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bpf: add TCP_SAVE_SYN/TCP_SAVED_SYN sample program

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Sample program which shows TCP_SAVE_SYN/TCP_SAVED_SYN usage example:
bpf program which is doing TOS/TCLASS reflection (server would reply
with a same TOS/TCLASS as client).

Signed-off-by: Nikita V. Shirokov <tehnerd@fb.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
This commit is contained in:
Nikita V. Shirokov 2018-08-30 07:51:54 -07:00 committed by Daniel Borkmann
parent 1e215300f1
commit acb4ea9564
2 changed files with 88 additions and 0 deletions
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1
samples/bpf/Makefile
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@ -153,6 +153,7 @@ always += tcp_cong_kern.o
always += tcp_iw_kern.o
always += tcp_clamp_kern.o
always += tcp_basertt_kern.o
always += tcp_tos_reflect_kern.o
always += xdp_redirect_kern.o
always += xdp_redirect_map_kern.o
always += xdp_redirect_cpu_kern.o

87
samples/bpf/tcp_tos_reflect_kern.c Normal file
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@ -0,0 +1,87 @@
// SPDX-License-Identifier: GPL-2.0
/*
* Copyright (c) 2018 Facebook
*
* BPF program to automatically reflect TOS option from received syn packet
*
* Use load_sock_ops to load this BPF program.
*/
#include <uapi/linux/bpf.h>
#include <uapi/linux/tcp.h>
#include <uapi/linux/if_ether.h>
#include <uapi/linux/if_packet.h>
#include <uapi/linux/ip.h>
#include <uapi/linux/ipv6.h>
#include <uapi/linux/in.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_basertt(struct bpf_sock_ops *skops)
{
char header[sizeof(struct ipv6hdr)];
struct ipv6hdr *hdr6;
struct iphdr *hdr;
int hdr_size = 0;
int save_syn = 1;
int tos = 0;
int rv = 0;
int op;
op = (int) skops->op;
#ifdef DEBUG
bpf_printk("BPF command: %d\n", op);
#endif
switch (op) {
case BPF_SOCK_OPS_TCP_LISTEN_CB:
rv = bpf_setsockopt(skops, SOL_TCP, TCP_SAVE_SYN,
&save_syn, sizeof(save_syn));
break;
case BPF_SOCK_OPS_PASSIVE_ESTABLISHED_CB:
if (skops->family == AF_INET)
hdr_size = sizeof(struct iphdr);
else
hdr_size = sizeof(struct ipv6hdr);
rv = bpf_getsockopt(skops, SOL_TCP, TCP_SAVED_SYN,
header, hdr_size);
if (!rv) {
if (skops->family == AF_INET) {
hdr = (struct iphdr *) header;
tos = hdr->tos;
if (tos != 0)
bpf_setsockopt(skops, SOL_IP, IP_TOS,
&tos, sizeof(tos));
} else {
hdr6 = (struct ipv6hdr *) header;
tos = ((hdr6->priority) << 4 |
(hdr6->flow_lbl[0]) >> 4);
if (tos)
bpf_setsockopt(skops, SOL_IPV6,
IPV6_TCLASS,
&tos, sizeof(tos));
}
rv = 0;
}
break;
default:
rv = -1;
}
#ifdef DEBUG
bpf_printk("Returning %d\n", rv);
#endif
skops->reply = rv;
return 1;
}
char _license[] SEC("license") = "GPL";