/*
   *  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>
  #include <net/checksum.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(const struct iphdr *iph, const struct tcphdr *tcph,
  			    int len, const 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) {
  		__be32 *topt = (__be32 *)(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;
  	__be32 *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 = (__be32 *)(tcph + 1);
  		*(p+2) = lro_desc->tcp_rcv_tsecr;
  	}
  
  	csum_replace2(&iph->check, iph->tot_len, htons(lro_desc->ip_tot_len));
  	iph->tot_len = htons(lro_desc->ip_tot_len);
  
  	tcph->check = 0;
  	tcp_hdr_csum = csum_partial(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(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)
  {
  	int nr_frags;
  	__be32 *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 = 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 = (__be32 *)(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->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;
  	__be32 *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 = (__be32 *) (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 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_mgr->features & LRO_F_NAPI)
  		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,
  			  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)) &&
  	    !(lro_mgr->features & LRO_F_EXTRACT_VLAN_ID))
  		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);
  		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:
  	return 1;
  }
  
  void lro_receive_skb(struct net_lro_mgr *lro_mgr,
  		     struct sk_buff *skb,
  		     void *priv)
  {
  	if (__lro_proc_skb(lro_mgr, skb, priv)) {
  		if (lro_mgr->features & LRO_F_NAPI)
  			netif_receive_skb(skb);
  		else
  			netif_rx(skb);
  	}
  }
  EXPORT_SYMBOL(lro_receive_skb);
  
  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);