void init() noexcept {
ip4_header().version_ihl = 0x45;
ip4_header().tos = 0;
ip4_header().id = 0;
ip4_header().frag_off_flags = 0;
ip4_header().ttl = DEFAULT_TTL;
}
void IP4::transmit(Packet_ptr pckt) {
assert(pckt->size() > sizeof(IP4::full_header));
auto ip4_pckt = std::static_pointer_cast<PacketIP4>(pckt);
ip4_pckt->make_flight_ready();
IP4::ip_header& hdr = ip4_pckt->ip4_header();
// Create local and target subnets
addr target = hdr.daddr & stack_.netmask();
addr local = stack_.ip_addr() & stack_.netmask();
// Compare subnets to know where to send packet
pckt->next_hop(target == local ? hdr.daddr : stack_.router());
debug("<IP4 TOP> Next hop for %s, (netmask %s, local IP: %s, gateway: %s) == %s\n",
hdr.daddr.str().c_str(),
stack_.netmask().str().c_str(),
stack_.ip_addr().str().c_str(),
stack_.router().str().c_str(),
target == local ? "DIRECT" : "GATEWAY");
debug("<IP4 transmit> my ip: %s, Next hop: %s, Packet size: %i IP4-size: %i\n",
stack_.ip_addr().str().c_str(),
pckt->next_hop().str().c_str(),
pckt->size(),
ip4_pckt->ip4_segment_size()
);
linklayer_out_(pckt);
}
void set_ip4_checksum() noexcept {
auto& hdr = ip4_header();
hdr.check = 0;
hdr.check = net::checksum(&hdr, sizeof(IP4::ip_header));
}
/**
* Set IP4 header length
*
* Inferred from packet size and linklayer header size
*/
void set_segment_length() noexcept
{ ip4_header().tot_len = htons(size() - sizeof(LinkLayer::header)); }
/** Last modifications before transmission */
void make_flight_ready() noexcept {
assert( ip4_header().protocol );
set_segment_length();
set_ip4_checksum();
}
uint16_t ip4_segment_size() const noexcept
{ return ntohs(ip4_header().tot_len); }
uint8_t protocol() const noexcept
{ return ip4_header().protocol; }
void set_protocol(IP4::proto p) noexcept
{ ip4_header().protocol = p; }
void set_dst(const IP4::addr& addr) noexcept
{ ip4_header().daddr = addr; }
const IP4::addr& dst() const noexcept
{ return ip4_header().daddr; }
void set_src(const IP4::addr& addr) noexcept
{ ip4_header().saddr = addr; }
const IP4::addr& src() const noexcept
{ return ip4_header().saddr; }