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authorLawrence Brakmo <brakmo@fb.com>2017-06-30 20:02:45 -0700
committerDavid S. Miller <davem@davemloft.net>2017-07-01 16:15:13 -0700
commitc400296bf63d234899cf2448cd3d17199676f188 (patch)
tree84d78d648f2ee14f815e27d9d34e0b19fe39f064 /samples/bpf/tcp_rwnd_kern.c
parent13d3b1ebe28762c79e981931a41914fae5d04386 (diff)
download96b-common-c400296bf63d234899cf2448cd3d17199676f188.tar.gz
bpf: Sample bpf program to set initial window
The sample bpf program, tcp_rwnd_kern.c, sets the initial advertized window to 40 packets in an environment where distinct IPv6 prefixes indicate that both hosts are not 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>
Diffstat (limited to 'samples/bpf/tcp_rwnd_kern.c')
-rw-r--r--samples/bpf/tcp_rwnd_kern.c69
1 files changed, 69 insertions, 0 deletions
diff --git a/samples/bpf/tcp_rwnd_kern.c b/samples/bpf/tcp_rwnd_kern.c
new file mode 100644
index 000000000000..3f2a228f81ce
--- /dev/null
+++ b/samples/bpf/tcp_rwnd_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 initial receive window to 40 packets when using IPv6
+ * and the first 5.5 bytes of the IPv6 addresses are not the same (in this
+ * example that means both hosts are not 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_rwnd(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 RWND_INIT operation and IPv6 addresses */
+ if (op == BPF_SOCK_OPS_RWND_INIT &&
+ skops->family == AF_INET6) {
+
+ /* If the first 5.5 bytes of the IPv6 address are not the same
+ * then both hosts are not in the same datacenter
+ * so use a larger initial advertized window (40 packets)
+ */
+ if (skops->local_ip6[0] != skops->remote_ip6[0] ||
+ (bpf_ntohl(skops->local_ip6[1]) & 0xfffff000) !=
+ (bpf_ntohl(skops->remote_ip6[1]) & 0xfffff000))
+ rv = 40;
+ }
+#ifdef DEBUG
+ bpf_printk("Returning %d\n", rv);
+#endif
+ skops->reply = rv;
+ return 1;
+}
+char _license[] SEC("license") = "GPL";