bpf: add XDP prog type for early driver filter

Add a new bpf prog type that is intended to run in early stages of the
packet rx path. Only minimal packet metadata will be available, hence a
new context type, struct xdp_md, is exposed to userspace. So far only
expose the packet start and end pointers, and only in read mode.

An XDP program must return one of the well known enum values, all other
return codes are reserved for future use. Unfortunately, this
restriction is hard to enforce at verification time, so take the
approach of warning at runtime when such programs are encountered. Out
of bounds return codes should alias to XDP_ABORTED.

Signed-off-by: Brenden Blanco <bblanco@plumgrid.com>
Acked-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

2 files changed, 38 insertions, 0 deletions

diff --git a/include/linux/filter.h b/include/linux/filter.h
index 6fc31ef1da2d..15d816a8b755 100644
--- a/include/linux/filter.h
+++ b/include/linux/filter.h
@@ -368,6 +368,11 @@ struct bpf_skb_data_end {
 	void *data_end;
 };
 
+struct xdp_buff {
+	void *data;
+	void *data_end;
+};
+
 /* compute the linear packet data range [data, data_end) which
  * will be accessed by cls_bpf and act_bpf programs
  */
@@ -429,6 +434,18 @@ static inline u32 bpf_prog_run_clear_cb(const struct bpf_prog *prog,
 	return BPF_PROG_RUN(prog, skb);
 }
 
+static inline u32 bpf_prog_run_xdp(const struct bpf_prog *prog,
+				   struct xdp_buff *xdp)
+{
+	u32 ret;
+
+	rcu_read_lock();
+	ret = BPF_PROG_RUN(prog, (void *)xdp);
+	rcu_read_unlock();
+
+	return ret;
+}
+
 static inline unsigned int bpf_prog_size(unsigned int proglen)
 {
 	return max(sizeof(struct bpf_prog),
@@ -509,6 +526,7 @@ bool bpf_helper_changes_skb_data(void *func);
 
 struct bpf_prog *bpf_patch_insn_single(struct bpf_prog *prog, u32 off,
 				       const struct bpf_insn *patch, u32 len);
+void bpf_warn_invalid_xdp_action(u32 act);
 
 #ifdef CONFIG_BPF_JIT
 extern int bpf_jit_enable;
diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h
index c4d922439d20..a51786566c2f 100644
--- a/include/uapi/linux/bpf.h
+++ b/include/uapi/linux/bpf.h
@@ -94,6 +94,7 @@ enum bpf_prog_type {
 	BPF_PROG_TYPE_SCHED_CLS,
 	BPF_PROG_TYPE_SCHED_ACT,
 	BPF_PROG_TYPE_TRACEPOINT,
+	BPF_PROG_TYPE_XDP,
 };
 
 #define BPF_PSEUDO_MAP_FD	1
@@ -439,4 +440,23 @@ struct bpf_tunnel_key {
 	__u32 tunnel_label;
 };
 
+/* User return codes for XDP prog type.
+ * A valid XDP program must return one of these defined values. All other
+ * return codes are reserved for future use. Unknown return codes will result
+ * in packet drop.
+ */
+enum xdp_action {
+	XDP_ABORTED = 0,
+	XDP_DROP,
+	XDP_PASS,
+};
+
+/* user accessible metadata for XDP packet hook
+ * new fields must be added to the end of this structure
+ */
+struct xdp_md {
+	__u32 data;
+	__u32 data_end;
+};
+
 #endif /* _UAPI__LINUX_BPF_H__ */