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add proc for serializing IpPackets

This commit is contained in:
Christian Ulrich 2020-07-10 19:37:47 +02:00
parent 4e554b5a83
commit 466d34963b
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1 changed files with 32 additions and 0 deletions
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32
ip_packet.nim
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@ -62,6 +62,7 @@ type
var var
ETHERTYPE_IP {.importc: "ETHERTYPE_IP", header: "<netinet/if_ether.h>".}: cushort ETHERTYPE_IP {.importc: "ETHERTYPE_IP", header: "<netinet/if_ether.h>".}: cushort
IPPROTO_TCP {.importc: "IPPROTO_TCP", header: "<netinet/in.h>".}: cint IPPROTO_TCP {.importc: "IPPROTO_TCP", header: "<netinet/in.h>".}: cint
TH_SYN {.importc: "TH_SYN", header: "<netinet/tcp.h>".}: uint8
proc parseEthernetPacket*(input: string): IpPacket = proc parseEthernetPacket*(input: string): IpPacket =
let etherHeader = cast[ptr Ether_header](input.cstring) let etherHeader = cast[ptr Ether_header](input.cstring)
@ -85,3 +86,34 @@ proc parseEthernetPacket*(input: string): IpPacket =
result = IpPacket(protocol: other) result = IpPacket(protocol: other)
else: else:
result = IpPacket(protocol: other) result = IpPacket(protocol: other)
proc serialize*(packet: IpPacket): string =
case packet.protocol
of tcp:
let srcIp = InAddr(s_addr: htonl(cast[uint32](packet.tcpIpSrc.address_v4)))
let dstIp = InAddr(s_addr: htonl(cast[uint32](packet.tcpIpDst.address_v4)))
var ipHeader = Ip(ip_hl: 5,
ip_v: 4,
ip_tos: 0,
ip_len: htons(40),
ip_id: htons(54321), # FIXME: random number
ip_off: 0,
ip_ttl: 64,
ip_p: 6.cuchar,
ip_sum: htons(0), # done by kernel
ip_src: srcIp,
ip_dst: dstIp)
var tcpHeader = Tcphdr(th_sport: htons(packet.tcpPortSrc.uint16),
th_dport: htons(packet.tcpPortDst.uint16),
th_seq: htonl(packet.tcpSeqNumber),
th_ack: 0,
th_off: 5,
th_flags: TH_SYN,
th_win: 1452 * 10,
th_sum: 0,
th_urp: 0)
result = newString(sizeof(Ip) + sizeof(Tcphdr))
copyMem(addr result[0], addr ipHeader, sizeof(Ip))
copyMem(addr result[sizeof(Ip)], addr tcpHeader, sizeof(Tcphdr))
else:
raise newException(ValueError, "protocol not supported")