[NET]: Add software TSOv4

This patch adds the GSO implementation for IPv4 TCP.

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

2 files changed, 113 insertions, 0 deletions

diff --git a/net/ipv4/af_inet.c b/net/ipv4/af_inet.c
index 0a277453526b..461216b47948 100644
--- a/net/ipv4/af_inet.c
+++ b/net/ipv4/af_inet.c
@@ -68,6 +68,7 @@
  */
 
 #include <linux/config.h>
+#include <linux/err.h>
 #include <linux/errno.h>
 #include <linux/types.h>
 #include <linux/socket.h>
@@ -1096,6 +1097,54 @@ int inet_sk_rebuild_header(struct sock *sk)
 
 EXPORT_SYMBOL(inet_sk_rebuild_header);
 
+static struct sk_buff *inet_gso_segment(struct sk_buff *skb, int sg)
+{
+        struct sk_buff *segs = ERR_PTR(-EINVAL);
+        struct iphdr *iph;
+        struct net_protocol *ops;
+        int proto;
+        int ihl;
+        int id;
+
+        if (!pskb_may_pull(skb, sizeof(*iph)))
+                goto out;
+
+        iph = skb->nh.iph;
+        ihl = iph->ihl * 4;
+        if (ihl < sizeof(*iph))
+                goto out;
+
+        if (!pskb_may_pull(skb, ihl))
+                goto out;
+
+        skb->h.raw = __skb_pull(skb, ihl);
+        iph = skb->nh.iph;
+        id = ntohs(iph->id);
+        proto = iph->protocol & (MAX_INET_PROTOS - 1);
+        segs = ERR_PTR(-EPROTONOSUPPORT);
+
+        rcu_read_lock();
+        ops = rcu_dereference(inet_protos[proto]);
+        if (ops && ops->gso_segment)
+                segs = ops->gso_segment(skb, sg);
+        rcu_read_unlock();
+
+        if (IS_ERR(segs))
+                goto out;
+
+        skb = segs;
+        do {
+                iph = skb->nh.iph;
+                iph->id = htons(id++);
+                iph->tot_len = htons(skb->len - skb->mac_len);
+                iph->check = 0;
+                iph->check = ip_fast_csum(skb->nh.raw, iph->ihl);
+        } while ((skb = skb->next));
+
+out:
+        return segs;
+}
+
 #ifdef CONFIG_IP_MULTICAST
 static struct net_protocol igmp_protocol = {
         .handler =      igmp_rcv,
@@ -1105,6 +1154,7 @@ static struct net_protocol igmp_protocol = {
 static struct net_protocol tcp_protocol = {
         .handler =      tcp_v4_rcv,
         .err_handler =  tcp_v4_err,
+        .gso_segment =  tcp_tso_segment,
         .no_policy =    1,
 };
 
@@ -1150,6 +1200,7 @@ static int ipv4_proc_init(void);
 static struct packet_type ip_packet_type = {
         .type = __constant_htons(ETH_P_IP),
         .func = ip_rcv,
+        .gso_segment = inet_gso_segment,
 };
 
 static int __init inet_init(void)
diff --git a/net/ipv4/tcp.c b/net/ipv4/tcp.c
index 062dd1a0d8a8..0e029c4e2903 100644
--- a/net/ipv4/tcp.c
+++ b/net/ipv4/tcp.c
@@ -258,6 +258,7 @@
 #include <linux/random.h>
 #include <linux/bootmem.h>
 #include <linux/cache.h>
+#include <linux/err.h>
 
 #include <net/icmp.h>
 #include <net/tcp.h>
@@ -2144,6 +2145,67 @@ int compat_tcp_getsockopt(struct sock *sk, int level, int optname,
 EXPORT_SYMBOL(compat_tcp_getsockopt);
 #endif
 
+struct sk_buff *tcp_tso_segment(struct sk_buff *skb, int sg)
+{
+        struct sk_buff *segs = ERR_PTR(-EINVAL);
+        struct tcphdr *th;
+        unsigned thlen;
+        unsigned int seq;
+        unsigned int delta;
+        unsigned int oldlen;
+        unsigned int len;
+
+        if (!pskb_may_pull(skb, sizeof(*th)))
+                goto out;
+
+        th = skb->h.th;
+        thlen = th->doff * 4;
+        if (thlen < sizeof(*th))
+                goto out;
+
+        if (!pskb_may_pull(skb, thlen))
+                goto out;
+
+        oldlen = ~htonl(skb->len);
+        __skb_pull(skb, thlen);
+
+        segs = skb_segment(skb, sg);
+        if (IS_ERR(segs))
+                goto out;
+
+        len = skb_shinfo(skb)->gso_size;
+        delta = csum_add(oldlen, htonl(thlen + len));
+
+        skb = segs;
+        th = skb->h.th;
+        seq = ntohl(th->seq);
+
+        do {
+                th->fin = th->psh = 0;
+
+                if (skb->ip_summed == CHECKSUM_NONE) {
+                        th->check = csum_fold(csum_partial(
+                                skb->h.raw, thlen, csum_add(skb->csum, delta)));
+                }
+
+                seq += len;
+                skb = skb->next;
+                th = skb->h.th;
+
+                th->seq = htonl(seq);
+                th->cwr = 0;
+        } while (skb->next);
+
+        if (skb->ip_summed == CHECKSUM_NONE) {
+                delta = csum_add(oldlen, htonl(skb->tail - skb->h.raw));
+                th->check = csum_fold(csum_partial(
+                        skb->h.raw, thlen, csum_add(skb->csum, delta)));
+        }
+
+out:
+        return segs;
+}
+
 extern void __skb_cb_too_small_for_tcp(int, int);
 extern struct tcp_congestion_ops tcp_reno;