[SK_BUFF]: Convert skb->tail to sk_buff_data_t
So that it is also an offset from skb->head, reduces its size from 8 to 4 bytes
on 64bit architectures, allowing us to combine the 4 bytes hole left by the
layer headers conversion, reducing struct sk_buff size to 256 bytes, i.e. 4
64byte cachelines, and since the sk_buff slab cache is SLAB_HWCACHE_ALIGN...
:-)
Many calculations that previously required that skb->{transport,network,
mac}_header be first converted to a pointer now can be done directly, being
meaningful as offsets or pointers.
Signed-off-by: Arnaldo Carvalho de Melo <[email protected]>
Signed-off-by: David S. Miller <[email protected]>
diff --git a/include/linux/netfilter/nfnetlink.h b/include/linux/netfilter/nfnetlink.h
index 6179648..e1ea5df 100644
--- a/include/linux/netfilter/nfnetlink.h
+++ b/include/linux/netfilter/nfnetlink.h
@@ -62,11 +62,11 @@
#define NFA_DATA(nfa) ((void *)(((char *)(nfa)) + NFA_LENGTH(0)))
#define NFA_PAYLOAD(nfa) ((int)((nfa)->nfa_len) - NFA_LENGTH(0))
#define NFA_NEST(skb, type) \
-({ struct nfattr *__start = (struct nfattr *) (skb)->tail; \
+({ struct nfattr *__start = (struct nfattr *)skb_tail_pointer(skb); \
NFA_PUT(skb, (NFNL_NFA_NEST | type), 0, NULL); \
__start; })
#define NFA_NEST_END(skb, start) \
-({ (start)->nfa_len = ((skb)->tail - (unsigned char *) (start)); \
+({ (start)->nfa_len = skb_tail_pointer(skb) - (unsigned char *)(start); \
(skb)->len; })
#define NFA_NEST_CANCEL(skb, start) \
({ if (start) \
diff --git a/include/linux/netlink.h b/include/linux/netlink.h
index a9d3ad5..68a632b 100644
--- a/include/linux/netlink.h
+++ b/include/linux/netlink.h
@@ -229,7 +229,7 @@
(cb)->nlh->nlmsg_seq, type, len, flags)
#define NLMSG_END(skb, nlh) \
-({ (nlh)->nlmsg_len = (skb)->tail - (unsigned char *) (nlh); \
+({ (nlh)->nlmsg_len = skb_tail_pointer(skb) - (unsigned char *)(nlh); \
(skb)->len; })
#define NLMSG_CANCEL(skb, nlh) \
diff --git a/include/linux/rtnetlink.h b/include/linux/rtnetlink.h
index 4a629ea..3a4cb24 100644
--- a/include/linux/rtnetlink.h
+++ b/include/linux/rtnetlink.h
@@ -605,7 +605,7 @@
#define RTA_PUT_NOHDR(skb, attrlen, data) \
({ RTA_APPEND(skb, RTA_ALIGN(attrlen), data); \
- memset(skb->tail - (RTA_ALIGN(attrlen) - attrlen), 0, \
+ memset(skb_tail_pointer(skb) - (RTA_ALIGN(attrlen) - attrlen), 0, \
RTA_ALIGN(attrlen) - attrlen); })
#define RTA_PUT_U8(skb, attrtype, value) \
@@ -637,12 +637,12 @@
RTA_PUT(skb, attrtype, 0, NULL);
#define RTA_NEST(skb, type) \
-({ struct rtattr *__start = (struct rtattr *) (skb)->tail; \
+({ struct rtattr *__start = (struct rtattr *)skb_tail_pointer(skb); \
RTA_PUT(skb, type, 0, NULL); \
__start; })
#define RTA_NEST_END(skb, start) \
-({ (start)->rta_len = ((skb)->tail - (unsigned char *) (start)); \
+({ (start)->rta_len = skb_tail_pointer(skb) - (unsigned char *)(start); \
(skb)->len; })
#define RTA_NEST_CANCEL(skb, start) \
diff --git a/include/linux/skbuff.h b/include/linux/skbuff.h
index 2e74055..e1c2392 100644
--- a/include/linux/skbuff.h
+++ b/include/linux/skbuff.h
@@ -246,9 +246,6 @@
int iif;
/* 4 byte hole on 64 bit*/
- sk_buff_data_t transport_header;
- sk_buff_data_t network_header;
- sk_buff_data_t mac_header;
struct dst_entry *dst;
struct sec_path *sp;
@@ -303,13 +300,16 @@
__u32 mark;
+ sk_buff_data_t transport_header;
+ sk_buff_data_t network_header;
+ sk_buff_data_t mac_header;
/* These elements must be at the end, see alloc_skb() for details. */
- unsigned int truesize;
- atomic_t users;
+ sk_buff_data_t tail;
unsigned char *head,
*data,
- *tail,
*end;
+ unsigned int truesize;
+ atomic_t users;
};
#ifdef __KERNEL__
@@ -812,12 +812,45 @@
#define SKB_FRAG_ASSERT(skb) BUG_ON(skb_shinfo(skb)->frag_list)
#define SKB_LINEAR_ASSERT(skb) BUG_ON(skb_is_nonlinear(skb))
+#ifdef NET_SKBUFF_DATA_USES_OFFSET
+static inline unsigned char *skb_tail_pointer(const struct sk_buff *skb)
+{
+ return skb->head + skb->tail;
+}
+
+static inline void skb_reset_tail_pointer(struct sk_buff *skb)
+{
+ skb->tail = skb->data - skb->head;
+}
+
+static inline void skb_set_tail_pointer(struct sk_buff *skb, const int offset)
+{
+ skb_reset_tail_pointer(skb);
+ skb->tail += offset;
+}
+#else /* NET_SKBUFF_DATA_USES_OFFSET */
+static inline unsigned char *skb_tail_pointer(const struct sk_buff *skb)
+{
+ return skb->tail;
+}
+
+static inline void skb_reset_tail_pointer(struct sk_buff *skb)
+{
+ skb->tail = skb->data;
+}
+
+static inline void skb_set_tail_pointer(struct sk_buff *skb, const int offset)
+{
+ skb->tail = skb->data + offset;
+}
+#endif /* NET_SKBUFF_DATA_USES_OFFSET */
+
/*
* Add data to an sk_buff
*/
static inline unsigned char *__skb_put(struct sk_buff *skb, unsigned int len)
{
- unsigned char *tmp = skb->tail;
+ unsigned char *tmp = skb_tail_pointer(skb);
SKB_LINEAR_ASSERT(skb);
skb->tail += len;
skb->len += len;
@@ -835,11 +868,11 @@
*/
static inline unsigned char *skb_put(struct sk_buff *skb, unsigned int len)
{
- unsigned char *tmp = skb->tail;
+ unsigned char *tmp = skb_tail_pointer(skb);
SKB_LINEAR_ASSERT(skb);
skb->tail += len;
skb->len += len;
- if (unlikely(skb->tail>skb->end))
+ if (unlikely(skb_tail_pointer(skb) > skb->end))
skb_over_panic(skb, len, current_text_addr());
return tmp;
}
@@ -935,7 +968,7 @@
*/
static inline int skb_tailroom(const struct sk_buff *skb)
{
- return skb_is_nonlinear(skb) ? 0 : skb->end - skb->tail;
+ return skb_is_nonlinear(skb) ? 0 : skb->end - skb_tail_pointer(skb);
}
/**
@@ -1127,8 +1160,8 @@
WARN_ON(1);
return;
}
- skb->len = len;
- skb->tail = skb->data + len;
+ skb->len = len;
+ skb_set_tail_pointer(skb, len);
}
/**
