netdev - [PATCH bpf 05/11] bpf: Adds field bpf_sock_ops_flags to tcp

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Message-ID: <20171219062200.372711-6-brakmo@fb.com>
Date:   Mon, 18 Dec 2017 22:21:54 -0800
From:   Lawrence Brakmo <brakmo@...com>
To:     netdev <netdev@...r.kernel.org>
CC:     Kernel Team <kernel-team@...com>, Blake Matheny <bmatheny@...com>,
        "Alexei Starovoitov" <ast@...com>,
        Daniel Borkmann <daniel@...earbox.net>
Subject: [PATCH bpf 05/11] bpf: Adds field bpf_sock_ops_flags to tcp_sock

Adds field bpf_sock_ops_flags to tcp_sock and bpf_sock_ops. Its primary
use is to determine if there should be calls to sock_ops bpf program at
various points in the TCP code. The field is initialized to zero,
disabling the calls. A sock_ops BPF program can set, per connection and
as necessary, when the connection is established.

It also adds support for reading and writting the field within a
sock_ops BPF program.

Examples of where to call the bpf program:

1) When RTO fires
2) When a packet is retransmitted
3) When the connection terminates
4) When a packet is sent
5) When a packet is received

Signed-off-by: Lawrence Brakmo <brakmo@...com>
---
 include/linux/tcp.h      | 8 ++++++++
 include/uapi/linux/bpf.h | 1 +
 net/core/filter.c        | 6 ++++++
 3 files changed, 15 insertions(+)

diff --git a/include/linux/tcp.h b/include/linux/tcp.h
index df5d97a..c46553f 100644
--- a/include/linux/tcp.h
+++ b/include/linux/tcp.h
@@ -372,6 +372,14 @@ struct tcp_sock {
 	 */
 	struct request_sock *fastopen_rsk;
 	u32	*saved_syn;
+
+/* Sock_ops bpf program related variables */
+#ifdef CONFIG_BPF
+	u32     bpf_sock_ops_flags;     /* values defined in uapi/linux/tcp.h */
+#define BPF_SOCK_OPS_TEST_FLAG(TP, ARG) (TP->bpf_sock_ops_flags & ARG)
+#else
+#define BPF_SOCK_OPS_TEST_FLAG(TP, ARG) 0
+#endif
 };
 
 enum tsq_enum {
diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h
index addd849..dfbf43a 100644
--- a/include/uapi/linux/bpf.h
+++ b/include/uapi/linux/bpf.h
@@ -953,6 +953,7 @@ struct bpf_sock_ops {
 				 */
 	__u32 snd_cwnd;
 	__u32 srtt_us;		/* Averaged RTT << 3 in usecs */
+	__u32 bpf_sock_ops_flags; /* flags defined in uapi/linux/tcp.h */
 };
 
 /* List of known BPF sock_ops operators.
diff --git a/net/core/filter.c b/net/core/filter.c
index 97e65df..2692514 100644
--- a/net/core/filter.c
+++ b/net/core/filter.c
@@ -3842,6 +3842,7 @@ static bool sock_ops_is_valid_access(int off, int size,
 		switch (off) {
 		case offsetof(struct bpf_sock_ops, op) ...
 		     offsetof(struct bpf_sock_ops, replylong[3]):
+		case offsetof(struct bpf_sock_ops, bpf_sock_ops_flags):
 			break;
 		default:
 			return false;
@@ -4522,6 +4523,11 @@ static u32 sock_ops_convert_ctx_access(enum bpf_access_type type,
 	case offsetof(struct bpf_sock_ops, srtt_us):
 		SOCK_OPS_GET_FIELD(srtt_us, struct tcp_sock);
 		break;
+
+	case offsetof(struct bpf_sock_ops, bpf_sock_ops_flags):
+		SOCK_OPS_GET_OR_SET_FIELD(bpf_sock_ops_flags, struct tcp_sock,
+					  type);
+		break;
 	}
 	return insn - insn_buf;
 }
-- 
2.9.5