[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>

12 files changed, 33 insertions, 28 deletions

diff --git a/net/ipv4/esp4.c b/net/ipv4/esp4.c
index de019f9fbfe..5e5613930ff 100644
--- a/net/ipv4/esp4.c
+++ b/net/ipv4/esp4.c
@@ -21,6 +21,7 @@ static int esp_output(struct xfrm_state *x, struct sk_buff *skb)
 	struct blkcipher_desc desc;
 	struct esp_data *esp;
 	struct sk_buff *trailer;
+	u8 *tail;
 	int blksize;
 	int clen;
 	int alen;
@@ -49,12 +50,13 @@ static int esp_output(struct xfrm_state *x, struct sk_buff *skb)
 		goto error;
 
 	/* Fill padding... */
+	tail = skb_tail_pointer(trailer);
 	do {
 		int i;
 		for (i=0; i<clen-skb->len - 2; i++)
-			*(u8*)(trailer->tail + i) = i+1;
+			tail[i] = i + 1;
 	} while (0);
-	*(u8*)(trailer->tail + clen-skb->len - 2) = (clen - skb->len)-2;
+	tail[clen - skb->len - 2] = (clen - skb->len) - 2;
 	pskb_put(skb, trailer, clen - skb->len);
 
 	__skb_push(skb, skb->data - skb_network_header(skb));
@@ -62,7 +64,7 @@ static int esp_output(struct xfrm_state *x, struct sk_buff *skb)
 	esph = (struct ip_esp_hdr *)(skb_network_header(skb) +
 				     top_iph->ihl * 4);
 	top_iph->tot_len = htons(skb->len + alen);
-	*(u8*)(trailer->tail - 1) = top_iph->protocol;
+	*(skb_tail_pointer(skb) - 1) = top_iph->protocol;
 
 	/* this is non-NULL only with UDP Encapsulation */
 	if (x->encap) {
diff --git a/net/ipv4/icmp.c b/net/ipv4/icmp.c
index 8372f8b8f0c..d38cbba92a4 100644
--- a/net/ipv4/icmp.c
+++ b/net/ipv4/icmp.c
@@ -450,7 +450,8 @@ void icmp_send(struct sk_buff *skb_in, int type, int code, __be32 info)
 	 */
 	iph = ip_hdr(skb_in);
 
-	if ((u8 *)iph < skb_in->head || (u8 *)(iph + 1) > skb_in->tail)
+	if ((u8 *)iph < skb_in->head ||
+	    (skb_in->network_header + sizeof(*iph)) > skb_in->tail)
 		goto out;
 
 	/*
diff --git a/net/ipv4/igmp.c b/net/ipv4/igmp.c
index 1fc637fb675..2506021c293 100644
--- a/net/ipv4/igmp.c
+++ b/net/ipv4/igmp.c
@@ -348,8 +348,8 @@ static int igmpv3_sendpack(struct sk_buff *skb)
 {
 	struct iphdr *pip = ip_hdr(skb);
 	struct igmphdr *pig = igmp_hdr(skb);
-	const int iplen = skb->tail - skb_network_header(skb);
-	const int igmplen = skb->tail - skb_transport_header(skb);
+	const int iplen = skb->tail - skb->network_header;
+	const int igmplen = skb->tail - skb->transport_header;
 
 	pip->tot_len = htons(iplen);
 	ip_send_check(pip);
diff --git a/net/ipv4/inet_diag.c b/net/ipv4/inet_diag.c
index 5df71cd08da..37362cd1d07 100644
--- a/net/ipv4/inet_diag.c
+++ b/net/ipv4/inet_diag.c
@@ -60,7 +60,7 @@ static int inet_csk_diag_fill(struct sock *sk,
 	struct nlmsghdr  *nlh;
 	void *info = NULL;
 	struct inet_diag_meminfo  *minfo = NULL;
-	unsigned char	 *b = skb->tail;
+	unsigned char	 *b = skb_tail_pointer(skb);
 	const struct inet_diag_handler *handler;
 
 	handler = inet_diag_table[unlh->nlmsg_type];
@@ -147,7 +147,7 @@ static int inet_csk_diag_fill(struct sock *sk,
 	    icsk->icsk_ca_ops && icsk->icsk_ca_ops->get_info)
 		icsk->icsk_ca_ops->get_info(sk, ext, skb);
 
-	nlh->nlmsg_len = skb->tail - b;
+	nlh->nlmsg_len = skb_tail_pointer(skb) - b;
 	return skb->len;
 
 rtattr_failure:
@@ -163,7 +163,7 @@ static int inet_twsk_diag_fill(struct inet_timewait_sock *tw,
 {
 	long tmo;
 	struct inet_diag_msg *r;
-	const unsigned char *previous_tail = skb->tail;
+	const unsigned char *previous_tail = skb_tail_pointer(skb);
 	struct nlmsghdr *nlh = NLMSG_PUT(skb, pid, seq,
 					 unlh->nlmsg_type, sizeof(*r));
 
@@ -205,7 +205,7 @@ static int inet_twsk_diag_fill(struct inet_timewait_sock *tw,
 			       &tw6->tw_v6_daddr);
 	}
 #endif
-	nlh->nlmsg_len = skb->tail - previous_tail;
+	nlh->nlmsg_len = skb_tail_pointer(skb) - previous_tail;
 	return skb->len;
 nlmsg_failure:
 	skb_trim(skb, previous_tail - skb->data);
@@ -535,7 +535,7 @@ static int inet_diag_fill_req(struct sk_buff *skb, struct sock *sk,
 {
 	const struct inet_request_sock *ireq = inet_rsk(req);
 	struct inet_sock *inet = inet_sk(sk);
-	unsigned char *b = skb->tail;
+	unsigned char *b = skb_tail_pointer(skb);
 	struct inet_diag_msg *r;
 	struct nlmsghdr *nlh;
 	long tmo;
@@ -574,7 +574,7 @@ static int inet_diag_fill_req(struct sk_buff *skb, struct sock *sk,
 			       &inet6_rsk(req)->rmt_addr);
 	}
 #endif
-	nlh->nlmsg_len = skb->tail - b;
+	nlh->nlmsg_len = skb_tail_pointer(skb) - b;
 
 	return skb->len;
 
diff --git a/net/ipv4/ip_sockglue.c b/net/ipv4/ip_sockglue.c
index fcb35cd5ccf..c199d231173 100644
--- a/net/ipv4/ip_sockglue.c
+++ b/net/ipv4/ip_sockglue.c
@@ -316,7 +316,7 @@ void ip_local_error(struct sock *sk, int err, __be32 daddr, __be16 port, u32 inf
 	serr->addr_offset = (u8 *)&iph->daddr - skb_network_header(skb);
 	serr->port = port;
 
-	__skb_pull(skb, skb->tail - skb->data);
+	__skb_pull(skb, skb_tail_pointer(skb) - skb->data);
 	skb_reset_transport_header(skb);
 
 	if (sock_queue_err_skb(sk, skb))
diff --git a/net/ipv4/ipmr.c b/net/ipv4/ipmr.c
index 50d0b301380..ea0a491dce9 100644
--- a/net/ipv4/ipmr.c
+++ b/net/ipv4/ipmr.c
@@ -513,7 +513,8 @@ static void ipmr_cache_resolve(struct mfc_cache *uc, struct mfc_cache *c)
 			struct nlmsghdr *nlh = (struct nlmsghdr *)skb_pull(skb, sizeof(struct iphdr));
 
 			if (ipmr_fill_mroute(skb, c, NLMSG_DATA(nlh)) > 0) {
-				nlh->nlmsg_len = skb->tail - (u8*)nlh;
+				nlh->nlmsg_len = (skb_tail_pointer(skb) -
+						  (u8 *)nlh);
 			} else {
 				nlh->nlmsg_type = NLMSG_ERROR;
 				nlh->nlmsg_len = NLMSG_LENGTH(sizeof(struct nlmsgerr));
@@ -580,7 +581,7 @@ static int ipmr_cache_report(struct sk_buff *pkt, vifi_t vifi, int assert)
 	 *	Copy the IP header
 	 */
 
-	skb_set_network_header(skb, skb->tail - skb->data);
+	skb->network_header = skb->tail;
 	skb_put(skb, ihl);
 	memcpy(skb->data,pkt->data,ihl);
 	ip_hdr(skb)->protocol = 0;			/* Flag to the kernel this is a route add */
@@ -1544,7 +1545,7 @@ ipmr_fill_mroute(struct sk_buff *skb, struct mfc_cache *c, struct rtmsg *rtm)
 	int ct;
 	struct rtnexthop *nhp;
 	struct net_device *dev = vif_table[c->mfc_parent].dev;
-	u8 *b = skb->tail;
+	u8 *b = skb_tail_pointer(skb);
 	struct rtattr *mp_head;
 
 	if (dev)
@@ -1564,7 +1565,7 @@ ipmr_fill_mroute(struct sk_buff *skb, struct mfc_cache *c, struct rtmsg *rtm)
 		}
 	}
 	mp_head->rta_type = RTA_MULTIPATH;
-	mp_head->rta_len = skb->tail - (u8*)mp_head;
+	mp_head->rta_len = skb_tail_pointer(skb) - (u8 *)mp_head;
 	rtm->rtm_type = RTN_MULTICAST;
 	return 1;
 
diff --git a/net/ipv4/ipvs/ip_vs_ftp.c b/net/ipv4/ipvs/ip_vs_ftp.c
index 25bd6896730..344ddbbdc75 100644
--- a/net/ipv4/ipvs/ip_vs_ftp.c
+++ b/net/ipv4/ipvs/ip_vs_ftp.c
@@ -162,7 +162,7 @@ static int ip_vs_ftp_out(struct ip_vs_app *app, struct ip_vs_conn *cp,
 		iph = ip_hdr(*pskb);
 		th = (struct tcphdr *)&(((char *)iph)[iph->ihl*4]);
 		data = (char *)th + (th->doff << 2);
-		data_limit = (*pskb)->tail;
+		data_limit = skb_tail_pointer(*pskb);
 
 		if (ip_vs_ftp_get_addrport(data, data_limit,
 					   SERVER_STRING,
@@ -269,7 +269,7 @@ static int ip_vs_ftp_in(struct ip_vs_app *app, struct ip_vs_conn *cp,
 	   the length of the header in 32-bit multiples, it is accurate
 	   to calculate data address by th+HLEN*4 */
 	data = data_start = (char *)th + (th->doff << 2);
-	data_limit = (*pskb)->tail;
+	data_limit = skb_tail_pointer(*pskb);
 
 	while (data <= data_limit - 6) {
 		if (strnicmp(data, "PASV\r\n", 6) == 0) {
diff --git a/net/ipv4/netfilter/arpt_mangle.c b/net/ipv4/netfilter/arpt_mangle.c
index b4450f1ccc1..6298d404e7c 100644
--- a/net/ipv4/netfilter/arpt_mangle.c
+++ b/net/ipv4/netfilter/arpt_mangle.c
@@ -37,28 +37,28 @@ target(struct sk_buff **pskb,
 	/* We assume that pln and hln were checked in the match */
 	if (mangle->flags & ARPT_MANGLE_SDEV) {
 		if (ARPT_DEV_ADDR_LEN_MAX < hln ||
-		   (arpptr + hln > (**pskb).tail))
+		   (arpptr + hln > skb_tail_pointer(*pskb)))
 			return NF_DROP;
 		memcpy(arpptr, mangle->src_devaddr, hln);
 	}
 	arpptr += hln;
 	if (mangle->flags & ARPT_MANGLE_SIP) {
 		if (ARPT_MANGLE_ADDR_LEN_MAX < pln ||
-		   (arpptr + pln > (**pskb).tail))
+		   (arpptr + pln > skb_tail_pointer(*pskb)))
 			return NF_DROP;
 		memcpy(arpptr, &mangle->u_s.src_ip, pln);
 	}
 	arpptr += pln;
 	if (mangle->flags & ARPT_MANGLE_TDEV) {
 		if (ARPT_DEV_ADDR_LEN_MAX < hln ||
-		   (arpptr + hln > (**pskb).tail))
+		   (arpptr + hln > skb_tail_pointer(*pskb)))
 			return NF_DROP;
 		memcpy(arpptr, mangle->tgt_devaddr, hln);
 	}
 	arpptr += hln;
 	if (mangle->flags & ARPT_MANGLE_TIP) {
 		if (ARPT_MANGLE_ADDR_LEN_MAX < pln ||
-		   (arpptr + pln > (**pskb).tail))
+		   (arpptr + pln > skb_tail_pointer(*pskb)))
 			return NF_DROP;
 		memcpy(arpptr, &mangle->u_t.tgt_ip, pln);
 	}
diff --git a/net/ipv4/netfilter/ip_queue.c b/net/ipv4/netfilter/ip_queue.c
index 5842f1aa973..15e0d200223 100644
--- a/net/ipv4/netfilter/ip_queue.c
+++ b/net/ipv4/netfilter/ip_queue.c
@@ -191,7 +191,7 @@ ipq_flush(int verdict)
 static struct sk_buff *
 ipq_build_packet_message(struct ipq_queue_entry *entry, int *errp)
 {
-	unsigned char *old_tail;
+	sk_buff_data_t old_tail;
 	size_t size = 0;
 	size_t data_len = 0;
 	struct sk_buff *skb;
@@ -235,7 +235,7 @@ ipq_build_packet_message(struct ipq_queue_entry *entry, int *errp)
 	if (!skb)
 		goto nlmsg_failure;
 
-	old_tail= skb->tail;
+	old_tail = skb->tail;
 	nlh = NLMSG_PUT(skb, 0, 0, IPQM_PACKET, size - sizeof(*nlh));
 	pmsg = NLMSG_DATA(nlh);
 	memset(pmsg, 0, sizeof(*pmsg));
diff --git a/net/ipv4/netfilter/nf_nat_helper.c b/net/ipv4/netfilter/nf_nat_helper.c
index c2c92ff1278..8a40fbe842b 100644
--- a/net/ipv4/netfilter/nf_nat_helper.c
+++ b/net/ipv4/netfilter/nf_nat_helper.c
@@ -92,7 +92,8 @@ static void mangle_contents(struct sk_buff *skb,
 	/* move post-replacement */
 	memmove(data + match_offset + rep_len,
 		data + match_offset + match_len,
-		skb->tail - (data + match_offset + match_len));
+		skb->tail - (skb->network_header + dataoff +
+			     match_offset + match_len));
 
 	/* insert data from buffer */
 	memcpy(data + match_offset, rep_buffer, rep_len);
diff --git a/net/ipv4/tcp.c b/net/ipv4/tcp.c
index 2b214cc3724..18a09a78ca0 100644
--- a/net/ipv4/tcp.c
+++ b/net/ipv4/tcp.c
@@ -2231,7 +2231,7 @@ struct sk_buff *tcp_tso_segment(struct sk_buff *skb, int features)
 		th->cwr = 0;
 	} while (skb->next);
 
-	delta = htonl(oldlen + (skb->tail - skb_transport_header(skb)) +
+	delta = htonl(oldlen + (skb->tail - skb->transport_header) +
 		      skb->data_len);
 	th->check = ~csum_fold((__force __wsum)((__force u32)th->check +
 				(__force u32)delta));
diff --git a/net/ipv4/tcp_output.c b/net/ipv4/tcp_output.c
index 29c53fbb220..c22cdcd8432 100644
--- a/net/ipv4/tcp_output.c
+++ b/net/ipv4/tcp_output.c
@@ -733,7 +733,7 @@ static void __pskb_trim_head(struct sk_buff *skb, int len)
 	}
 	skb_shinfo(skb)->nr_frags = k;
 
-	skb->tail = skb->data;
+	skb_reset_tail_pointer(skb);
 	skb->data_len -= len;
 	skb->len = skb->data_len;
 }