bpf: Allow bpf_map_lookup_elem() on an xskmap

Currently, the AF_XDP code uses a separate map in order to
determine if an xsk is bound to a queue.  Instead of doing this,
have bpf_map_lookup_elem() return a xdp_sock.

Rearrange some xdp_sock members to eliminate structure holes.

Remove selftest - will be added back in later patch.

Signed-off-by: Jonathan Lemon <jonathan.lemon@gmail.com>
Acked-by: Martin KaFai Lau <kafai@fb.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

1 files changed, 40 insertions, 0 deletions

diff --git a/net/core/filter.c b/net/core/filter.c
index f2777dc0b624..a5e4ac7fcbe5 100644
--- a/net/core/filter.c
+++ b/net/core/filter.c
@@ -5680,6 +5680,46 @@ BPF_CALL_1(bpf_skb_ecn_set_ce, struct sk_buff *, skb)
 	return INET_ECN_set_ce(skb);
 }
 
+bool bpf_xdp_sock_is_valid_access(int off, int size, enum bpf_access_type type,
+				  struct bpf_insn_access_aux *info)
+{
+	if (off < 0 || off >= offsetofend(struct bpf_xdp_sock, queue_id))
+		return false;
+
+	if (off % size != 0)
+		return false;
+
+	switch (off) {
+	default:
+		return size == sizeof(__u32);
+	}
+}
+
+u32 bpf_xdp_sock_convert_ctx_access(enum bpf_access_type type,
+				    const struct bpf_insn *si,
+				    struct bpf_insn *insn_buf,
+				    struct bpf_prog *prog, u32 *target_size)
+{
+	struct bpf_insn *insn = insn_buf;
+
+#define BPF_XDP_SOCK_GET(FIELD)						\
+	do {								\
+		BUILD_BUG_ON(FIELD_SIZEOF(struct xdp_sock, FIELD) >	\
+			     FIELD_SIZEOF(struct bpf_xdp_sock, FIELD));	\
+		*insn++ = BPF_LDX_MEM(BPF_FIELD_SIZEOF(struct xdp_sock, FIELD),\
+				      si->dst_reg, si->src_reg,		\
+				      offsetof(struct xdp_sock, FIELD)); \
+	} while (0)
+
+	switch (si->off) {
+	case offsetof(struct bpf_xdp_sock, queue_id):
+		BPF_XDP_SOCK_GET(queue_id);
+		break;
+	}
+
+	return insn - insn_buf;
+}
+
 static const struct bpf_func_proto bpf_skb_ecn_set_ce_proto = {
 	.func           = bpf_skb_ecn_set_ce,
 	.gpl_only       = false,