src/cc/bpf_helpers.h

#ifndef __BPF_HELPERS_H
#define __BPF_HELPERS_H

#include <linux/bpf.h>
#include <linux/filter.h>
#include <linux/if_packet.h>
#include <linux/version.h>

/* helper macro to place programs, maps, license in
 * different sections in elf_bpf file. Section names
 * are interpreted by elf_bpf loader
 */
#define SEC(NAME) __attribute__((section(NAME), used))

// Changes to the macro require changes in BFrontendAction classes
#define BPF_TABLE(_table_type, _key_type, _leaf_type, _name, _max_entries) \
struct _name##_table_t { \
  _key_type key; \
  _leaf_type leaf; \
  _leaf_type * (*lookup) (_key_type *); \
  _leaf_type * (*lookup_or_init) (_key_type *, _leaf_type *); \
  int (*update) (_key_type *, _leaf_type *); \
  int (*delete) (_key_type *); \
  void (*call) (void *, int index); \
  _leaf_type data[_max_entries]; \
}; \
__attribute__((section("maps/" _table_type))) \
struct _name##_table_t _name

// packet parsing state machine helpers
#define STATE_MACHINE(name) \
  BPF_EXPORT(name) int _##name(struct __sk_buff *skb)
#define BEGIN(next) \
  u64 _parse_cursor = 0; \
  u64 _parse_base = skb->pkt_type == PACKET_OUTGOING ? 0 : BPF_LL_OFF; \
  goto next

#define PROTO(name) \
  goto EOP; \
name: ; \
  struct name##_t *name __attribute__((deprecated("packet"))) = (void *)_parse_cursor; \
  _parse_cursor += sizeof(*name);

// export this function to llvm by putting it into a specially named section
//#define BPF_EXPORT(_ret, _name, ...) SEC("." #_name) _ret _name(__VA_ARGS__)
#define BPF_EXPORT(_name) __attribute__((section("." #_name)))

char _license[4] SEC("license") = "GPL";

unsigned _version SEC("version") = LINUX_VERSION_CODE;

/* helper functions called from eBPF programs written in C */
static void *(*bpf_map_lookup_elem)(void *map, void *key) =
	(void *) BPF_FUNC_map_lookup_elem;
static int (*bpf_map_update_elem)(void *map, void *key, void *value, u64 flags) =
	(void *) BPF_FUNC_map_update_elem;
static int (*bpf_map_delete_elem)(void *map, void *key) =
	(void *) BPF_FUNC_map_delete_elem;
static int (*bpf_probe_read)(void *dst, u64 size, void *unsafe_ptr) =
	(void *) BPF_FUNC_probe_read;
static u64 (*bpf_ktime_get_ns)(void) =
	(void *) BPF_FUNC_ktime_get_ns;
static int (*bpf_trace_printk)(const char *fmt, u64 fmt_size, ...) =
	(void *) BPF_FUNC_trace_printk;
static void bpf_tail_call_(u64 map_fd, void *ctx, int index) {
  ((void (*)(void *, u64, int))BPF_FUNC_tail_call)(ctx, map_fd, index);
}

/* llvm builtin functions that eBPF C program may use to
 * emit BPF_LD_ABS and BPF_LD_IND instructions
 */
struct sk_buff;
unsigned long long load_byte(void *skb,
			     unsigned long long off) asm("llvm.bpf.load.byte");
unsigned long long load_half(void *skb,
			     unsigned long long off) asm("llvm.bpf.load.half");
unsigned long long load_word(void *skb,
			     unsigned long long off) asm("llvm.bpf.load.word");

/* a helper structure used by eBPF C program
 * to describe map attributes to elf_bpf loader
 */
struct bpf_map_def {
	unsigned int type;
	unsigned int key_size;
	unsigned int value_size;
	unsigned int max_entries;
};

static int (*bpf_skb_store_bytes)(void *ctx, unsigned long long off, void *from,
				  unsigned long long len, unsigned long long flags) =
	(void *) BPF_FUNC_skb_store_bytes;
static int (*bpf_l3_csum_replace)(void *ctx, unsigned long long off, unsigned long long from,
				  unsigned long long to, unsigned long long flags) =
	(void *) BPF_FUNC_l3_csum_replace;
static int (*bpf_l4_csum_replace)(void *ctx, unsigned long long off, unsigned long long from,
				  unsigned long long to, unsigned long long flags) =
	(void *) BPF_FUNC_l4_csum_replace;

static inline u16 bpf_ntohs(u16 val) {
  /* will be recognized by gcc into rotate insn and eventually rolw 8 */
  return (val << 8) | (val >> 8);
}

static inline u32 bpf_ntohl(u32 val) {
  /* gcc will use bswapsi2 insn */
  return __builtin_bswap32(val);
}

static inline u64 bpf_ntohll(u64 val) {
  /* gcc will use bswapdi2 insn */
  return __builtin_bswap64(val);
}

static inline unsigned __int128 bpf_ntoh128(unsigned __int128 val) {
  return (((unsigned __int128)bpf_ntohll(val) << 64) | (u64)bpf_ntohll(val >> 64));
}

static inline u16 bpf_htons(u16 val) {
  return bpf_ntohs(val);
}

static inline u32 bpf_htonl(u32 val) {
  return bpf_ntohl(val);
}
static inline u64 bpf_htonll(u64 val) {
  return bpf_ntohll(val);
}
static inline unsigned __int128 bpf_hton128(unsigned __int128 val) {
  return bpf_ntoh128(val);
}

static inline u64 load_dword(void *skb, u64 off) {
  return ((u64)load_word(skb, off) << 4) | load_word(skb, off + 4);
}

void bpf_store_byte(void *skb, u64 off, u64 val) asm("llvm.bpf.store.byte");
void bpf_store_half(void *skb, u64 off, u64 val) asm("llvm.bpf.store.half");
void bpf_store_word(void *skb, u64 off, u64 val) asm("llvm.bpf.store.word");
u64 bpf_pseudo_fd(u64, u64) asm("llvm.bpf.pseudo");
static inline void bpf_store_dword(void *skb, u64 off, u64 val) {
  bpf_store_word(skb, off, (u32)val);
  bpf_store_word(skb, off + 4, val >> 32);
}

#define MASK(_n) ((_n) < 64 ? (1ull << (_n)) - 1 : ((u64)-1LL))
#define MASK128(_n) ((_n) < 128 ? ((unsigned __int128)1 << (_n)) - 1 : ((unsigned __int128)-1))

struct bpf_context;

//static inline __attribute__((always_inline))
SEC("helpers")
u64 bpf_dext_pkt(void *pkt, u64 off, u64 bofs, u64 bsz) {
  if (bofs == 0 && bsz == 8) {
    return load_byte(pkt, off);
  } else if (bofs + bsz <= 8) {
    return load_byte(pkt, off) >> (8 - (bofs + bsz))  &  MASK(bsz);
  } else if (bofs == 0 && bsz == 16) {
    return load_half(pkt, off);
  } else if (bofs + bsz <= 16) {
    return load_half(pkt, off) >> (16 - (bofs + bsz))  &  MASK(bsz);
  } else if (bofs == 0 && bsz == 32) {
    return load_word(pkt, off);
  } else if (bofs + bsz <= 32) {
    return load_word(pkt, off) >> (32 - (bofs + bsz))  &  MASK(bsz);
  } else if (bofs + bsz <= 64) {
    return bpf_ntohll(load_dword(pkt, off)) >> (64 - (bofs + bsz))  &  MASK(bsz);
  }
  return 0;
}

//static inline __attribute__((always_inline))
SEC("helpers")
void bpf_dins_pkt(void *pkt, u64 off, u64 bofs, u64 bsz, u64 val) {
  // The load_xxx function does a bswap before returning the short/word/dword,
  // so the value in register will always be host endian. However, the bytes
  // written back need to be in network order.
  if (bofs == 0 && bsz == 8) {
    bpf_skb_store_bytes(pkt, off, &val, 1, 0);
  } else if (bofs + bsz <= 8) {
    u8 v = load_byte(pkt, off);
    v &= ~(MASK(bsz) << (8 - (bofs + bsz)));
    v |= ((val & MASK(bsz)) << (8 - (bofs + bsz)));
    bpf_skb_store_bytes(pkt, off, &v, 1, 0);
  } else if (bofs == 0 && bsz == 16) {
    u16 v = bpf_htons(val);
    bpf_skb_store_bytes(pkt, off, &v, 2, 0);
  } else if (bofs + bsz <= 16) {
    u16 v = load_half(pkt, off);
    v &= ~(MASK(bsz) << (16 - (bofs + bsz)));
    v |= ((val & MASK(bsz)) << (16 - (bofs + bsz)));
    v = bpf_htons(v);
    bpf_skb_store_bytes(pkt, off, &v, 2, 0);
  } else if (bofs == 0 && bsz == 32) {
    u32 v = bpf_htonl(val);
    bpf_skb_store_bytes(pkt, off, &v, 4, 0);
  } else if (bofs + bsz <= 32) {
    u32 v = load_word(pkt, off);
    v &= ~(MASK(bsz) << (32 - (bofs + bsz)));
    v |= ((val & MASK(bsz)) << (32 - (bofs + bsz)));
    v = bpf_htonl(v);
    bpf_skb_store_bytes(pkt, off, &v, 4, 0);
  } else if (bofs == 0 && bsz == 64) {
    u64 v = bpf_htonll(val);
    bpf_skb_store_bytes(pkt, off, &v, 8, 0);
  } else if (bofs + bsz <= 64) {
    u64 v = load_dword(pkt, off);
    v &= ~(MASK(bsz) << (64 - (bofs + bsz)));
    v |= ((val & MASK(bsz)) << (64 - (bofs + bsz)));
    v = bpf_htonll(v);
    bpf_skb_store_bytes(pkt, off, &v, 8, 0);
  }
}

SEC("helpers")
void * bpf_map_lookup_elem_(uintptr_t map, void *key) {
  return bpf_map_lookup_elem((void *)map, key);
}

SEC("helpers")
int bpf_map_update_elem_(uintptr_t map, void *key, void *value, u64 flags) {
  return bpf_map_update_elem((void *)map, key, value, flags);
}

SEC("helpers")
int bpf_map_delete_elem_(uintptr_t map, void *key) {
  return bpf_map_delete_elem((void *)map, key);
}

SEC("helpers")
int bpf_l3_csum_replace_(void *ctx, u64 off, u64 from, u64 to, u64 flags) {
  switch (flags & 0xf) {
    case 2:
      return bpf_l3_csum_replace(ctx, off, bpf_htons(from), bpf_htons(to), flags);
    case 4:
      return bpf_l3_csum_replace(ctx, off, bpf_htonl(from), bpf_htonl(to), flags);
    case 8:
      return bpf_l3_csum_replace(ctx, off, bpf_htonll(from), bpf_htonll(to), flags);
    default:
      {}
  }
  return bpf_l3_csum_replace(ctx, off, from, to, flags);
}

SEC("helpers")
int bpf_l4_csum_replace_(void *ctx, u64 off, u64 from, u64 to, u64 flags) {
  switch (flags & 0xf) {
    case 2:
      return bpf_l4_csum_replace(ctx, off, bpf_htons(from), bpf_htons(to), flags);
    case 4:
      return bpf_l4_csum_replace(ctx, off, bpf_htonl(from), bpf_htonl(to), flags);
    case 8:
      return bpf_l4_csum_replace(ctx, off, bpf_htonll(from), bpf_htonll(to), flags);
    default:
      {}
  }
  return bpf_l4_csum_replace(ctx, off, from, to, flags);
}

#define incr_cksum_l3(expr, oldval, newval) \
  bpf_l3_csum_replace_(skb, (u64)expr, oldval, newval, sizeof(newval))
#define incr_cksum_l4(expr, oldval, newval, is_pseudo) \
  bpf_l4_csum_replace_(skb, (u64)expr, oldval, newval, ((is_pseudo & 0x1) << 4) | sizeof(newval))

#define lock_xadd(ptr, val) ((void)__sync_fetch_and_add(ptr, val))

#endif