selftests/bpf: Add tests for accessing ingress_ifindex in bpf_sk_lookup

A new field was added to the bpf_sk_lookup data that users can access.
Add tests that validate that the new ingress_ifindex field contains the
right data.
Signed-off-by: Mark Pashmfouroush <markpash@cloudflare.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Link: https://lore.kernel.org/bpf/20211110111016.5670-3-markpash@cloudflare.com

tools/testing/selftests/bpf/prog_tests/sk_lookup.c

@@ -937,6 +937,37 @@ static void test_drop_on_lookup(struct test_sk_lookup *skel)
 			.connect_to	= { EXT_IP6, EXT_PORT },
 			.listen_at	= { EXT_IP6, INT_PORT },
 		},
+		/* The program will drop on success, meaning that the ifindex
+		 * was 1.
+		 */
+		{
+			.desc		= "TCP IPv4 drop on valid ifindex",
+			.lookup_prog	= skel->progs.check_ifindex,
+			.sotype		= SOCK_STREAM,
+			.connect_to	= { EXT_IP4, EXT_PORT },
+			.listen_at	= { EXT_IP4, EXT_PORT },
+		},
+		{
+			.desc		= "TCP IPv6 drop on valid ifindex",
+			.lookup_prog	= skel->progs.check_ifindex,
+			.sotype		= SOCK_STREAM,
+			.connect_to	= { EXT_IP6, EXT_PORT },
+			.listen_at	= { EXT_IP6, EXT_PORT },
+		},
+		{
+			.desc		= "UDP IPv4 drop on valid ifindex",
+			.lookup_prog	= skel->progs.check_ifindex,
+			.sotype		= SOCK_DGRAM,
+			.connect_to	= { EXT_IP4, EXT_PORT },
+			.listen_at	= { EXT_IP4, EXT_PORT },
+		},
+		{
+			.desc		= "UDP IPv6 drop on valid ifindex",
+			.lookup_prog	= skel->progs.check_ifindex,
+			.sotype		= SOCK_DGRAM,
+			.connect_to	= { EXT_IP6, EXT_PORT },
+			.listen_at	= { EXT_IP6, EXT_PORT },
+		},
 	};
 	const struct test *t;
 

tools/testing/selftests/bpf/progs/test_sk_lookup.c

@@ -84,6 +84,14 @@ int lookup_drop(struct bpf_sk_lookup *ctx)
 	return SK_DROP;
 }
 
+SEC("sk_lookup")
+int check_ifindex(struct bpf_sk_lookup *ctx)
+{
+	if (ctx->ingress_ifindex == 1)
+		return SK_DROP;
+	return SK_PASS;
+}
+
 SEC("sk_reuseport")
 int reuseport_pass(struct sk_reuseport_md *ctx)
 {

tools/testing/selftests/bpf/verifier/ctx_sk_lookup.c

@@ -229,6 +229,24 @@
 		BPF_LDX_MEM(BPF_W, BPF_REG_0, BPF_REG_1,
 			    offsetof(struct bpf_sk_lookup, local_port)),
 
+		/* 1-byte read from ingress_ifindex field */
+		BPF_LDX_MEM(BPF_B, BPF_REG_0, BPF_REG_1,
+			    offsetof(struct bpf_sk_lookup, ingress_ifindex)),
+		BPF_LDX_MEM(BPF_B, BPF_REG_0, BPF_REG_1,
+			    offsetof(struct bpf_sk_lookup, ingress_ifindex) + 1),
+		BPF_LDX_MEM(BPF_B, BPF_REG_0, BPF_REG_1,
+			    offsetof(struct bpf_sk_lookup, ingress_ifindex) + 2),
+		BPF_LDX_MEM(BPF_B, BPF_REG_0, BPF_REG_1,
+			    offsetof(struct bpf_sk_lookup, ingress_ifindex) + 3),
+		/* 2-byte read from ingress_ifindex field */
+		BPF_LDX_MEM(BPF_H, BPF_REG_0, BPF_REG_1,
+			    offsetof(struct bpf_sk_lookup, ingress_ifindex)),
+		BPF_LDX_MEM(BPF_H, BPF_REG_0, BPF_REG_1,
+			    offsetof(struct bpf_sk_lookup, ingress_ifindex) + 2),
+		/* 4-byte read from ingress_ifindex field */
+		BPF_LDX_MEM(BPF_W, BPF_REG_0, BPF_REG_1,
+			    offsetof(struct bpf_sk_lookup, ingress_ifindex)),
+
 		/* 8-byte read from sk field */
 		BPF_LDX_MEM(BPF_DW, BPF_REG_0, BPF_REG_1,
 			    offsetof(struct bpf_sk_lookup, sk)),
@@ -351,6 +369,20 @@
 	.expected_attach_type = BPF_SK_LOOKUP,
 	.flags = F_NEEDS_EFFICIENT_UNALIGNED_ACCESS,
 },
+{
+	"invalid 8-byte read from bpf_sk_lookup ingress_ifindex field",
+	.insns = {
+		BPF_LDX_MEM(BPF_DW, BPF_REG_0, BPF_REG_1,
+			    offsetof(struct bpf_sk_lookup, ingress_ifindex)),
+		BPF_MOV32_IMM(BPF_REG_0, 0),
+		BPF_EXIT_INSN(),
+	},
+	.errstr = "invalid bpf_context access",
+	.result = REJECT,
+	.prog_type = BPF_PROG_TYPE_SK_LOOKUP,
+	.expected_attach_type = BPF_SK_LOOKUP,
+	.flags = F_NEEDS_EFFICIENT_UNALIGNED_ACCESS,
+},
 /* invalid 1,2,4-byte reads from 8-byte fields in bpf_sk_lookup */
 {
 	"invalid 4-byte read from bpf_sk_lookup sk field",