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derp/xdp,cmd/xdpderper: initial skeleton (#12390)

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This commit introduces a userspace program for managing an experimental
eBPF XDP STUN server program. derp/xdp contains the eBPF pseudo-C along
with a Go pkg for loading it and exporting its metrics.
cmd/xdpderper is a package main user of derp/xdp.

Updates tailscale/corp#20689

Signed-off-by: Jordan Whited <jordan@tailscale.com>
This commit is contained in:
Jordan Whited
2024-06-14 08:45:24 -07:00
committed by GitHub
parent 6908fb0de3
commit 65888d95c9
22 changed files with 8684 additions and 11 deletions
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99
derp/xdp/headers/bpf_endian.h Normal file
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/* SPDX-License-Identifier: (LGPL-2.1 OR BSD-2-Clause) */
#ifndef __BPF_ENDIAN__
#define __BPF_ENDIAN__
/*
* Isolate byte #n and put it into byte #m, for __u##b type.
* E.g., moving byte #6 (nnnnnnnn) into byte #1 (mmmmmmmm) for __u64:
* 1) xxxxxxxx nnnnnnnn xxxxxxxx xxxxxxxx xxxxxxxx xxxxxxxx mmmmmmmm xxxxxxxx
* 2) nnnnnnnn xxxxxxxx xxxxxxxx xxxxxxxx xxxxxxxx mmmmmmmm xxxxxxxx 00000000
* 3) 00000000 00000000 00000000 00000000 00000000 00000000 00000000 nnnnnnnn
* 4) 00000000 00000000 00000000 00000000 00000000 00000000 nnnnnnnn 00000000
*/
#define ___bpf_mvb(x, b, n, m) ((__u##b)(x) << (b-(n+1)*8) >> (b-8) << (m*8))
#define ___bpf_swab16(x) ((__u16)( \
___bpf_mvb(x, 16, 0, 1) | \
___bpf_mvb(x, 16, 1, 0)))
#define ___bpf_swab32(x) ((__u32)( \
___bpf_mvb(x, 32, 0, 3) | \
___bpf_mvb(x, 32, 1, 2) | \
___bpf_mvb(x, 32, 2, 1) | \
___bpf_mvb(x, 32, 3, 0)))
#define ___bpf_swab64(x) ((__u64)( \
___bpf_mvb(x, 64, 0, 7) | \
___bpf_mvb(x, 64, 1, 6) | \
___bpf_mvb(x, 64, 2, 5) | \
___bpf_mvb(x, 64, 3, 4) | \
___bpf_mvb(x, 64, 4, 3) | \
___bpf_mvb(x, 64, 5, 2) | \
___bpf_mvb(x, 64, 6, 1) | \
___bpf_mvb(x, 64, 7, 0)))
/* LLVM's BPF target selects the endianness of the CPU
* it compiles on, or the user specifies (bpfel/bpfeb),
* respectively. The used __BYTE_ORDER__ is defined by
* the compiler, we cannot rely on __BYTE_ORDER from
* libc headers, since it doesn't reflect the actual
* requested byte order.
*
* Note, LLVM's BPF target has different __builtin_bswapX()
* semantics. It does map to BPF_ALU | BPF_END | BPF_TO_BE
* in bpfel and bpfeb case, which means below, that we map
* to cpu_to_be16(). We could use it unconditionally in BPF
* case, but better not rely on it, so that this header here
* can be used from application and BPF program side, which
* use different targets.
*/
#if __BYTE_ORDER__ == __ORDER_LITTLE_ENDIAN__
# define __bpf_ntohs(x) __builtin_bswap16(x)
# define __bpf_htons(x) __builtin_bswap16(x)
# define __bpf_constant_ntohs(x) ___bpf_swab16(x)
# define __bpf_constant_htons(x) ___bpf_swab16(x)
# define __bpf_ntohl(x) __builtin_bswap32(x)
# define __bpf_htonl(x) __builtin_bswap32(x)
# define __bpf_constant_ntohl(x) ___bpf_swab32(x)
# define __bpf_constant_htonl(x) ___bpf_swab32(x)
# define __bpf_be64_to_cpu(x) __builtin_bswap64(x)
# define __bpf_cpu_to_be64(x) __builtin_bswap64(x)
# define __bpf_constant_be64_to_cpu(x) ___bpf_swab64(x)
# define __bpf_constant_cpu_to_be64(x) ___bpf_swab64(x)
#elif __BYTE_ORDER__ == __ORDER_BIG_ENDIAN__
# define __bpf_ntohs(x) (x)
# define __bpf_htons(x) (x)
# define __bpf_constant_ntohs(x) (x)
# define __bpf_constant_htons(x) (x)
# define __bpf_ntohl(x) (x)
# define __bpf_htonl(x) (x)
# define __bpf_constant_ntohl(x) (x)
# define __bpf_constant_htonl(x) (x)
# define __bpf_be64_to_cpu(x) (x)
# define __bpf_cpu_to_be64(x) (x)
# define __bpf_constant_be64_to_cpu(x) (x)
# define __bpf_constant_cpu_to_be64(x) (x)
#else
# error "Fix your compiler's __BYTE_ORDER__?!"
#endif
#define bpf_htons(x) \
(__builtin_constant_p(x) ? \
__bpf_constant_htons(x) : __bpf_htons(x))
#define bpf_ntohs(x) \
(__builtin_constant_p(x) ? \
__bpf_constant_ntohs(x) : __bpf_ntohs(x))
#define bpf_htonl(x) \
(__builtin_constant_p(x) ? \
__bpf_constant_htonl(x) : __bpf_htonl(x))
#define bpf_ntohl(x) \
(__builtin_constant_p(x) ? \
__bpf_constant_ntohl(x) : __bpf_ntohl(x))
#define bpf_cpu_to_be64(x) \
(__builtin_constant_p(x) ? \
__bpf_constant_cpu_to_be64(x) : __bpf_cpu_to_be64(x))
#define bpf_be64_to_cpu(x) \
(__builtin_constant_p(x) ? \
__bpf_constant_be64_to_cpu(x) : __bpf_be64_to_cpu(x))
#endif /* __BPF_ENDIAN__ */