[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 <acme@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

3 files changed, 9 insertions, 14 deletions

diff --git a/net/netfilter/nf_conntrack_netlink.c b/net/netfilter/nf_conntrack_netlink.c
index 48f05314ebf..442300c633d 100644
--- a/net/netfilter/nf_conntrack_netlink.c
+++ b/net/netfilter/nf_conntrack_netlink.c
@@ -268,9 +268,7 @@ ctnetlink_fill_info(struct sk_buff *skb, u32 pid, u32 seq,
 	struct nlmsghdr *nlh;
 	struct nfgenmsg *nfmsg;
 	struct nfattr *nest_parms;
-	unsigned char *b;
-
-	b = skb->tail;
+	unsigned char *b = skb_tail_pointer(skb);
 
 	event |= NFNL_SUBSYS_CTNETLINK << 8;
 	nlh    = NLMSG_PUT(skb, pid, seq, event, sizeof(struct nfgenmsg));
@@ -303,7 +301,7 @@ ctnetlink_fill_info(struct sk_buff *skb, u32 pid, u32 seq,
 	    ctnetlink_dump_use(skb, ct) < 0)
 		goto nfattr_failure;
 
-	nlh->nlmsg_len = skb->tail - b;
+	nlh->nlmsg_len = skb_tail_pointer(skb) - b;
 	return skb->len;
 
 nlmsg_failure:
@@ -322,7 +320,7 @@ static int ctnetlink_conntrack_event(struct notifier_block *this,
 	struct nf_conn *ct = (struct nf_conn *)ptr;
 	struct sk_buff *skb;
 	unsigned int type;
-	unsigned char *b;
+	sk_buff_data_t b;
 	unsigned int flags = 0, group;
 
 	/* ignore our fake conntrack entry */
@@ -1152,9 +1150,7 @@ ctnetlink_exp_fill_info(struct sk_buff *skb, u32 pid, u32 seq,
 {
 	struct nlmsghdr *nlh;
 	struct nfgenmsg *nfmsg;
-	unsigned char *b;
-
-	b = skb->tail;
+	unsigned char *b = skb_tail_pointer(skb);
 
 	event |= NFNL_SUBSYS_CTNETLINK_EXP << 8;
 	nlh    = NLMSG_PUT(skb, pid, seq, event, sizeof(struct nfgenmsg));
@@ -1168,7 +1164,7 @@ ctnetlink_exp_fill_info(struct sk_buff *skb, u32 pid, u32 seq,
 	if (ctnetlink_exp_dump_expect(skb, exp) < 0)
 		goto nfattr_failure;
 
-	nlh->nlmsg_len = skb->tail - b;
+	nlh->nlmsg_len = skb_tail_pointer(skb) - b;
 	return skb->len;
 
 nlmsg_failure:
@@ -1186,7 +1182,7 @@ static int ctnetlink_expect_event(struct notifier_block *this,
 	struct nf_conntrack_expect *exp = (struct nf_conntrack_expect *)ptr;
 	struct sk_buff *skb;
 	unsigned int type;
-	unsigned char *b;
+	sk_buff_data_t b;
 	int flags = 0;
 
 	if (events & IPEXP_NEW) {
diff --git a/net/netfilter/nfnetlink_log.c b/net/netfilter/nfnetlink_log.c
index 5eeebd2efa7..9709f94787f 100644
--- a/net/netfilter/nfnetlink_log.c
+++ b/net/netfilter/nfnetlink_log.c
@@ -409,15 +409,14 @@ __build_packet_message(struct nfulnl_instance *inst,
 			const struct nf_loginfo *li,
 			const char *prefix, unsigned int plen)
 {
-	unsigned char *old_tail;
 	struct nfulnl_msg_packet_hdr pmsg;
 	struct nlmsghdr *nlh;
 	struct nfgenmsg *nfmsg;
 	__be32 tmp_uint;
+	sk_buff_data_t old_tail = inst->skb->tail;
 
 	UDEBUG("entered\n");
 
-	old_tail = inst->skb->tail;
 	nlh = NLMSG_PUT(inst->skb, 0, 0,
 			NFNL_SUBSYS_ULOG << 8 | NFULNL_MSG_PACKET,
 			sizeof(struct nfgenmsg));
diff --git a/net/netfilter/nfnetlink_queue.c b/net/netfilter/nfnetlink_queue.c
index cfbee39f61d..b6585caa431 100644
--- a/net/netfilter/nfnetlink_queue.c
+++ b/net/netfilter/nfnetlink_queue.c
@@ -338,7 +338,7 @@ static struct sk_buff *
 nfqnl_build_packet_message(struct nfqnl_instance *queue,
 			   struct nfqnl_queue_entry *entry, int *errp)
 {
-	unsigned char *old_tail;
+	sk_buff_data_t old_tail;
 	size_t size;
 	size_t data_len = 0;
 	struct sk_buff *skb;
@@ -404,7 +404,7 @@ nfqnl_build_packet_message(struct nfqnl_instance *queue,
 	if (!skb)
 		goto nlmsg_failure;
 
-	old_tail= skb->tail;
+	old_tail = skb->tail;
 	nlh = NLMSG_PUT(skb, 0, 0,
 			NFNL_SUBSYS_QUEUE << 8 | NFQNL_MSG_PACKET,
 			sizeof(struct nfgenmsg));