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<!doctype html public "-//w3c//dtd html 4.0 transitional//en">
<html>
<head>
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<meta name="Generator" content="Microsoft Word 97">
<meta name="GENERATOR" content="Mozilla/4.6 [en] (Win98; I) [Netscape]">
<title>Introduction</title>
</head>
<body text="#000000" bgcolor="#CCCCCC" link="#0000FF" vlink="#800080" alink="#FF0000">
<a href="6.html">Next</a> <a href="4.html">Previous</a> <a href="lrm.html">Top</a>
<p>
<hr ALIGN="LEFT">
<br><b><font size=+2>5. Library Internals</font></b>
<p><font size=-1>This section is devoted to the internals of the library.
First covered are all the user-accessible functions, then constants, macros
and finally libnet-specific data structures.</font>
<p><font size=-1>Proceeding each function prototype is a small table listing
the return values of the function, whether or not the function is reentrant
(a function is considered reentrant if it may be called repeatedly, or
may be called before previous invocations have completed, and each invocation
is independent of all other invocations) and a brief description of the
function's arguments.</font>
<p><a NAME="s5_1"></a><b><font size=+2>5.1 Memory Management Functions</font></b>
<br>
<hr ALIGN="LEFT">
<br><b>int libnet_init_packet(u_short packet_size, u_char **buf);</b>
<br>
<br>
<table BORDER WIDTH="498" >
<tr>
<td VALIGN=CENTER><font size=-1>return value upon success</font></td>
<td VALIGN=CENTER><font size=-1>1</font></td>
</tr>
<tr>
<td VALIGN=CENTER><font size=-1>return value upon failure</font></td>
<td VALIGN=CENTER><font size=-1>-1</font></td>
</tr>
<tr>
<td VALIGN=CENTER><font size=-1>re-entrant</font></td>
<td VALIGN=CENTER><font size=-1>yes</font></td>
</tr>
<tr>
<td VALIGN=CENTER><font size=-1>arguments</font></td>
<td VALIGN=CENTER><font size=-1>1 - desired packet size</font>
<br><font size=-1>2 - address of a u_char pointer</font></td>
</tr>
</table>
<p><font size=-1>libnet_init_packet() creates memory for a packet (it doesn't
so much create memory as it requests it from the underlying operating system
via malloc()). Upon success the memory is zero-filled. The
function accepts two arguments, the packet size and the address of the
pointer to the packet. The packet size parameter may be 0, in which
case the library will attempt to guess a packet size for you. Passing
in the pointer to a pointer (passing by address) is necessary as we are
allocating memory locally. If we instead passed in just a pointer
(passing by value) the allocated memory would be lost.</font>
<p><font size=-1>This function is a good example of interface hiding.
This function is essentially a malloc() wrapper. By using this function
the details of what's really happening are abstracted so that you, the
programmer, can worry about your task at hand.</font>
<br>
<hr ALIGN="LEFT">
<br><b>void libnet_destroy_packet(u_char **buf);</b>
<br>
<br>
<table BORDER WIDTH="486" >
<tr>
<td VALIGN=CENTER><font size=-1>return value upon success</font></td>
<td VALIGN=CENTER><font size=-1>NA</font></td>
</tr>
<tr>
<td VALIGN=CENTER><font size=-1>return value upon failure</font></td>
<td VALIGN=CENTER><font size=-1>NA</font></td>
</tr>
<tr>
<td VALIGN=CENTER><font size=-1>re-entrant</font></td>
<td VALIGN=CENTER><font size=-1>yes</font></td>
</tr>
<tr>
<td VALIGN=CENTER><font size=-1>arguments</font></td>
<td VALIGN=CENTER><font size=-1>1 - address of a u_char pointer </font></td>
</tr>
</table>
<p><font size=-1>libnet_destroy_packet() is the free() analog to libnet_init_packet.
It destroys the packet referenced by 'buf'. In reality, it is of
course a simple free() wrapper. It frees the heap memory and points
`buf` to NULL to dispel the dangling pointer. The function does make
the assertion that `buf` is not NULL. A pointer to a pointer is passed
to maintain interface consistency.</font>
<br>
<hr ALIGN="LEFT">
<br><b>int libnet_init_packet_arena(struct libnet_arena **arena, u_short
packet_size, u_short packet_size);</b>
<br>
<br>
<table BORDER WIDTH="566" >
<tr>
<td VALIGN=CENTER><font size=-1>return value upon success</font></td>
<td VALIGN=CENTER><font size=-1>1</font></td>
</tr>
<tr>
<td VALIGN=CENTER><font size=-1>return value upon failure</font></td>
<td VALIGN=CENTER><font size=-1>-1</font></td>
</tr>
<tr>
<td VALIGN=CENTER><font size=-1>re-entrant</font></td>
<td VALIGN=CENTER><font size=-1>yes</font></td>
</tr>
<tr>
<td VALIGN=CENTER><font size=-1>arguments</font></td>
<td VALIGN=CENTER><font size=-1>1 - pointer to an arena structure pointer</font>
<br><font size=-1>2 - number of packets</font>
<br><font size=-1>3 - packet size</font></td>
</tr>
</table>
<p><font size=-1>libnet_init_packet_arena() allocates and initializes a
memory pool. If you plan on building and sending several different
packets, this is a good choice. It allocates a pool of memory from
which you can grab chunks to build packets (see next_packet_from_arena()).
It takes the address to an arena structure pointer, and hints on
the possible packet size and number of packets. The last two arguments
are used to compute the size of the memory pool. As before, they
can be set to 0 and the library will attempt to choose a decent value.
The function returns -1 if the malloc fails or 1 if everything goes ok.</font>
<br>
<hr ALIGN="LEFT">
<br><b>u_char *libnet_next_packet_from_arena(struct libnet_arena **arena,
u_short packet_size);</b>
<br>
<br>
<table BORDER WIDTH="517" >
<tr>
<td VALIGN=CENTER><font size=-1>return value upon success</font></td>
<td VALIGN=CENTER><font size=-1>pointer to the request packet memory</font></td>
</tr>
<tr>
<td VALIGN=CENTER><font size=-1>return value upon failure</font></td>
<td VALIGN=CENTER><font size=-1>NULL</font></td>
</tr>
<tr>
<td VALIGN=CENTER><font size=-1>re-entrant</font></td>
<td VALIGN=CENTER><font size=-1>yes</font></td>
</tr>
<tr>
<td VALIGN=CENTER><font size=-1>arguments</font></td>
<td VALIGN=CENTER><font size=-1>1 - pointer to the arena</font>
<br><font size=-1>2 - requested packet size</font></td>
</tr>
</table>
<p><font size=-1>libnet_next_packet_from_arena() returns a chunk of memory
from the specified arena of the requested size and decrements the arenas
available byte counter. If the requested memory is not available
from the arena, the function returns NULL. Note that there is nothing
preventing a poorly coded application from using more memory than requested
and causing all kinds of problems. Take heed.</font>
<br>
<hr ALIGN="LEFT">
<br><b>void libnet_destroy_packet_arena(struct libnet_arena **arena);</b>
<br>
<br>
<table BORDER WIDTH="436" >
<tr>
<td VALIGN=CENTER><font size=-1>return value upon success</font></td>
<td VALIGN=CENTER><font size=-1>NA</font></td>
</tr>
<tr>
<td VALIGN=CENTER><font size=-1>return value upon failure</font></td>
<td VALIGN=CENTER><font size=-1>NA</font></td>
</tr>
<tr>
<td VALIGN=CENTER><font size=-1>re-entrant</font></td>
<td VALIGN=CENTER><font size=-1>yes</font></td>
</tr>
<tr>
<td VALIGN=CENTER><font size=-1>arguments</font></td>
<td VALIGN=CENTER><font size=-1>1 - pointer to the arena</font></td>
</tr>
</table>
<p><font size=-1>libnet_destroy_packet_arena() frees the memory associated
with the specified arena.</font>
<br>
<hr ALIGN="LEFT">
<br><a NAME="s5_2"></a><b><font size=+2>5.2 Address Resolution Functions</font></b>
<br>
<hr ALIGN="LEFT">
<br><b>u_char *libnet_host_lookup(u_long ip, u_short use_name);</b>
<br>
<br>
<br>
<table BORDER WIDTH="521" >
<tr>
<td VALIGN=CENTER><font size=-1>return value upon success</font></td>
<td VALIGN=CENTER><font size=-1>pointer to the converted IP address</font></td>
</tr>
<tr>
<td VALIGN=CENTER><font size=-1>return value upon failure</font></td>
<td VALIGN=CENTER><font size=-1>NULL</font></td>
</tr>
<tr>
<td VALIGN=CENTER><font size=-1>re-entrant</font></td>
<td VALIGN=CENTER><font size=-1>no</font></td>
</tr>
<tr>
<td VALIGN=CENTER><font size=-1>arguments</font></td>
<td VALIGN=CENTER><font size=-1>1 - network-byte ordered IP address</font>
<br><font size=-1>2 - use_name flag</font></td>
</tr>
</table>
<p><font size=-1>libnet_host_lookup() converts the supplied network-ordered
(big-endian) IP address into its human-readable counterpart. If the
usename flag is LIBNET_RESOLVE, the function will attempt to resolve the
IP address (possibly incurring DNS network traffic) and return a canonical
hostname, otherwise if it is LIBNET_DONT_RESOLVE (or if the lookup fails),
the function returns a dotted-decimal ASCII string. This function
is hopelessly non reentrant as it uses static data.</font>
<br>
<hr ALIGN="LEFT">
<br><b>void libnet_host_lookup_r(u_long ip, u_short use_name, u_char *buf);</b>
<br>
<br>
<table BORDER WIDTH="579" >
<tr>
<td VALIGN=CENTER><font size=-1>return value upon success</font></td>
<td VALIGN=CENTER><font size=-1>NA</font></td>
</tr>
<tr>
<td VALIGN=CENTER><font size=-1>return value upon failure</font></td>
<td VALIGN=CENTER><font size=-1>NA</font></td>
</tr>
<tr>
<td VALIGN=CENTER><font size=-1>re-entrant</font></td>
<td VALIGN=CENTER><font size=-1>depends on architecture</font></td>
</tr>
<tr>
<td VALIGN=CENTER><font size=-1>arguments</font></td>
<td VALIGN=CENTER><font size=-1>1 - network-byte ordered IP address</font>
<br><font size=-1>2 - use_name flag</font>
<br><font size=-1>3 - buffer to contain the converted IP address</font></td>
</tr>
</table>
<p><font size=-1>libnet_host_lookup_r() is the planned reentrant version
of the above function. If reentrant network resolver libraries become
available, this function will likewise be reentrant. An additional
argument of a buffer to store the converted (or resolved) IP address is
supplied by the user.</font>
<br>
<hr ALIGN="LEFT">
<br><b>u_long libnet_name_resolve(u_char *ip, u_short use_name);</b>
<br>
<br>
<table BORDER WIDTH="578" >
<tr>
<td VALIGN=CENTER><font size=-1>return value upon success</font></td>
<td VALIGN=CENTER><font size=-1>network-byte ordered IP address</font></td>
</tr>
<tr>
<td VALIGN=CENTER><font size=-1>return value upon failure</font></td>
<td VALIGN=CENTER><font size=-1>-1</font></td>
</tr>
<tr>
<td VALIGN=CENTER><font size=-1>re-entrant</font></td>
<td VALIGN=CENTER><font size=-1>yes</font></td>
</tr>
<tr>
<td VALIGN=CENTER><font size=-1>arguments</font></td>
<td VALIGN=CENTER><font size=-1>1 - human readable IP address or FQDN</font>
<br><font size=-1>2 - use_name flag</font></td>
</tr>
</table>
<p><font size=-1>libnet_name_resolve() takes a NULL terminated ASCII string
representation of an IP address (dots and decimals or, if the usename flag
is LIBNET_RESOLVE, a canonical hostname) and converts it into a network-ordered
(big-endian) unsigned long value.</font>
<hr ALIGN="LEFT">
<br><b>u_long libnet_get_ipaddr(struct libnet_link_int *l, const u_char
*device, const u_char *ebuf);</b>
<br>
<br>
<table BORDER WIDTH="729" >
<tr>
<td VALIGN=CENTER><font size=-1>return value upon success</font></td>
<td VALIGN=CENTER><font size=-1>requested IP address</font></td>
</tr>
<tr>
<td VALIGN=CENTER><font size=-1>return value upon failure</font></td>
<td VALIGN=CENTER><font size=-1>-1</font></td>
</tr>
<tr>
<td VALIGN=CENTER><font size=-1>re-entrant</font></td>
<td VALIGN=CENTER><font size=-1>yes</font></td>
</tr>
<tr>
<td VALIGN=CENTER><font size=-1>arguments</font></td>
<td VALIGN=CENTER><font size=-1>1 - pointer to a link interface structure</font>
<br><font size=-1>2 - pointer to the device to query</font>
<br><font size=-1>3 - pointer to a buffer to contain a possible error message</font></td>
</tr>
</table>
<p><font size=-1>libnet_get_ipaddr() returns the IP address of a specified
network device. The function takes a pointer to a link layer interface
structure, a pointer to the network device name, and an empty buffer to
be used in case of error. Upon success the function returns the IP
address of the specified interface in network-byte order or 0 upon error
(and errbuf will contain a reason).</font>
<br>
<hr ALIGN="LEFT">
<br><b>struct ether_addr *libnet_get_hwaddr(struct libnet_link_int *l,
const u_char *device, const u_char *ebuf);</b>
<br>
<br>
<table BORDER WIDTH="720" >
<tr>
<td VALIGN=CENTER><font size=-1>return value upon success</font></td>
<td VALIGN=CENTER><font size=-1>pointer to the requested ethernet address</font></td>
</tr>
<tr>
<td VALIGN=CENTER><font size=-1>return value upon failure</font></td>
<td VALIGN=CENTER><font size=-1>NULL</font></td>
</tr>
<tr>
<td VALIGN=CENTER><font size=-1>re-entrant</font></td>
<td VALIGN=CENTER><font size=-1>depends on architecture</font></td>
</tr>
<tr>
<td VALIGN=CENTER><font size=-1>arguments</font></td>
<td VALIGN=CENTER><font size=-1>1 - pointer to a link interface structure</font>
<br><font size=-1>2 - pointer to the device to query</font>
<br><font size=-1>3 - pointer to a buffer to contain a possible error message</font></td>
</tr>
</table>
<p><font size=-1>libnet_get_hwaddr() returns the hardware address of a
specified network device. At the time of this writing, only ethernet
is supported. The function takes a pointer to a link layer interface
structure, a pointer to the network device name, and an empty buffer to
be used in case of error. The function returns the MAC address of
the specified interface upon success or NULL upon error (and errbuf will
contain a reason).</font>
<br>
<hr ALIGN="LEFT">
<br><a NAME="s5_3"></a><b><font size=+2>5.3 Packet Injection Support Functions</font></b>
<br>
<hr ALIGN="LEFT">
<br><b>int libnet_open_raw_sock(int protocol);</b>
<br>
<br>
<table BORDER WIDTH="601" >
<tr>
<td VALIGN=CENTER><font size=-1>return value upon success</font></td>
<td VALIGN=CENTER><font size=-1>opened socket</font></td>
</tr>
<tr>
<td VALIGN=CENTER><font size=-1>return value upon failure</font></td>
<td VALIGN=CENTER><font size=-1>-1</font></td>
</tr>
<tr>
<td VALIGN=CENTER><font size=-1>re-entrant</font></td>
<td VALIGN=CENTER><font size=-1>yes</font></td>
</tr>
<tr>
<td VALIGN=CENTER><font size=-1>arguments</font></td>
<td VALIGN=CENTER><font size=-1>1 - protocol number of desired socket type</font></td>
</tr>
</table>
<p><font size=-1>libnet_open_raw_sock() opens a raw IP socket of the specified
protocol type (supported types vary from system to system, but usually
you'll want to open an IPPROTO_RAW socket). The function also sets
the IP_HDRINCL socket option. Returned is the socket file descriptor
or -1 on error. The function can fail if either of the underlying
calls to socket or setsockopt fails. Checking errno will reveal the
reason for the error.</font>
<br>
<hr ALIGN="LEFT">
<br><b>int libnet_close_raw_sock(int socket);</b>
<br>
<br>
<table BORDER WIDTH="436" >
<tr>
<td VALIGN=CENTER><font size=-1>return value upon success</font></td>
<td VALIGN=CENTER><font size=-1>1</font></td>
</tr>
<tr>
<td VALIGN=CENTER><font size=-1>return value upon failure</font></td>
<td VALIGN=CENTER><font size=-1>-1</font></td>
</tr>
<tr>
<td VALIGN=CENTER><font size=-1>re-entrant</font></td>
<td VALIGN=CENTER><font size=-1>yes</font></td>
</tr>
<tr>
<td VALIGN=CENTER><font size=-1>arguments</font></td>
<td VALIGN=CENTER><font size=-1>1 - socket to be closed</font></td>
</tr>
</table>
<p><font size=-1>libnet_close_raw_sock() will close the referenced raw
socket.</font>
<br>
<hr ALIGN="LEFT">
<br><b>int libnet_select_device(struct sockaddr_in *sin, u_char **device,
u_char *ebuf);</b>
<br>
<br>
<table BORDER WIDTH="693" >
<tr>
<td VALIGN=CENTER><font size=-1>return value upon success</font></td>
<td VALIGN=CENTER><font size=-1>1</font></td>
</tr>
<tr>
<td VALIGN=CENTER><font size=-1>return value upon failure</font></td>
<td VALIGN=CENTER><font size=-1>-1</font></td>
</tr>
<tr>
<td VALIGN=CENTER><font size=-1>re-entrant</font></td>
<td VALIGN=CENTER><font size=-1>no</font></td>
</tr>
<tr>
<td VALIGN=CENTER><font size=-1>arguments</font></td>
<td VALIGN=CENTER><font size=-1>1 - pointer to a sockaddr_in structure
pointer</font>
<br><font size=-1>2 - pointer to the device to query</font>
<br><font size=-1>3 - pointer to a buffer to contain a possible error message</font></td>
</tr>
</table>
<p><font size=-1>libnet_select_device() will run through the list of interfaces
and select one for use (ignoring the loopback device). If the device
argument points to NULL (don't pass in a NULL pointer, the function expects
a pointer to a pointer, and C can't derefrence a NULL pointer) it will
try to fill it in with the first non-loopback device it finds, otherwise,
it will try to open the specified device. If successful, 1 is returned
(and if device was NULL, it will now contain the device name which can
be used in libnet_*link*() type calls). The function can fail for
a variety of reasons, including socket system call failures, ioctl failures,
if no interfaces are found, etc.. If such an error occurs, -1 is
returned and errbuf will contain a reason.</font>
<br>
<hr ALIGN="LEFT">
<br><b>struct libnet_link_int *libnet_open_link_interface(char *device,
char *ebuf);</b>
<br>
<br>
<table BORDER WIDTH="733" >
<tr>
<td VALIGN=CENTER><font size=-1>return value upon success</font></td>
<td VALIGN=CENTER><font size=-1>pointer to a link interface structure</font></td>
</tr>
<tr>
<td VALIGN=CENTER><font size=-1>return value upon failure</font></td>
<td VALIGN=CENTER><font size=-1>NULL</font></td>
</tr>
<tr>
<td VALIGN=CENTER><font size=-1>re-entrant</font></td>
<td VALIGN=CENTER><font size=-1>yes</font></td>
</tr>
<tr>
<td VALIGN=CENTER><font size=-1>arguments</font></td>
<td VALIGN=CENTER><font size=-1>1 - pointer to a device</font>
<br><font size=-1>2 - pointer to a buffer to contain a possible error message</font></td>
</tr>
</table>
<p><font size=-1>libnet_open_link_interface() opens a low-level packet
interface. This is required in order to be able inject link layer
frames. Supplied is a u_char pointer to the interface device name
and a u_char pointer to an error buffer. Returned is a filled-in
link_int structure or NULL on error (with the error buffer containing the
reason). The function can fail for a variety of reasons due to the
fact that it is architecture specific.</font>
<br>
<hr ALIGN="LEFT">
<br><b>int libnet_close_link_interface(struct libnet_link_int *l);</b>
<br>
<br>
<table BORDER WIDTH="712" >
<tr>
<td VALIGN=CENTER><font size=-1>return value upon success</font></td>
<td VALIGN=CENTER><font size=-1>1</font></td>
</tr>
<tr>
<td VALIGN=CENTER><font size=-1>return value upon failure</font></td>
<td VALIGN=CENTER><font size=-1>-1</font></td>
</tr>
<tr>
<td VALIGN=CENTER><font size=-1>re-entrant</font></td>
<td VALIGN=CENTER><font size=-1>yes</font></td>
</tr>
<tr>
<td VALIGN=CENTER><font size=-1>arguments</font></td>
<td VALIGN=CENTER><font size=-1>1 - pointer to a link interface structure</font></td>
</tr>
</table>
<p><font size=-1>libnet_close_link_interface() closes an opened low-level
packet interface.</font>
<br>
<hr ALIGN="LEFT">
<br><b>int libnet_write_ip(int socket, u_char *packet, int packet_size);</b>
<br>
<br>
<table BORDER WIDTH="436" >
<tr>
<td VALIGN=CENTER><font size=-1>return value upon success</font></td>
<td VALIGN=CENTER><font size=-1>packet size</font></td>
</tr>
<tr>
<td VALIGN=CENTER><font size=-1>return value upon failure</font></td>
<td VALIGN=CENTER><font size=-1>-1</font></td>
</tr>
<tr>
<td VALIGN=CENTER><font size=-1>re-entrant</font></td>
<td VALIGN=CENTER><font size=-1>yes</font></td>
</tr>
<tr>
<td VALIGN=CENTER><font size=-1>arguments</font></td>
<td VALIGN=CENTER><font size=-1>1 - socket</font>
<br><font size=-1>2 - pointer to the packet</font>
<br><font size=-1>3 - packet size</font></td>
</tr>
</table>
<p><font size=-1>libnet_write_ip() writes an IP packet to the network.
The first argument is the socket created with a previous call to libnet_open_raw_sock,
the second is a pointer to a buffer containing a complete IP datagram,
and the third argument is the total packet size. The function returns
the number of bytes written upon success or -1 on error (with errno containing
the reason).</font>
<br>
<hr ALIGN="LEFT">
<br><b>int libnet_write_link_layer(struct libnet_link_int *l, const u_char
*device, u_char *packet, int packet_size);</b>
<br>
<br>
<table BORDER WIDTH="666" >
<tr>
<td VALIGN=CENTER><font size=-1>return value upon success</font></td>
<td VALIGN=CENTER><font size=-1>packet size</font></td>
</tr>
<tr>
<td VALIGN=CENTER><font size=-1>return value upon failure</font></td>
<td VALIGN=CENTER><font size=-1>-1</font></td>
</tr>
<tr>
<td VALIGN=CENTER><font size=-1>re-entrant</font></td>
<td VALIGN=CENTER><font size=-1>depends on architecture</font></td>
</tr>
<tr>
<td VALIGN=CENTER><font size=-1>arguments</font></td>
<td VALIGN=CENTER><font size=-1>1 - pointer to a link interface structure</font>
<br><font size=-1>2 - pointer to the network device</font>
<br><font size=-1>3 - pointer to the packet</font>
<br><font size=-1>4 - packet size</font></td>
</tr>
</table>
<p><font size=-1>libnet_write_link_layer() writes a link-layer frame to
the network. The first argument is a pointer to a filled-in libnet_link_int
structure, the next is a pointer to the network device, the third is the
raw packet and the last is the packet size. Returned is the number
of bytes written or -1 on error.</font>
<br>
<hr ALIGN="LEFT">
<br><b>int libnet_do_checksum(u_char *packet, int protocol, int packet_size);</b>
<br>
<br>
<table BORDER WIDTH="659" >
<tr>
<td VALIGN=CENTER><font size=-1>return value upon success</font></td>
<td VALIGN=CENTER><font size=-1>1</font></td>
</tr>
<tr>
<td VALIGN=CENTER><font size=-1>return value upon failure</font></td>
<td VALIGN=CENTER><font size=-1>-1</font></td>
</tr>
<tr>
<td VALIGN=CENTER><font size=-1>re-entrant</font></td>
<td VALIGN=CENTER><font size=-1>yes</font></td>
</tr>
<tr>
<td VALIGN=CENTER><font size=-1>arguments</font></td>
<td VALIGN=CENTER><font size=-1>1 - pointer to a packet</font>
<br><font size=-1>2 - protocol number of packet type</font>
<br><font size=-1>3 - packet size</font></td>
</tr>
</table>
<p><font size=-1>libnet_do_checksum() calculates the checksum for a packet.
The first argument is a pointer to a fully built IP packet. The second
is the transport protocol of the packet and the third is the packet length
(not including the IP header). The function calculates the checksum
for the transport protocol and fills it in at the appropriate header location
(this function should be called only after a complete packet has been built).</font>
<p><font size=-1>Note that when using raw sockets the IP checksum is always
computed by the kernel and does not need to done by the user. When
using the link layer interface the IP checksum must be explicitly computed
(in this case, the protocol would be of type IPPROTO_IP and the size would
include IP_H). The function returns 1 upon success or -1 if the protocol
is of an unsupported type. Currently supported are:</font>
<br>
<br>
<table BORDER WIDTH="366" >
<tr>
<td VALIGN=CENTER><b>VALUE</b></td>
<td VALIGN=CENTER><b>PROTOCOL</b></td>
</tr>
<tr>
<td VALIGN=CENTER><font size=-1>IPPROTO_TCP</font></td>
<td VALIGN=CENTER><font size=-1>TCP</font></td>
</tr>
<tr>
<td VALIGN=CENTER><font size=-1>IPPROTO_UDP</font></td>
<td VALIGN=CENTER><font size=-1>UDP</font></td>
</tr>
<tr>
<td VALIGN=CENTER><font size=-1>IPPROTO_ICMP</font></td>
<td VALIGN=CENTER><font size=-1>ICMP</font></td>
</tr>
<tr>
<td VALIGN=CENTER><font size=-1>IPPROTO_IGMP</font></td>
<td VALIGN=CENTER><font size=-1>IGMP</font></td>
</tr>
<tr>
<td VALIGN=CENTER><font size=-1>IPPROTO_IP</font></td>
<td VALIGN=CENTER><font size=-1>IP (for the link-layer api)</font></td>
</tr>
<tr>
<td VALIGN=CENTER><font size=-1>IPPROTO_OSPF</font></td>
<td VALIGN=CENTER><font size=-1>OSPF</font></td>
</tr>
<tr>
<td VALIGN=CENTER><font size=-1>IPPROTO_OSPF</font></td>
<td VALIGN=CENTER><font size=-1>OSPF_LSA</font></td>
</tr>
</table>
<hr ALIGN="LEFT">
<br><a NAME="s5_4"></a><b><font size=+2>5.4 Packet Construction Functions</font></b>
<br>
<hr ALIGN="LEFT">
<br><font size=-1>All libnet packet creation functions contain the same
three terminal arguments: a pointer to an optional payload (or NULL if
no payload is to be included), the length of the payload in bytes (or 0
if no payload is included) and most importantly, a pointer to a pre-allocated
block of memory (which must be large enough to accommodate the entire packet
and payload).</font>
<p><font size=-1>The only way for any libnet packet construction function
will return an error is if the memory which is supposed to be pre-allocated
points to NULL.</font>
<p><b>libnet_build_arp(u_short hrdw, u_short prot, u_short h_len, u_short
p_len, u_short op, u_char *s_ha, u_char *s_pa, u_char *t_ha, u_char *t_pa,
const u_char *payload, int payload_len, u_char *packet_buf);</b>
<br>
<br>
<table BORDER WIDTH="656" >
<tr>
<td VALIGN=CENTER><font size=-1>return value upon success</font></td>
<td VALIGN=CENTER><font size=-1>1</font></td>
</tr>
<tr>
<td VALIGN=CENTER><font size=-1>return value upon failure</font></td>
<td VALIGN=CENTER><font size=-1>-1</font></td>
</tr>
<tr>
<td VALIGN=CENTER><font size=-1>re-entrant</font></td>
<td VALIGN=CENTER><font size=-1>yes</font></td>
</tr>
<tr>
<td VALIGN=CENTER><font size=-1>arguments</font></td>
<td VALIGN=CENTER><font size=-1>1 - hardware address format (ARPHRD_ETHER)</font>
<br><font size=-1>2 - protocol address format</font>
<br><font size=-1>3 - length of the hardware address</font>
<br><font size=-1>4 - length of the protocol address</font>
<br><font size=-1>5 - ARP operation type</font>
<br><font size=-1>6 - sender's hardware address</font>
<br><font size=-1>7 - sender's protocol address</font>
<br><font size=-1>8 - target's hardware address</font>
<br><font size=-1>9 - target's protocol address</font>
<br><font size=-1>10 - pointer to packet payload</font>
<br><font size=-1>11 - packet payload length</font>
<br><font size=-1>12 - pointer to pre-allocated packet memory</font></td>
</tr>
</table>
<p><font size=-1>libnet_build_arp() constructs an ARP (RARP) packet.
At this point in the library, the function only builds ethernet/ARP packets,
but this will be easy enough to change (whenever I get around to it).
The first nine arguments are standard ARP header arguments, with the last
three being standard libnet packet creation arguments. The ARP operation
type should be one of the following symbolic types:</font>
<br>
<table BORDER WIDTH="472" >
<tr>
<td VALIGN=CENTER><b>VALUE</b></td>
<td VALIGN=CENTER><b>DESCRIPTION</b></td>
</tr>
<tr>
<td VALIGN=CENTER><font size=-1>ARPOP_REQUEST</font></td>
<td VALIGN=CENTER><font size=-1>ARP request</font></td>
</tr>
<tr>
<td VALIGN=CENTER><font size=-1>ARPOP_REPLY</font></td>
<td VALIGN=CENTER><font size=-1>ARP reply</font></td>
</tr>
<tr>
<td VALIGN=CENTER><font size=-1>ARPOP_REVREQUEST</font></td>
<td VALIGN=CENTER><font size=-1>RARP request</font></td>
</tr>
<tr>
<td VALIGN=CENTER><font size=-1>ARPOP_REVREPLY</font></td>
<td VALIGN=CENTER><font size=-1>RARP reply</font></td>
</tr>
<tr>
<td VALIGN=CENTER><font size=-1>ARPOP_INVREQUEST </font></td>
<td VALIGN=CENTER><font size=-1>request to identify peer</font></td>
</tr>
<tr>
<td VALIGN=CENTER><font size=-1>ARPOP_INVREPLY</font></td>
<td VALIGN=CENTER><font size=-1>reply identifying peer</font></td>
</tr>
</table>
<hr ALIGN="LEFT">
<br><b>int libnet_build_dns(u_short id, u_short flags, u_short num_q, u_short
num_answ_rr, u_short num_auth_rr, u_short num_add_rr, const u_char * payload,
int payload_len, u_char *packet_buf);</b>
<br>
<br>
<table BORDER WIDTH="658" >
<tr>
<td VALIGN=CENTER><font size=-1>return value upon success</font></td>
<td VALIGN=CENTER><font size=-1>1</font></td>
</tr>
<tr>
<td VALIGN=CENTER><font size=-1>return value upon failure</font></td>
<td VALIGN=CENTER><font size=-1>-1</font></td>
</tr>
<tr>
<td VALIGN=CENTER><font size=-1>re-entrant</font></td>
<td VALIGN=CENTER><font size=-1>yes</font></td>
</tr>
<tr>
<td VALIGN=CENTER><font size=-1>arguments</font></td>
<td VALIGN=CENTER><font size=-1>1 - packet id</font>
<br><font size=-1>2 - control flags</font>
<br><font size=-1>3 - number of questions</font>
<br><font size=-1>4 - number of answer resource records</font>
<br><font size=-1>5 - number of authority resource records</font>
<br><font size=-1>6 - number of additional resource records</font>
<br><font size=-1>7 - pointer to packet payload</font>
<br><font size=-1>8 - packet payload length</font>
<br><font size=-1>9 - pointer to pre-allocated packet memory</font></td>
</tr>
</table>
<p><font size=-1>libnet_build_dns() constructs a DNS packet. The
static DNS fields are included as the first six arguments, but the optional
variable length fields must be included with the payload interface.</font>
<br>
<hr ALIGN="LEFT">
<br><b>int libnet_build_ethernet(u_char *daddr, u_char *saddr, u_short
id, const u_char *payload, int payload_len, u_char *packet_buf);</b>
<br>
<br>
<table BORDER WIDTH="574" >
<tr>
<td VALIGN=CENTER><font size=-1>return value upon success</font></td>
<td VALIGN=CENTER><font size=-1>1</font></td>
</tr>
<tr>
<td VALIGN=CENTER><font size=-1>return value upon failure</font></td>
<td VALIGN=CENTER><font size=-1>-1</font></td>
</tr>
<tr>
<td VALIGN=CENTER><font size=-1>re-entrant</font></td>
<td VALIGN=CENTER><font size=-1>yes</font></td>
</tr>
<tr>
<td VALIGN=CENTER><font size=-1>arguments</font></td>
<td VALIGN=CENTER><font size=-1>1 - pointer to the destination address</font>
<br><font size=-1>2 - pointer to the source address</font>
<br><font size=-1>3 - ethernet packet type</font>
<br><font size=-1>4 - pointer to packet payload</font>
<br><font size=-1>5 - packet payload size</font>
<br><font size=-1>6 - pointer to pre-allocated packet memory</font></td>
</tr>
</table>
<p><font size=-1>libnet_build_ethernet() constructs an ethernet packet.
The destination address and source address arguments are expected to be
arrays of unsigned character bytes. The packet type should be one
of the following:</font>
<br>
<table BORDER WIDTH="469" >
<tr>
<td VALIGN=CENTER><b>VALUE</b></td>
<td VALIGN=CENTER><b>PROTOCOL</b></td>
</tr>
<tr>
<td VALIGN=CENTER><font size=-1>ETHERTYPE_PUP</font></td>
<td VALIGN=CENTER><font size=-1>PUP</font></td>
</tr>
<tr>
<td VALIGN=CENTER><font size=-1>ETHERTYPE_IP</font></td>
<td VALIGN=CENTER><font size=-1>IP</font></td>
</tr>
<tr>
<td VALIGN=CENTER><font size=-1>ETHERTYPE_ARP</font></td>
<td VALIGN=CENTER><font size=-1>ARP</font></td>
</tr>
<tr>
<td VALIGN=CENTER><font size=-1>ETHERTYPE_REVARP</font></td>
<td VALIGN=CENTER><font size=-1>RARP</font></td>
</tr>
<tr>
<td VALIGN=CENTER><font size=-1>ETHERTYPE_VLAN</font></td>
<td VALIGN=CENTER><font size=-1>IEEE VLAN tagging</font></td>
</tr>
<tr>
<td VALIGN=CENTER><font size=-1>ETHERTYPE_LOOPBACK</font></td>
<td VALIGN=CENTER><font size=-1>loopback test</font></td>
</tr>
</table>
<hr ALIGN="LEFT">
<br><b>int libnet_build_icmp_echo(u_char type, u_char code, u_short id,
u_short seq, const u_char *payload, int payload_len, u_char *packet_buf);</b>
<br>
<br>
<table BORDER WIDTH="557" >
<tr>
<td VALIGN=CENTER><font size=-1>return value upon success</font></td>
<td VALIGN=CENTER><font size=-1>1</font></td>
</tr>
<tr>
<td VALIGN=CENTER><font size=-1>return value upon failure</font></td>
<td VALIGN=CENTER><font size=-1>-1</font></td>
</tr>
<tr>
<td VALIGN=CENTER><font size=-1>re-entrant</font></td>
<td VALIGN=CENTER><font size=-1>yes</font></td>
</tr>
<tr>
<td VALIGN=CENTER><font size=-1>arguments</font></td>
<td VALIGN=CENTER><font size=-1>1- packet type</font>
<br><font size=-1>2 - packet code</font>
<br><font size=-1>3 - packet id</font>
<br><font size=-1>4 - packet sequence number</font>
<br><font size=-1>5 - pointer to packet payload</font>
<br><font size=-1>6 - packet payload size</font>
<br><font size=-1>7 - pointer to pre-allocated packet memory</font></td>
</tr>
</table>
<p><font size=-1>libnet_build_icmp_echo() constructs an ICMP_ECHO / ICMP_ECHOREPLY
packet. The packet type should be ICMP_ECHOREPLY or ICMP_ECHO and
the code should be 0.</font>
<br>
<hr ALIGN="LEFT">
<br><b>int libnet_build_icmp_mask(u_char type, u_char code, u_short id,
u_short seq, u_long mask, const u_char *payload, int payload_len, u_char
*packet_buf);</b>
<br>
<br>
<table BORDER WIDTH="596" >
<tr>
<td VALIGN=CENTER><font size=-1>return value upon success</font></td>
<td VALIGN=CENTER><font size=-1>1</font></td>
</tr>
<tr>
<td VALIGN=CENTER><font size=-1>return value upon failure</font></td>
<td VALIGN=CENTER><font size=-1>-1</font></td>
</tr>
<tr>
<td VALIGN=CENTER><font size=-1>re-entrant</font></td>
<td VALIGN=CENTER><font size=-1>yes</font></td>
</tr>
<tr>
<td VALIGN=CENTER><font size=-1>arguments</font></td>
<td VALIGN=CENTER><font size=-1>1 - packet type</font>
<br><font size=-1>2 - packet code</font>
<br><font size=-1>3 - packet id</font>
<br><font size=-1>4 - packet sequence number</font>
<br><font size=-1>5 - IP netmask</font>
<br><font size=-1>6 - pointer to packet payload</font>
<br><font size=-1>7 - packet payload length</font>
<br><font size=-1>8 - pointer to pre-allocated packet memory</font></td>
</tr>
</table>
<p><font size=-1>libnet_build_icmp_mask() constructs an ICMP_MASKREQ /
ICMP_MASKREPLY packet. The packet type should be either ICMP_MASKREQ
or ICMP_MASKREPLY and the code should be 0. The IP netmask argument
should be a 32-bit network-byte ordered subnet mask.</font>
<br>
<hr ALIGN="LEFT">
<br><b>int libnet_build_icmp_unreach(u_char type, u_char code, u_short
orig_len, u_char orig_tos, u_short orig_id, u_short orig_frag, u_char orig_ttl,
u_char orig_prot, u_long orig_saddr, u_long orig_daddr, const u_char *payload,
int payload_len, u_char *packet_buf);</b>
<br>
<br>
<table BORDER WIDTH="592" >
<tr>
<td VALIGN=CENTER><font size=-1>return value upon success</font></td>
<td VALIGN=CENTER><font size=-1>1</font></td>
</tr>
<tr>
<td VALIGN=CENTER><font size=-1>return value upon failure</font></td>
<td VALIGN=CENTER><font size=-1>-1</font></td>
</tr>
<tr>
<td VALIGN=CENTER><font size=-1>re-entrant</font></td>
<td VALIGN=CENTER><font size=-1>yes</font></td>
</tr>
<tr>
<td VALIGN=CENTER><font size=-1>arguments</font></td>
<td VALIGN=CENTER><font size=-1>1 - packet type</font>
<br><font size=-1>2 - packet code</font>
<br><font size=-1>3 - original IP length</font>
<br><font size=-1>4 - original IP TOS</font>
<br><font size=-1>5 - original IP id</font>
<br><font size=-1>6 - original IP fragmentation bits</font>
<br><font size=-1>7 - original IP time to live</font>
<br><font size=-1>8 - original IP protocol</font>
<br><font size=-1>9 - original IP source address</font>
<br><font size=-1>10 - original IP destination address</font>
<br><font size=-1>11 - pointer to original IP payload</font>
<br><font size=-1>12 - original IP payload size</font>
<br><font size=-1>13 - pointer to pre-allocated packet memory</font></td>
</tr>
</table>
<p><font size=-1>libnet_build_icmp_unreach() constructs an ICMP_UNREACH
packet. The 3rd through the 12th arguments are used to build the
IP header of the original packet that caused the error message (the ICMP
unreachable). The packet type should be ICMP_UNREACH and the code
should be one of the following:</font>
<br>
<table BORDER WIDTH="699" >
<tr>
<td VALIGN=CENTER><b>VALUE</b></td>
<td VALIGN=CENTER><b>DESCSRIPTION</b></td>
</tr>
<tr>
<td VALIGN=CENTER><font size=-1>ICMP_UNREACH_NET</font></td>
<td VALIGN=CENTER><font size=-1>network is unreachable</font></td>
</tr>
<tr>
<td VALIGN=CENTER><font size=-1>ICMP_UNREACH_HOST</font></td>
<td VALIGN=CENTER><font size=-1>host is unreachable</font></td>
</tr>
<tr>
<td VALIGN=CENTER><font size=-1>ICMP_UNREACH_PROTOCOL</font></td>
<td VALIGN=CENTER><font size=-1>protocol is unreachable</font></td>
</tr>
<tr>
<td VALIGN=CENTER><font size=-1>ICMP_UNREACH_PORT</font></td>
<td VALIGN=CENTER><font size=-1>port is unreachable</font></td>
</tr>
<tr>
<td VALIGN=CENTER><font size=-1>ICMP_UNREACH_NEEDFRAG</font></td>
<td VALIGN=CENTER><font size=-1>fragmentation required but DF bit set</font></td>
</tr>
<tr>
<td VALIGN=CENTER><font size=-1>ICMP_UNREACH_SRCFAIL</font></td>
<td VALIGN=CENTER><font size=-1>source routing failed</font></td>
</tr>
<tr>
<td VALIGN=CENTER><font size=-1>ICMP_UNREACH_NET_UNKOWN</font></td>
<td VALIGN=CENTER><font size=-1>network is unknown</font></td>
</tr>
<tr>
<td VALIGN=CENTER><font size=-1>ICMP_UNREACH_HOST_PROHIB</font></td>
<td VALIGN=CENTER><font size=-1>host is prohibited</font></td>
</tr>
<tr>
<td VALIGN=CENTER><font size=-1>ICMP_UNREACH_TOSNET</font></td>
<td VALIGN=CENTER><font size=-1>IP TOS and network</font></td>
</tr>
<tr>
<td VALIGN=CENTER><font size=-1>ICMP_UNREACH_TOSHOST</font></td>
<td VALIGN=CENTER><font size=-1>IP TOS and host</font></td>
</tr>
<tr>
<td VALIGN=CENTER><font size=-1>ICMP_UNREACH_FILTER_PROHIB</font></td>
<td VALIGN=CENTER><font size=-1>prohibitive filtering</font></td>
</tr>
<tr>
<td VALIGN=CENTER><font size=-1>ICMP_UNREACH_HOST_PRECEDENCE</font></td>
<td VALIGN=CENTER><font size=-1>host precedence</font></td>
</tr>
<tr>
<td VALIGN=CENTER><font size=-1>ICMP_UNREACH_PRECEDENCE_CUTOFF</font></td>
<td VALIGN=CENTER><font size=-1>host precedence cut-off</font></td>
</tr>
</table>
<hr ALIGN="LEFT">
<br><b>int libnet_build_icmp_timeexceed(u_char, u_char, u_short, u_char,
u_short, u_short, u_char, u_char, u_long, u_long, const u_char *, int,
u_char *);</b>
<br>
<br>
<table BORDER WIDTH="637" >
<tr>
<td VALIGN=CENTER><font size=-1>return value upon success</font></td>
<td VALIGN=CENTER><font size=-1>1</font></td>
</tr>
<tr>
<td VALIGN=CENTER><font size=-1>return value upon failure</font></td>
<td VALIGN=CENTER><font size=-1>-1</font></td>
</tr>
<tr>
<td VALIGN=CENTER><font size=-1>re-entrant</font></td>
<td VALIGN=CENTER><font size=-1>yes</font></td>
</tr>
<tr>
<td VALIGN=CENTER><font size=-1>arguments</font></td>
<td VALIGN=CENTER><font size=-1>1 - packet type</font>
<br><font size=-1>2 - packet code</font>
<br><font size=-1>3 - original IP length</font>
<br><font size=-1>4 - original IP TOS</font>
<br><font size=-1>5 - original IP id</font>
<br><font size=-1>6 - original IP fragmentation bits</font>
<br><font size=-1>7 - original IP time to live</font>
<br><font size=-1>8 - original IP protocol</font>
<br><font size=-1>9 - original IP source address</font>
<br><font size=-1>10 - original IP destination address</font>
<br><font size=-1>11 - pointer to original IP payload</font>
<br><font size=-1>12 - original IP payload size</font>
<br><font size=-1>13 - pointer to pre-allocated packet memory</font></td>
</tr>
</table>
<p><font size=-1>libnet_build_icmp_timeexceed() constructs an ICMP_TIMEXCEED
packet. This function is identical to libnet_build_icmp_unreach with
the exception of the packet type and code. The packet type should
be either ICMP_TIMXCEED_INTRANS for packets that expired in transit (TTL
expired) or ICMP_TIMXCEED_REASS for packets that expired in the fragmentation
reassembly queue.</font>
<br>
<hr ALIGN="LEFT">
<br><b>int libnet_build_icmp_redirect(u_char type, u_char code, u_long
gateway, u_short orig_len, u_char orig_tos, u_short orig_id, u_short orig_frag,
u_char orig_ttl, u_char orig_prot, u_long orig_saddr, u_long orig_daddr,
const u_char *payload, int payload_len, u_char *packet_buf);</b>
<br>
<br>
<table BORDER WIDTH="590" >
<tr>
<td VALIGN=CENTER><font size=-1>return value upon success</font></td>
<td VALIGN=CENTER><font size=-1>1</font></td>
</tr>
<tr>
<td VALIGN=CENTER><font size=-1>return value upon failure</font></td>
<td VALIGN=CENTER><font size=-1>-1</font></td>
</tr>
<tr>
<td VALIGN=CENTER><font size=-1>re-entrant</font></td>
<td VALIGN=CENTER><font size=-1>yes</font></td>
</tr>
<tr>
<td VALIGN=CENTER><font size=-1>arguments</font></td>
<td VALIGN=CENTER><font size=-1>1 - packet type</font>
<br><font size=-1>2 - packet code</font>
<br><font size=-1>3 - IP address of the gateway</font>
<br><font size=-1>4 - original IP length</font>
<br><font size=-1>5 - original IP TOS</font>
<br><font size=-1>6 - original IP id</font>
<br><font size=-1>7 - original IP fragmentation bits</font>
<br><font size=-1>8 - original IP time to live</font>
<br><font size=-1>9 - original IP protocol</font>
<br><font size=-1>10 - original IP source address</font>
<br><font size=-1>11 - original IP destination address</font>
<br><font size=-1>12 - pointer to original IP payload</font>
<br><font size=-1>13 - original IP payload size</font>
<br><font size=-1>14 - pointer to pre-allocated packet memory</font></td>
</tr>
</table>
<p><font size=-1>libnet_build_icmp_redirect() constructs an ICMP_REDIRECT
packet. This function is similar to libnet_build_icmp_unreach, the
differences being the type and code and the addition of an argument to
hold the IP address of the gateway that should be used (hence the redirect).
The packet type should be ICMP_REDIRECT and the code should be one of the
following:</font>
<br>
<table BORDER WIDTH="545" >
<tr>
<td VALIGN=CENTER><b>VALUE</b></td>
<td VALIGN=CENTER><b>DESCSRIPTION</b></td>
</tr>
<tr>
<td VALIGN=CENTER><font size=-1>ICMP_UNREACH_NET</font></td>
<td VALIGN=CENTER><font size=-1>redirect for network</font></td>
</tr>
<tr>
<td VALIGN=CENTER><font size=-1>ICMP_UNREACH_HOST</font></td>
<td VALIGN=CENTER><font size=-1>redirect for host</font></td>
</tr>
<tr>
<td VALIGN=CENTER><font size=-1>ICMP_UNREACH_PROTOCOL</font></td>
<td VALIGN=CENTER><font size=-1>redirect for TOS and network</font></td>
</tr>
<tr>
<td VALIGN=CENTER><font size=-1>ICMP_UNREACH_PORT</font></td>
<td VALIGN=CENTER><font size=-1>redirect for TOS and host</font></td>
</tr>
</table>
<hr ALIGN="LEFT">
<br><b>int libnet_build_icmp_timestamp(u_char type, u_char code, u_short
id, u_short seq, n_time otime, n_time rtime, n_time ttime, const u_char
*payload, int payload_len, u_char *packet_buf);</b>
<br>
<br>
<table BORDER WIDTH="566" >
<tr>
<td VALIGN=CENTER><font size=-1>return value upon success</font></td>
<td VALIGN=CENTER><font size=-1>1</font></td>
</tr>
<tr>
<td VALIGN=CENTER><font size=-1>return value upon failure</font></td>
<td VALIGN=CENTER><font size=-1>-1</font></td>
</tr>
<tr>
<td VALIGN=CENTER><font size=-1>re-entrant</font></td>
<td VALIGN=CENTER><font size=-1>yes</font></td>
</tr>
<tr>
<td VALIGN=CENTER><font size=-1>arguments</font></td>
<td VALIGN=CENTER><font size=-1>1 - packet type</font>
<br><font size=-1>2 - packet code</font>
<br><font size=-1>3 - packet id</font>
<br><font size=-1>4 - packet sequence number</font>
<br><font size=-1>5 - originate timestamp</font>
<br><font size=-1>6 - receive timestamp</font>
<br><font size=-1>7 - transmit timestamp</font>
<br><font size=-1>8 - pointer to packet payload</font>
<br><font size=-1>9 - packet payload size</font>
<br><font size=-1>10 - pointer to pre-allocated packet memory</font></td>
</tr>
</table>
<p><font size=-1>libnet_build_icmp_timestamp() constructs an ICMP_TSTAMP
/ ICMP_TSTAMPREPLY packet. The packet type should be ICMP_TSTAMP
or ICMP_TSTAMPREPLY and the code should be 0.</font>
<br>
<hr ALIGN="LEFT">
<br><b>int libnet_build_igmp(u_char type, u_char code, u_long ip, const
u_char *payload, int payload_len, u_char *packet_buf);</b>
<br>
<table BORDER WIDTH="607" >
<tr>
<td VALIGN=CENTER><font size=-1>return value upon success</font></td>
<td VALIGN=CENTER><font size=-1>1</font></td>
</tr>
<tr>
<td VALIGN=CENTER><font size=-1>return value upon failure</font></td>
<td VALIGN=CENTER><font size=-1>-1</font></td>
</tr>
<tr>
<td VALIGN=CENTER><font size=-1>re-entrant</font></td>
<td VALIGN=CENTER><font size=-1>yes</font></td>
</tr>
<tr>
<td VALIGN=CENTER><font size=-1>arguments</font></td>
<td VALIGN=CENTER><font size=-1>1 - packet type</font>
<br><font size=-1>2 - packet code</font>
<br><font size=-1>3 - IP address</font>
<br><font size=-1>4 - pointer to packet payload</font>
<br><font size=-1>5 - packet payload size</font>
<br><font size=-1>6 - pointer to pre-allocated packet memory</font></td>
</tr>
</table>
<p><font size=-1>libnet_build_igmp() constructs an IGMP packet. The
packet type should be one of the following:</font>
<br>
<table BORDER WIDTH="597" >
<tr>
<td VALIGN=CENTER><b>VALUE</b></td>
<td VALIGN=CENTER><b>DESCSRIPTION</b></td>
</tr>
<tr>
<td VALIGN=CENTER><font size=-1>IGMP_MEMBERSHIP_QUERY</font></td>
<td VALIGN=CENTER><font size=-1>membership query</font></td>
</tr>
<tr>
<td VALIGN=CENTER><font size=-1>IGMP_V1_MEMBERSHIP_REPORT</font></td>
<td VALIGN=CENTER><font size=-1>version 1 membership report</font></td>
</tr>
<tr>
<td VALIGN=CENTER><font size=-1>IGMP_V2_MEMBERSHIP_REPORT</font></td>
<td VALIGN=CENTER><font size=-1>version 2 membership report</font></td>
</tr>
<tr>
<td VALIGN=CENTER><font size=-1>IGMP_LEAVE_GROUP</font></td>
<td VALIGN=CENTER><font size=-1>leave-group message</font></td>
</tr>
</table>
<p><font size=-1>The code, which is a routing sub-message, should probably
be left to 0, unless you know what you're doing.</font>
<br>
<hr ALIGN="LEFT">
<br><b>int libnet_build_ip(u_short len, u_char tos, u_short ip_id, u_short
frag, u_char ttl, u_char protocol, u_long saddr, u_long daddr, const u_char
*payload, int payload_len, u_char *packet_buf);</b>
<br>
<br>
<table BORDER WIDTH="622" >
<tr>
<td VALIGN=CENTER><font size=-1>return value upon success</font></td>
<td VALIGN=CENTER><font size=-1>1</font></td>
</tr>
<tr>
<td VALIGN=CENTER><font size=-1>return value upon failure</font></td>
<td VALIGN=CENTER><font size=-1>-1</font></td>
</tr>
<tr>
<td VALIGN=CENTER><font size=-1>re-entrant</font></td>
<td VALIGN=CENTER><font size=-1>yes</font></td>
</tr>
<tr>
<td VALIGN=CENTER><font size=-1>arguments</font></td>
<td VALIGN=CENTER><font size=-1>1 - packet length (not including the IP
header)</font>
<br><font size=-1>2 - type of service</font>
<br><font size=-1>3 - packet id</font>
<br><font size=-1>4 - fragmentation bits / offset</font>
<br><font size=-1>5 - time to live</font>
<br><font size=-1>6 - protocol</font>
<br><font size=-1>7 - source address</font>
<br><font size=-1>8 - destination address</font>
<br><font size=-1>9 - pointer to packet payload</font>
<br><font size=-1>10 - packet payload length</font>
<br><font size=-1>11 - pointer to pre-allocated packet memory</font></td>
</tr>
</table>
<p><font size=-1>libnet_build_ip() constructs the mighty IP packet.
The fragmentation field may be 0 or contain some combination of the following:</font>
<br>
<table BORDER WIDTH="654" >
<tr>
<td VALIGN=CENTER><b>VALUE</b></td>
<td VALIGN=CENTER><b>DESCRIPTION</b></td>
</tr>
<tr>
<td VALIGN=CENTER><font size=-1>IP_DF</font></td>
<td VALIGN=CENTER><font size=-1>don't fragment this datagram (only valid
when alone)</font></td>
</tr>
<tr>
<td VALIGN=CENTER><font size=-1>IP_MF</font></td>
<td VALIGN=CENTER><font size=-1>more fragments on the way (OR'd together
with an offset value)</font></td>
</tr>
</table>
<p><font size=-1>The IP_OFFMASK is used to retrieve the offset from the
fragmentation field. IP packets may be no larger than IP_MAXPACKET
bytes. The source and destination addresses need to be in network-byte
order. The payload interface should only be used to construct an
arbitrary or non-supported type IP datagram. To construct a TCP,
UDP, or similar type packet, use the relevant libnet_build function.</font>
<br>
<hr ALIGN="LEFT">
<br><b>int libnet_build_ospf(u_short len, u_char type, u_long router_id,
u_long area_id, u_short auth_type, const char *payload, int payload_s,
u_char *buf);</b>
<br>
<table BORDER WIDTH="651" >
<tr>
<td VALIGN=CENTER><font size=-1>return value upon success</font></td>
<td VALIGN=CENTER><font size=-1>1</font></td>
</tr>
<tr>
<td VALIGN=CENTER><font size=-1>return value upon failure</font></td>
<td VALIGN=CENTER><font size=-1>-1</font></td>
</tr>
<tr>
<td VALIGN=CENTER><font size=-1>re-entrant</font></td>
<td VALIGN=CENTER><font size=-1>yes</font></td>
</tr>
<tr>
<td VALIGN=CENTER><font size=-1>arguments</font></td>
<td VALIGN=CENTER><font size=-1>1 - packet length (not including the OSPF
header)</font>
<br><font size=-1>2 - packet type</font>
<br><font size=-1>3 - router ID</font>
<br><font size=-1>4 - area ID</font>
<br><font size=-1>5 - authentication type</font>
<br><font size=-1>6 - pointer to packet payload</font>
<br><font size=-1>7 - packet payload length</font>
<br><font size=-1>8 - pointer to pre-allocated packet memory</font></td>
</tr>
</table>
<p><font size=-1>libnet_build_ospf() builds a OSPF packet. You pass
the packet length (not including the OSPF header), the packet type, 32-bit
router ID, 32-bit area ID, the authentication type, a pointer to an optional
data payload, the payload length, and a pointer to a pre-allocated block
of memory for the packet. The payload should not be used to build
the Hello, LSA, LSU, LSR, or DBD packets as there are specific construction
functions for those packet types. The following variables are to
be used for the OSPF packet type:</font>
<br>
<table BORDER WIDTH="435" >
<tr>
<td VALIGN=CENTER><b>VALUE</b></td>
<td VALIGN=CENTER><b>DESCSRIPTION</b></td>
</tr>
<tr>
<td VALIGN=CENTER><font size=-1>OSPF_UMD</font></td>
<td VALIGN=CENTER><font size=-1>UMD monitoring packet</font></td>
</tr>
<tr>
<td VALIGN=CENTER><font size=-1>OSPF_HELLO</font></td>
<td VALIGN=CENTER><font size=-1>Hello packet</font></td>
</tr>
<tr>
<td VALIGN=CENTER><font size=-1>OSPF_DBD</font></td>
<td VALIGN=CENTER><font size=-1>Database description packet</font></td>
</tr>
<tr>
<td VALIGN=CENTER><font size=-1>OSPF_LSR</font></td>
<td VALIGN=CENTER><font size=-1>Link state request packet</font></td>
</tr>
<tr>
<td VALIGN=CENTER><font size=-1>OSPF_LSU</font></td>
<td VALIGN=CENTER><font size=-1>Link state update packet</font></td>
</tr>
<tr>
<td VALIGN=CENTER><font size=-1>OSPF_LSA</font></td>
<td VALIGN=CENTER><font size=-1>Link state acknowledgement packet</font></td>
</tr>
</table>
<p><font size=-1>The following are the possible authentication types:</font>
<br>
<table BORDER WIDTH="513" >
<tr>
<td VALIGN=CENTER><b>VALUE</b></td>
<td VALIGN=CENTER><b>DESCRIPTION</b></td>
</tr>
<tr>
<td VALIGN=CENTER><font size=-1>OSPF_AUTH_NULL</font></td>
<td VALIGN=CENTER><font size=-1>NULL password</font></td>
</tr>
<tr>
<td VALIGN=CENTER><font size=-1>OSPF_AUTH_SIMPLE</font></td>
<td VALIGN=CENTER><font size=-1>plaintext, 8 character password</font></td>
</tr>
<tr>
<td VALIGN=CENTER><font size=-1>OSPF_AUTH_MD5</font></td>
<td VALIGN=CENTER><font size=-1>MD5</font></td>
</tr>
</table>
<p><font size=-1>The following is the structure used for the 64 bit field
when using MD5:</font>
<p><tt> struct auth {</tt>
<br><tt> u_short ospf_auth_null;
/* NULL 16 bits */</tt>
<br><tt> u_char ospf_auth_keyid;
/* Key ID */</tt>
<br><tt> u_char ospf_auth_len;
/* Auth data len */</tt>
<br><tt> u_int ospf_auth_seq;
/* Sequence num */</tt>
<br><tt> };</tt>
<br>
<hr ALIGN="LEFT">
<br><b>int libnet_build_ospf_hello(u_long netmask, u_short interval, u_char
options, u_char priority, u_int dead_interval, u_long des_router, u_long
backup, u_long neighbor, const char *payload, int payload_s, u_char *buf);</b>
<br>
<br>
<table BORDER WIDTH="609" >
<tr>
<td VALIGN=CENTER><font size=-1>return value upon success</font></td>
<td VALIGN=CENTER><font size=-1>1</font></td>
</tr>
<tr>
<td VALIGN=CENTER><font size=-1>return value upon failure</font></td>
<td VALIGN=CENTER><font size=-1>-1</font></td>
</tr>
<tr>
<td VALIGN=CENTER><font size=-1>re-entrant</font></td>
<td VALIGN=CENTER><font size=-1>yes</font></td>
</tr>
<tr>
<td VALIGN=CENTER><font size=-1>arguments</font></td>
<td VALIGN=CENTER><font size=-1>1 - netmask for interface</font>
<br><font size=-1>2 - num of seconds since last packet was sent</font>
<br><font size=-1>3 - options</font>
<br><font size=-1>4 - priority</font>
<br><font size=-1>5 - num of seconds until router is deemed dead</font>
<br><font size=-1>6 - designated router</font>
<br><font size=-1>7 - backup router</font>
<br><font size=-1>8 - neighbor</font>
<br><font size=-1>9 - packet payload</font>
<br><font size=-1>10 - payload length</font>
<br><font size=-1>11 - pointer to pre-allocated packet memory</font></td>
</tr>
</table>
<p><font size=-1>libnet_build_ospf_hello() builds an OSPF Hello packet.
You pass the netmask for the interface, the number of seconds since the
last packet was sent, possible options, the router's priority (if 0, it
can't be a backup router), the time (in seconds) until a router is deemed
down, the networks designated router, the networks backup router, a neighbor,
a pointer to an optional data payload, the payload length, and a pointer
to a pre-allocated block of memory used for the packet. If there
is more than one neighbor that is to be included in the packet, just allocate
enough space for the packet buf, and pass the neighbors as the "optional
data payload."</font>
<br>
<hr ALIGN="LEFT">
<br><b>int libnet_build_ospf_dbd(u_short len, u_char options, u_char type,
u_int sequence_num, const char *payload, int payload_s, u_char *buf);</b>
<br>
<br>
<table BORDER WIDTH="603" >
<tr>
<td VALIGN=CENTER><font size=-1>return value upon success</font></td>
<td VALIGN=CENTER><font size=-1>1</font></td>
</tr>
<tr>
<td VALIGN=CENTER><font size=-1>return value upon failure</font></td>
<td VALIGN=CENTER><font size=-1>-1</font></td>
</tr>
<tr>
<td VALIGN=CENTER><font size=-1>re-entrant</font></td>
<td VALIGN=CENTER><font size=-1>yes</font></td>
</tr>
<tr>
<td VALIGN=CENTER><font size=-1>arguments</font></td>
<td VALIGN=CENTER><font size=-1>1 - length</font>
<br><font size=-1>2 - options</font>
<br><font size=-1>3 - type</font>
<br><font size=-1>4 - sequence number</font>
<br><font size=-1>5 - packet payload</font>
<br><font size=-1>6 - payload length</font>
<br><font size=-1>7 - pointer to pre-allocated packet memory</font></td>
</tr>
</table>
<p><font size=-1>libnet_build_ospf_dbd() builds an OSPF DataBase Description
(DBD) packet. You pass the maximum length of an IP packet the interface
can use, packet options, the type of exchange occurring, a sequence number,
a pointer to an optional data payload, the payload length, and a pointer
to a pre-allocated block of memory for the packet. The following
can be used for the type variable:</font>
<br>
<table BORDER WIDTH="382" >
<tr>
<td VALIGN=CENTER><b>VALUE</b></td>
<td VALIGN=CENTER><b>DESCRIPTION</b></td>
</tr>
<tr>
<td VALIGN=CENTER><font size=-1>DBD_IBIT</font></td>
<td VALIGN=CENTER><font size=-1>Initialization bit</font></td>
</tr>
<tr>
<td VALIGN=CENTER><font size=-1>DBD_MBIT</font></td>
<td VALIGN=CENTER><font size=-1>More DBD packets en route</font></td>
</tr>
<tr>
<td VALIGN=CENTER><font size=-1>DBD_MSBIT</font></td>
<td VALIGN=CENTER><font size=-1>Sender is the master</font></td>
</tr>
</table>
<hr ALIGN="LEFT">
<br><b>int libnet_build_ospf_lsr(u_int type, u_int ls_id, u_long adv_router,
const char *payload, int payload_s, u_char *buf);</b>
<br>
<br>
<table BORDER WIDTH="594" >
<tr>
<td VALIGN=CENTER><font size=-1>return value upon success</font></td>
<td VALIGN=CENTER><font size=-1>1</font></td>
</tr>
<tr>
<td VALIGN=CENTER><font size=-1>return value upon failure</font></td>
<td VALIGN=CENTER><font size=-1>-1</font></td>
</tr>
<tr>
<td VALIGN=CENTER><font size=-1>re-entrant</font></td>
<td VALIGN=CENTER><font size=-1>yes</font></td>
</tr>
<tr>
<td VALIGN=CENTER><font size=-1>arguments</font></td>
<td VALIGN=CENTER><font size=-1>1 - type</font>
<br><font size=-1>2 - ID</font>
<br><font size=-1>3 - advertising router</font>
<br><font size=-1>4 - packet payload</font>
<br><font size=-1>5 - payload length</font>
<br><font size=-1>6 - pointer to pre-allocated packet memory</font></td>
</tr>
</table>
<p><font size=-1>libnet_build_ospf_lsr() builds an OSPF Link State Request
(LSR) packet. You pass the type of link state packet being requested, the
link state ID, the advertising router, a pointer to an optional data payload,
the payload length, and a pointer to a pre-allocated block of memory for
the packet. See the libnet_build_ospf_lsa() section for more information
regarding variables.</font>
<br>
<hr ALIGN="LEFT">
<br><b>int libnet_build_ospf_lsu(u_int num, const char *payload, int payload_s,
u_char *buf);</b>
<br>
<table BORDER WIDTH="611" >
<tr>
<td VALIGN=CENTER><font size=-1>return value upon success</font></td>
<td VALIGN=CENTER><font size=-1>1</font></td>
</tr>
<tr>
<td VALIGN=CENTER><font size=-1>return value upon failure</font></td>
<td VALIGN=CENTER><font size=-1>-1</font></td>
</tr>
<tr>
<td VALIGN=CENTER><font size=-1>re-entrant</font></td>
<td VALIGN=CENTER><font size=-1>yes</font></td>
</tr>
<tr>
<td VALIGN=CENTER><font size=-1>arguments</font></td>
<td VALIGN=CENTER><font size=-1>1 - number of LSA packets inside</font>
<br><font size=-1>2 - packet payload</font>
<br><font size=-1>3 - payload length</font>
<br><font size=-1>4 - pointer to pre-allocated packet memory</font></td>
</tr>
</table>
<p><font size=-1>libnet_build_ospf_lsu() builds an OSPF Link State Update
(LSU) packet. You pass the number of Link State Acknowledgment (LSA)
packets that will be in the packet, a pointer to an optional data payload,
the payload length, and a pointer to a pre-allocated block of memory for
the packet.</font>
<br>
<hr ALIGN="LEFT">
<br><b>int libnet_build_ospf_lsa(u_short age, u_char options, u_char type,
u_int ls_id, u_long adv_router, u_int sequence_num, u_short len, const
char *payload, int payload_s, u_char *buf);</b>
<br>
<table BORDER WIDTH="597" >
<tr>
<td VALIGN=CENTER><font size=-1>return value upon success</font></td>
<td VALIGN=CENTER><font size=-1>1</font></td>
</tr>
<tr>
<td VALIGN=CENTER><font size=-1>return value upon failure</font></td>
<td VALIGN=CENTER><font size=-1>-1</font></td>
</tr>
<tr>
<td VALIGN=CENTER><font size=-1>re-entrant</font></td>
<td VALIGN=CENTER><font size=-1>yes</font></td>
</tr>
<tr>
<td VALIGN=CENTER><font size=-1>arguments</font></td>
<td VALIGN=CENTER><font size=-1>1 - link state age</font>
<br><font size=-1>2 - options</font>
<br><font size=-1>3 - type</font>
<br><font size=-1>4 - link state ID</font>
<br><font size=-1>5 - advertising router</font>
<br><font size=-1>6 - sequence number</font>
<br><font size=-1>7 - length not including LSA header</font>
<br><font size=-1>8 - packet payload</font>
<br><font size=-1>9 - payload length</font>
<br><font size=-1>10 - pointer to pre-allocated packet memory</font></td>
</tr>
</table>
<p><font size=-1>libnet_build_ospf_lsa() builds an OSPF Link State Acknowledgement
(LSA) packet. You pass the link state age, packet options, type of
LSA, the link state ID, the advertising router, the packet's sequence number,
the length of the packet (_not_ including the LSA header length), a pointer
to an optional data payload, the payload length, and a pointer to a pre-allocated
block of memory for the packet. The following variables can be used
for the type of LSA:</font>
<br>
<table BORDER WIDTH="469" >
<tr>
<td VALIGN=CENTER><b>VALUE</b></td>
<td VALIGN=CENTER><b>DESCRIPTION</b></td>
</tr>
<tr>
<td VALIGN=CENTER><font size=-1>LS_TYPE_RTR</font></td>
<td VALIGN=CENTER><font size=-1>Router LSA</font></td>
</tr>
<tr>
<td VALIGN=CENTER><font size=-1>LS_TYPE_NET</font></td>
<td VALIGN=CENTER><font size=-1>Network LSA</font></td>
</tr>
<tr>
<td VALIGN=CENTER><font size=-1>LS_TYPE_IP</font></td>
<td VALIGN=CENTER><font size=-1>Summary LSA (IP network)</font></td>
</tr>
<tr>
<td VALIGN=CENTER><font size=-1>LS_TYPE_ASBR</font></td>
<td VALIGN=CENTER><font size=-1>Summary LSA (ASBR)</font></td>
</tr>
<tr>
<td VALIGN=CENTER><font size=-1>LS_TYPE_ASEXT</font></td>
<td VALIGN=CENTER><font size=-1>AS-External LSA</font></td>
</tr>
</table>
<hr ALIGN="LEFT">
<br><b>int libnet_build_ospf_lsa_rtr(u_short flags, u_short num, u_int
id, u_int data, u_char type, u_char tos, u_short metric, const char *payload,
int payload_s, u_char *buf);</b>
<br>
<table BORDER WIDTH="605" >
<tr>
<td VALIGN=CENTER><font size=-1>return value upon success</font></td>
<td VALIGN=CENTER><font size=-1>1</font></td>
</tr>
<tr>
<td VALIGN=CENTER><font size=-1>return value upon failure</font></td>
<td VALIGN=CENTER><font size=-1>-1</font></td>
</tr>
<tr>
<td VALIGN=CENTER><font size=-1>re-entrant</font></td>
<td VALIGN=CENTER><font size=-1>yes</font></td>
</tr>
<tr>
<td VALIGN=CENTER><font size=-1>arguments</font></td>
<td VALIGN=CENTER><font size=-1>1 - flags</font>
<br><font size=-1>2 - number of links</font>
<br><font size=-1>3 - link ID</font>
<br><font size=-1>4 - info for link ID</font>
<br><font size=-1>5 - router link type</font>
<br><font size=-1>6 - TOS metrics</font>
<br><font size=-1>7 - packet payload</font>
<br><font size=-1>8 - payload length</font>
<br><font size=-1>9 - pointer to pre-allocated packet memory</font></td>
</tr>
</table>
<p><font size=-1>libnet_build_ospf_lsa_rtr() builds an OSPF Link State
Router packet. You pass the optional packet flags, the number of
links within that packet, the link ID (helps describe the next variable),
the info for the specified link ID, the type of router link, the number
of TOS metrics for this link, the metric (the cost of using the link),
a pointer to an optional data payload, the payload length, and a pointer
to a pre-allocated block of memory for the packet. The possible flags
(not including 0x00) are as follows:</font>
<br>
<table BORDER WIDTH="255" >
<tr>
<td VALIGN=CENTER><b>VALUE</b></td>
<td VALIGN=CENTER><b>DESCRIPTION</b></td>
</tr>
<tr>
<td VALIGN=CENTER><font size=-1>RTR_FLAGS_W</font></td>
<td VALIGN=CENTER><font size=-1>W bit</font></td>
</tr>
<tr>
<td VALIGN=CENTER><font size=-1>RTR_FLAGS_E</font></td>
<td VALIGN=CENTER><font size=-1>E bit</font></td>
</tr>
<tr>
<td VALIGN=CENTER><font size=-1>RTR_FLAGS_B</font></td>
<td VALIGN=CENTER><font size=-1>B bit</font></td>
</tr>
</table>
<p><font size=-1>The possible link ID's are as follows:</font>
<br>
<table BORDER WIDTH="255" >
<tr>
<td VALIGN=CENTER><b>VALUE</b></td>
<td VALIGN=CENTER><b>DESCRIPTION</b></td>
</tr>
<tr>
<td VALIGN=CENTER><font size=-1>LINK_ID_NBR_ID</font></td>
<td VALIGN=CENTER><font size=-1>Neighbors router ID</font></td>
</tr>
<tr>
<td VALIGN=CENTER><font size=-1>LINK_ID_IP_DES</font></td>
<td VALIGN=CENTER><font size=-1>IP address of router</font></td>
</tr>
<tr>
<td VALIGN=CENTER><font size=-1>LINK_ID_SUB</font></td>
<td VALIGN=CENTER><font size=-1>IP subnet number</font></td>
</tr>
</table>
<p><font size=-1>The possible values for the router type are as follows:</font>
<br>
<table BORDER WIDTH="255" >
<tr>
<td VALIGN=CENTER><b>VALUE</b></td>
<td VALIGN=CENTER><b>DESCRIPTION</b></td>
</tr>
<tr>
<td VALIGN=CENTER><font size=-1>RTR_TYPE_PTP</font></td>
<td VALIGN=CENTER><font size=-1>Point to point</font></td>
</tr>
<tr>
<td VALIGN=CENTER><font size=-1>RTR_TYPE_TRANS</font></td>
<td VALIGN=CENTER><font size=-1>Connection to a `transit network`</font></td>
</tr>
<tr>
<td VALIGN=CENTER><font size=-1>RTR_TYPE_STUB</font></td>
<td VALIGN=CENTER><font size=-1>Connection to a `stub network`</font></td>
</tr>
<tr>
<td VALIGN=CENTER><font size=-1>RTR_TYPE_VRTL</font></td>
<td VALIGN=CENTER><font size=-1>Connection to a `virtual link`</font></td>
</tr>
</table>
<hr ALIGN="LEFT">
<br><b>int libnet_build_ospf_lsa_net(u_long netmask, u_int router_id, const
char *payload, int payload_s, u_char *buf);</b>
<br>
<table BORDER WIDTH="573" >
<tr>
<td VALIGN=CENTER><font size=-1>return value upon success</font></td>
<td VALIGN=CENTER><font size=-1>1</font></td>
</tr>
<tr>
<td VALIGN=CENTER><font size=-1>return value upon failure</font></td>
<td VALIGN=CENTER><font size=-1>-1</font></td>
</tr>
<tr>
<td VALIGN=CENTER><font size=-1>re-entrant</font></td>
<td VALIGN=CENTER><font size=-1>yes</font></td>
</tr>
<tr>
<td VALIGN=CENTER><font size=-1>arguments</font></td>
<td VALIGN=CENTER><font size=-1>1 - netmask</font>
<br><font size=-1>2 - router ID</font>
<br><font size=-1>3 - packet payload</font>
<br><font size=-1>4 - packet payload length</font>
<br><font size=-1>5 - pointer to pre-allocated packet memory</font></td>
</tr>
</table>
<p><font size=-1>libnet_build_ospf_lsa_net() builds an OSPF Link Sate Network
packet. You pass the interface's netmask, the router ID, a pointer
to an optional data payload, the payload length, and a pointer to a pre-allocated
block of memory for the packet.</font>
<br>
<hr ALIGN="LEFT">
<br><b>int libnet_build_ospf_lsa_sum(u_long netmask, u_int metric, u_int
tos, const char *payload, int payload_s, u_char *buf);</b>
<br>
<br>
<table BORDER WIDTH="622" >
<tr>
<td VALIGN=CENTER><font size=-1>return value upon success</font></td>
<td VALIGN=CENTER><font size=-1>1</font></td>
</tr>
<tr>
<td VALIGN=CENTER><font size=-1>return value upon failure</font></td>
<td VALIGN=CENTER><font size=-1>-1</font></td>
</tr>
<tr>
<td VALIGN=CENTER><font size=-1>re-entrant</font></td>
<td VALIGN=CENTER><font size=-1>yes</font></td>
</tr>
<tr>
<td VALIGN=CENTER><font size=-1>arguments</font></td>
<td VALIGN=CENTER><font size=-1>1 - netmask</font>
<br><font size=-1>2 - metric</font>
<br><font size=-1>3 - TOS</font>
<br><font size=-1>4 - packet payload</font>
<br><font size=-1>5 - packet payload length</font>
<br><font size=-1>6 - pointer to pre-allocated packet memory</font></td>
</tr>
</table>
<p><font size=-1>libnet_build_ospf_lsa_sum() builds an OSPF Link State
Summary packet. You pass the interface's netmask, the cost of using
the link (metric), the TOS, which is passed as a unsigned integer but the
first 8 bits are the TOS and the last 24 bits are the TOS metric, a pointer
to an optional data payload, the payload length, and a pointer to a pre-allocated
block of memory for the packet.</font>
<br>
<hr ALIGN="LEFT">
<br><b>int libnet_build_ospf_lsa_as(u_long netmask, u_int metric, u_long
fwd_addr, u_int tag, const char *payload, int payload_s, u_char *buf);</b>
<br>
<table BORDER WIDTH="578" >
<tr>
<td VALIGN=CENTER><font size=-1>return value upon success</font></td>
<td VALIGN=CENTER><font size=-1>1</font></td>
</tr>
<tr>
<td VALIGN=CENTER><font size=-1>return value upon failure</font></td>
<td VALIGN=CENTER><font size=-1>-1</font></td>
</tr>
<tr>
<td VALIGN=CENTER><font size=-1>re-entrant</font></td>
<td VALIGN=CENTER><font size=-1>yes</font></td>
</tr>
<tr>
<td VALIGN=CENTER><font size=-1>arguments</font></td>
<td VALIGN=CENTER><font size=-1>1 - netmask</font>
<br><font size=-1>2 - metric</font>
<br><font size=-1>3 - forwarding address</font>
<br><font size=-1>4 - external route tag</font>
<br><font size=-1>6 - packet payload</font>
<br><font size=-1>7 - packet payload length</font>
<br><font size=-1>8 - pointer to pre-allocated packet memory</font></td>
</tr>
</table>
<p><font size=-1>libnet_buils_ospf_lsa_as() builds an OSPF Link State AS
External packet. You pass the interface's netmask, the cost of using the
link (metric), the forwarding address, the external route tag, a pointer
to an optional data payload, the payload length, and a pointer to a pre-allocated
block of memory for the packet. In reality, the metric only uses
the last 24 bits of the unsigned int. The first 8bits are reserved
for a possible bit to be set (the E bit, see above for more info).
The variable AS_E_BIT_ON can be used logically to set the E bit on.</font>
<br>
<hr ALIGN="LEFT">
<br><b>int libnet_build_rip(u_char cmd, u_char ver, u_short domain, u_short
addr_fam, u_short route_tag, u_long ip, u_long mask, u_long next_hop, u_long
metric, const u_char *payload, int payload_len, u_char *packet_buf);</b>
<br>
<table BORDER WIDTH="604" >
<tr>
<td VALIGN=CENTER><font size=-1>return value upon success</font></td>
<td VALIGN=CENTER><font size=-1>1</font></td>
</tr>
<tr>
<td VALIGN=CENTER><font size=-1>return value upon failure</font></td>
<td VALIGN=CENTER><font size=-1>-1</font></td>
</tr>
<tr>
<td VALIGN=CENTER><font size=-1>re-entrant</font></td>
<td VALIGN=CENTER><font size=-1>yes</font></td>
</tr>
<tr>
<td VALIGN=CENTER><font size=-1>arguments</font></td>
<td VALIGN=CENTER><font size=-1>1 - command</font>
<br><font size=-1>2 - version</font>
<br><font size=-1>3 - routing domain (or zero)</font>
<br><font size=-1>4 - address family</font>
<br><font size=-1>5 - route tag (or zero)</font>
<br><font size=-1>6 - IP address</font>
<br><font size=-1>7 - netmask (or zero)</font>
<br><font size=-1>8 - next hop IP address (or zero)</font>
<br><font size=-1>9 - metric</font>
<br><font size=-1>10 - pointer to packet payload</font>
<br><font size=-1>11 - packet payload length</font>
<br><font size=-1>12 - pointer to pre-allocated packet memory</font></td>
</tr>
</table>
<p><font size=-1>libnet_build_rip() constructs a RIP packet. Depending
on the version of RIP you are using, packet fields are slightly different.
The following chart highlights these differences:</font>
<br>
<table BORDER WIDTH="457" >
<tr>
<td VALIGN=CENTER><b>ARGUMENT</b></td>
<td VALIGN=CENTER><b>VERSION 1</b></td>
<td VALIGN=CENTER><b>VERSION 2</b></td>
</tr>
<tr>
<td VALIGN=CENTER><font size=-1>1</font></td>
<td VALIGN=CENTER><font size=-1>command</font></td>
<td VALIGN=CENTER><font size=-1>command</font></td>
</tr>
<tr>
<td VALIGN=CENTER><font size=-1>2</font></td>
<td VALIGN=CENTER><font size=-1>RIPVER_1</font></td>
<td VALIGN=CENTER><font size=-1>RIPVER_2</font></td>
</tr>
<tr>
<td VALIGN=CENTER><font size=-1>3</font></td>
<td VALIGN=CENTER><font size=-1>zero</font></td>
<td VALIGN=CENTER><font size=-1>routing domain</font></td>
</tr>
<tr>
<td VALIGN=CENTER><font size=-1>4</font></td>
<td VALIGN=CENTER><font size=-1>address family</font></td>
<td VALIGN=CENTER><font size=-1>address family</font></td>
</tr>
<tr>
<td VALIGN=CENTER><font size=-1>5</font></td>
<td VALIGN=CENTER><font size=-1>zero</font></td>
<td VALIGN=CENTER><font size=-1>subnet mask</font></td>
</tr>
<tr>
<td VALIGN=CENTER><font size=-1>6</font></td>
<td VALIGN=CENTER><font size=-1>IP address</font></td>
<td VALIGN=CENTER><font size=-1>IP address</font></td>
</tr>
<tr>
<td VALIGN=CENTER><font size=-1>7</font></td>
<td VALIGN=CENTER><font size=-1>zero</font></td>
<td VALIGN=CENTER><font size=-1>subnet mask</font></td>
</tr>
<tr>
<td VALIGN=CENTER><font size=-1>8</font></td>
<td VALIGN=CENTER><font size=-1>zero</font></td>
<td VALIGN=CENTER><font size=-1>next hop ip</font></td>
</tr>
<tr>
<td VALIGN=CENTER><font size=-1>9</font></td>
<td VALIGN=CENTER><font size=-1>metric</font></td>
<td VALIGN=CENTER><font size=-1>metric</font></td>
</tr>
</table>
<p><font size=-1>The RIP commands should be one of the following:</font>
<br>
<table BORDER WIDTH="255" >
<tr>
<td VALIGN=CENTER><b>VALUE</b></td>
<td VALIGN=CENTER><b>DESCRIPTION</b></td>
</tr>
<tr>
<td VALIGN=CENTER><font size=-1>RIPCMD_REQUEST</font></td>
<td VALIGN=CENTER><font size=-1>RIP request</font></td>
</tr>
<tr>
<td VALIGN=CENTER><font size=-1>RIPCMD_RESPONSE</font></td>
<td VALIGN=CENTER><font size=-1>RIP response</font></td>
</tr>
<tr>
<td VALIGN=CENTER><font size=-1>RIPCMD_TRACEON</font></td>
<td VALIGN=CENTER><font size=-1>RIP tracing on</font></td>
</tr>
<tr>
<td VALIGN=CENTER><font size=-1>RIPCMD_TRACEOFF</font></td>
<td VALIGN=CENTER><font size=-1>RIP tracing off</font></td>
</tr>
<tr>
<td VALIGN=CENTER><font size=-1>RIPCMD_POLL</font></td>
<td VALIGN=CENTER><font size=-1>RIP polling</font></td>
</tr>
<tr>
<td VALIGN=CENTER><font size=-1>RIPCMD_POLLENTRY</font></td>
<td VALIGN=CENTER><font size=-1>RIP poll entry</font></td>
</tr>
<tr>
<td VALIGN=CENTER><font size=-1>RIPCMD_MAX</font></td>
<td VALIGN=CENTER> </td>
</tr>
</table>
<hr ALIGN="LEFT">
<br><b>int libnet_build_tcp(u_short th_sport, u_short th_dport, u_long
th_seq, u_long th_ack, u_char th_flags, u_short th_win, u_short th_urg,
const u_char *payload, int payload_len, u_char *packet_buf);</b>
<br>
<table BORDER WIDTH="565" >
<tr>
<td VALIGN=CENTER><font size=-1>return value upon success</font></td>
<td VALIGN=CENTER><font size=-1>1</font></td>
</tr>
<tr>
<td VALIGN=CENTER><font size=-1>return value upon failure</font></td>
<td VALIGN=CENTER><font size=-1>-1</font></td>
</tr>
<tr>
<td VALIGN=CENTER><font size=-1>re-entrant</font></td>
<td VALIGN=CENTER><font size=-1>yes</font></td>
</tr>
<tr>
<td VALIGN=CENTER><font size=-1>arguments</font></td>
<td VALIGN=CENTER><font size=-1>1 - source port</font>
<br><font size=-1>2 - destination port</font>
<br><font size=-1>3 - sequence number</font>
<br><font size=-1>4 - acknowledgement number</font>
<br><font size=-1>5 - control flags </font>
<br><font size=-1>6 - window size</font>
<br><font size=-1>7 - urgent pointer</font>
<br><font size=-1>8 - pointer to packet payload</font>
<br><font size=-1>9 - packet payload size</font>
<br><font size=-1>10 - pointer to pre-allocated packet memory</font></td>
</tr>
</table>
<p><font size=-1>libnet_build_tcp() constructs a TCP packet. The
control flags should be one or more of the following (OR'd together if
need be):</font>
<br>
<table BORDER WIDTH="517" >
<tr>
<td VALIGN=CENTER><b>VALUE</b></td>
<td VALIGN=CENTER><b>DESCSRIPTION</b></td>
</tr>
<tr>
<td VALIGN=CENTER><font size=-1>TH_URG</font></td>
<td VALIGN=CENTER><font size=-1>urgent data is present</font></td>
</tr>
<tr>
<td VALIGN=CENTER><font size=-1>TH_ACK</font></td>
<td VALIGN=CENTER><font size=-1>acknowledgement number field should be
checked</font></td>
</tr>
<tr>
<td VALIGN=CENTER><font size=-1>TH_PSH</font></td>
<td VALIGN=CENTER><font size=-1>push this data to the application</font></td>
</tr>
<tr>
<td VALIGN=CENTER><font size=-1>TH_RST</font></td>
<td VALIGN=CENTER><font size=-1>reset the referenced connection</font></td>
</tr>
<tr>
<td VALIGN=CENTER><font size=-1>TH_SYN</font></td>
<td VALIGN=CENTER><font size=-1>synchronize connection sequence numbers</font></td>
</tr>
<tr>
<td VALIGN=CENTER><font size=-1>TH_FIN</font></td>
<td VALIGN=CENTER><font size=-1>sender is finished sending data</font></td>
</tr>
</table>
<hr ALIGN="LEFT">
<br><b>int libnet_build_udp(u_short sport, u_short dport, const u_char
*payload, int payload_len, u_char *packet_buf);</b>
<br>
<table BORDER WIDTH="560" >
<tr>
<td VALIGN=CENTER><font size=-1>return value upon success</font></td>
<td VALIGN=CENTER><font size=-1>1</font></td>
</tr>
<tr>
<td VALIGN=CENTER><font size=-1>return value upon failure</font></td>
<td VALIGN=CENTER><font size=-1>-1</font></td>
</tr>
<tr>
<td VALIGN=CENTER><font size=-1>re-entrant</font></td>
<td VALIGN=CENTER><font size=-1>yes</font></td>
</tr>
<tr>
<td VALIGN=CENTER><font size=-1>arguments</font></td>
<td VALIGN=CENTER><font size=-1>1 - source port</font>
<br><font size=-1>2 - destination port</font>
<br><font size=-1>3 - pointer to packet payload</font>
<br><font size=-1>4 - packet payload size</font>
<br><font size=-1>5 - pointer to pre-allocated packet memory</font></td>
</tr>
</table>
<p><font size=-1>libnet_build_udp() constructs a UDP packet. Please
remember that UDP checksums are considered mandatory by the host requirements
RFC.</font>
<br>
<hr ALIGN="LEFT">
<br><b>int libnet_insert_ipo(struct ipoption *opt, u_char opt_len, u_char
*packet_buf);</b>
<br>
<table BORDER WIDTH="632" >
<tr>
<td VALIGN=CENTER><font size=-1>return value upon success</font></td>
<td VALIGN=CENTER><font size=-1>1</font></td>
</tr>
<tr>
<td VALIGN=CENTER><font size=-1>return value upon failure</font></td>
<td VALIGN=CENTER><font size=-1>-1</font></td>
</tr>
<tr>
<td VALIGN=CENTER><font size=-1>re-entrant</font></td>
<td VALIGN=CENTER><font size=-1>yes</font></td>
</tr>
<tr>
<td VALIGN=CENTER><font size=-1>arguments</font></td>
<td VALIGN=CENTER><font size=-1>1 - pointer to a IP options structure (filled
in)</font>
<br><font size=-1>2 - options length</font>
<br><font size=-1>3 - pointer to a complete IP packet</font></td>
</tr>
</table>
<p><font size=-1>libnet_insert_ipo() inserts IP options into a pre-built
IP packet. Supplied is a pointer to an ip options structure, the
size of this options list, and a pointer the pre-built packet. The
options list should be constructed as they will appear on the wire, as
they are simply inserted into the packet at the appropriate location.</font>
<p><font size=-1>The function returns -1 if the options would result in
packet too large (greater then 65535 bytes), or if the packet buffer is
NULL. It is an unchecked runtime error for the user to have not allocated
enough heap memory for the IP packet plus the IP options.</font>
<br>
<hr ALIGN="LEFT">
<br><b>int libnet_insert_tcpo(struct tcpoption *opt, u_char opt_len, u_char
*packet_buf);</b>
<br>
<table BORDER WIDTH="615" >
<tr>
<td VALIGN=CENTER><font size=-1>return value upon success</font></td>
<td VALIGN=CENTER><font size=-1>1</font></td>
</tr>
<tr>
<td VALIGN=CENTER><font size=-1>return value upon failure</font></td>
<td VALIGN=CENTER><font size=-1>-1</font></td>
</tr>
<tr>
<td VALIGN=CENTER><font size=-1>re-entrant</font></td>
<td VALIGN=CENTER><font size=-1>yes</font></td>
</tr>
<tr>
<td VALIGN=CENTER><font size=-1>arguments</font></td>
<td VALIGN=CENTER><font size=-1>1 - pointer to a TCP options structure
(filled in)</font>
<br><font size=-1>2 - options length</font>
<br><font size=-1>3 - pointer to a complete IP/TCP packet</font></td>
</tr>
</table>
<p><font size=-1>libnet_insert_tcpo() inserts TCP options into a pre-built
IP/TCP packet. Supplied is a pointer to a tcp options structure, the size
of this options list, and a pointer the pre-built packet. The options
list should be constructed as they will appear on the wire, as they are
simply inserted into the packet at the appropriate location.</font>
<p><font size=-1>The function returns -1 if the options would result in
packet too large (greater then 65535 bytes), if the packet isn't an IP/TCP
packet, if the options list if longer than 20 bytes, or if the packet buffer
is NULL. It is an unchecked runtime error for the user to have not
allocated enough heap memory for the IP/TCP packet plus the IP options.</font>
<br>
<hr ALIGN="LEFT">
<br><a NAME="s5_5"></a><b><font size=+2>5.5 Support Functions</font></b>
<br>
<hr ALIGN="LEFT">
<br><b>int libnet_seed_prand();</b>
<br>
<table BORDER WIDTH="436" >
<tr>
<td VALIGN=CENTER><font size=-1>return value upon success</font></td>
<td VALIGN=CENTER><font size=-1>1</font></td>
</tr>
<tr>
<td VALIGN=CENTER><font size=-1>return value upon failure</font></td>
<td VALIGN=CENTER><font size=-1>-1</font></td>
</tr>
<tr>
<td VALIGN=CENTER><font size=-1>re-entrant</font></td>
<td VALIGN=CENTER><font size=-1>yes</font></td>
</tr>
<tr>
<td VALIGN=CENTER><font size=-1>arguments</font></td>
<td VALIGN=CENTER><font size=-1>NA</font></td>
</tr>
</table>
<p><font size=-1>libnet_seed_prand() seeds the pseudo-random number generator.
The function is basically a wrapper to srandom. It makes a call to
gettimeofday to get entropy. It can return -1 if the call to gettimeofday
fails (check errno). It otherwise returns 1.</font>
<br>
<hr ALIGN="LEFT">
<br><b>u_long libnet_get_prand(int modulus);</b>
<br>
<br>
<table BORDER WIDTH="690" >
<tr>
<td VALIGN=CENTER><font size=-1>return value upon success</font></td>
<td VALIGN=CENTER><font size=-1>1</font></td>
</tr>
<tr>
<td VALIGN=CENTER><font size=-1>return value upon failure</font></td>
<td VALIGN=CENTER><font size=-1>NA</font></td>
</tr>
<tr>
<td VALIGN=CENTER><font size=-1>re-entrant</font></td>
<td VALIGN=CENTER><font size=-1>yes</font></td>
</tr>
<tr>
<td VALIGN=CENTER><font size=-1>arguments</font></td>
<td VALIGN=CENTER><font size=-1>1 - maximum size of pseudo-random number
desired</font></td>
</tr>
</table>
<p><font size=-1>libnet_get_prand() generates a psuedo-random number.
The range of the returned number is controlled by the function's only argument:</font>
<br>
<table BORDER WIDTH="255" >
<tr>
<td VALIGN=CENTER><b>VALUE</b></td>
<td VALIGN=CENTER><b>DESCSRIPTION</b></td>
</tr>
<tr>
<td VALIGN=CENTER><font size=-1>LIBNET_PR2</font></td>
<td VALIGN=CENTER><font size=-1>0 - 1</font></td>
</tr>
<tr>
<td VALIGN=CENTER><font size=-1>LIBNET_PR8</font></td>
<td VALIGN=CENTER><font size=-1>0 - 255</font></td>
</tr>
<tr>
<td VALIGN=CENTER><font size=-1>LIBNET_PR16</font></td>
<td VALIGN=CENTER><font size=-1>0 - 32767</font></td>
</tr>
<tr>
<td VALIGN=CENTER><font size=-1>LIBNET_PRu16</font></td>
<td VALIGN=CENTER><font size=-1>0 - 65535</font></td>
</tr>
<tr>
<td VALIGN=CENTER><font size=-1>LIBNET_PR32</font></td>
<td VALIGN=CENTER><font size=-1>0 - 2147483647</font></td>
</tr>
<tr>
<td VALIGN=CENTER><font size=-1>LIBNET_PRu32</font></td>
<td VALIGN=CENTER><font size=-1>0 - 4294967295</font></td>
</tr>
</table>
<p><font size=-1>The function does not fail.</font>
<br>
<hr ALIGN="LEFT">
<br><b>void libnet_hex_dump(u_char * buf, int len, int swap, FILE *stream);</b>
<br>
<table BORDER WIDTH="699" >
<tr>
<td VALIGN=CENTER><font size=-1>return value upon success</font></td>
<td VALIGN=CENTER><font size=-1>NA</font></td>
</tr>
<tr>
<td VALIGN=CENTER><font size=-1>return value upon failure</font></td>
<td VALIGN=CENTER><font size=-1>NA</font></td>
</tr>
<tr>
<td VALIGN=CENTER><font size=-1>re-entrant</font></td>
<td VALIGN=CENTER><font size=-1>yes</font></td>
</tr>
<tr>
<td VALIGN=CENTER><font size=-1>arguments</font></td>
<td VALIGN=CENTER><font size=-1>1 - packet to dump</font>
<br><font size=-1>2 - packet length</font>
<br><font size=-1>3 - byte swap flag</font>
<br><font size=-1>4 - previously opened stream in which to dump packet</font></td>
</tr>
</table>
<p><font size=-1>libnet_hex_dump() prints out a packet in hexadecimal.
It will print the packet as it appears in memory, or as it will appear
on the wire, depending on the value of the byte-swap flag. The function
prints the packet to a previously opened stream (such as stdout).
Note that on big-endian architectures such as Solaris, the packet will
appear the same in memory as it will on the wire.</font>
<br>
<hr ALIGN="LEFT">
<br><b>int libnet_plist_chain_new(struct libnet_plist_chain **plist, char
*token_list);</b>
<br>
<table BORDER WIDTH="558" >
<tr>
<td VALIGN=CENTER><font size=-1>return value upon success</font></td>
<td VALIGN=CENTER><font size=-1>1</font></td>
</tr>
<tr>
<td VALIGN=CENTER><font size=-1>return value upon failure</font></td>
<td VALIGN=CENTER><font size=-1>-1</font></td>
</tr>
<tr>
<td VALIGN=CENTER><font size=-1>re-entrant</font></td>
<td VALIGN=CENTER><font size=-1>yes</font></td>
</tr>
<tr>
<td VALIGN=CENTER><font size=-1>arguments</font></td>
<td VALIGN=CENTER><font size=-1>1 - pointer to a libnet_plist_chain pointer</font>
<br><font size=-1>2 - pointer to token list</font></td>
</tr>
</table>
<p><font size=-1>libnet_plist_chain_new() constructs a new libnet port-list
chain. A libnet port-list chain is a fast and simple way of implementing
port-list ranges (useful for applications that employ a list of ports -
like a port scanner). You'll see naive implementations that allocate
an entire array of 65535 bytes and fill in the desired ports one by one.
However, we only really need to store the beginning port and the ending
port, and we can efficiently store multiple port ranges (delimited by commas)
by using a linked list chain with each node holding the beginning and ending
port for a particular range. For example, The port range `1-1024`
would occupy one node with the beginning port being 1 and the ending port
being 1024. The port range `25,110-161,6000` would result in 3 nodes
being allocated. Single ports are taken as single ranges (port 25
ends up being 25-25). A port list range without a terminating port
(port_num - ) is considered shorthand for (port_num - 65535).</font>
<p><font size=-1>The arguments are a pointer to libnet_plist_chain pointer
(which will end up being the head of the linked list) which needs to deference
an allocated libnet_plist_chain structure and pointer to the port-list
(token-list) itself.</font>
<p><font size=-1>The function checks this character port list for valid
tokens (1234567890,- ) and returns an error if an unrecognized token is
found.</font>
<p><font size=-1>Upon success the function returns 1, and head points to
the newly formed port-list (and also contains the number of nodes in the
list. If an error occurs (an unrecognized token is found or malloc
fails) -1 is returned and head is set to NULL.</font>
<p><font size=-1>libnet_plist_chain_next_pair() should be used to extract
port list pairs.</font>
<br>
<hr ALIGN="LEFT">
<br><b>int libnet_plist_chain_next_pair(struct libnet_plist_chain *plist,
u_short *bport, u_short *eport);</b>
<br>
<table BORDER WIDTH="603" >
<tr>
<td VALIGN=CENTER><font size=-1>return value upon success</font></td>
<td VALIGN=CENTER><font size=-1>1, 0</font></td>
</tr>
<tr>
<td VALIGN=CENTER><font size=-1>return value upon failure</font></td>
<td VALIGN=CENTER><font size=-1>-1</font></td>
</tr>
<tr>
<td VALIGN=CENTER><font size=-1>re-entrant</font></td>
<td VALIGN=CENTER><font size=-1>yes</font></td>
</tr>
<tr>
<td VALIGN=CENTER><font size=-1>arguments</font></td>
<td VALIGN=CENTER><font size=-1>1 - pointer to a libnet_plist_chain pointer</font>
<br><font size=-1>2 - pointer to the beginning port (to be filled in)</font>
<br><font size=-1>3 - pointer to the ending port (to be filled in)</font></td>
</tr>
</table>
<p><font size=-1>libnet_plist_chain_next_pair() fetches the next pair of
ports from the list. The function takes a pointer to the head of
the prebuilt list and a pointer to a u_short that will contain the beginning
port and a pointer to a u_short that will contain the ending port.</font>
<p><font size=-1>The function returns 1 and fills in these values if there
are nodes remaining, or if the port list chain is exhausted, it returns
0. If an error occurs (the libnet_plist_chain pointer is NULL) the
function</font>
<br><font size=-1>returns -1.</font>
<br>
<hr ALIGN="LEFT">
<br><b>int libnet_plist_chain_dump(struct libnet_plist_chain *plist);</b>
<br>
<br>
<table BORDER WIDTH="539" >
<tr>
<td VALIGN=CENTER><font size=-1>return value upon success</font></td>
<td VALIGN=CENTER><font size=-1>1</font></td>
</tr>
<tr>
<td VALIGN=CENTER><font size=-1>return value upon failure</font></td>
<td VALIGN=CENTER><font size=-1>-1</font></td>
</tr>
<tr>
<td VALIGN=CENTER><font size=-1>re-entrant</font></td>
<td VALIGN=CENTER><font size=-1>yes</font></td>
</tr>
<tr>
<td VALIGN=CENTER><font size=-1>arguments</font></td>
<td VALIGN=CENTER><font size=-1>1 - pointer to a libnet_plist_chain pointer</font></td>
</tr>
</table>
<p><font size=-1>libnet_plist_chain_dump() dumps the port-list chain referenced
by the argument. The function prints the list to stdout (it's mainly
meant as a debugging tool). It returns 1 upon success or if an error
occurs (the libnet_plist_chain pointer is NULL) the function returns -1.</font>
<br>
<hr ALIGN="LEFT">
<br><b>u_char *libnet_plist_chain_dump_string(struct libnet_plist_chain
*plist);</b>
<br>
<table BORDER WIDTH="557" >
<tr>
<td VALIGN=CENTER><font size=-1>return value upon success</font></td>
<td VALIGN=CENTER><font size=-1>pointer to the token list</font></td>
</tr>
<tr>
<td VALIGN=CENTER><font size=-1>return value upon failure</font></td>
<td VALIGN=CENTER><font size=-1>NULL</font></td>
</tr>
<tr>
<td VALIGN=CENTER><font size=-1>re-entrant</font></td>
<td VALIGN=CENTER><font size=-1>no</font></td>
</tr>
<tr>
<td VALIGN=CENTER><font size=-1>arguments</font></td>
<td VALIGN=CENTER><font size=-1>1 - pointer to a libnet_plist_chain pointer</font></td>
</tr>
</table>
<p><font size=-1>libnet_plist_chain_dump_string() returns the port-list
chain referenced by the argument as a string. It returns the port
list string upon success or if an error occurs (the libnet_plist_chain
pointer is NULL) the function returns NULL.</font>
<br>
<hr ALIGN="LEFT">
<br><b>void libnet_plist_chain_free(struct libnet_plist_chain *plist);</b>
<br>
<table BORDER WIDTH="559" >
<tr>
<td VALIGN=CENTER><font size=-1>return value upon success</font></td>
<td VALIGN=CENTER><font size=-1>NA</font></td>
</tr>
<tr>
<td VALIGN=CENTER><font size=-1>return value upon failure</font></td>
<td VALIGN=CENTER><font size=-1>NA</font></td>
</tr>
<tr>
<td VALIGN=CENTER><font size=-1>re-entrant</font></td>
<td VALIGN=CENTER><font size=-1>yes</font></td>
</tr>
<tr>
<td VALIGN=CENTER><font size=-1>arguments</font></td>
<td VALIGN=CENTER><font size=-1>1 - pointer to a libnet_plist_chain pointer</font></td>
</tr>
</table>
<p><font size=-1>libnet_plist_chain_free() frees the memory associated
with the libnet port list chain.</font>
<br>
<hr ALIGN="LEFT">
<br><a NAME="s5_6"></a><b><font size=+2>5.6 Symbolic Constants</font></b>
<br>
<hr ALIGN="LEFT">
<br><font size=-1>Libnet conveniently defines standard packet header sizes,
for use with many packet manipulation functions, as per the following chart:</font>
<br>
<table BORDER CELLSPACING=3 CELLPADDING=3 >
<tr>
<td VALIGN=CENTER><b>SYMBOLIC CONSTANT </b></td>
<td VALIGN=CENTER><b>SIZE IN BYTES</b></td>
</tr>
<tr>
<td VALIGN=CENTER><font size=-1>LIBNET_ARP_H</font></td>
<td VALIGN=CENTER><font size=-1>28</font></td>
</tr>
<tr>
<td VALIGN=CENTER><font size=-1>LIBNET_DNS_H</font></td>
<td VALIGN=CENTER><font size=-1>12</font></td>
</tr>
<tr>
<td VALIGN=CENTER><font size=-1>LIBNET_ETH_H</font></td>
<td VALIGN=CENTER><font size=-1>14</font></td>
</tr>
<tr>
<td VALIGN=CENTER><font size=-1>LIBNET_ICMP_H (deprecated)</font></td>
<td VALIGN=CENTER><font size=-1>4</font></td>
</tr>
<tr>
<td VALIGN=CENTER><font size=-1>LIBNET_ICMP_ECHO_H</font></td>
<td VALIGN=CENTER><font size=-1>8</font></td>
</tr>
<tr>
<td VALIGN=CENTER><font size=-1>LIBNET_ICMP_MASK_H </font></td>
<td VALIGN=CENTER><font size=-1>12</font></td>
</tr>
<tr>
<td VALIGN=CENTER><font size=-1>LIBNET_ICMP_UNREACH_H </font></td>
<td VALIGN=CENTER><font size=-1>8</font></td>
</tr>
<tr>
<td VALIGN=CENTER><font size=-1>LIBNET_ICMP_TIMXCEED_H</font></td>
<td VALIGN=CENTER><font size=-1>8 </font></td>
</tr>
<tr>
<td VALIGN=CENTER><font size=-1>LIBNET_ICMP_REDIRECT_H</font></td>
<td VALIGN=CENTER><font size=-1>8 </font></td>
</tr>
<tr>
<td VALIGN=CENTER><font size=-1>LIBNET_ICMP_TS_H </font></td>
<td VALIGN=CENTER><font size=-1>20</font></td>
</tr>
<tr>
<td VALIGN=CENTER><font size=-1>LIBNET_IGMP_H</font></td>
<td VALIGN=CENTER><font size=-1>8</font></td>
</tr>
<tr>
<td VALIGN=CENTER><font size=-1>LIBNET_IP_H</font></td>
<td VALIGN=CENTER><font size=-1>20</font></td>
</tr>
<tr>
<td VALIGN=CENTER><font size=-1>LIBNET_RIP_H</font></td>
<td VALIGN=CENTER><font size=-1>24</font></td>
</tr>
<tr>
<td VALIGN=CENTER><font size=-1>LIBNET_TCP_H</font></td>
<td VALIGN=CENTER><font size=-1>20</font></td>
</tr>
<tr>
<td VALIGN=CENTER><font size=-1>LIBNET_UDP_H</font></td>
<td VALIGN=CENTER><font size=-1>8</font></td>
</tr>
</table>
<p><font size=-1>More packet memory constants:</font>
<br>
<table BORDER CELLSPACING=3 CELLPADDING=3 >
<tr>
<td VALIGN=CENTER><b>SYMBOLIC CONSTANT</b></td>
<td VALIGN=CENTER><b>MEANING</b></td>
</tr>
<tr>
<td VALIGN=CENTER><font size=-1>LIBNET_PACKET</font></td>
<td VALIGN=CENTER><font size=-1>enough memory for a TCP or UDP header and
an IP header</font></td>
</tr>
<tr>
<td VALIGN=CENTER><font size=-1>LIBNET_OPTS</font></td>
<td VALIGN=CENTER><font size=-1>enough memory for IP or TCP options (40
bytes)</font></td>
</tr>
<tr>
<td VALIGN=CENTER><font size=-1>LIBNET_MAX_PACKET</font></td>
<td VALIGN=CENTER><font size=-1>enough memory for IP_MAXPACKET (65535 bytes)</font></td>
</tr>
</table>
<p><font size=-1>The following are used for psuedo random number generation,
with libnet_get_prand():</font>
<br>
<br>
<table BORDER CELLSPACING=3 CELLPADDING=3 >
<tr>
<td VALIGN=CENTER><b>SYMBOLIC CONSTANT </b></td>
<td VALIGN=CENTER><b>RANGE</b></td>
</tr>
<tr>
<td VALIGN=CENTER><font size=-1>LIBNET_PRAND_MAX</font></td>
<td VALIGN=CENTER><font size=-1>65535</font></td>
</tr>
<tr>
<td VALIGN=CENTER><font size=-1>LIBNET_PR2</font></td>
<td VALIGN=CENTER><font size=-1>0 - 2</font></td>
</tr>
<tr>
<td VALIGN=CENTER><font size=-1>LIBNET_PR8</font></td>
<td VALIGN=CENTER><font size=-1>0 - 255</font></td>
</tr>
<tr>
<td VALIGN=CENTER><font size=-1>LIBNET_PR16</font></td>
<td VALIGN=CENTER><font size=-1>0 - 32767</font></td>
</tr>
<tr>
<td VALIGN=CENTER><font size=-1>LIBNET_PRu16</font></td>
<td VALIGN=CENTER><font size=-1>0 - 65535</font></td>
</tr>
<tr>
<td VALIGN=CENTER><font size=-1>LIBNET_PR32</font></td>
<td VALIGN=CENTER><font size=-1>0 - 2147483647</font></td>
</tr>
<tr>
<td VALIGN=CENTER><font size=-1>LIBNET_PRu32</font></td>
<td VALIGN=CENTER><font size=-1>0 - 4294967295</font></td>
</tr>
</table>
<p><font size=-1>For error messaging, used in conjunction with libnet_error():</font>
<br>
<table BORDER CELLSPACING=3 CELLPADDING=3 >
<tr>
<td VALIGN=CENTER><b>SYMBOLIC CONSTANT</b></td>
<td VALIGN=CENTER><b>MEANING</b></td>
</tr>
<tr>
<td VALIGN=CENTER><font size=-1>LIBNET_ERR_WARNING</font></td>
<td VALIGN=CENTER>warning error message</td>
</tr>
<tr>
<td VALIGN=CENTER><font size=-1>LIBNET_ERR_CRITICAL</font></td>
<td VALIGN=CENTER>critical error message</td>
</tr>
<tr>
<td VALIGN=CENTER><font size=-1>LIBNET_ERR_FATAL</font></td>
<td VALIGN=CENTER>fatal error message (program will exit)</td>
</tr>
</table>
<p><font size=-1>For use with libnet_host_lookup(), libnet_host_lookup_r(),
and libnet_name_resolve():</font>
<br>
<table BORDER CELLSPACING=3 CELLPADDING=3 >
<tr>
<td VALIGN=CENTER><b>SYMBOLIC CONSTANT </b></td>
<td VALIGN=CENTER><b>MEANING</b></td>
</tr>
<tr>
<td VALIGN=CENTER><font size=-1>LIBNET_DONT_RESOLVE </font></td>
<td VALIGN=CENTER><font size=-1>do not resolve IP addresses into FQDNs</font></td>
</tr>
<tr>
<td VALIGN=CENTER><font size=-1>LIBNET_RESOLVE </font></td>
<td VALIGN=CENTER><font size=-1>attempt to resolve IP addresses into FQDNs</font></td>
</tr>
</table>
<p>
<hr ALIGN="LEFT">
<br><a NAME="s5_7"></a><b><font size=+2>5.7 Macros</font></b>
<br>
<hr ALIGN="LEFT">
<p><font size=-1>The arena interface defines the following macros:</font>
<br>
<table BORDER CELLSPACING=3 CELLPADDING=3 >
<tr>
<td VALIGN=CENTER><b>MACRO</b></td>
<td VALIGN=CENTER><b>MEANING</b></td>
</tr>
<tr>
<td VALIGN=CENTER><font size=-1>LIBNET_GET_ARENA_SIZE(</font><tt>arena</tt><font size=-1>)</font></td>
<td VALIGN=CENTER><font size=-1>returns the size of the arena</font></td>
</tr>
<tr>
<td VALIGN=CENTER><font size=-1>LIBNET_GET_ARENA_REMAINING_BYTES(</font><tt>arena</tt><font size=-1>)</font></td>
<td VALIGN=CENTER><font size=-1>returns the number of bytes left in the
arena</font></td>
</tr>
</table>
<p><font size=-1>To print the ethernet address from an ether_addr struct
use the following macro:</font>
<br>
<table BORDER CELLSPACING=3 CELLPADDING=3 >
<tr>
<td VALIGN=CENTER><b>MACRO</b></td>
<td VALIGN=CENTER><b>MEANING</b></td>
</tr>
<tr>
<td VALIGN=CENTER><font size=-1>LIBNET_PRINT_ETH_ADDR(</font><tt>e</tt><font size=-1>)</font></td>
<td VALIGN=CENTER><font size=-1>Prints the ethernet address of the ether_addr
struct</font></td>
</tr>
</table>
<hr ALIGN="LEFT">
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