[PATCH 1/2] net: add and use skb_gso_transport_seglen()

[Florian Westphal <fw@strlen.de>]

This moves part of Eric Dumazets skb_gso_seglen helper from tbf sched to
skbuff core so it may be reused by upcoming ip forwarding path patch.

Signed-off-by: Florian Westphal <fw@strlen.de>
---
 include/linux/skbuff.h |  1 +
 net/core/skbuff.c      | 26 ++++++++++++++++++++++++++
 net/sched/sch_tbf.c    | 12 +++---------
 3 files changed, 30 insertions(+), 9 deletions(-)

diff --git a/include/linux/skbuff.h b/include/linux/skbuff.h
index 6f69b3f..3d76066 100644
--- a/include/linux/skbuff.h
+++ b/include/linux/skbuff.h
@@ -2371,6 +2371,7 @@ void skb_copy_and_csum_dev(const struct sk_buff *skb, u8 *to);
 void skb_split(struct sk_buff *skb, struct sk_buff *skb1, const u32 len);
 int skb_shift(struct sk_buff *tgt, struct sk_buff *skb, int shiftlen);
 void skb_scrub_packet(struct sk_buff *skb, bool xnet);
+unsigned int skb_gso_transport_seglen(const struct sk_buff *skb);
 struct sk_buff *skb_segment(struct sk_buff *skb, netdev_features_t features);
 
 struct skb_checksum_ops {
diff --git a/net/core/skbuff.c b/net/core/skbuff.c
index 06e72d3..2e1fd75 100644
--- a/net/core/skbuff.c
+++ b/net/core/skbuff.c
@@ -45,6 +45,7 @@
 #include <linux/mm.h>
 #include <linux/interrupt.h>
 #include <linux/in.h>
+#include <linux/tcp.h>
 #include <linux/inet.h>
 #include <linux/slab.h>
 #include <linux/netdevice.h>
@@ -71,6 +72,8 @@
 #include <trace/events/skb.h>
 #include <linux/highmem.h>
 
+#include <uapi/linux/udp.h>
+
 struct kmem_cache *skbuff_head_cache __read_mostly;
 static struct kmem_cache *skbuff_fclone_cache __read_mostly;
 
@@ -3592,3 +3595,26 @@ void skb_scrub_packet(struct sk_buff *skb, bool xnet)
 	nf_reset_trace(skb);
 }
 EXPORT_SYMBOL_GPL(skb_scrub_packet);
+
+/**
+ * skb_gso_transport_seglen - Return length of individual segments of a gso packet
+ *
+ * @skb: GSO skb
+ *
+ * skb_gso_transport_seglen is used to determine the real size of the
+ * individual segments, including Layer4 headers (TCP/UDP).
+ *
+ * The MAC/L2 or network (IP, IPv6) headers are not accounted for.
+ */
+unsigned int skb_gso_transport_seglen(const struct sk_buff *skb)
+{
+	const struct skb_shared_info *shinfo = skb_shinfo(skb);
+	unsigned int hdr_len;
+
+	if (likely(shinfo->gso_type & (SKB_GSO_TCPV4 | SKB_GSO_TCPV6)))
+		hdr_len = tcp_hdrlen(skb);
+	else
+		hdr_len = sizeof(struct udphdr);
+	return hdr_len + shinfo->gso_size;
+}
+EXPORT_SYMBOL_GPL(skb_gso_transport_seglen);
diff --git a/net/sched/sch_tbf.c b/net/sched/sch_tbf.c
index 887e672..837a61b 100644
--- a/net/sched/sch_tbf.c
+++ b/net/sched/sch_tbf.c
@@ -148,16 +148,10 @@ static u64 psched_ns_t2l(const struct psched_ratecfg *r,
  * Return length of individual segments of a gso packet,
  * including all headers (MAC, IP, TCP/UDP)
  */
-static unsigned int skb_gso_seglen(const struct sk_buff *skb)
+static unsigned int skb_gso_mac_seglen(const struct sk_buff *skb)
 {
 	unsigned int hdr_len = skb_transport_header(skb) - skb_mac_header(skb);
-	const struct skb_shared_info *shinfo = skb_shinfo(skb);
-
-	if (likely(shinfo->gso_type & (SKB_GSO_TCPV4 | SKB_GSO_TCPV6)))
-		hdr_len += tcp_hdrlen(skb);
-	else
-		hdr_len += sizeof(struct udphdr);
-	return hdr_len + shinfo->gso_size;
+	return hdr_len + skb_gso_transport_seglen(skb);
 }
 
 /* GSO packet is too big, segment it so that tbf can transmit
@@ -202,7 +196,7 @@ static int tbf_enqueue(struct sk_buff *skb, struct Qdisc *sch)
 	int ret;
 
 	if (qdisc_pkt_len(skb) > q->max_size) {
-		if (skb_is_gso(skb) && skb_gso_seglen(skb) <= q->max_size)
+		if (skb_is_gso(skb) && skb_gso_mac_seglen(skb) <= q->max_size)
 			return tbf_segment(skb, sch);
 		return qdisc_reshape_fail(skb, sch);
 	}
-- 
1.8.1.5