[NET]: Merge TSO/UFO fields in sk_buff

Having separate fields in sk_buff for TSO/UFO (tso_size/ufo_size) is not
going to scale if we add any more segmentation methods (e.g., DCCP).  So
let's merge them.

They were used to tell the protocol of a packet.  This function has been
subsumed by the new gso_type field.  This is essentially a set of netdev
feature bits (shifted by 16 bits) that are required to process a specific
skb.  As such it's easy to tell whether a given device can process a GSO
skb: you just have to and the gso_type field and the netdev's features
field.

I've made gso_type a conjunction.  The idea is that you have a base type
(e.g., SKB_GSO_TCPV4) that can be modified further to support new features.
For example, if we add a hardware TSO type that supports ECN, they would
declare NETIF_F_TSO | NETIF_F_TSO_ECN.  All TSO packets with CWR set would
have a gso_type of SKB_GSO_TCPV4 | SKB_GSO_TCPV4_ECN while all other TSO
packets would be SKB_GSO_TCPV4.  This means that only the CWR packets need
to be emulated in software.

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

3 files changed, 23 insertions, 7 deletions

diff --git a/include/linux/netdevice.h b/include/linux/netdevice.h
index cead6be467ed..fa5671307b90 100644
--- a/include/linux/netdevice.h
+++ b/include/linux/netdevice.h
@@ -308,9 +308,12 @@ struct net_device
 #define NETIF_F_HW_VLAN_RX      256     /* Receive VLAN hw acceleration */
 #define NETIF_F_HW_VLAN_FILTER  512     /* Receive filtering on VLAN */
 #define NETIF_F_VLAN_CHALLENGED 1024    /* Device cannot handle VLAN packets */
-#define NETIF_F_TSO             2048    /* Can offload TCP/IP segmentation */
 #define NETIF_F_LLTX            4096    /* LockLess TX */
-#define NETIF_F_UFO             8192    /* Can offload UDP Large Send*/
+
+        /* Segmentation offload features */
+#define NETIF_F_GSO_SHIFT       16
+#define NETIF_F_TSO             (SKB_GSO_TCPV4 << NETIF_F_GSO_SHIFT)
+#define NETIF_F_UFO             (SKB_GSO_UDPV4 << NETIF_F_GSO_SHIFT)
 
 #define NETIF_F_GEN_CSUM        (NETIF_F_NO_CSUM | NETIF_F_HW_CSUM)
 #define NETIF_F_ALL_CSUM        (NETIF_F_IP_CSUM | NETIF_F_GEN_CSUM)
@@ -979,6 +982,13 @@ extern void dev_seq_stop(struct seq_file *seq, void *v);
 
 extern void linkwatch_run_queue(void);
 
+static inline int netif_needs_gso(struct net_device *dev, struct sk_buff *skb)
+{
+        int feature = skb_shinfo(skb)->gso_type << NETIF_F_GSO_SHIFT;
+        return skb_shinfo(skb)->gso_size &&
+               (dev->features & feature) != feature;
+}
+
 #endif /* __KERNEL__ */
 
 #endif  /* _LINUX_DEV_H */
diff --git a/include/linux/skbuff.h b/include/linux/skbuff.h
index f8c7eb79a27f..97b0d2d1a6b0 100644
--- a/include/linux/skbuff.h
+++ b/include/linux/skbuff.h
@@ -134,9 +134,10 @@ struct skb_frag_struct {
 struct skb_shared_info {
         atomic_t        dataref;
         unsigned short  nr_frags;
-        unsigned short  tso_size;
-        unsigned short  tso_segs;
-        unsigned short  ufo_size;
+        unsigned short  gso_size;
+        /* Warning: this field is not always filled in (UFO)! */
+        unsigned short  gso_segs;
+        unsigned short  gso_type;
         unsigned int    ip6_frag_id;
         struct sk_buff  *frag_list;
         skb_frag_t      frags[MAX_SKB_FRAGS];
@@ -168,6 +169,11 @@ enum {
         SKB_FCLONE_CLONE,
 };
 
+enum {
+        SKB_GSO_TCPV4 = 1 << 0,
+        SKB_GSO_UDPV4 = 1 << 1,
+};
+
 /** 
  *      struct sk_buff - socket buffer
  *      @next: Next buffer in list
diff --git a/include/net/tcp.h b/include/net/tcp.h
index 5f4eb5c79689..b197a9e615c1 100644
--- a/include/net/tcp.h
+++ b/include/net/tcp.h
@@ -569,13 +569,13 @@ struct tcp_skb_cb {
  */
 static inline int tcp_skb_pcount(const struct sk_buff *skb)
 {
-        return skb_shinfo(skb)->tso_segs;
+        return skb_shinfo(skb)->gso_segs;
 }
 
 /* This is valid iff tcp_skb_pcount() > 1. */
 static inline int tcp_skb_mss(const struct sk_buff *skb)
 {
-        return skb_shinfo(skb)->tso_size;
+        return skb_shinfo(skb)->gso_size;
 }
 
 static inline void tcp_dec_pcount_approx(__u32 *count,