[PATCH 2/2] ibmveth: calculate gso_segs for large packets

[Tim Gardner]

From: Thomas Falcon <tlfalcon at linux.vnet.ibm.com>

BugLink: http://bugs.launchpad.net/bugs/1655420

Include calculations to compute the number of segments
that comprise an aggregated large packet.

Signed-off-by: Thomas Falcon <tlfalcon at linux.vnet.ibm.com>
Reviewed-by: Marcelo Ricardo Leitner <marcelo.leitner at gmail.com>
Reviewed-by: Jonathan Maxwell <jmaxwell37 at gmail.com>
Signed-off-by: David S. Miller <davem at davemloft.net>
(cherry picked from commit 94acf164dc8f1184e8d0737be7125134c2701dbe)
Signed-off-by: Tim Gardner <tim.gardner at canonical.com>
---
 drivers/net/ethernet/ibm/ibmveth.c | 12 ++++++++++--
 1 file changed, 10 insertions(+), 2 deletions(-)

diff --git a/drivers/net/ethernet/ibm/ibmveth.c b/drivers/net/ethernet/ibm/ibmveth.c
index 855c43d..f9e4988 100644
--- a/drivers/net/ethernet/ibm/ibmveth.c
+++ b/drivers/net/ethernet/ibm/ibmveth.c
@@ -1179,7 +1179,9 @@ map_failed:
 
 static void ibmveth_rx_mss_helper(struct sk_buff *skb, u16 mss, int lrg_pkt)
 {
+	struct tcphdr *tcph;
 	int offset = 0;
+	int hdr_len;
 
 	/* only TCP packets will be aggregated */
 	if (skb->protocol == htons(ETH_P_IP)) {
@@ -1206,14 +1208,20 @@ static void ibmveth_rx_mss_helper(struct sk_buff *skb, u16 mss, int lrg_pkt)
 	/* if mss is not set through Large Packet bit/mss in rx buffer,
 	 * expect that the mss will be written to the tcp header checksum.
 	 */
+	tcph = (struct tcphdr *)(skb->data + offset);
 	if (lrg_pkt) {
 		skb_shinfo(skb)->gso_size = mss;
 	} else if (offset) {
-		struct tcphdr *tcph = (struct tcphdr *)(skb->data + offset);
-
 		skb_shinfo(skb)->gso_size = ntohs(tcph->check);
 		tcph->check = 0;
 	}
+
+	if (skb_shinfo(skb)->gso_size) {
+		hdr_len = offset + tcph->doff * 4;
+		skb_shinfo(skb)->gso_segs =
+				DIV_ROUND_UP(skb->len - hdr_len,
+					     skb_shinfo(skb)->gso_size);
+	}
 }
 
 static int ibmveth_poll(struct napi_struct *napi, int budget)
-- 
2.7.4