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// SPDX-License-Identifier: GPL-2.0
#include <netinet/in.h>
#include <linux/bpf.h>
#include <bpf/bpf_helpers.h>
char _license[] SEC("license") = "GPL";
__u32 page_size = 0;
SEC("cgroup/getsockopt")
int _getsockopt_child(struct bpf_sockopt *ctx)
{
__u8 *optval_end = ctx->optval_end;
__u8 *optval = ctx->optval;
if (ctx->level != SOL_IP || ctx->optname != IP_TOS)
goto out;
if (optval + 1 > optval_end)
return 0; /* EPERM, bounds check */
if (optval[0] != 0x80)
return 0; /* EPERM, unexpected optval from the kernel */
ctx->retval = 0; /* Reset system call return value to zero */
optval[0] = 0x90;
ctx->optlen = 1;
return 1;
out:
/* optval larger than PAGE_SIZE use kernel's buffer. */
if (ctx->optlen > page_size)
ctx->optlen = 0;
return 1;
}
SEC("cgroup/getsockopt")
int _getsockopt_parent(struct bpf_sockopt *ctx)
{
__u8 *optval_end = ctx->optval_end;
__u8 *optval = ctx->optval;
if (ctx->level != SOL_IP || ctx->optname != IP_TOS)
goto out;
if (optval + 1 > optval_end)
return 0; /* EPERM, bounds check */
if (optval[0] != 0x90)
return 0; /* EPERM, unexpected optval from the kernel */
ctx->retval = 0; /* Reset system call return value to zero */
optval[0] = 0xA0;
ctx->optlen = 1;
return 1;
out:
/* optval larger than PAGE_SIZE use kernel's buffer. */
if (ctx->optlen > page_size)
ctx->optlen = 0;
return 1;
}
SEC("cgroup/setsockopt")
int _setsockopt(struct bpf_sockopt *ctx)
{
__u8 *optval_end = ctx->optval_end;
__u8 *optval = ctx->optval;
if (ctx->level != SOL_IP || ctx->optname != IP_TOS)
goto out;
if (optval + 1 > optval_end)
return 0; /* EPERM, bounds check */
optval[0] += 0x10;
ctx->optlen = 1;
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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