83 lines
3.0 KiB
Nim
83 lines
3.0 KiB
Nim
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from nativesockets import Port, ntohs, ntohl
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from posix import InAddr, inet_ntoa
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type
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Ether_header {.importc: "struct ether_header", pure, final,
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header: "<netinet/if_ether.h>".} = object
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ether_dhost: array[6, cuchar]
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ether_shost: array[6, cuchar]
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ether_type: cushort
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Ip {.importc: "struct ip", pure, final,
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header: "<netinet/ip.h>".} = object
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when cpuEndian == littleEndian:
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ip_hl {.bitsize:4.}: cuchar # header length
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ip_v {.bitsize:4.}: cuchar # version
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else:
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ip_v {.bitsize:4.}: cuchar # version
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ip_hl {.bitsize:4.}: cuchar # header length
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ip_tos: cuchar # type of service
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ip_len: cshort # total length
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ip_id: cushort # identification
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ip_off: cshort # fragment offset field
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ip_ttl: cuchar # time to live
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ip_p: cuchar # protocol
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ip_sum: cushort # checksum
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ip_src: InAddr # source address
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ip_dst: InAddr # destination address
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Tcphdr {.importc: "struct tcphdr", pure, final,
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header: "<netinet/tcp.h>".} = object
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th_sport: cushort # source port
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th_dport: cushort # destination port
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th_seq: uint32 # sequence number
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th_ack: uint32 # ackkowledgment number
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when cpuEndian == littleEndian:
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th_x2 {.bitsize:4.}: cuchar # (unused)
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th_off {.bitsize:4.}: cuchar # data offset
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else:
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th_off {.bitsize:4.}: cuchar # (unused)
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th_x2 {.bitsize:4.}: cuchar # data offset
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th_flags: cuchar # flags
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th_win: cushort # window
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th_sum: cushort # checksum
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th_urp: cushort # urgent pointer
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Protocol* = enum
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tcp
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other
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IpPacket* = object
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case protocol*: Protocol
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of tcp:
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tcpIpSrc*: string
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tcpIpDst*: string
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tcpPortSrc*: Port
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tcpPortDst*: Port
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tcpSeqNumber*: uint32
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else:
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discard
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var
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ETHERTYPE_IP {.importc: "ETHERTYPE_IP", header: "<netinet/if_ether.h>".}: cushort
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IPPROTO_TCP {.importc: "IPPROTO_TCP", header: "<netinet/in.h>".}: cint
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proc parseEthernetPacket*(input: string): IpPacket =
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let etherHeader = cast[ptr Ether_header](input.cstring)
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if ntohs(etherHeader.ether_type) == ETHERTYPE_IP:
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let ipHeader = cast[ptr Ip](cast[int](input.cstring) + sizeof(Ether_header))
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let ipSrc = $inet_ntoa(ipHeader.ip_src)
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let ipDst = $inet_ntoa(ipHeader.ip_dst)
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if ipHeader.ip_p.int == IPPROTO_TCP:
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let tcpHeader = cast[ptr Tcphdr](cast[int](ipHeader) + ipHeader.ip_hl.int * 4)
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result = IpPacket(protocol: tcp,
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tcpIpSrc: ipSrc,
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tcpIpDst: ipDst,
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tcpPortSrc: Port(ntohs(tcpHeader.th_sport)),
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tcpPortDst: Port(ntohs(tcpHeader.th_dport)),
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tcpSeqNumber: ntohl(tcpHeader.th_seq))
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else:
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result = IpPacket(protocol: other)
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else:
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result = IpPacket(protocol: other)
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