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// SPDX-License-Identifier: GPL-2.0
/* Copyright (c) 2021 Facebook */
#include <string.h>
#include <linux/tcp.h>
#include <netinet/in.h>
#include <linux/bpf.h>
#include <bpf/bpf_helpers.h>
#include "bpf_tcp_helpers.h"
char _license[] SEC("license") = "GPL";
__s32 page_size = 0;
SEC("cgroup/setsockopt")
int sockopt_qos_to_cc(struct bpf_sockopt *ctx)
{
void *optval_end = ctx->optval_end;
int *optval = ctx->optval;
char buf[TCP_CA_NAME_MAX];
char cc_reno[TCP_CA_NAME_MAX] = "reno";
char cc_cubic[TCP_CA_NAME_MAX] = "cubic";
if (ctx->level != SOL_IPV6 || ctx->optname != IPV6_TCLASS)
goto out;
if (optval + 1 > optval_end)
return 0; /* EPERM, bounds check */
if (bpf_getsockopt(ctx->sk, SOL_TCP, TCP_CONGESTION, &buf, sizeof(buf)))
return 0;
if (!tcp_cc_eq(buf, cc_cubic))
return 0;
if (*optval == 0x2d) {
if (bpf_setsockopt(ctx->sk, SOL_TCP, TCP_CONGESTION, &cc_reno,
sizeof(cc_reno)))
return 0;
}
return 1;
out:
/* optval larger than PAGE_SIZE use kernel's buffer. */
if (ctx->optlen > page_size)
ctx->optlen = 0;
return 1;
}
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