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// SPDX-License-Identifier: GPL-2.0
// Copyright (c) 2018 Facebook
#include <string.h>
#include <linux/stddef.h>
#include <linux/bpf.h>
#include <linux/in.h>
#include <linux/in6.h>
#include <sys/socket.h>
#include <netinet/tcp.h>
#include <bpf/bpf_helpers.h>
#include <bpf/bpf_endian.h>
#define SRC_REWRITE_IP4 0x7f000004U
#define DST_REWRITE_IP4 0x7f000001U
#define DST_REWRITE_PORT4 4444
#ifndef TCP_CA_NAME_MAX
#define TCP_CA_NAME_MAX 16
#endif
int _version SEC("version") = 1;
__attribute__ ((noinline))
int do_bind(struct bpf_sock_addr *ctx)
{
struct sockaddr_in sa = {};
sa.sin_family = AF_INET;
sa.sin_port = bpf_htons(0);
sa.sin_addr.s_addr = bpf_htonl(SRC_REWRITE_IP4);
if (bpf_bind(ctx, (struct sockaddr *)&sa, sizeof(sa)) != 0)
return 0;
return 1;
}
static __inline int verify_cc(struct bpf_sock_addr *ctx,
char expected[TCP_CA_NAME_MAX])
{
char buf[TCP_CA_NAME_MAX];
int i;
if (bpf_getsockopt(ctx, SOL_TCP, TCP_CONGESTION, &buf, sizeof(buf)))
return 1;
for (i = 0; i < TCP_CA_NAME_MAX; i++) {
if (buf[i] != expected[i])
return 1;
if (buf[i] == 0)
break;
}
return 0;
}
static __inline int set_cc(struct bpf_sock_addr *ctx)
{
char reno[TCP_CA_NAME_MAX] = "reno";
char cubic[TCP_CA_NAME_MAX] = "cubic";
if (bpf_setsockopt(ctx, SOL_TCP, TCP_CONGESTION, &reno, sizeof(reno)))
return 1;
if (verify_cc(ctx, reno))
return 1;
if (bpf_setsockopt(ctx, SOL_TCP, TCP_CONGESTION, &cubic, sizeof(cubic)))
return 1;
if (verify_cc(ctx, cubic))
return 1;
return 0;
}
SEC("cgroup/connect4")
int connect_v4_prog(struct bpf_sock_addr *ctx)
{
struct bpf_sock_tuple tuple = {};
struct bpf_sock *sk;
/* Verify that new destination is available. */
memset(&tuple.ipv4.saddr, 0, sizeof(tuple.ipv4.saddr));
memset(&tuple.ipv4.sport, 0, sizeof(tuple.ipv4.sport));
tuple.ipv4.daddr = bpf_htonl(DST_REWRITE_IP4);
tuple.ipv4.dport = bpf_htons(DST_REWRITE_PORT4);
if (ctx->type != SOCK_STREAM && ctx->type != SOCK_DGRAM)
return 0;
else if (ctx->type == SOCK_STREAM)
sk = bpf_sk_lookup_tcp(ctx, &tuple, sizeof(tuple.ipv4),
BPF_F_CURRENT_NETNS, 0);
else
sk = bpf_sk_lookup_udp(ctx, &tuple, sizeof(tuple.ipv4),
BPF_F_CURRENT_NETNS, 0);
if (!sk)
return 0;
if (sk->src_ip4 != tuple.ipv4.daddr ||
sk->src_port != DST_REWRITE_PORT4) {
bpf_sk_release(sk);
return 0;
}
bpf_sk_release(sk);
/* Rewrite congestion control. */
if (ctx->type == SOCK_STREAM && set_cc(ctx))
return 0;
/* Rewrite destination. */
ctx->user_ip4 = bpf_htonl(DST_REWRITE_IP4);
ctx->user_port = bpf_htons(DST_REWRITE_PORT4);
return do_bind(ctx) ? 1 : 0;
}
char _license[] SEC("license") = "GPL";
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