netdev - [PATCH bpf-next v4 11/14] selftests/bpf: Optionally select broadcasting flags

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Message-Id: <20250131-redirect-multi-v4-11-970b33678512@bootlin.com>
Date: Fri, 31 Jan 2025 08:21:50 +0100
From: "Bastien Curutchet (eBPF Foundation)" <bastien.curutchet@...tlin.com>
To: Alexei Starovoitov <ast@...nel.org>, 
 Daniel Borkmann <daniel@...earbox.net>, 
 "David S. Miller" <davem@...emloft.net>, Jakub Kicinski <kuba@...nel.org>, 
 Jesper Dangaard Brouer <hawk@...nel.org>, 
 John Fastabend <john.fastabend@...il.com>, 
 Andrii Nakryiko <andrii@...nel.org>, 
 Martin KaFai Lau <martin.lau@...ux.dev>, 
 Eduard Zingerman <eddyz87@...il.com>, Song Liu <song@...nel.org>, 
 Yonghong Song <yonghong.song@...ux.dev>, KP Singh <kpsingh@...nel.org>, 
 Stanislav Fomichev <sdf@...ichev.me>, Hao Luo <haoluo@...gle.com>, 
 Jiri Olsa <jolsa@...nel.org>, Mykola Lysenko <mykolal@...com>, 
 Shuah Khan <shuah@...nel.org>
Cc: Alexis Lothore <alexis.lothore@...tlin.com>, 
 Thomas Petazzoni <thomas.petazzoni@...tlin.com>, netdev@...r.kernel.org, 
 bpf@...r.kernel.org, linux-kselftest@...r.kernel.org, 
 linux-kernel@...r.kernel.org, 
 "Bastien Curutchet (eBPF Foundation)" <bastien.curutchet@...tlin.com>
Subject: [PATCH bpf-next v4 11/14] selftests/bpf: Optionally select
 broadcasting flags

Broadcasting flags are hardcoded for each kind for protocol.

Create a redirect_flags map that allows to select the broadcasting flags
to use in the bpf_redirect_map(). The protocol ID is used as a key.
Set the old hardcoded values as default if the map isn't filled by the
BPF caller.

Acked-by: Stanislav Fomichev <sdf@...ichev.me>
Signed-off-by: Bastien Curutchet (eBPF Foundation) <bastien.curutchet@...tlin.com>
---
 .../selftests/bpf/progs/xdp_redirect_multi_kern.c  | 41 +++++++++++++++-------
 1 file changed, 29 insertions(+), 12 deletions(-)

diff --git a/tools/testing/selftests/bpf/progs/xdp_redirect_multi_kern.c b/tools/testing/selftests/bpf/progs/xdp_redirect_multi_kern.c
index 97b26a30b59a758f5a5f2152af509acef80031ce..bc2945ed8a8017021c2792671b4de9aa4928a3e4 100644
--- a/tools/testing/selftests/bpf/progs/xdp_redirect_multi_kern.c
+++ b/tools/testing/selftests/bpf/progs/xdp_redirect_multi_kern.c
@@ -34,6 +34,14 @@ struct {
 	__uint(max_entries, 128);
 } mac_map SEC(".maps");

+/* map to store redirect flags for each protocol*/
+struct {
+	__uint(type, BPF_MAP_TYPE_HASH);
+	__type(key, __u16);
+	__type(value, __u64);
+	__uint(max_entries, 16);
+} redirect_flags SEC(".maps");
+
 SEC("xdp")
 int xdp_redirect_map_multi_prog(struct xdp_md *ctx)
 {
@@ -41,25 +49,34 @@ int xdp_redirect_map_multi_prog(struct xdp_md *ctx)
 	void *data = (void *)(long)ctx->data;
 	int if_index = ctx->ingress_ifindex;
 	struct ethhdr *eth = data;
+	__u64 *flags_from_map;
 	__u16 h_proto;
 	__u64 nh_off;
+	__u64 flags;

 	nh_off = sizeof(*eth);
 	if (data + nh_off > data_end)
 		return XDP_DROP;

-	h_proto = eth->h_proto;
-
-	/* Using IPv4 for (BPF_F_BROADCAST | BPF_F_EXCLUDE_INGRESS) testing */
-	if (h_proto == bpf_htons(ETH_P_IP))
-		return bpf_redirect_map(&map_all, 0,
-					BPF_F_BROADCAST | BPF_F_EXCLUDE_INGRESS);
-	/* Using IPv6 for none flag testing */
-	else if (h_proto == bpf_htons(ETH_P_IPV6))
-		return bpf_redirect_map(&map_all, if_index, 0);
-	/* All others for BPF_F_BROADCAST testing */
-	else
-		return bpf_redirect_map(&map_all, 0, BPF_F_BROADCAST);
+	h_proto = bpf_htons(eth->h_proto);
+
+	flags_from_map = bpf_map_lookup_elem(&redirect_flags, &h_proto);
+
+	/* Default flags for IPv4 : (BPF_F_BROADCAST | BPF_F_EXCLUDE_INGRESS) */
+	if (h_proto == ETH_P_IP) {
+		flags = flags_from_map ? *flags_from_map : BPF_F_BROADCAST | BPF_F_EXCLUDE_INGRESS;
+		return bpf_redirect_map(&map_all, 0, flags);
+	}
+	/* Default flags for IPv6 : 0 */
+	if (h_proto == ETH_P_IPV6) {
+		flags = flags_from_map ? *flags_from_map : 0;
+		return bpf_redirect_map(&map_all, if_index, flags);
+	}
+	/* Default flags for others BPF_F_BROADCAST : 0 */
+	else {
+		flags = flags_from_map ? *flags_from_map : BPF_F_BROADCAST;
+		return bpf_redirect_map(&map_all, 0, flags);
+	}
 }

 /* The following 2 progs are for 2nd devmap prog testing */

-- 
2.48.1