From b8a55871d5af6f5b8694b1cb5eacbc629734e403 Mon Sep 17 00:00:00 2001
From: Jun Qiu <jun.qiu@jaguarmicro.com>
Date: Wed, 27 Jul 2022 08:00:36 +0000
Subject: [PATCH] gro: trim tail padding bytes

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>
Acked-by: Jiayu Hu <Jiayu.hu@intel.com>
---
 lib/gro/gro_tcp4.c | 7 ++++++-
 2 files changed, 10 insertions(+), 1 deletion(-)

diff --git a/lib/librte_gro/gro_tcp4.c b/lib/librte_gro/gro_tcp4.c
index 9758e28fd5..8f5e800250 100644
--- a/lib/librte_gro/gro_tcp4.c
+++ b/lib/librte_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.
-- 
2.23.0

