[PATCH] gro: fix gro with ethernet tail padding bytes

[Jun Qiu <jun.qiu@jaguarmicro.com>]

Exclude CRC fields, the minimum Ethernet packet
length is 60 bytes. When the actual packet length
is less than 60 bytes, padding is added to the tail.
When GRO is performed on a packet containing a padding
field, mbuf->pkt_len is the one that contains the
padding field, which leads to the error of thinking
of the padding field as the actual content of the packet.
We need to trim away this extra padding field during
GRO processing.

Fixes: 0d2cbe59b719 ("lib/gro: support TCP/IPv4")
Cc: stable@dpdk.org

Signed-off-by: Jun Qiu <jun.qiu@jaguarmicro.com>
---
 lib/gro/gro_tcp4.c | 7 ++++++-
 lib/gro/gro_udp4.c | 4 ++++
 2 files changed, 10 insertions(+), 1 deletion(-)

diff --git a/lib/gro/gro_tcp4.c b/lib/gro/gro_tcp4.c
index 7849a2bd1d..0110db5748 100644
--- a/lib/gro/gro_tcp4.c
+++ b/lib/gro/gro_tcp4.c
@@ -198,7 +198,7 @@ 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, hdr_len, frag_off, ip_tlen;
 	uint8_t is_atomic;
 
 	struct tcp4_flow_key key;
@@ -233,6 +233,11 @@ gro_tcp4_reassemble(struct rte_mbuf *pkt,
 	if (tcp_dl <= 0)
 		return -1;
 
+	/* trim the tail padding bytes */
+	ip_tlen = rte_be_to_cpu_16(ipv4_hdr->total_length);
+	if (pkt->pkt_len > (uint32_t)(ip_tlen + pkt->l2_len))
+		rte_pktmbuf_trim(pkt, pkt->pkt_len - ip_tlen - pkt->l2_len);
+
 	/*
 	 * Save IPv4 ID for the packet whose DF bit is 0. For the packet
 	 * whose DF bit is 1, IPv4 ID is ignored.
diff --git a/lib/gro/gro_udp4.c b/lib/gro/gro_udp4.c
index dd71135ada..839f9748b7 100644
--- a/lib/gro/gro_udp4.c
+++ b/lib/gro/gro_udp4.c
@@ -231,6 +231,10 @@ gro_udp4_reassemble(struct rte_mbuf *pkt,
 	if (ip_dl <= pkt->l3_len)
 		return -1;
 
+	/* trim the tail padding bytes */
+	if (pkt->pkt_len > (uint32_t)(ip_dl + pkt->l2_len))
+		rte_pktmbuf_trim(pkt, pkt->pkt_len - ip_dl - pkt->l2_len);
+
 	ip_dl -= pkt->l3_len;
 	ip_id = rte_be_to_cpu_16(ipv4_hdr->packet_id);
 	frag_offset = rte_be_to_cpu_16(ipv4_hdr->fragment_offset);
-- 
2.25.1