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authorLawrence Brakmo <brakmo@fb.com>2017-06-30 20:02:43 -0700
committerDavid S. Miller <davem@davemloft.net>2017-07-01 16:15:13 -0700
commit61bc4d8daa7af018d7ea084ea38648828a5a90d5 (patch)
treedbf9fe12d50f65750e82e921831118cd02535ea8
parent8550f328f45db6d37981eb2041bc465810245c03 (diff)
download96b-common-61bc4d8daa7af018d7ea084ea38648828a5a90d5.tar.gz
bpf: Sample bpf program to set SYN/SYN-ACK RTOs
The sample BPF program, tcp_synrto_kern.c, sets the SYN and SYN-ACK RTOs to 10ms when both hosts are within the same datacenter (i.e. small RTTs) in an environment where common IPv6 prefixes indicate both hosts are in the same data center. Signed-off-by: Lawrence Brakmo <brakmo@fb.com> Acked-by: Daniel Borkmann <daniel@iogearbox.net> Signed-off-by: David S. Miller <davem@davemloft.net>
-rw-r--r--samples/bpf/Makefile1
-rw-r--r--samples/bpf/tcp_synrto_kern.c69
2 files changed, 70 insertions, 0 deletions
diff --git a/samples/bpf/Makefile b/samples/bpf/Makefile
index 015589b50c37..e29370a19957 100644
--- a/samples/bpf/Makefile
+++ b/samples/bpf/Makefile
@@ -113,6 +113,7 @@ always += lwt_len_hist_kern.o
always += xdp_tx_iptunnel_kern.o
always += test_map_in_map_kern.o
always += cookie_uid_helper_example.o
+always += tcp_synrto_kern.o
HOSTCFLAGS += -I$(objtree)/usr/include
HOSTCFLAGS += -I$(srctree)/tools/lib/
diff --git a/samples/bpf/tcp_synrto_kern.c b/samples/bpf/tcp_synrto_kern.c
new file mode 100644
index 000000000000..3c3fc83d81cb
--- /dev/null
+++ b/samples/bpf/tcp_synrto_kern.c
@@ -0,0 +1,69 @@
+/* Copyright (c) 2017 Facebook
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of version 2 of the GNU General Public
+ * License as published by the Free Software Foundation.
+ *
+ * BPF program to set SYN and SYN-ACK RTOs to 10ms when using IPv6 addresses
+ * and the first 5.5 bytes of the IPv6 addresses are the same (in this example
+ * that means both hosts are in the same datacenter).
+ *
+ * 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 1
+
+#define bpf_printk(fmt, ...) \
+({ \
+ char ____fmt[] = fmt; \
+ bpf_trace_printk(____fmt, sizeof(____fmt), \
+ ##__VA_ARGS__); \
+})
+
+SEC("sockops")
+int bpf_synrto(struct bpf_sock_ops *skops)
+{
+ int rv = -1;
+ int op;
+
+ /* For testing purposes, only execute rest of BPF program
+ * if neither port numberis 55601
+ */
+ if (bpf_ntohl(skops->remote_port) != 55601 &&
+ skops->local_port != 55601)
+ return -1;
+
+ op = (int) skops->op;
+
+#ifdef DEBUG
+ bpf_printk("BPF command: %d\n", op);
+#endif
+
+ /* Check for TIMEOUT_INIT operation and IPv6 addresses */
+ if (op == BPF_SOCK_OPS_TIMEOUT_INIT &&
+ skops->family == AF_INET6) {
+
+ /* If the first 5.5 bytes of the IPv6 address are the same
+ * then both hosts are in the same datacenter
+ * so use an RTO of 10ms
+ */
+ if (skops->local_ip6[0] == skops->remote_ip6[0] &&
+ (bpf_ntohl(skops->local_ip6[1]) & 0xfff00000) ==
+ (bpf_ntohl(skops->remote_ip6[1]) & 0xfff00000))
+ rv = 10;
+ }
+#ifdef DEBUG
+ bpf_printk("Returning %d\n", rv);
+#endif
+ skops->reply = rv;
+ return 1;
+}
+char _license[] SEC("license") = "GPL";