[PATCH bpf-next] bpf: Export rx queue info for reuseport ebpf prog

[Joe Damato <jdamato@fastly.com>]

BPF_PROG_TYPE_SK_REUSEPORT / sk_reuseport ebpf programs do not have
access to the queue_mapping or napi_id of the incoming skb. Having
this information can help ebpf progs determine which listen socket to
select.

This patch exposes both queue_mapping and napi_id so that
sk_reuseport ebpf programs can use this information to direct incoming
connections to the correct listen socket in the SOCKMAP.

For example:

A multi-threaded userland program with several threads accepting client
connections via a reuseport listen socket group might want to direct
incoming connections from specific receive queues (or NAPI IDs) to specific
listen sockets to maximize locality or for use with epoll busy-poll.

Signed-off-by: Joe Damato <jdamato@fastly.com>
---
 include/uapi/linux/bpf.h |  2 ++
 net/core/filter.c        | 10 ++++++++++
 2 files changed, 12 insertions(+)

diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h
index 9273c654743c..31560b506535 100644
--- a/include/uapi/linux/bpf.h
+++ b/include/uapi/linux/bpf.h
@@ -6286,6 +6286,8 @@ struct sk_reuseport_md {
 	 */
 	__u32 eth_protocol;
 	__u32 ip_protocol;	/* IP protocol. e.g. IPPROTO_TCP, IPPROTO_UDP */
+	__u32 rx_queue_mapping; /* Rx queue associated with the skb */
+	__u32 napi_id;          /* napi id associated with the skb */
 	__u32 bind_inany;	/* Is sock bound to an INANY address? */
 	__u32 hash;		/* A hash of the packet 4 tuples */
 	/* When reuse->migrating_sk is NULL, it is selecting a sk for the
diff --git a/net/core/filter.c b/net/core/filter.c
index 968139f4a1ac..71826e1ef7dc 100644
--- a/net/core/filter.c
+++ b/net/core/filter.c
@@ -11134,6 +11134,8 @@ sk_reuseport_is_valid_access(int off, int size,
 	case bpf_ctx_range(struct sk_reuseport_md, ip_protocol):
 	case bpf_ctx_range(struct sk_reuseport_md, bind_inany):
 	case bpf_ctx_range(struct sk_reuseport_md, len):
+	case bpf_ctx_range(struct sk_reuseport_md, rx_queue_mapping):
+	case bpf_ctx_range(struct sk_reuseport_md, napi_id):
 		bpf_ctx_record_field_size(info, size_default);
 		return bpf_ctx_narrow_access_ok(off, size, size_default);
 
@@ -11183,6 +11185,14 @@ static u32 sk_reuseport_convert_ctx_access(enum bpf_access_type type,
 		SK_REUSEPORT_LOAD_SKB_FIELD(protocol);
 		break;
 
+	case offsetof(struct sk_reuseport_md, rx_queue_mapping):
+		SK_REUSEPORT_LOAD_SKB_FIELD(queue_mapping);
+		break;
+
+	case offsetof(struct sk_reuseport_md, napi_id):
+		SK_REUSEPORT_LOAD_SKB_FIELD(napi_id);
+		break;
+
 	case offsetof(struct sk_reuseport_md, ip_protocol):
 		SK_REUSEPORT_LOAD_SK_FIELD(sk_protocol);
 		break;
-- 
2.25.1