134 lines
3.1 KiB
C
134 lines
3.1 KiB
C
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// SPDX-License-Identifier: GPL-2.0
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#include <string.h>
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#include <netinet/in.h>
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#include <netinet/tcp.h>
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#include <linux/bpf.h>
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#include "bpf_helpers.h"
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char _license[] SEC("license") = "GPL";
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__u32 _version SEC("version") = 1;
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#define SOL_CUSTOM 0xdeadbeef
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struct sockopt_sk {
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__u8 val;
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};
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struct bpf_map_def SEC("maps") socket_storage_map = {
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.type = BPF_MAP_TYPE_SK_STORAGE,
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.key_size = sizeof(int),
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.value_size = sizeof(struct sockopt_sk),
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.map_flags = BPF_F_NO_PREALLOC,
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};
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BPF_ANNOTATE_KV_PAIR(socket_storage_map, int, struct sockopt_sk);
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SEC("cgroup/getsockopt")
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int _getsockopt(struct bpf_sockopt *ctx)
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{
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__u8 *optval_end = ctx->optval_end;
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__u8 *optval = ctx->optval;
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struct sockopt_sk *storage;
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if (ctx->level == SOL_IP && ctx->optname == IP_TOS)
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/* Not interested in SOL_IP:IP_TOS;
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* let next BPF program in the cgroup chain or kernel
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* handle it.
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*/
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return 1;
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if (ctx->level == SOL_SOCKET && ctx->optname == SO_SNDBUF) {
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/* Not interested in SOL_SOCKET:SO_SNDBUF;
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* let next BPF program in the cgroup chain or kernel
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* handle it.
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*/
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return 1;
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}
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if (ctx->level == SOL_TCP && ctx->optname == TCP_CONGESTION) {
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/* Not interested in SOL_TCP:TCP_CONGESTION;
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* let next BPF program in the cgroup chain or kernel
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* handle it.
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*/
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return 1;
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}
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if (ctx->level != SOL_CUSTOM)
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return 0; /* EPERM, deny everything except custom level */
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if (optval + 1 > optval_end)
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return 0; /* EPERM, bounds check */
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storage = bpf_sk_storage_get(&socket_storage_map, ctx->sk, 0,
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BPF_SK_STORAGE_GET_F_CREATE);
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if (!storage)
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return 0; /* EPERM, couldn't get sk storage */
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if (!ctx->retval)
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return 0; /* EPERM, kernel should not have handled
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* SOL_CUSTOM, something is wrong!
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*/
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ctx->retval = 0; /* Reset system call return value to zero */
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optval[0] = storage->val;
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ctx->optlen = 1;
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return 1;
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}
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SEC("cgroup/setsockopt")
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int _setsockopt(struct bpf_sockopt *ctx)
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{
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__u8 *optval_end = ctx->optval_end;
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__u8 *optval = ctx->optval;
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struct sockopt_sk *storage;
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if (ctx->level == SOL_IP && ctx->optname == IP_TOS)
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/* Not interested in SOL_IP:IP_TOS;
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* let next BPF program in the cgroup chain or kernel
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* handle it.
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*/
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return 1;
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if (ctx->level == SOL_SOCKET && ctx->optname == SO_SNDBUF) {
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/* Overwrite SO_SNDBUF value */
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if (optval + sizeof(__u32) > optval_end)
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return 0; /* EPERM, bounds check */
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*(__u32 *)optval = 0x55AA;
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ctx->optlen = 4;
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return 1;
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}
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if (ctx->level == SOL_TCP && ctx->optname == TCP_CONGESTION) {
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/* Always use cubic */
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if (optval + 5 > optval_end)
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return 0; /* EPERM, bounds check */
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memcpy(optval, "cubic", 5);
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ctx->optlen = 5;
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return 1;
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}
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if (ctx->level != SOL_CUSTOM)
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return 0; /* EPERM, deny everything except custom level */
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if (optval + 1 > optval_end)
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return 0; /* EPERM, bounds check */
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storage = bpf_sk_storage_get(&socket_storage_map, ctx->sk, 0,
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BPF_SK_STORAGE_GET_F_CREATE);
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if (!storage)
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return 0; /* EPERM, couldn't get sk storage */
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storage->val = optval[0];
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ctx->optlen = -1; /* BPF has consumed this option, don't call kernel
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* setsockopt handler.
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*/
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return 1;
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}
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