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lokinet/llarp/net/ip_packet.cpp
dr7ana f574cd798f Clang format include sorting + CMake 
- includes are now sorted in consistent, logical order; first step in an attempt to fix the tomfoolery (no relation to Tom) brought in by include-what-you-use
- shuffled around some cmake linking to simplify dependency graph
- superfluous files removed
2024-01-31 07:54:12 -08:00

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#include "ip_packet.hpp"
#include "ip.hpp"
#include <llarp/constants/net.hpp>
#include <llarp/util/buffer.hpp>
#include <llarp/util/str.hpp>
#ifndef _WIN32
#include <netinet/in.h>
#endif
#include <oxenc/endian.h>
#include <algorithm>
namespace llarp::net
{
constexpr uint32_t ipv6_flowlabel_mask = 0b0000'0000'0000'1111'1111'1111'1111'1111;
/// get 20 bit truncated flow label in network order
llarp::nuint32_t
ipv6_header::FlowLabel() const
{
return llarp::nuint32_t{preamble.flowlabel & htonl(ipv6_flowlabel_mask)};
}
/// put 20 bit truncated flow label network order
void
ipv6_header::FlowLabel(llarp::nuint32_t label)
{
// the ipv6 flow label is the last 20 bits in the first 32 bits of the header
preamble.flowlabel =
(htonl(ipv6_flowlabel_mask) & label.n) | (preamble.flowlabel & htonl(~ipv6_flowlabel_mask));
};
std::string
IPProtocolName(IPProtocol proto)
{
if (const auto* ent = ::getprotobynumber(static_cast<uint8_t>(proto)))
{
return ent->p_name;
}
throw std::invalid_argument{
"cannot determine protocol name for ip proto '" + std::to_string(static_cast<int>(proto))
+ "'"};
}
IPProtocol
ParseIPProtocol(std::string data)
{
if (const auto* ent = ::getprotobyname(data.c_str()))
{
return static_cast<IPProtocol>(ent->p_proto);
}
if (starts_with(data, "0x"))
{
if (const int intVal = std::stoi(data.substr(2), nullptr, 16); intVal > 0)
return static_cast<IPProtocol>(intVal);
}
throw std::invalid_argument{"no such ip protocol: '" + data + "'"};
}
inline static uint32_t*
in6_uint32_ptr(in6_addr& addr)
{
return (uint32_t*)addr.s6_addr;
}
inline static const uint32_t*
in6_uint32_ptr(const in6_addr& addr)
{
return (uint32_t*)addr.s6_addr;
}
huint128_t
IPPacket::srcv6() const
{
if (IsV6())
return In6ToHUInt(HeaderV6()->srcaddr);
return ExpandV4(srcv4());
}
huint128_t
IPPacket::dstv6() const
{
if (IsV6())
return In6ToHUInt(HeaderV6()->dstaddr);
return ExpandV4(dstv4());
}
IPPacket::IPPacket(byte_view_t view)
{
if (view.size() < MinSize)
{
_buf.resize(0);
return;
}
_buf.resize(view.size());
std::copy_n(view.data(), size(), data());
}
IPPacket::IPPacket(size_t sz)
{
if (sz and sz < MinSize)
throw std::invalid_argument{"buffer size is too small to hold an ip packet"};
_buf.resize(sz);
}
SockAddr
IPPacket::src() const
{
const auto port = SrcPort().value_or(net::port_t{});
if (IsV4())
return SockAddr{ToNet(srcv4()), port};
else
return SockAddr{ToNet(srcv6()), port};
}
SockAddr
IPPacket::dst() const
{
auto port = *DstPort();
if (IsV4())
return SockAddr{ToNet(dstv4()), port};
else
return SockAddr{ToNet(dstv6()), port};
}
IPPacket::IPPacket(std::vector<byte_t>&& stolen) : _buf{stolen}
{
if (size() < MinSize)
_buf.resize(0);
}
byte_view_t
IPPacket::view() const
{
return byte_view_t{data(), size()};
}
std::optional<nuint16_t>
IPPacket::DstPort() const
{
switch (IPProtocol{Header()->protocol})
{
case IPProtocol::TCP:
case IPProtocol::UDP:
return nuint16_t{*reinterpret_cast<const uint16_t*>(data() + (Header()->ihl * 4) + 2)};
default:
return std::nullopt;
}
}
std::optional<nuint16_t>
IPPacket::SrcPort() const
{
IPProtocol proto{Header()->protocol};
switch (proto)
{
case IPProtocol::TCP:
case IPProtocol::UDP:
return nuint16_t{*reinterpret_cast<const uint16_t*>(data() + (Header()->ihl * 4))};
default:
return std::nullopt;
}
}
huint32_t
IPPacket::srcv4() const
{
return huint32_t{ntohl(Header()->saddr)};
}
huint32_t
IPPacket::dstv4() const
{
return huint32_t{ntohl(Header()->daddr)};
}
huint128_t
IPPacket::dst4to6() const
{
return ExpandV4(dstv4());
}
huint128_t
IPPacket::src4to6() const
{
return ExpandV4(srcv4());
}
huint128_t
IPPacket::dst4to6Lan() const
{
return ExpandV4Lan(dstv4());
}
huint128_t
IPPacket::src4to6Lan() const
{
return ExpandV4Lan(srcv4());
}
uint16_t
ipchksum(const byte_t* buf, size_t sz, uint32_t sum)
{
while (sz > 1)
{
sum += *(const uint16_t*)buf;
sz -= sizeof(uint16_t);
buf += sizeof(uint16_t);
}
if (sz != 0)
{
uint16_t x = 0;
*(byte_t*)&x = *(const byte_t*)buf;
sum += x;
}
// only need to do it 2 times to be sure
// proof: 0xFFff + 0xFFff = 0x1FFfe -> 0xFFff
sum = (sum & 0xFFff) + (sum >> 16);
sum += sum >> 16;
return uint16_t((~sum) & 0xFFff);
}
#define ADD32CS(x) ((uint32_t)(x & 0xFFff) + (uint32_t)(x >> 16))
#define SUB32CS(x) ((uint32_t)((~x) & 0xFFff) + (uint32_t)((~x) >> 16))
static nuint16_t
deltaIPv4Checksum(
nuint16_t old_sum,
nuint32_t old_src_ip,
nuint32_t old_dst_ip,
nuint32_t new_src_ip,
nuint32_t new_dst_ip)
{
uint32_t sum = uint32_t(old_sum.n) + ADD32CS(old_src_ip.n) + ADD32CS(old_dst_ip.n)
+ SUB32CS(new_src_ip.n) + SUB32CS(new_dst_ip.n);
// only need to do it 2 times to be sure
// proof: 0xFFff + 0xFFff = 0x1FFfe -> 0xFFff
sum = (sum & 0xFFff) + (sum >> 16);
sum += sum >> 16;
return nuint16_t{uint16_t(sum & 0xFFff)};
}
static nuint16_t
deltaIPv6Checksum(
nuint16_t old_sum,
const uint32_t old_src_ip[4],
const uint32_t old_dst_ip[4],
const uint32_t new_src_ip[4],
const uint32_t new_dst_ip[4])
{
/* we don't actually care in what way integers are arranged in memory
* internally */
/* as long as uint16 pairs are swapped in correct direction, result will
* be correct (assuming there are no gaps in structure) */
/* we represent 128bit stuff there as 4 32bit ints, that should be more or
* less correct */
/* we could do 64bit ints too but then we couldn't reuse 32bit macros and
* that'd suck for 32bit cpus */
#define ADDN128CS(x) (ADD32CS(x[0]) + ADD32CS(x[1]) + ADD32CS(x[2]) + ADD32CS(x[3]))
#define SUBN128CS(x) (SUB32CS(x[0]) + SUB32CS(x[1]) + SUB32CS(x[2]) + SUB32CS(x[3]))
uint32_t sum = uint32_t(old_sum.n) + ADDN128CS(old_src_ip) + ADDN128CS(old_dst_ip)
+ SUBN128CS(new_src_ip) + SUBN128CS(new_dst_ip);
#undef ADDN128CS
#undef SUBN128CS
// only need to do it 2 times to be sure
// proof: 0xFFff + 0xFFff = 0x1FFfe -> 0xFFff
sum = (sum & 0xFFff) + (sum >> 16);
sum += sum >> 16;
return nuint16_t{uint16_t(sum & 0xFFff)};
}
#undef ADD32CS
#undef SUB32CS
static void
deltaChecksumIPv4TCP(
byte_t* pld,
size_t psz,
size_t fragoff,
size_t chksumoff,
nuint32_t oSrcIP,
nuint32_t oDstIP,
nuint32_t nSrcIP,
nuint32_t nDstIP)
{
if (fragoff > chksumoff || psz < chksumoff - fragoff + 2)
return;
auto check = (nuint16_t*)(pld + chksumoff - fragoff);
*check = deltaIPv4Checksum(*check, oSrcIP, oDstIP, nSrcIP, nDstIP);
// usually, TCP checksum field cannot be 0xFFff,
// because one's complement addition cannot result in 0x0000,
// and there's inversion in the end;
// emulate that.
if (check->n == 0xFFff)
check->n = 0x0000;
}
static void
deltaChecksumIPv6TCP(
byte_t* pld,
size_t psz,
size_t fragoff,
size_t chksumoff,
const uint32_t oSrcIP[4],
const uint32_t oDstIP[4],
const uint32_t nSrcIP[4],
const uint32_t nDstIP[4])
{
if (fragoff > chksumoff || psz < chksumoff - fragoff + 2)
return;
auto check = (nuint16_t*)(pld + chksumoff - fragoff);
*check = deltaIPv6Checksum(*check, oSrcIP, oDstIP, nSrcIP, nDstIP);
// usually, TCP checksum field cannot be 0xFFff,
// because one's complement addition cannot result in 0x0000,
// and there's inversion in the end;
// emulate that.
if (check->n == 0xFFff)
check->n = 0x0000;
}
static void
deltaChecksumIPv4UDP(
byte_t* pld,
size_t psz,
size_t fragoff,
nuint32_t oSrcIP,
nuint32_t oDstIP,
nuint32_t nSrcIP,
nuint32_t nDstIP)
{
if (fragoff > 6 || psz < 6 + 2)
return;
auto check = (nuint16_t*)(pld + 6);
if (check->n == 0x0000)
return; // 0 is used to indicate "no checksum", don't change
*check = deltaIPv4Checksum(*check, oSrcIP, oDstIP, nSrcIP, nDstIP);
// 0 is used to indicate "no checksum"
// 0xFFff and 0 are equivalent in one's complement math
// 0xFFff + 1 = 0x10000 -> 0x0001 (same as 0 + 1)
// infact it's impossible to get 0 with such addition,
// when starting from non-0 value.
// inside deltachksum we don't invert so it's safe to skip check there
// if(check->n == 0x0000)
// check->n = 0xFFff;
}
static void
deltaChecksumIPv6UDP(
byte_t* pld,
size_t psz,
size_t fragoff,
const uint32_t oSrcIP[4],
const uint32_t oDstIP[4],
const uint32_t nSrcIP[4],
const uint32_t nDstIP[4])
{
if (fragoff > 6 || psz < 6 + 2)
return;
auto check = (nuint16_t*)(pld + 6);
// 0 is used to indicate "no checksum", don't change
// even tho this shouldn't happen for IPv6, handle it properly
// we actually should drop/log 0-checksum packets per spec
// but that should be done at upper level than this function
// it's better to do correct thing there regardless
// XXX or maybe we should change this function to be able to return error?
// either way that's not a priority
if (check->n == 0x0000)
return;
*check = deltaIPv6Checksum(*check, oSrcIP, oDstIP, nSrcIP, nDstIP);
// 0 is used to indicate "no checksum"
// 0xFFff and 0 are equivalent in one's complement math
// 0xFFff + 1 = 0x10000 -> 0x0001 (same as 0 + 1)
// infact it's impossible to get 0 with such addition,
// when starting from non-0 value.
// inside deltachksum we don't invert so it's safe to skip check there
// if(check->n == 0x0000)
// check->n = 0xFFff;
}
void
IPPacket::UpdateIPv4Address(nuint32_t nSrcIP, nuint32_t nDstIP)
{
llarp::LogDebug("set src=", nSrcIP, " dst=", nDstIP);
auto hdr = Header();
auto oSrcIP = nuint32_t{hdr->saddr};
auto oDstIP = nuint32_t{hdr->daddr};
auto* buf = data();
auto sz = size();
// L4 checksum
auto ihs = size_t(hdr->ihl * 4);
if (ihs <= sz)
{
auto pld = buf + ihs;
auto psz = sz - ihs;
auto fragoff = size_t((ntohs(hdr->frag_off) & 0x1Fff) * 8);
switch (hdr->protocol)
{
case 6: // TCP
deltaChecksumIPv4TCP(pld, psz, fragoff, 16, oSrcIP, oDstIP, nSrcIP, nDstIP);
break;
case 17: // UDP
case 136: // UDP-Lite - same checksum place, same 0->0xFFff condition
deltaChecksumIPv4UDP(pld, psz, fragoff, oSrcIP, oDstIP, nSrcIP, nDstIP);
break;
case 33: // DCCP
deltaChecksumIPv4TCP(pld, psz, fragoff, 6, oSrcIP, oDstIP, nSrcIP, nDstIP);
break;
}
}
// IPv4 checksum
auto v4chk = (nuint16_t*)&(hdr->check);
*v4chk = deltaIPv4Checksum(*v4chk, oSrcIP, oDstIP, nSrcIP, nDstIP);
// write new IP addresses
hdr->saddr = nSrcIP.n;
hdr->daddr = nDstIP.n;
}
void
IPPacket::UpdateIPv6Address(huint128_t src, huint128_t dst, std::optional<nuint32_t> flowlabel)
{
const size_t ihs = 4 + 4 + 16 + 16;
const auto sz = size();
// XXX should've been checked at upper level?
if (sz <= ihs)
return;
auto hdr = HeaderV6();
if (flowlabel.has_value())
{
// set flow label if desired
hdr->FlowLabel(*flowlabel);
}
const auto oldSrcIP = hdr->srcaddr;
const auto oldDstIP = hdr->dstaddr;
const uint32_t* oSrcIP = in6_uint32_ptr(oldSrcIP);
const uint32_t* oDstIP = in6_uint32_ptr(oldDstIP);
// IPv6 address
hdr->srcaddr = HUIntToIn6(src);
hdr->dstaddr = HUIntToIn6(dst);
const uint32_t* nSrcIP = in6_uint32_ptr(hdr->srcaddr);
const uint32_t* nDstIP = in6_uint32_ptr(hdr->dstaddr);
// TODO IPv6 header options
auto* pld = data() + ihs;
auto psz = sz - ihs;
size_t fragoff = 0;
auto nextproto = hdr->protocol;
for (;;)
{
switch (nextproto)
{
case 0: // Hop-by-Hop Options
case 43: // Routing Header
case 60: // Destination Options
{
nextproto = pld[0];
auto addlen = (size_t(pld[1]) + 1) * 8;
if (psz < addlen)
return;
pld += addlen;
psz -= addlen;
break;
}
case 44: // Fragment Header
/*
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Next Header | Reserved | Fragment Offset |Res|M|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Identification |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
*/
nextproto = pld[0];
fragoff = (uint16_t(pld[2]) << 8) | (uint16_t(pld[3]) & 0xFC);
if (psz < 8)
return;
pld += 8;
psz -= 8;
// jump straight to payload processing
if (fragoff != 0)
goto endprotohdrs;
break;
default:
goto endprotohdrs;
}
}
endprotohdrs:
switch (nextproto)
{
case 6: // TCP
deltaChecksumIPv6TCP(pld, psz, fragoff, 16, oSrcIP, oDstIP, nSrcIP, nDstIP);
break;
case 17: // UDP
case 136: // UDP-Lite - same checksum place, same 0->0xFFff condition
deltaChecksumIPv6UDP(pld, psz, fragoff, oSrcIP, oDstIP, nSrcIP, nDstIP);
break;
case 33: // DCCP
deltaChecksumIPv6TCP(pld, psz, fragoff, 6, oSrcIP, oDstIP, nSrcIP, nDstIP);
break;
}
}
void
IPPacket::ZeroAddresses(std::optional<nuint32_t> flowlabel)
{
if (IsV4())
{
UpdateIPv4Address({0}, {0});
}
else if (IsV6())
{
UpdateIPv6Address({0}, {0}, flowlabel);
}
}
void
IPPacket::ZeroSourceAddress(std::optional<nuint32_t> flowlabel)
{
if (IsV4())
{
UpdateIPv4Address({0}, xhtonl(dstv4()));
}
else if (IsV6())
{
UpdateIPv6Address({0}, dstv6(), flowlabel);
}
}
std::optional<IPPacket>
IPPacket::MakeICMPUnreachable() const
{
if (IsV4())
{
constexpr auto icmp_Header_size = 8;
auto ip_Header_size = Header()->ihl * 4;
auto pkt_size = (icmp_Header_size + ip_Header_size) * 2;
net::IPPacket pkt{static_cast<size_t>(pkt_size)};
auto* pkt_Header = pkt.Header();
pkt_Header->version = 4;
pkt_Header->ihl = 0x05;
pkt_Header->tos = 0;
pkt_Header->check = 0;
pkt_Header->tot_len = ntohs(pkt_size);
pkt_Header->saddr = Header()->daddr;
pkt_Header->daddr = Header()->saddr;
pkt_Header->protocol = 1; // ICMP
pkt_Header->ttl = Header()->ttl;
pkt_Header->frag_off = htons(0b0100000000000000);
uint16_t* checksum;
uint8_t* itr = pkt.data() + ip_Header_size;
uint8_t* icmp_begin = itr; // type 'destination unreachable'
*itr++ = 3;
// code 'Destination host unknown error'
*itr++ = 7;
// checksum + unused
oxenc::write_host_as_big<uint32_t>(0, itr);
checksum = (uint16_t*)itr;
itr += 4;
// next hop mtu is ignored but let's put something here anyways just in case tm
oxenc::write_host_as_big<uint16_t>(1500, itr);
itr += 2;
// copy ip header and first 8 bytes of datagram for icmp rject
std::copy_n(data(), ip_Header_size + icmp_Header_size, itr);
itr += ip_Header_size + icmp_Header_size;
// calculate checksum of ip header
pkt_Header->check = ipchksum(pkt.data(), ip_Header_size);
const auto icmp_size = std::distance(icmp_begin, itr);
// calculate icmp checksum
*checksum = ipchksum(icmp_begin, icmp_size);
return pkt;
}
return std::nullopt;
}
std::optional<std::pair<const char*, size_t>>
IPPacket::L4Data() const
{
const auto* hdr = Header();
size_t l4_HeaderSize = 0;
if (hdr->protocol == 0x11)
{
l4_HeaderSize = 8;
}
else
return std::nullopt;
// check for invalid size
if (size() < (hdr->ihl * 4) + l4_HeaderSize)
return std::nullopt;
const uint8_t* ptr = data() + ((hdr->ihl * 4) + l4_HeaderSize);
return std::make_pair(reinterpret_cast<const char*>(ptr), std::distance(ptr, data() + size()));
}
namespace
{
IPPacket
make_ip4_udp(
net::ipv4addr_t srcaddr,
net::port_t srcport,
net::ipv4addr_t dstaddr,
net::port_t dstport,
std::vector<byte_t> udp_data)
{
constexpr auto pkt_overhead = constants::udp_header_bytes + constants::ip_header_min_bytes;
net::IPPacket pkt{udp_data.size() + pkt_overhead};
auto* hdr = pkt.Header();
pkt.data()[1] = 0;
hdr->version = 4;
hdr->ihl = 5;
hdr->tot_len = htons(pkt_overhead + udp_data.size());
hdr->protocol = 0x11; // udp
hdr->ttl = 64;
hdr->frag_off = htons(0b0100000000000000);
hdr->saddr = srcaddr.n;
hdr->daddr = dstaddr.n;
// make udp packet
uint8_t* ptr = pkt.data() + constants::ip_header_min_bytes;
std::memcpy(ptr, &srcport.n, 2);
ptr += 2;
std::memcpy(ptr, &dstport.n, 2);
ptr += 2;
oxenc::write_host_as_big(
static_cast<uint16_t>(udp_data.size() + constants::udp_header_bytes), ptr);
ptr += 2;
oxenc::write_host_as_big(uint16_t{0}, ptr); // checksum
ptr += 2;
std::copy_n(udp_data.data(), udp_data.size(), ptr);
hdr->check = 0;
hdr->check = net::ipchksum(pkt.data(), 20);
return pkt;
}
} // namespace
IPPacket
IPPacket::make_udp(
net::ipaddr_t srcaddr,
net::port_t srcport,
net::ipaddr_t dstaddr,
net::port_t dstport,
std::vector<byte_t> udp_data)
{
auto getfam = [](auto&& v) {
if (std::holds_alternative<net::ipv4addr_t>(v))
return AF_INET;
else if (std::holds_alternative<net::ipv6addr_t>(v))
return AF_INET6;
else
return AF_UNSPEC;
};
auto fam = getfam(srcaddr);
if (fam != getfam(dstaddr))
return net::IPPacket{size_t{}};
if (fam == AF_INET)
{
return make_ip4_udp(
*std::get_if<net::ipv4addr_t>(&srcaddr),
srcport,
*std::get_if<net::ipv4addr_t>(&dstaddr),
dstport,
std::move(udp_data));
}
// TODO: ipv6
return net::IPPacket{size_t{}};
}
} // namespace llarp::net
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