// SPDX-License-Identifier: GPL-2.0 #include <netinet/in.h> #include <linux/bpf.h> #include <bpf/bpf_helpers.h> char _license[] SEC("license") = "GPL"; 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) return 1; 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; } 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) return 1; 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; } 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) return 1; if (optval + 1 > optval_end) return 0; /* EPERM, bounds check */ optval[0] += 0x10; ctx->optlen = 1; return 1; }