[NET]: Generic Large Receive Offload for TCP traffic

This patch provides generic Large Receive Offload (LRO) functionality
for IPv4/TCP traffic.

LRO combines received tcp packets to a single larger tcp packet and
passes them then to the network stack in order to increase performance
(throughput). The interface supports two modes: Drivers can either
pass SKBs or fragment lists to the LRO engine.
Signed-off-by: Jan-Bernd Themann <themann@de.ibm.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

include/linux/inet_lro.h

+/*
+ *  linux/include/linux/inet_lro.h
+ *
+ *  Large Receive Offload (ipv4 / tcp)
+ *
+ *  (C) Copyright IBM Corp. 2007
+ *
+ *  Authors:
+ *       Jan-Bernd Themann <themann@de.ibm.com>
+ *       Christoph Raisch <raisch@de.ibm.com>
+ *
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2, or (at your option)
+ * any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
+ */
+
+#ifndef __INET_LRO_H_
+#define __INET_LRO_H_
+
+#include <net/ip.h>
+#include <net/tcp.h>
+
+/*
+ * LRO statistics
+ */
+
+struct net_lro_stats {
+	unsigned long aggregated;
+	unsigned long flushed;
+	unsigned long no_desc;
+};
+
+/*
+ * LRO descriptor for a tcp session
+ */
+struct net_lro_desc {
+	struct sk_buff *parent;
+	struct sk_buff *last_skb;
+	struct skb_frag_struct *next_frag;
+	struct iphdr *iph;
+	struct tcphdr *tcph;
+	struct vlan_group *vgrp;
+	__wsum  data_csum;
+	u32 tcp_rcv_tsecr;
+	u32 tcp_rcv_tsval;
+	u32 tcp_ack;
+	u32 tcp_next_seq;
+	u32 skb_tot_frags_len;
+	u16 ip_tot_len;
+	u16 tcp_saw_tstamp; 		/* timestamps enabled */
+	u16 tcp_window;
+	u16 vlan_tag;
+	int pkt_aggr_cnt;		/* counts aggregated packets */
+	int vlan_packet;
+	int mss;
+	int active;
+};
+
+/*
+ * Large Receive Offload (LRO) Manager
+ *
+ * Fields must be set by driver
+ */
+
+struct net_lro_mgr {
+	struct net_device *dev;
+	struct net_lro_stats stats;
+
+	/* LRO features */
+	unsigned long features;
+#define LRO_F_NAPI            1  /* Pass packets to stack via NAPI */
+#define LRO_F_EXTRACT_VLAN_ID 2  /* Set flag if VLAN IDs are extracted
+				    from received packets and eth protocol
+				    is still ETH_P_8021Q */
+
+	u32 ip_summed;      /* Set in non generated SKBs in page mode */
+	u32 ip_summed_aggr; /* Set in aggregated SKBs: CHECKSUM_UNNECESSARY
+			     * or CHECKSUM_NONE */
+
+	int max_desc; /* Max number of LRO descriptors  */
+	int max_aggr; /* Max number of LRO packets to be aggregated */
+
+	struct net_lro_desc *lro_arr; /* Array of LRO descriptors */
+
+	/*
+	 * Optimized driver functions
+	 *
+	 * get_skb_header: returns tcp and ip header for packet in SKB
+	 */
+	int (*get_skb_header)(struct sk_buff *skb, void **ip_hdr,
+			      void **tcpudp_hdr, u64 *hdr_flags, void *priv);
+
+	/* hdr_flags: */
+#define LRO_IPV4 1 /* ip_hdr is IPv4 header */
+#define LRO_TCP  2 /* tcpudp_hdr is TCP header */
+
+	/*
+	 * get_frag_header: returns mac, tcp and ip header for packet in SKB
+	 *
+	 * @hdr_flags: Indicate what kind of LRO has to be done
+	 *             (IPv4/IPv6/TCP/UDP)
+	 */
+	int (*get_frag_header)(struct skb_frag_struct *frag, void **mac_hdr,
+			       void **ip_hdr, void **tcpudp_hdr, u64 *hdr_flags,
+			       void *priv);
+};
+
+/*
+ * Processes a SKB
+ *
+ * @lro_mgr: LRO manager to use
+ * @skb: SKB to aggregate
+ * @priv: Private data that may be used by driver functions
+ *        (for example get_tcp_ip_hdr)
+ */
+
+void lro_receive_skb(struct net_lro_mgr *lro_mgr,
+		     struct sk_buff *skb,
+		     void *priv);
+
+/*
+ * Processes a SKB with VLAN HW acceleration support
+ */
+
+void lro_vlan_hwaccel_receive_skb(struct net_lro_mgr *lro_mgr,
+				  struct sk_buff *skb,
+				  struct vlan_group *vgrp,
+				  u16 vlan_tag,
+				  void *priv);
+
+/*
+ * Processes a fragment list
+ *
+ * This functions aggregate fragments and generate SKBs do pass
+ * the packets to the stack.
+ *
+ * @lro_mgr: LRO manager to use
+ * @frags: Fragment to be processed. Must contain entire header in first
+ *         element.
+ * @len: Length of received data
+ * @true_size: Actual size of memory the fragment is consuming
+ * @priv: Private data that may be used by driver functions
+ *        (for example get_tcp_ip_hdr)
+ */
+
+void lro_receive_frags(struct net_lro_mgr *lro_mgr,
+		       struct skb_frag_struct *frags,
+		       int len, int true_size, void *priv, __wsum sum);
+
+void lro_vlan_hwaccel_receive_frags(struct net_lro_mgr *lro_mgr,
+				    struct skb_frag_struct *frags,
+				    int len, int true_size,
+				    struct vlan_group *vgrp,
+				    u16 vlan_tag,
+				    void *priv, __wsum sum);
+
+/*
+ * Forward all aggregated SKBs held by lro_mgr to network stack
+ */
+
+void lro_flush_all(struct net_lro_mgr *lro_mgr);
+
+void lro_flush_pkt(struct net_lro_mgr *lro_mgr,
+		   struct iphdr *iph, struct tcphdr *tcph);
+
+#endif

net/ipv4/Kconfig

@@ -394,6 +394,14 @@ config INET_XFRM_MODE_BEET
 
 	  If unsure, say Y.
 
+config INET_LRO
+	tristate "Large Receive Offload (ipv4/tcp)"
+
+	---help---
+	  Support for Large Receive Offload (ipv4/tcp).
+
+	  If unsure, say Y.
+
 config INET_DIAG
 	tristate "INET: socket monitoring interface"
 	default y

net/ipv4/Makefile

@@ -25,6 +25,7 @@ obj-$(CONFIG_INET_ESP) += esp4.o
 obj-$(CONFIG_INET_IPCOMP) += ipcomp.o
 obj-$(CONFIG_INET_XFRM_TUNNEL) += xfrm4_tunnel.o
 obj-$(CONFIG_INET_XFRM_MODE_BEET) += xfrm4_mode_beet.o
+obj-$(CONFIG_INET_LRO) += inet_lro.o
 obj-$(CONFIG_INET_TUNNEL) += tunnel4.o
 obj-$(CONFIG_INET_XFRM_MODE_TRANSPORT) += xfrm4_mode_transport.o
 obj-$(CONFIG_INET_XFRM_MODE_TUNNEL) += xfrm4_mode_tunnel.o