[PATCH v2] gro: bug fix in identifying 0 length tcp packets

[Kumara Parameshwaran]

From: Kumara Parameshwaran <kumaraparamesh92 at gmail.com>

As the minimum Ethernet frame size is 64 bytes, a 0 length
tcp payload without tcp options would be 54 bytes and hence
there would be padding. So it would be incorrect to use the
packet length to determine the tcp data length.

Fixes: 1e4cf4d6d4fb ("gro: cleanup")
Cc: stable at dpdk.org

Signed-off-by: Kumara Parameshwaran <kparameshwar at vmware.com>
---
v1:
	Do not use packet length to determine the tcp data length as 
	the packet length could have padded bytes. This would lead 
	to addition of 0 length tcp packets into the GRO layer when 
	there ethernet fram is padded.
v2:
	Since using ip packet length to determine the tcp data length, 
	validate the ip packet length

 lib/gro/gro_tcp4.c | 9 +++++----
 1 file changed, 5 insertions(+), 4 deletions(-)

diff --git a/lib/gro/gro_tcp4.c b/lib/gro/gro_tcp4.c
index 7498c66..30f5922 100644
--- a/lib/gro/gro_tcp4.c
+++ b/lib/gro/gro_tcp4.c
@@ -198,7 +198,8 @@ gro_tcp4_reassemble(struct rte_mbuf *pkt,
 	struct rte_tcp_hdr *tcp_hdr;
 	uint32_t sent_seq;
 	int32_t tcp_dl;
-	uint16_t ip_id, hdr_len, frag_off;
+	uint16_t ip_id, frag_off;
+	uint16_t ip_len;
 	uint8_t is_atomic;
 
 	struct tcp4_flow_key key;
@@ -217,7 +218,6 @@ gro_tcp4_reassemble(struct rte_mbuf *pkt,
 	eth_hdr = rte_pktmbuf_mtod(pkt, struct rte_ether_hdr *);
 	ipv4_hdr = (struct rte_ipv4_hdr *)((char *)eth_hdr + pkt->l2_len);
 	tcp_hdr = (struct rte_tcp_hdr *)((char *)ipv4_hdr + pkt->l3_len);
-	hdr_len = pkt->l2_len + pkt->l3_len + pkt->l4_len;
 
 	/*
 	 * Don't process the packet which has FIN, SYN, RST, PSH, URG, ECE
@@ -229,8 +229,9 @@ gro_tcp4_reassemble(struct rte_mbuf *pkt,
 	 * Don't process the packet whose payload length is less than or
 	 * equal to 0.
 	 */
-	tcp_dl = pkt->pkt_len - hdr_len;
-	if (tcp_dl <= 0)
+	ip_len = rte_be_to_cpu_16(ipv4_hdr->total_length);
+	tcp_dl = ip_len - (pkt->l3_len + pkt->l4_len);
+	if (tcp_dl <= 0 || ip_len > pkt->pkt_len)
 		return -1;
 
 	/*
-- 
2.7.4