linux-kernel - [PATCH] samples: bpf: add an explict comment to handle nested vlan tagging.

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Message-Id: <20210809070046.32142-1-falakreyaz@gmail.com>
Date:   Mon,  9 Aug 2021 12:30:46 +0530
From:   Muhammad Falak R Wani <falakreyaz@...il.com>
To:     Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        Andrii Nakryiko <andrii@...nel.org>
Cc:     bpf@...r.kernel.org, netdev@...r.kernel.org,
        KP Singh <kpsingh@...nel.org>, Yonghong Song <yhs@...com>,
        Song Liu <songliubraving@...com>,
        Martin KaFai Lau <kafai@...com>,
        John Fastabend <john.fastabend@...il.com>,
        Jesper Dangaard Brouer <hawk@...nel.org>,
        Jakub Kicinski <kuba@...nel.org>,
        "David S . Miller" <davem@...emloft.net>,
        linux-kernel@...r.kernel.org,
        Muhammad Falak R Wani <falakreyaz@...il.com>
Subject: [PATCH] samples: bpf: add an explict comment to handle nested vlan tagging.

A codeblock for handling nested vlan trips newbies into thinking it as
duplicate code. Explicitly add a comment to clarify.

Signed-off-by: Muhammad Falak R Wani <falakreyaz@...il.com>
---
 samples/bpf/xdp1_kern.c | 2 ++
 samples/bpf/xdp2_kern.c | 2 ++
 2 files changed, 4 insertions(+)

diff --git a/samples/bpf/xdp1_kern.c b/samples/bpf/xdp1_kern.c
index 34b64394ed9c..f0c5d95084de 100644
--- a/samples/bpf/xdp1_kern.c
+++ b/samples/bpf/xdp1_kern.c
@@ -57,6 +57,7 @@ int xdp_prog1(struct xdp_md *ctx)
 
 	h_proto = eth->h_proto;
 
+	/* Handle VLAN tagged packet */
 	if (h_proto == htons(ETH_P_8021Q) || h_proto == htons(ETH_P_8021AD)) {
 		struct vlan_hdr *vhdr;
 
@@ -66,6 +67,7 @@ int xdp_prog1(struct xdp_md *ctx)
 			return rc;
 		h_proto = vhdr->h_vlan_encapsulated_proto;
 	}
+	/* Handle double VLAN tagged packet */
 	if (h_proto == htons(ETH_P_8021Q) || h_proto == htons(ETH_P_8021AD)) {
 		struct vlan_hdr *vhdr;
 
diff --git a/samples/bpf/xdp2_kern.c b/samples/bpf/xdp2_kern.c
index c787f4b49646..d8a64ab077b0 100644
--- a/samples/bpf/xdp2_kern.c
+++ b/samples/bpf/xdp2_kern.c
@@ -73,6 +73,7 @@ int xdp_prog1(struct xdp_md *ctx)
 
 	h_proto = eth->h_proto;
 
+	/* Handle VLAN tagged packet */
 	if (h_proto == htons(ETH_P_8021Q) || h_proto == htons(ETH_P_8021AD)) {
 		struct vlan_hdr *vhdr;
 
@@ -82,6 +83,7 @@ int xdp_prog1(struct xdp_md *ctx)
 			return rc;
 		h_proto = vhdr->h_vlan_encapsulated_proto;
 	}
+	/* Handle double VLAN tagged packet */
 	if (h_proto == htons(ETH_P_8021Q) || h_proto == htons(ETH_P_8021AD)) {
 		struct vlan_hdr *vhdr;
 
-- 
2.17.1