ip-header

IP header parsing.

Example

var IpHeader = require('ip-header');
 
// parse an IP header from buffer
var iph = new IpHeader(buf);
iph.src === '1.1.1.1';            // source IP address
iph.dst === '2.2.2.2';            // destination IP address
iph.flags.df === true;            // don't fragment flag
iph.flags.mf === false;           // more fragments flag
iph.id === 12345;                 // IP identifier for frag reassembly
iph.offset === 0;                 // fragment offset
iph.ttl === 64;                   // time-to-live
iph.protocol === 'tcp';           // payload protocol
iph.protocolCode === 6;           // code for the payload protocol
iph.length === 20;                // length of IP header in bytes
iph.totalLength === 520;          // total length of IP packet in bytes
iph.dataLength === 500;           // size of data payload (total - header)
var data = buf.slice(iph.length, iph.totalLength);
 
// create a new IP header from scratch
var iph2 = new IpHeader({
  src: '1.1.1.1',
  dst: '3.3.3.3',
  protocol: 'udp',
  flags: { df: true },
  dataLength: 58
});
var out = iph2.toBuffer();         // write header out to new buffer
 
// operate on buffers in place
var iph3 = new IpHeader(buf, offset);
var iph4 = IpHeader.fromBuffer(buf, offset);
iph3.toBuffer(buf, offset);

Limitations

• Only supports IPv4. Buffer parsing throws if an IPv6 header is seen.
• Only supports common protocols as readable strings. Throws if other protocols are seen. If you need another protocol, send a pull request to add it.
  • 'icmp' - 1
  • 'igmp' - 2
  • 'tcp' - 6
  • 'udp' - 17
  • 'encap' - 41
  • 'ospf' - 89
  • 'sctp' - 132
• Does not support options. Throws if the IP header length is not exactly 20 bytes.