flow_dissector: implements flow dissector BPF hook

Adds a hook for programs of type BPF_PROG_TYPE_FLOW_DISSECTOR and
attach type BPF_FLOW_DISSECTOR that is executed in the flow dissector
path. The BPF program is per-network namespace.

Signed-off-by: Petar Penkov <ppenkov@google.com>
Signed-off-by: Willem de Bruijn <willemb@google.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

1 files changed, 70 insertions, 0 deletions

diff --git a/net/core/filter.c b/net/core/filter.c
index bf5b6efd369a..9cc76f134ddb 100644
--- a/net/core/filter.c
+++ b/net/core/filter.c
@@ -5124,6 +5124,17 @@ sk_skb_func_proto(enum bpf_func_id func_id, const struct bpf_prog *prog)
 }
 
 static const struct bpf_func_proto *
+flow_dissector_func_proto(enum bpf_func_id func_id, const struct bpf_prog *prog)
+{
+	switch (func_id) {
+	case BPF_FUNC_skb_load_bytes:
+		return &bpf_skb_load_bytes_proto;
+	default:
+		return bpf_base_func_proto(func_id);
+	}
+}
+
+static const struct bpf_func_proto *
 lwt_out_func_proto(enum bpf_func_id func_id, const struct bpf_prog *prog)
 {
 	switch (func_id) {
@@ -5241,6 +5252,10 @@ static bool bpf_skb_is_valid_access(int off, int size, enum bpf_access_type type
 		if (size != size_default)
 			return false;
 		break;
+	case bpf_ctx_range(struct __sk_buff, flow_keys):
+		if (size != sizeof(struct bpf_flow_keys *))
+			return false;
+		break;
 	default:
 		/* Only narrow read access allowed for now. */
 		if (type == BPF_WRITE) {
@@ -5266,6 +5281,7 @@ static bool sk_filter_is_valid_access(int off, int size,
 	case bpf_ctx_range(struct __sk_buff, data):
 	case bpf_ctx_range(struct __sk_buff, data_meta):
 	case bpf_ctx_range(struct __sk_buff, data_end):
+	case bpf_ctx_range(struct __sk_buff, flow_keys):
 	case bpf_ctx_range_till(struct __sk_buff, family, local_port):
 		return false;
 	}
@@ -5291,6 +5307,7 @@ static bool lwt_is_valid_access(int off, int size,
 	case bpf_ctx_range(struct __sk_buff, tc_classid):
 	case bpf_ctx_range_till(struct __sk_buff, family, local_port):
 	case bpf_ctx_range(struct __sk_buff, data_meta):
+	case bpf_ctx_range(struct __sk_buff, flow_keys):
 		return false;
 	}
 
@@ -5501,6 +5518,7 @@ static bool tc_cls_act_is_valid_access(int off, int size,
 	case bpf_ctx_range(struct __sk_buff, data_end):
 		info->reg_type = PTR_TO_PACKET_END;
 		break;
+	case bpf_ctx_range(struct __sk_buff, flow_keys):
 	case bpf_ctx_range_till(struct __sk_buff, family, local_port):
 		return false;
 	}
@@ -5702,6 +5720,7 @@ static bool sk_skb_is_valid_access(int off, int size,
 	switch (off) {
 	case bpf_ctx_range(struct __sk_buff, tc_classid):
 	case bpf_ctx_range(struct __sk_buff, data_meta):
+	case bpf_ctx_range(struct __sk_buff, flow_keys):
 		return false;
 	}
 
@@ -5761,6 +5780,39 @@ static bool sk_msg_is_valid_access(int off, int size,
 	return true;
 }
 
+static bool flow_dissector_is_valid_access(int off, int size,
+					   enum bpf_access_type type,
+					   const struct bpf_prog *prog,
+					   struct bpf_insn_access_aux *info)
+{
+	if (type == BPF_WRITE) {
+		switch (off) {
+		case bpf_ctx_range_till(struct __sk_buff, cb[0], cb[4]):
+			break;
+		default:
+			return false;
+		}
+	}
+
+	switch (off) {
+	case bpf_ctx_range(struct __sk_buff, data):
+		info->reg_type = PTR_TO_PACKET;
+		break;
+	case bpf_ctx_range(struct __sk_buff, data_end):
+		info->reg_type = PTR_TO_PACKET_END;
+		break;
+	case bpf_ctx_range(struct __sk_buff, flow_keys):
+		info->reg_type = PTR_TO_FLOW_KEYS;
+		break;
+	case bpf_ctx_range(struct __sk_buff, tc_classid):
+	case bpf_ctx_range(struct __sk_buff, data_meta):
+	case bpf_ctx_range_till(struct __sk_buff, family, local_port):
+		return false;
+	}
+
+	return bpf_skb_is_valid_access(off, size, type, prog, info);
+}
+
 static u32 bpf_convert_ctx_access(enum bpf_access_type type,
 				  const struct bpf_insn *si,
 				  struct bpf_insn *insn_buf,
@@ -6055,6 +6107,15 @@ static u32 bpf_convert_ctx_access(enum bpf_access_type type,
 				      bpf_target_off(struct sock_common,
 						     skc_num, 2, target_size));
 		break;
+
+	case offsetof(struct __sk_buff, flow_keys):
+		off  = si->off;
+		off -= offsetof(struct __sk_buff, flow_keys);
+		off += offsetof(struct sk_buff, cb);
+		off += offsetof(struct qdisc_skb_cb, flow_keys);
+		*insn++ = BPF_LDX_MEM(BPF_SIZEOF(void *), si->dst_reg,
+				      si->src_reg, off);
+		break;
 	}
 
 	return insn - insn_buf;
@@ -7018,6 +7079,15 @@ const struct bpf_verifier_ops sk_msg_verifier_ops = {
 const struct bpf_prog_ops sk_msg_prog_ops = {
 };
 
+const struct bpf_verifier_ops flow_dissector_verifier_ops = {
+	.get_func_proto		= flow_dissector_func_proto,
+	.is_valid_access	= flow_dissector_is_valid_access,
+	.convert_ctx_access	= bpf_convert_ctx_access,
+};
+
+const struct bpf_prog_ops flow_dissector_prog_ops = {
+};
+
 int sk_detach_filter(struct sock *sk)
 {
 	int ret = -ENOENT;