public static BufferSegment ToArray(IPFrame frame)
{
if (frame == null)
{
throw new ArgumentNullException(nameof(frame));
}
BufferSegment payload_segment = frame.Payload;
BufferSegment options_segment = frame.Options;
int options_size = options_segment?.Length ?? 0;
int payload_offset = sizeof(ip_hdr) + options_size;
int payload_size = payload_segment?.Length ?? 0;
byte[] message_data = new byte[payload_offset + payload_size];
fixed(byte *pinned = message_data)
{
ip_hdr *iphdr = (ip_hdr *)pinned;
iphdr->dest = frame.DestinationAddressV4;
iphdr->src = frame.SourceAddressV4;
iphdr->_ttl = (byte)frame.Ttl;
iphdr->_proto = (byte)frame.ProtocolType;
iphdr->_v_hl = (byte)(4 << 4 | payload_offset >> 2);
iphdr->_tos = frame.Tos; // Routine Mode
iphdr->_len = CheckSum.htons((ushort)message_data.Length);
iphdr->_id = CheckSum.htons(frame.Id);
iphdr->_flags = CheckSum.ntohs((ushort)frame.Flags);
if (options_size > 0)
{
IntPtr destination_options = (IntPtr)(pinned + sizeof(ip_hdr));
Marshal.Copy(options_segment.Buffer, options_segment.Offset, destination_options, options_size);
}
if (payload_size > 0)
{
using (MemoryStream ms = new MemoryStream(message_data, payload_offset, payload_size))
{
ms.Write(payload_segment.Buffer, payload_segment.Offset, payload_size);
}
}
iphdr->_chksum = CheckSum.inet_chksum(pinned, payload_offset);
if (iphdr->_chksum == 0)
{
iphdr->_chksum = 0xffff;
}
}
return(new BufferSegment(message_data));
}
public static IPFrame ParseFrame(BufferSegment packet, bool checksum = true)
{
if (packet == null)
{
return(null);
}
IPFrame frame = null;
packet.UnsafeAddrOfPinnedArrayElement((payload) =>
{
ip_hdr *iphdr = (ip_hdr *)payload;
if (iphdr == null)
{
return;
}
if (ip_hdr.IPH_V(iphdr) != 4)
{
return;
}
int iphdr_hlen = ip_hdr.IPH_HL(iphdr) << 2;
if (iphdr_hlen > packet.Length)
{
return;
}
if (iphdr_hlen < IP_HLEN)
{
return;
}
int ttl = ip_hdr.IPH_TTL(iphdr);
if (ttl <= 0)
{
return;
}
if (checksum && iphdr->_chksum != 0)
{
int cksum = CheckSum.inet_chksum(iphdr, iphdr_hlen);
if (cksum != 0)
{
return;
}
}
if (ip_addr_isbroadcast(iphdr->src) || ip_addr_isbroadcast(iphdr->dest))
{
return;
}
if ((ip_hdr.IPH_OFFSET(iphdr) & CheckSum.ntohs((ushort)(IPFlags.IP_OFFMASK | IPFlags.IP_MF))) != 0) // 不允许IP分片(NAT不太容易处理好分片)
{
return;
}
ProtocolType protocolType = (ProtocolType)ip_hdr.IPH_PROTO(iphdr);
if (protocolType == (ProtocolType)IP_PROTO_UDP ||
protocolType == (ProtocolType)IP_PROTO_TCP ||
protocolType == (ProtocolType)IP_PROTO_ICMP ||
protocolType == (ProtocolType)IP_PROTO_GRE)
{
BufferSegment message_data = new BufferSegment(packet.Buffer,
packet.Offset + iphdr_hlen,
packet.Length - iphdr_hlen);
BufferSegment options_data = null;
int options_size = (iphdr_hlen - sizeof(ip_hdr));
if (options_size <= 0)
{
options_data = new BufferSegment(BufferSegment.Empty);
}
else
{
options_data = new BufferSegment(packet.Buffer,
packet.Offset + sizeof(ip_hdr), options_size);
}
frame = new IPFrame(protocolType,
new IPAddress(iphdr->src),
new IPAddress(iphdr->dest),
message_data)
{
Id = CheckSum.ntohs(iphdr->_id),
Ttl = ttl,
Tos = iphdr->_tos,
Options = options_data,
Flags = (IPFlags)CheckSum.ntohs(iphdr->_flags),
};
}
});
return(frame);
}
public static int IPH_TTL(ip_hdr *hdr)
{
return((hdr)->_ttl & 0xff);
}
public static int IPH_OFFSET(ip_hdr *hdr)
{
return((hdr)->_flags);
}
public static int IPH_PROTO(ip_hdr *hdr)
{
return((hdr)->_proto & 0xff);
}
public static int IPH_HL(ip_hdr *hdr)
{
return((hdr)->_v_hl & 0x0f);
}
#pragma warning restore 0649
public static int IPH_V(ip_hdr *hdr)
{
return((hdr)->_v_hl >> 4);
}