netdev - [PATCH RFC net-next 3/3] bpf: Added a sample for tcp_info

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Date:   Mon, 22 Oct 2018 08:24:00 -0700
From:   Sowmini Varadhan <sowmini.varadhan@...cle.com>
To:     sowmini.varadhan@...cle.com, netdev@...r.kernel.org
Cc:     edumazet@...gle.com, brakmo@...com
Subject: [PATCH RFC net-next 3/3] bpf: Added a sample for tcp_info_notify callback

Simple Proof-Of-Concept test program for BPF_TCP_INFO_NOTIFY
(will move this to testing/selftests/net later)

Signed-off-by: Sowmini Varadhan <sowmini.varadhan@...cle.com>
---
 samples/bpf/Makefile          |    1 +
 samples/bpf/tcp_notify_kern.c |   73 +++++++++++++++++++++++++++++++++++++++++
 2 files changed, 74 insertions(+), 0 deletions(-)
 create mode 100644 samples/bpf/tcp_notify_kern.c

diff --git a/samples/bpf/Makefile b/samples/bpf/Makefile
index be0a961..d937bd2 100644
--- a/samples/bpf/Makefile
+++ b/samples/bpf/Makefile
@@ -152,6 +152,7 @@ always += tcp_bufs_kern.o
 always += tcp_cong_kern.o
 always += tcp_iw_kern.o
 always += tcp_clamp_kern.o
+always += tcp_notify_kern.o
 always += tcp_basertt_kern.o
 always += tcp_tos_reflect_kern.o
 always += xdp_redirect_kern.o
diff --git a/samples/bpf/tcp_notify_kern.c b/samples/bpf/tcp_notify_kern.c
new file mode 100644
index 0000000..bc4efd8
--- /dev/null
+++ b/samples/bpf/tcp_notify_kern.c
@@ -0,0 +1,73 @@
+/* Sample BPF program to demonstrate how to triger async tcp_info
+ * notification based on thresholds determeined in the filter.
+ * The example here will trigger notification if  skops->total_retrans > 16
+ *
+ * Use load_sock_ops to load this BPF program.
+ */
+
+#include <uapi/linux/bpf.h>
+#include <uapi/linux/if_ether.h>
+#include <uapi/linux/if_packet.h>
+#include <uapi/linux/ip.h>
+#include <linux/socket.h>
+#include "bpf_helpers.h"
+#include "bpf_endian.h"
+
+#define DEBUG 0
+
+#define bpf_printk(fmt, ...)					\
+({								\
+	       char ____fmt[] = fmt;				\
+	       bpf_trace_printk(____fmt, sizeof(____fmt),	\
+				##__VA_ARGS__);			\
+})
+
+SEC("sockops")
+int bpf_tcp_info_notify(struct bpf_sock_ops *skops)
+{
+	int bufsize = 150000;
+	int to_init = 10;
+	int clamp = 100;
+	int rv = 0;
+	int op;
+
+	/* For testing purposes, only execute rest of BPF program
+	 * if neither port numberis 5001 (default iperf port)
+	 */
+	if (bpf_ntohl(skops->remote_port) != 5001 &&
+	    skops->local_port != 5001) {
+		skops->reply = -1;
+		return 0;
+	}
+
+	op = (int) skops->op;
+
+#ifdef DEBUG
+	bpf_printk("BPF command: %d\n", op);
+#endif
+
+	switch (op) {
+	case BPF_SOCK_OPS_ACTIVE_ESTABLISHED_CB:
+	case BPF_SOCK_OPS_PASSIVE_ESTABLISHED_CB:
+		bpf_sock_ops_cb_flags_set(skops,
+			(BPF_SOCK_OPS_RETRANS_CB_FLAG|
+			BPF_SOCK_OPS_RTO_CB_FLAG));
+		rv = 1;
+		break;
+	case BPF_SOCK_OPS_RETRANS_CB:
+	case BPF_SOCK_OPS_RTO_CB:
+		if (skops->total_retrans < 16)
+			rv = 1; /* skip */
+		else
+			rv = BPF_TCP_INFO_NOTIFY;
+		break;
+	default:
+		rv = -1;
+	}
+#ifdef DEBUG
+	bpf_printk("Returning %d\n", rv);
+#endif
+	skops->reply = rv;
+	return 1;
+}
+char _license[] SEC("license") = "GPL";
-- 
1.7.1