[PATCH v2] app/testpmd: fix VLAN header parsing

[Raslan Darawsheh <rasland@nvidia.com>]

When processing VLAN or QinQ packets, an infinite loop occurred,
preventing the csum forward engine from proceeding and causing
testpmd to hang during shutdown attempts.

Updated the `get_ethertype_by_ptype` function to correctly parse
VLAN headers.

Fixes: 76730c7b9b5a ("app/testpmd: use packet type parsing API")
Cc: haijie1@huawei.com

Signed-off-by: Raslan Darawsheh <rasland@nvidia.com>
---
v2: update commit log
    fixed pointer handling to actually move the pointer
---
 app/test-pmd/csumonly.c | 9 +++++----
 1 file changed, 5 insertions(+), 4 deletions(-)

diff --git a/app/test-pmd/csumonly.c b/app/test-pmd/csumonly.c
index 5b906eaa53..7bd1040c72 100644
--- a/app/test-pmd/csumonly.c
+++ b/app/test-pmd/csumonly.c
@@ -486,10 +486,11 @@ get_ethertype_by_ptype(struct rte_ether_hdr *eth_hdr, uint32_t ptype)
 		return _htons(RTE_ETHER_TYPE_IPV6);
 	default:
 		ethertype = eth_hdr->ether_type;
-		while (eth_hdr->ether_type == _htons(RTE_ETHER_TYPE_VLAN) ||
-			eth_hdr->ether_type == _htons(RTE_ETHER_TYPE_QINQ)) {
-			vlan_hdr = (struct rte_vlan_hdr *)
-				((char *)eth_hdr + sizeof(*eth_hdr));
+		vlan_hdr = (struct rte_vlan_hdr *) RTE_PTR_ADD(eth_hdr,
+				 offsetof(struct rte_ether_hdr, ether_type));
+		while ((ethertype == _htons(RTE_ETHER_TYPE_VLAN) ||
+			ethertype == _htons(RTE_ETHER_TYPE_QINQ))) {
+			vlan_hdr++;
 			ethertype = vlan_hdr->eth_proto;
 		}
 		return ethertype;
-- 
2.39.5 (Apple Git-154)