tcp: Add GRO support

This patch adds the TCP-specific portion of GRO.  The criterion for
merging is extremely strict (the TCP header must match exactly apart
from the checksum) so as to allow refragmentation.  Otherwise this
is pretty much identical to LRO, except that we support the merging
of ECN packets.

Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
Signed-off-by: David S. Miller <davem@davemloft.net>

3 files changed, 137 insertions, 0 deletions

diff --git a/net/ipv4/af_inet.c b/net/ipv4/af_inet.c
index a85595307fa..664ff0ee1c8 100644
--- a/net/ipv4/af_inet.c
+++ b/net/ipv4/af_inet.c
@@ -1410,6 +1410,8 @@ static struct net_protocol tcp_protocol = {
 	.err_handler =	tcp_v4_err,
 	.gso_send_check = tcp_v4_gso_send_check,
 	.gso_segment =	tcp_tso_segment,
+	.gro_receive =	tcp4_gro_receive,
+	.gro_complete =	tcp4_gro_complete,
 	.no_policy =	1,
 	.netns_ok =	1,
 };
diff --git a/net/ipv4/tcp.c b/net/ipv4/tcp.c
index 01924340862..1f3d52946b3 100644
--- a/net/ipv4/tcp.c
+++ b/net/ipv4/tcp.c
@@ -2465,6 +2465,106 @@ out:
 }
 EXPORT_SYMBOL(tcp_tso_segment);
 
+struct sk_buff **tcp_gro_receive(struct sk_buff **head, struct sk_buff *skb)
+{
+	struct sk_buff **pp = NULL;
+	struct sk_buff *p;
+	struct tcphdr *th;
+	struct tcphdr *th2;
+	unsigned int thlen;
+	unsigned int flags;
+	unsigned int total;
+	unsigned int mss = 1;
+	int flush = 1;
+
+	if (!pskb_may_pull(skb, sizeof(*th)))
+		goto out;
+
+	th = tcp_hdr(skb);
+	thlen = th->doff * 4;
+	if (thlen < sizeof(*th))
+		goto out;
+
+	if (!pskb_may_pull(skb, thlen))
+		goto out;
+
+	th = tcp_hdr(skb);
+	__skb_pull(skb, thlen);
+
+	flags = tcp_flag_word(th);
+
+	for (; (p = *head); head = &p->next) {
+		if (!NAPI_GRO_CB(p)->same_flow)
+			continue;
+
+		th2 = tcp_hdr(p);
+
+		if (th->source != th2->source || th->dest != th2->dest) {
+			NAPI_GRO_CB(p)->same_flow = 0;
+			continue;
+		}
+
+		goto found;
+	}
+
+	goto out_check_final;
+
+found:
+	flush = NAPI_GRO_CB(p)->flush;
+	flush |= flags & TCP_FLAG_CWR;
+	flush |= (flags ^ tcp_flag_word(th2)) &
+		  ~(TCP_FLAG_CWR | TCP_FLAG_FIN | TCP_FLAG_PSH);
+	flush |= th->ack_seq != th2->ack_seq || th->window != th2->window;
+	flush |= memcmp(th + 1, th2 + 1, thlen - sizeof(*th));
+
+	total = p->len;
+	mss = total;
+	if (skb_shinfo(p)->frag_list)
+		mss = skb_shinfo(p)->frag_list->len;
+
+	flush |= skb->len > mss || skb->len <= 0;
+	flush |= ntohl(th2->seq) + total != ntohl(th->seq);
+
+	if (flush || skb_gro_receive(head, skb)) {
+		mss = 1;
+		goto out_check_final;
+	}
+
+	p = *head;
+	th2 = tcp_hdr(p);
+	tcp_flag_word(th2) |= flags & (TCP_FLAG_FIN | TCP_FLAG_PSH);
+
+out_check_final:
+	flush = skb->len < mss;
+	flush |= flags & (TCP_FLAG_URG | TCP_FLAG_PSH | TCP_FLAG_RST |
+			  TCP_FLAG_SYN | TCP_FLAG_FIN);
+
+	if (p && (!NAPI_GRO_CB(skb)->same_flow || flush))
+		pp = head;
+
+out:
+	NAPI_GRO_CB(skb)->flush |= flush;
+
+	return pp;
+}
+
+int tcp_gro_complete(struct sk_buff *skb)
+{
+	struct tcphdr *th = tcp_hdr(skb);
+
+	skb->csum_start = skb_transport_header(skb) - skb->head;
+	skb->csum_offset = offsetof(struct tcphdr, check);
+	skb->ip_summed = CHECKSUM_PARTIAL;
+
+	skb_shinfo(skb)->gso_size = skb_shinfo(skb)->frag_list->len;
+	skb_shinfo(skb)->gso_segs = NAPI_GRO_CB(skb)->count;
+
+	if (th->cwr)
+		skb_shinfo(skb)->gso_type |= SKB_GSO_TCP_ECN;
+
+	return 0;
+}
+
 #ifdef CONFIG_TCP_MD5SIG
 static unsigned long tcp_md5sig_users;
 static struct tcp_md5sig_pool **tcp_md5sig_pool;
diff --git a/net/ipv4/tcp_ipv4.c b/net/ipv4/tcp_ipv4.c
index 26b9030747c..10172487921 100644
--- a/net/ipv4/tcp_ipv4.c
+++ b/net/ipv4/tcp_ipv4.c
@@ -2346,6 +2346,41 @@ void tcp4_proc_exit(void)
 }
 #endif /* CONFIG_PROC_FS */
 
+struct sk_buff **tcp4_gro_receive(struct sk_buff **head, struct sk_buff *skb)
+{
+	struct iphdr *iph = ip_hdr(skb);
+
+	switch (skb->ip_summed) {
+	case CHECKSUM_COMPLETE:
+		if (!tcp_v4_check(skb->len, iph->saddr, iph->daddr,
+				  skb->csum)) {
+			skb->ip_summed = CHECKSUM_UNNECESSARY;
+			break;
+		}
+
+		/* fall through */
+	case CHECKSUM_NONE:
+		NAPI_GRO_CB(skb)->flush = 1;
+		return NULL;
+	}
+
+	return tcp_gro_receive(head, skb);
+}
+EXPORT_SYMBOL(tcp4_gro_receive);
+
+int tcp4_gro_complete(struct sk_buff *skb)
+{
+	struct iphdr *iph = ip_hdr(skb);
+	struct tcphdr *th = tcp_hdr(skb);
+
+	th->check = ~tcp_v4_check(skb->len - skb_transport_offset(skb),
+				  iph->saddr, iph->daddr, 0);
+	skb_shinfo(skb)->gso_type = SKB_GSO_TCPV4;
+
+	return tcp_gro_complete(skb);
+}
+EXPORT_SYMBOL(tcp4_gro_complete);
+
 struct proto tcp_prot = {
 	.name			= "TCP",
 	.owner			= THIS_MODULE,