iec61375-hello.bpf

  ld [2]                    ; check dest. MAC and other Ethernet stuff */
  jneq #0xc200000e, drop */
  ldh [0]
  jneq #0x0180, drop
  ld vlan_avail
  jneq #1, drop
  ld vlan_tci
  and #0x0FFF
  jneq #0x01EC, drop
  ldh [12]
  jneq #0x88CC, drop
  ld poff                   ; have M[0] hold the last ok header start position
  tax
  ld len
  sub x
  sub #2                    ; size of the first TLV header
  st M[0]
  ld #0x0e                  ; the first TLV header starts here
  ldx #0x0
  st M[1]                   ; this snippet tests whether we'd
  stx M[2]                  ; jump out of bounds, i.e. if
  ld M[0]                   ; ((accumulated TLV sizes in x) -
  ldx M[1]                  ; (packet payload size)) < 0
  sub x
  jset #0x80000000, drop
  ld M[1]
  ldx M[2]
  tax
  ldh [x + 0]               ; test one TLV - load TLV header
  and #0xFE00               ; extract type
  jeq #0x0000, drop         ; type 0 is EOF TLV
  jneq #0xFE00, skip_tlv_1  ; skip if not HELLO
  ldh [x + 0]               ; reload TLV header
  and #0x01FF               ; extract length
  jeq #0x56, okay           ; must be 86
skip_tlv_1: ldh [x + 0]     ; reload TLV header
  and #0x01FF               ; extract length
  add #2                    ; header length not included
  add x                     ; previous header offset
  st M[1]
  stx M[2]
  ld M[0]
  ldx M[1]
  sub x
  jset #0x80000000, drop
  ld M[1]
  ldx M[2]
  tax
  ldh [x + 0]               ; test next TLV... etc
  and #0xFE00
  jeq #0x0000, drop
  jneq #0xFE00, skip_tlv_2
  ldh [x + 0]
  and #0x01FF
  jeq #0x56, okay
skip_tlv_2: ldh [x + 0]
  and #0x01FF
  add #2
  add x
  st M[1]
  stx M[2]
  ld M[0]
  ldx M[1]
  sub x
  jset #0x80000000, drop
  ld M[1]
  ldx M[2]
  tax
  ldh [x + 0]
  and #0xFE00
  jeq #0x0000, drop
  jneq #0xFE00, skip_tlv_3
  ldh [x + 0]
  and #0x01FF
  jeq #0x56, okay
skip_tlv_3: ldh [x + 0]
  and #0x01FF
  add #2
  add x
  st M[1]
  stx M[2]
  ld M[0]
  ldx M[1]
  sub x
  jset #0x80000000, drop
  ld M[1]
  ldx M[2]
  tax
  ldh [x + 0]
  and #0xFE00
  jeq #0x0000, drop
  jneq #0xFE00, skip_tlv_4
  ldh [x + 0]
  and #0x01FF
  jeq #0x56, okay
skip_tlv_4: ldh [x + 0]
  and #0x01FF
  add #2
  add x
  st M[1]
  stx M[2]
  ld M[0]
  ldx M[1]
  sub x
  jset #0x80000000, drop
  ld M[1]
  ldx M[2]
  tax
  ldh [x + 0]
  and #0xFE00
  jeq #0x0000, drop
  jneq #0xFE00, skip_tlv_5
  ldh [x + 0]
  and #0x01FF
  jeq #0x56, okay
skip_tlv_5: ldh [x + 0]
  and #0x01FF
  add #2
  add x
  st M[1]
  stx M[2]
  ld M[0]
  ldx M[1]
  sub x
  jset #0x80000000, drop
  ld M[1]
  ldx M[2]
  tax
  ldh [x + 0]
  and #0xFE00
  jeq #0x0000, drop
  jneq #0xFE00, skip_tlv_6
  ldh [x + 0]
  and #0x01FF
  jeq #0x56, okay
skip_tlv_6: ldh [x + 0]
  and #0x01FF
  add #2
  add x
  st M[1]
  stx M[2]
  ld M[0]
  ldx M[1]
  sub x
  jset #0x80000000, drop
  ld M[1]
  ldx M[2]
  tax
  ldh [x + 0]
  and #0xFE00
  jeq #0x0000, drop
  jneq #0xFE00, skip_tlv_7
  ldh [x + 0]
  and #0x01FF
  jeq #0x56, okay
skip_tlv_7: ldh [x + 0]
  and #0x01FF
  add #2
  add x
  st M[1]
  stx M[2]
  ld M[0]
  ldx M[1]
  sub x
  jset #0x80000000, drop
  ld M[1]
  ldx M[2]
  tax
  ldh [x + 0]
  and #0xFE00
  jeq #0x0000, drop
  jneq #0xFE00, skip_tlv_8
  ldh [x + 0]
  and #0x01FF
  jeq #0x56, okay
skip_tlv_8: ldh [x + 0]
  and #0x01FF
  add #2
  add x
  st M[1]
  stx M[2]
  ld M[0]
  ldx M[1]
  sub x
  jset #0x80000000, drop
  ld M[1]
  ldx M[2]
  tax
  ldh [x + 0]
  and #0xFE00
  jeq #0x0000, drop
  jneq #0xFE00, skip_tlv_9
  ldh [x + 0]
  and #0x01FF
  jeq #0x56, okay
skip_tlv_9: ldh [x + 0]
  and #0x01FF
  add #2
  add x
  st M[1]
  stx M[2]
  ld M[0]
  ldx M[1]
  sub x
  jset #0x80000000, drop
  ld M[1]
  ldx M[2]
  tax
  ldh [x + 0]
  and #0xFE00
  jeq #0x0000, drop
  jneq #0xFE00, drop
  ldh [x + 0]
  and #0x01FF
  jeq #0x56, okay
  jmp drop
  okay: ret #-1             ; accept entire packet
  drop: ret #0              ; accept nothing