[PATCH net-next 3/5] selftests/xsk: expand XSKMAP capacity and add length-based XDP program

[Tushar Vyavahare <tushar.vyavahare@intel.com>]

Raise MAX_SOCKETS from 2 to 4 so the XSKMAP and test arrays can
accommodate the upcoming 4-socket shared-UMEM test. Update the XSKMAP
max_entries to use MAX_SOCKETS so the BPF and C sides stay in sync.

Add xsk_xdp_shared_umem_length_based() XDP program that routes packets
by total XDP-visible packet length (data_end - data): socket 0 for
packets <= SHARED_UMEM_LEN_SPLIT bytes and socket 1 for packets >
SHARED_UMEM_LEN_SPLIT bytes. Define SHARED_UMEM_LEN_SPLIT as 64 to avoid
hardcoded length thresholds in the classifier.

Signed-off-by: Magnus Karlsson <magnus.karlsson@intel.com>
Signed-off-by: Tushar Vyavahare <tushar.vyavahare@intel.com>
---
 .../selftests/bpf/progs/xsk_xdp_progs.c       | 19 ++++++++++++++++++-
 tools/testing/selftests/bpf/xsk_xdp_common.h  |  3 ++-
 2 files changed, 20 insertions(+), 2 deletions(-)

diff --git a/tools/testing/selftests/bpf/progs/xsk_xdp_progs.c b/tools/testing/selftests/bpf/progs/xsk_xdp_progs.c
index 023d8befd4ca..543b61df3a2b 100644
--- a/tools/testing/selftests/bpf/progs/xsk_xdp_progs.c
+++ b/tools/testing/selftests/bpf/progs/xsk_xdp_progs.c
@@ -10,7 +10,7 @@
 
 struct {
 	__uint(type, BPF_MAP_TYPE_XSKMAP);
-	__uint(max_entries, 2);
+	__uint(max_entries, MAX_SOCKETS);
 	__uint(key_size, sizeof(int));
 	__uint(value_size, sizeof(int));
 } xsk SEC(".maps");
@@ -75,6 +75,23 @@ SEC("xdp") int xsk_xdp_shared_umem(struct xdp_md *xdp)
 	return bpf_redirect_map(&xsk, idx, XDP_DROP);
 }
 
+SEC("xdp") int xsk_xdp_shared_umem_length_based(struct xdp_md *xdp)
+{
+	void *data = (void *)(long)xdp->data;
+	void *data_end = (void *)(long)xdp->data_end;
+	__u32 pkt_len = data_end - data;
+
+	/* 
+	 * Route packets by total XDP-visible packet length (data_end - data):
+	 * - Socket 0: packets <= SHARED_UMEM_LEN_SPLIT bytes
+	 * - Socket 1: packets > SHARED_UMEM_LEN_SPLIT bytes
+	 */
+	if (pkt_len <= SHARED_UMEM_LEN_SPLIT)
+		return bpf_redirect_map(&xsk, 0, XDP_DROP);
+	else
+		return bpf_redirect_map(&xsk, 1, XDP_DROP);
+}
+
 SEC("xdp.frags") int xsk_xdp_adjust_tail(struct xdp_md *xdp)
 {
 	__u32 buff_len, curr_buff_len;
diff --git a/tools/testing/selftests/bpf/xsk_xdp_common.h b/tools/testing/selftests/bpf/xsk_xdp_common.h
index 45810ff552da..bd9b5dcf8c8e 100644
--- a/tools/testing/selftests/bpf/xsk_xdp_common.h
+++ b/tools/testing/selftests/bpf/xsk_xdp_common.h
@@ -3,7 +3,8 @@
 #ifndef XSK_XDP_COMMON_H_
 #define XSK_XDP_COMMON_H_
 
-#define MAX_SOCKETS 2
+#define MAX_SOCKETS 4
+#define SHARED_UMEM_LEN_SPLIT 64
 #define PKT_HDR_ALIGN (sizeof(struct ethhdr) + 2) /* Just to align the data in the packet */
 
 struct xdp_info {
-- 
2.43.0