
	{		{
	struct net_device *dev = skb->dev;		struct net_device *dev = skb->dev;
	netdev_features_t features = dev->features;		netdev_features_t features = dev->features;
	u16 gso_segs = skb_shinfo(skb)->gso_segs;

	if (gso_segs > dev->gso_max_segs)		if (skb_is_gso(skb))
	features &= ~NETIF_F_GSO_MASK;		features = gso_features_check(skb, dev, features);

	/* If encapsulation offload request, verify we are testing		/* If encapsulation offload request, verify we are testing
	* hardware encapsulation features instead of standard		* hardware encapsulation features instead of standard
	@@ -4440,6 +4484,7 @@ static enum gro_result dev_gro_receive(struct napi_struct *napi, struct sk_buff
	NAPI_GRO_CB(skb)->free = 0;		NAPI_GRO_CB(skb)->free = 0;
	NAPI_GRO_CB(skb)->encap_mark = 0;		NAPI_GRO_CB(skb)->encap_mark = 0;
	NAPI_GRO_CB(skb)->is_fou = 0;		NAPI_GRO_CB(skb)->is_fou = 0;
			NAPI_GRO_CB(skb)->is_atomic = 1;
	NAPI_GRO_CB(skb)->gro_remcsum_start = 0;		NAPI_GRO_CB(skb)->gro_remcsum_start = 0;

	/* Setup for GRO checksum validation */		/* Setup for GRO checksum validation */
	@@ -6706,6 +6751,14 @@ static netdev_features_t netdev_fix_features(struct net_device *dev,
	}		}
	}		}

			/* GSO partial features require GSO partial be set */
			if ((features & dev->gso_partial_features) &&
			!(features & NETIF_F_GSO_PARTIAL)) {
			netdev_dbg(dev,
			"Dropping partially supported GSO features since no GSO partial.\n");
			features &= ~dev->gso_partial_features;
			}

	#ifdef CONFIG_NET_RX_BUSY_POLL		#ifdef CONFIG_NET_RX_BUSY_POLL
	if (dev->netdev_ops->ndo_busy_poll)		if (dev->netdev_ops->ndo_busy_poll)
	features \|= NETIF_F_BUSY_POLL;		features \|= NETIF_F_BUSY_POLL;
	@@ -6976,9 +7029,11 @@ int register_netdevice(struct net_device *dev)
	dev->features \|= NETIF_F_SOFT_FEATURES;		dev->features \|= NETIF_F_SOFT_FEATURES;
	dev->wanted_features = dev->features & dev->hw_features;		dev->wanted_features = dev->features & dev->hw_features;

	if (!(dev->flags & IFF_LOOPBACK)) {		if (!(dev->flags & IFF_LOOPBACK))
	dev->hw_features \|= NETIF_F_NOCACHE_COPY;		dev->hw_features \|= NETIF_F_NOCACHE_COPY;
	}
			if (dev->hw_features & NETIF_F_TSO)
			dev->hw_features \|= NETIF_F_TSO_MANGLEID;

	/* Make NETIF_F_HIGHDMA inheritable to VLAN devices.		/* Make NETIF_F_HIGHDMA inheritable to VLAN devices.
	*/		*/
	@@ -6986,7 +7041,7 @@ int register_netdevice(struct net_device *dev)

	/* Make NETIF_F_SG inheritable to tunnel devices.		/* Make NETIF_F_SG inheritable to tunnel devices.
	*/		*/
	dev->hw_enc_features \|= NETIF_F_SG;		dev->hw_enc_features \|= NETIF_F_SG \| NETIF_F_GSO_PARTIAL;

	/* Make NETIF_F_SG inheritable to MPLS.		/* Make NETIF_F_SG inheritable to MPLS.
	*/		*/

Original line number	Original line	Diff line number	Diff line
	@@ -39,6 +39,7 @@ enum {
	NETIF_F_UFO_BIT, /* ... UDPv4 fragmentation */		NETIF_F_UFO_BIT, /* ... UDPv4 fragmentation */
	NETIF_F_GSO_ROBUST_BIT, /* ... ->SKB_GSO_DODGY */		NETIF_F_GSO_ROBUST_BIT, /* ... ->SKB_GSO_DODGY */
	NETIF_F_TSO_ECN_BIT, /* ... TCP ECN support */		NETIF_F_TSO_ECN_BIT, /* ... TCP ECN support */
			NETIF_F_TSO_MANGLEID_BIT, /* ... IPV4 ID mangling allowed */
	NETIF_F_TSO6_BIT, /* ... TCPv6 segmentation */		NETIF_F_TSO6_BIT, /* ... TCPv6 segmentation */
	NETIF_F_FSO_BIT, /* ... FCoE segmentation */		NETIF_F_FSO_BIT, /* ... FCoE segmentation */
	NETIF_F_GSO_GRE_BIT, /* ... GRE with TSO */		NETIF_F_GSO_GRE_BIT, /* ... GRE with TSO */
	@@ -47,6 +48,10 @@ enum {
	NETIF_F_GSO_SIT_BIT, /* ... SIT tunnel with TSO */		NETIF_F_GSO_SIT_BIT, /* ... SIT tunnel with TSO */
	NETIF_F_GSO_UDP_TUNNEL_BIT, /* ... UDP TUNNEL with TSO */		NETIF_F_GSO_UDP_TUNNEL_BIT, /* ... UDP TUNNEL with TSO */
	NETIF_F_GSO_UDP_TUNNEL_CSUM_BIT,/* ... UDP TUNNEL with TSO & CSUM */		NETIF_F_GSO_UDP_TUNNEL_CSUM_BIT,/* ... UDP TUNNEL with TSO & CSUM */
			NETIF_F_GSO_PARTIAL_BIT, /* ... Only segment inner-most L4
			* in hardware and all other
			* headers in software.
			*/
	NETIF_F_GSO_TUNNEL_REMCSUM_BIT, /* ... TUNNEL with TSO & REMCSUM */		NETIF_F_GSO_TUNNEL_REMCSUM_BIT, /* ... TUNNEL with TSO & REMCSUM */
	/*/NETIF_F_GSO_LAST = / last bit, see GSO_MASK */		/*/NETIF_F_GSO_LAST = / last bit, see GSO_MASK */
	NETIF_F_GSO_TUNNEL_REMCSUM_BIT,		NETIF_F_GSO_TUNNEL_REMCSUM_BIT,
	@@ -120,6 +125,8 @@ enum {
	#define NETIF_F_GSO_SIT __NETIF_F(GSO_SIT)		#define NETIF_F_GSO_SIT __NETIF_F(GSO_SIT)
	#define NETIF_F_GSO_UDP_TUNNEL __NETIF_F(GSO_UDP_TUNNEL)		#define NETIF_F_GSO_UDP_TUNNEL __NETIF_F(GSO_UDP_TUNNEL)
	#define NETIF_F_GSO_UDP_TUNNEL_CSUM __NETIF_F(GSO_UDP_TUNNEL_CSUM)		#define NETIF_F_GSO_UDP_TUNNEL_CSUM __NETIF_F(GSO_UDP_TUNNEL_CSUM)
			#define NETIF_F_TSO_MANGLEID __NETIF_F(TSO_MANGLEID)
			#define NETIF_F_GSO_PARTIAL __NETIF_F(GSO_PARTIAL)
	#define NETIF_F_GSO_TUNNEL_REMCSUM __NETIF_F(GSO_TUNNEL_REMCSUM)		#define NETIF_F_GSO_TUNNEL_REMCSUM __NETIF_F(GSO_TUNNEL_REMCSUM)
	#define NETIF_F_HW_VLAN_STAG_FILTER __NETIF_F(HW_VLAN_STAG_FILTER)		#define NETIF_F_HW_VLAN_STAG_FILTER __NETIF_F(HW_VLAN_STAG_FILTER)
	#define NETIF_F_HW_VLAN_STAG_RX __NETIF_F(HW_VLAN_STAG_RX)		#define NETIF_F_HW_VLAN_STAG_RX __NETIF_F(HW_VLAN_STAG_RX)
	@@ -147,6 +154,7 @@ enum {

	/* List of features with software fallbacks. */		/* List of features with software fallbacks. */
	#define NETIF_F_GSO_SOFTWARE (NETIF_F_TSO \| NETIF_F_TSO_ECN \| \		#define NETIF_F_GSO_SOFTWARE (NETIF_F_TSO \| NETIF_F_TSO_ECN \| \
			NETIF_F_TSO_MANGLEID \| \
	NETIF_F_TSO6 \| NETIF_F_UFO)		NETIF_F_TSO6 \| NETIF_F_UFO)

	/* List of IP checksum features. Note that NETIF_F_ HW_CSUM should not be		/* List of IP checksum features. Note that NETIF_F_ HW_CSUM should not be