netdev - [PATCH bpf-next] samples/bpf: xdp1 and xdp2 reduce XDPBUFSIZE to 60

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Date: Tue, 30 May 2023 16:30:41 +0200
From: Jesper Dangaard Brouer <brouer@...hat.com>
To: Tariq Toukan <ttoukan.linux@...il.com>,
 Daniel Borkmann <borkmann@...earbox.net>,
 Alexei Starovoitov <ast@...nel.org>,
 Andrii Nakryiko <andrii.nakryiko@...il.com>, bpf@...r.kernel.org
Cc: Jesper Dangaard Brouer <brouer@...hat.com>,
 Tariq Toukan <tariqt@...dia.com>, gal@...dia.com, lorenzo@...nel.org,
 netdev@...r.kernel.org, andrew.gospodarek@...adcom.com
Subject: [PATCH bpf-next] samples/bpf: xdp1 and xdp2 reduce XDPBUFSIZE to 60

Default samples/pktgen scripts send 60 byte packets as hardware
adds 4-bytes FCS checksum, which fulfils minimum Ethernet 64 bytes
frame size.

XDP layer will not necessary have access to the 4-bytes FCS checksum.

This leads to bpf_xdp_load_bytes() failing as it tries to copy
64-bytes from an XDP packet that only have 60-bytes available.

Fixes: 772251742262 ("samples/bpf: fixup some tools to be able to support xdp multibuffer")
Signed-off-by: Jesper Dangaard Brouer <brouer@...hat.com>
---
 samples/bpf/xdp1_kern.c |    2 +-
 samples/bpf/xdp2_kern.c |    2 +-
 2 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/samples/bpf/xdp1_kern.c b/samples/bpf/xdp1_kern.c
index 0a5c704badd0..d91f27cbcfa9 100644
--- a/samples/bpf/xdp1_kern.c
+++ b/samples/bpf/xdp1_kern.c
@@ -39,7 +39,7 @@ static int parse_ipv6(void *data, u64 nh_off, void *data_end)
 	return ip6h->nexthdr;
 }
 
-#define XDPBUFSIZE	64
+#define XDPBUFSIZE	60
 SEC("xdp.frags")
 int xdp_prog1(struct xdp_md *ctx)
 {
diff --git a/samples/bpf/xdp2_kern.c b/samples/bpf/xdp2_kern.c
index 67804ecf7ce3..8bca674451ed 100644
--- a/samples/bpf/xdp2_kern.c
+++ b/samples/bpf/xdp2_kern.c
@@ -55,7 +55,7 @@ static int parse_ipv6(void *data, u64 nh_off, void *data_end)
 	return ip6h->nexthdr;
 }
 
-#define XDPBUFSIZE	64
+#define XDPBUFSIZE	60
 SEC("xdp.frags")
 int xdp_prog1(struct xdp_md *ctx)
 {