[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>

1 files changed, 600 insertions, 0 deletions

diff --git a/net/ipv4/inet_lro.c b/net/ipv4/inet_lro.c
new file mode 100644
index 0000000..20bc593
--- /dev/null
+++ b/net/ipv4/inet_lro.c
@@ -0,0 +1,600 @@
+/*
+ *  linux/net/ipv4/inet_lro.c
+ *
+ *  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.
+ */
+
+
+#include <linux/module.h>
+#include <linux/if_vlan.h>
+#include <linux/inet_lro.h>
+
+MODULE_LICENSE("GPL");
+MODULE_AUTHOR("Jan-Bernd Themann <themann@de.ibm.com>");
+MODULE_DESCRIPTION("Large Receive Offload (ipv4 / tcp)");
+
+#define TCP_HDR_LEN(tcph) (tcph->doff << 2)
+#define IP_HDR_LEN(iph) (iph->ihl << 2)
+#define TCP_PAYLOAD_LENGTH(iph, tcph) \
+	(ntohs(iph->tot_len) - IP_HDR_LEN(iph) - TCP_HDR_LEN(tcph))
+
+#define IPH_LEN_WO_OPTIONS 5
+#define TCPH_LEN_WO_OPTIONS 5
+#define TCPH_LEN_W_TIMESTAMP 8
+
+#define LRO_MAX_PG_HLEN 64
+
+#define LRO_INC_STATS(lro_mgr, attr) { lro_mgr->stats.attr++; }
+
+/*
+ * Basic tcp checks whether packet is suitable for LRO
+ */
+
+static int lro_tcp_ip_check(struct iphdr *iph, struct tcphdr *tcph,
+			    int len, struct net_lro_desc *lro_desc)
+{
+        /* check ip header: don't aggregate padded frames */
+	if (ntohs(iph->tot_len) != len)
+		return -1;
+
+	if (TCP_PAYLOAD_LENGTH(iph, tcph) == 0)
+		return -1;
+
+	if (iph->ihl != IPH_LEN_WO_OPTIONS)
+		return -1;
+
+	if (tcph->cwr || tcph->ece || tcph->urg || !tcph->ack
+	    || tcph->rst || tcph->syn || tcph->fin)
+		return -1;
+
+	if (INET_ECN_is_ce(ipv4_get_dsfield(iph)))
+		return -1;
+
+	if (tcph->doff != TCPH_LEN_WO_OPTIONS
+	    && tcph->doff != TCPH_LEN_W_TIMESTAMP)
+		return -1;
+
+	/* check tcp options (only timestamp allowed) */
+	if (tcph->doff == TCPH_LEN_W_TIMESTAMP) {
+		u32 *topt = (u32 *)(tcph + 1);
+
+		if (*topt != htonl((TCPOPT_NOP << 24) | (TCPOPT_NOP << 16)
+				   | (TCPOPT_TIMESTAMP << 8)
+				   | TCPOLEN_TIMESTAMP))
+			return -1;
+
+		/* timestamp should be in right order */
+		topt++;
+		if (lro_desc && after(ntohl(lro_desc->tcp_rcv_tsval),
+				      ntohl(*topt)))
+			return -1;
+
+		/* timestamp reply should not be zero */
+		topt++;
+		if (*topt == 0)
+			return -1;
+	}
+
+	return 0;
+}
+
+static void lro_update_tcp_ip_header(struct net_lro_desc *lro_desc)
+{
+	struct iphdr *iph = lro_desc->iph;
+	struct tcphdr *tcph = lro_desc->tcph;
+	u32 *p;
+	__wsum tcp_hdr_csum;
+
+	tcph->ack_seq = lro_desc->tcp_ack;
+	tcph->window = lro_desc->tcp_window;
+
+	if (lro_desc->tcp_saw_tstamp) {
+		p = (u32 *)(tcph + 1);
+		*(p+2) = lro_desc->tcp_rcv_tsecr;
+	}
+
+	iph->tot_len = htons(lro_desc->ip_tot_len);
+
+	iph->check = 0;
+	iph->check = ip_fast_csum((u8 *)lro_desc->iph, iph->ihl);
+
+	tcph->check = 0;
+	tcp_hdr_csum = csum_partial((u8 *)tcph, TCP_HDR_LEN(tcph), 0);
+	lro_desc->data_csum = csum_add(lro_desc->data_csum, tcp_hdr_csum);
+	tcph->check = csum_tcpudp_magic(iph->saddr, iph->daddr,
+					lro_desc->ip_tot_len -
+					IP_HDR_LEN(iph), IPPROTO_TCP,
+					lro_desc->data_csum);
+}
+
+static __wsum lro_tcp_data_csum(struct iphdr *iph, struct tcphdr *tcph, int len)
+{
+	__wsum tcp_csum;
+	__wsum tcp_hdr_csum;
+	__wsum tcp_ps_hdr_csum;
+
+	tcp_csum = ~csum_unfold(tcph->check);
+	tcp_hdr_csum = csum_partial((u8 *)tcph, TCP_HDR_LEN(tcph), tcp_csum);
+
+	tcp_ps_hdr_csum = csum_tcpudp_nofold(iph->saddr, iph->daddr,
+					     len + TCP_HDR_LEN(tcph),
+					     IPPROTO_TCP, 0);
+
+	return csum_sub(csum_sub(tcp_csum, tcp_hdr_csum),
+			tcp_ps_hdr_csum);
+}
+
+static void lro_init_desc(struct net_lro_desc *lro_desc, struct sk_buff *skb,
+			  struct iphdr *iph, struct tcphdr *tcph,
+			  u16 vlan_tag, struct vlan_group *vgrp)
+{
+	int nr_frags;
+	u32 *ptr;
+	u32 tcp_data_len = TCP_PAYLOAD_LENGTH(iph, tcph);
+
+	nr_frags = skb_shinfo(skb)->nr_frags;
+	lro_desc->parent = skb;
+	lro_desc->next_frag = &(skb_shinfo(skb)->frags[nr_frags]);
+	lro_desc->iph = iph;
+	lro_desc->tcph = tcph;
+	lro_desc->tcp_next_seq = ntohl(tcph->seq) + tcp_data_len;
+	lro_desc->tcp_ack = ntohl(tcph->ack_seq);
+	lro_desc->tcp_window = tcph->window;
+
+	lro_desc->pkt_aggr_cnt = 1;
+	lro_desc->ip_tot_len = ntohs(iph->tot_len);
+
+	if (tcph->doff == 8) {
+		ptr = (u32 *)(tcph+1);
+		lro_desc->tcp_saw_tstamp = 1;
+		lro_desc->tcp_rcv_tsval = *(ptr+1);
+		lro_desc->tcp_rcv_tsecr = *(ptr+2);
+	}
+
+	lro_desc->mss = tcp_data_len;
+	lro_desc->vgrp = vgrp;
+	lro_desc->vlan_tag = vlan_tag;
+	lro_desc->active = 1;
+
+	lro_desc->data_csum = lro_tcp_data_csum(iph, tcph,
+						tcp_data_len);
+}
+
+static inline void lro_clear_desc(struct net_lro_desc *lro_desc)
+{
+	memset(lro_desc, 0, sizeof(struct net_lro_desc));
+}
+
+static void lro_add_common(struct net_lro_desc *lro_desc, struct iphdr *iph,
+			   struct tcphdr *tcph, int tcp_data_len)
+{
+	struct sk_buff *parent = lro_desc->parent;
+	u32 *topt;
+
+	lro_desc->pkt_aggr_cnt++;
+	lro_desc->ip_tot_len += tcp_data_len;
+	lro_desc->tcp_next_seq += tcp_data_len;
+	lro_desc->tcp_window = tcph->window;
+	lro_desc->tcp_ack = tcph->ack_seq;
+
+	/* don't update tcp_rcv_tsval, would not work with PAWS */
+	if (lro_desc->tcp_saw_tstamp) {
+		topt = (u32 *) (tcph + 1);
+		lro_desc->tcp_rcv_tsecr = *(topt + 2);
+	}
+
+	lro_desc->data_csum = csum_block_add(lro_desc->data_csum,
+					     lro_tcp_data_csum(iph, tcph,
+							       tcp_data_len),
+					     parent->len);
+
+	parent->len += tcp_data_len;
+	parent->data_len += tcp_data_len;
+	if (tcp_data_len > lro_desc->mss)
+		lro_desc->mss = tcp_data_len;
+}
+
+static void lro_add_packet(struct net_lro_desc *lro_desc, struct sk_buff *skb,
+			   struct iphdr *iph, struct tcphdr *tcph)
+{
+	struct sk_buff *parent = lro_desc->parent;
+	int tcp_data_len = TCP_PAYLOAD_LENGTH(iph, tcph);
+
+	lro_add_common(lro_desc, iph, tcph, tcp_data_len);
+
+	skb_pull(skb, (skb->len - tcp_data_len));
+	parent->truesize += skb->truesize;
+
+	if (lro_desc->last_skb)
+		lro_desc->last_skb->next = skb;
+	else
+		skb_shinfo(parent)->frag_list = skb;
+
+	lro_desc->last_skb = skb;
+}
+
+static void lro_add_frags(struct net_lro_desc *lro_desc,
+			  int len, int hlen, int truesize,
+			  struct skb_frag_struct *skb_frags,
+			  struct iphdr *iph, struct tcphdr *tcph)
+{
+	struct sk_buff *skb = lro_desc->parent;
+	int tcp_data_len = TCP_PAYLOAD_LENGTH(iph, tcph);
+
+	lro_add_common(lro_desc, iph, tcph, tcp_data_len);
+
+	skb->truesize += truesize;
+
+	skb_frags[0].page_offset += hlen;
+	skb_frags[0].size -= hlen;
+
+	while (tcp_data_len > 0) {
+		*(lro_desc->next_frag) = *skb_frags;
+		tcp_data_len -= skb_frags->size;
+		lro_desc->next_frag++;
+		skb_frags++;
+		skb_shinfo(skb)->nr_frags++;
+	}
+}
+
+static int lro_check_tcp_conn(struct net_lro_desc *lro_desc,
+			      struct iphdr *iph,
+			      struct tcphdr *tcph)
+{
+	if ((lro_desc->iph->saddr != iph->saddr)
+	    || (lro_desc->iph->daddr != iph->daddr)
+	    || (lro_desc->tcph->source != tcph->source)
+	    || (lro_desc->tcph->dest != tcph->dest))
+		return -1;
+	return 0;
+}
+
+static struct net_lro_desc *lro_get_desc(struct net_lro_mgr *lro_mgr,
+					 struct net_lro_desc *lro_arr,
+					 struct iphdr *iph,
+					 struct tcphdr *tcph)
+{
+	struct net_lro_desc *lro_desc = NULL;
+	struct net_lro_desc *tmp;
+	int max_desc = lro_mgr->max_desc;
+	int i;
+
+	for (i = 0; i < max_desc; i++) {
+		tmp = &lro_arr[i];
+		if (tmp->active)
+			if (!lro_check_tcp_conn(tmp, iph, tcph)) {
+				lro_desc = tmp;
+				goto out;
+			}
+	}
+
+	for (i = 0; i < max_desc; i++) {
+		if (!lro_arr[i].active) {
+			lro_desc = &lro_arr[i];
+			goto out;
+		}
+	}
+
+	LRO_INC_STATS(lro_mgr, no_desc);
+out:
+	return lro_desc;
+}
+
+static void lro_flush(struct net_lro_mgr *lro_mgr,
+		      struct net_lro_desc *lro_desc)
+{
+	if (lro_desc->pkt_aggr_cnt > 1)
+		lro_update_tcp_ip_header(lro_desc);
+
+	skb_shinfo(lro_desc->parent)->gso_size = lro_desc->mss;
+
+	if (lro_desc->vgrp) {
+		if (test_bit(LRO_F_NAPI, &lro_mgr->features))
+			vlan_hwaccel_receive_skb(lro_desc->parent,
+						 lro_desc->vgrp,
+						 lro_desc->vlan_tag);
+		else
+			vlan_hwaccel_rx(lro_desc->parent,
+					lro_desc->vgrp,
+					lro_desc->vlan_tag);
+
+	} else {
+		if (test_bit(LRO_F_NAPI, &lro_mgr->features))
+			netif_receive_skb(lro_desc->parent);
+		else
+			netif_rx(lro_desc->parent);
+	}
+
+	LRO_INC_STATS(lro_mgr, flushed);
+	lro_clear_desc(lro_desc);
+}
+
+static int __lro_proc_skb(struct net_lro_mgr *lro_mgr, struct sk_buff *skb,
+			  struct vlan_group *vgrp, u16 vlan_tag, void *priv)
+{
+	struct net_lro_desc *lro_desc;
+	struct iphdr *iph;
+	struct tcphdr *tcph;
+	u64 flags;
+	int vlan_hdr_len = 0;
+
+	if (!lro_mgr->get_skb_header
+	    || lro_mgr->get_skb_header(skb, (void *)&iph, (void *)&tcph,
+				       &flags, priv))
+		goto out;
+
+	if (!(flags & LRO_IPV4) || !(flags & LRO_TCP))
+		goto out;
+
+	lro_desc = lro_get_desc(lro_mgr, lro_mgr->lro_arr, iph, tcph);
+	if (!lro_desc)
+		goto out;
+
+	if ((skb->protocol == htons(ETH_P_8021Q))
+	    && !test_bit(LRO_F_EXTRACT_VLAN_ID, &lro_mgr->features))
+		vlan_hdr_len = VLAN_HLEN;
+
+	if (!lro_desc->active) { /* start new lro session */
+		if (lro_tcp_ip_check(iph, tcph, skb->len - vlan_hdr_len, NULL))
+			goto out;
+
+		skb->ip_summed = lro_mgr->ip_summed_aggr;
+		lro_init_desc(lro_desc, skb, iph, tcph, vlan_tag, vgrp);
+		LRO_INC_STATS(lro_mgr, aggregated);
+		return 0;
+	}
+
+	if (lro_desc->tcp_next_seq != ntohl(tcph->seq))
+		goto out2;
+
+	if (lro_tcp_ip_check(iph, tcph, skb->len, lro_desc))
+		goto out2;
+
+	lro_add_packet(lro_desc, skb, iph, tcph);
+	LRO_INC_STATS(lro_mgr, aggregated);
+
+	if ((lro_desc->pkt_aggr_cnt >= lro_mgr->max_aggr) ||
+	    lro_desc->parent->len > (0xFFFF - lro_mgr->dev->mtu))
+		lro_flush(lro_mgr, lro_desc);
+
+	return 0;
+
+out2: /* send aggregated SKBs to stack */
+	lro_flush(lro_mgr, lro_desc);
+
+out:  /* Original SKB has to be posted to stack */
+	skb->ip_summed = lro_mgr->ip_summed;
+	return 1;
+}
+
+
+static struct sk_buff *lro_gen_skb(struct net_lro_mgr *lro_mgr,
+				   struct skb_frag_struct *frags,
+				   int len, int true_size,
+				   void *mac_hdr,
+				   int hlen, __wsum sum,
+				   u32 ip_summed)
+{
+	struct sk_buff *skb;
+	struct skb_frag_struct *skb_frags;
+	int data_len = len;
+	int hdr_len = min(len, hlen);
+
+	skb = netdev_alloc_skb(lro_mgr->dev, hlen);
+	if (!skb)
+		return NULL;
+
+	skb->len = len;
+	skb->data_len = len - hdr_len;
+	skb->truesize += true_size;
+	skb->tail += hdr_len;
+
+	memcpy(skb->data, mac_hdr, hdr_len);
+
+	skb_frags = skb_shinfo(skb)->frags;
+	while (data_len > 0) {
+		*skb_frags = *frags;
+		data_len -= frags->size;
+		skb_frags++;
+		frags++;
+		skb_shinfo(skb)->nr_frags++;
+	}
+
+	skb_shinfo(skb)->frags[0].page_offset += hdr_len;
+	skb_shinfo(skb)->frags[0].size -= hdr_len;
+
+	skb->ip_summed = ip_summed;
+	skb->csum = sum;
+	skb->protocol = eth_type_trans(skb, lro_mgr->dev);
+	return skb;
+}
+
+static struct sk_buff *__lro_proc_segment(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)
+{
+	struct net_lro_desc *lro_desc;
+	struct iphdr *iph;
+	struct tcphdr *tcph;
+	struct sk_buff *skb;
+	u64 flags;
+	void *mac_hdr;
+	int mac_hdr_len;
+	int hdr_len = LRO_MAX_PG_HLEN;
+	int vlan_hdr_len = 0;
+
+	if (!lro_mgr->get_frag_header
+	    || lro_mgr->get_frag_header(frags, (void *)&mac_hdr, (void *)&iph,
+					(void *)&tcph, &flags, priv)) {
+		mac_hdr = page_address(frags->page) + frags->page_offset;
+		goto out1;
+	}
+
+	if (!(flags & LRO_IPV4) || !(flags & LRO_TCP))
+		goto out1;
+
+	hdr_len = (int)((void *)(tcph) + TCP_HDR_LEN(tcph) - mac_hdr);
+	mac_hdr_len = (int)((void *)(iph) - mac_hdr);
+
+	lro_desc = lro_get_desc(lro_mgr, lro_mgr->lro_arr, iph, tcph);
+	if (!lro_desc)
+		goto out1;
+
+	if (!lro_desc->active) { /* start new lro session */
+		if (lro_tcp_ip_check(iph, tcph, len - mac_hdr_len, NULL))
+			goto out1;
+
+		skb = lro_gen_skb(lro_mgr, frags, len, true_size, mac_hdr,
+				  hdr_len, 0, lro_mgr->ip_summed_aggr);
+		if (!skb)
+			goto out;
+
+		if ((skb->protocol == htons(ETH_P_8021Q))
+		    && !test_bit(LRO_F_EXTRACT_VLAN_ID, &lro_mgr->features))
+			vlan_hdr_len = VLAN_HLEN;
+
+		iph = (void *)(skb->data + vlan_hdr_len);
+		tcph = (void *)((u8 *)skb->data + vlan_hdr_len
+				+ IP_HDR_LEN(iph));
+
+		lro_init_desc(lro_desc, skb, iph, tcph, 0, NULL);
+		LRO_INC_STATS(lro_mgr, aggregated);
+		return 0;
+	}
+
+	if (lro_desc->tcp_next_seq != ntohl(tcph->seq))
+		goto out2;
+
+	if (lro_tcp_ip_check(iph, tcph, len - mac_hdr_len, lro_desc))
+		goto out2;
+
+	lro_add_frags(lro_desc, len, hdr_len, true_size, frags, iph, tcph);
+	LRO_INC_STATS(lro_mgr, aggregated);
+
+	if ((skb_shinfo(lro_desc->parent)->nr_frags >= lro_mgr->max_aggr) ||
+	    lro_desc->parent->len > (0xFFFF - lro_mgr->dev->mtu))
+		lro_flush(lro_mgr, lro_desc);
+
+	return NULL;
+
+out2: /* send aggregated packets to the stack */
+	lro_flush(lro_mgr, lro_desc);
+
+out1:  /* Original packet has to be posted to the stack */
+	skb = lro_gen_skb(lro_mgr, frags, len, true_size, mac_hdr,
+			  hdr_len, sum, lro_mgr->ip_summed);
+out:
+	return skb;
+}
+
+void lro_receive_skb(struct net_lro_mgr *lro_mgr,
+		     struct sk_buff *skb,
+		     void *priv)
+{
+	if (__lro_proc_skb(lro_mgr, skb, NULL, 0, priv)) {
+		if (test_bit(LRO_F_NAPI, &lro_mgr->features))
+			netif_receive_skb(skb);
+		else
+			netif_rx(skb);
+	}
+}
+EXPORT_SYMBOL(lro_receive_skb);
+
+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)
+{
+	if (__lro_proc_skb(lro_mgr, skb, vgrp, vlan_tag, priv)) {
+		if (test_bit(LRO_F_NAPI, &lro_mgr->features))
+			vlan_hwaccel_receive_skb(skb, vgrp, vlan_tag);
+		else
+			vlan_hwaccel_rx(skb, vgrp, vlan_tag);
+	}
+}
+EXPORT_SYMBOL(lro_vlan_hwaccel_receive_skb);
+
+void lro_receive_frags(struct net_lro_mgr *lro_mgr,
+		       struct skb_frag_struct *frags,
+		       int len, int true_size, void *priv, __wsum sum)
+{
+	struct sk_buff *skb;
+
+	skb = __lro_proc_segment(lro_mgr, frags, len, true_size, NULL, 0,
+				 priv, sum);
+	if (!skb)
+		return;
+
+	if (test_bit(LRO_F_NAPI, &lro_mgr->features))
+		netif_receive_skb(skb);
+	else
+		netif_rx(skb);
+}
+EXPORT_SYMBOL(lro_receive_frags);
+
+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)
+{
+	struct sk_buff *skb;
+
+	skb = __lro_proc_segment(lro_mgr, frags, len, true_size, vgrp,
+				 vlan_tag, priv, sum);
+	if (!skb)
+		return;
+
+	if (test_bit(LRO_F_NAPI, &lro_mgr->features))
+		vlan_hwaccel_receive_skb(skb, vgrp, vlan_tag);
+	else
+		vlan_hwaccel_rx(skb, vgrp, vlan_tag);
+}
+EXPORT_SYMBOL(lro_vlan_hwaccel_receive_frags);
+
+void lro_flush_all(struct net_lro_mgr *lro_mgr)
+{
+	int i;
+	struct net_lro_desc *lro_desc = lro_mgr->lro_arr;
+
+	for (i = 0; i < lro_mgr->max_desc; i++) {
+		if (lro_desc[i].active)
+			lro_flush(lro_mgr, &lro_desc[i]);
+	}
+}
+EXPORT_SYMBOL(lro_flush_all);
+
+void lro_flush_pkt(struct net_lro_mgr *lro_mgr,
+		  struct iphdr *iph, struct tcphdr *tcph)
+{
+	struct net_lro_desc *lro_desc;
+
+	lro_desc = lro_get_desc(lro_mgr, lro_mgr->lro_arr, iph, tcph);
+	if (lro_desc->active)
+		lro_flush(lro_mgr, lro_desc);
+}
+EXPORT_SYMBOL(lro_flush_pkt);