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DNET(3) 			   BSD Library Functions Manual 			  DNET(3)

NAME
     dnet -- dumb networking library

SYNOPSIS
     #include <dnet.h>

   Network addressing
     int
     addr_cmp(const struct addr *a, const struct addr *b);

     int
     addr_bcast(const struct addr *a, struct addr *b);

     int
     addr_net(const struct addr *a, struct addr *b);

     char *
     addr_ntop(const struct addr *src, char *dst, size_t size);

     int
     addr_pton(const char *src, struct addr *dst);

     char *
     addr_ntoa(const struct addr *a);

     int
     addr_aton(const char *src, struct addr *dst);

     int
     addr_ntos(const struct addr *a, struct sockaddr *sa);

     int
     addr_ston(const struct sockaddr *sa, struct addr *a);

     int
     addr_btos(uint16_t bits, struct sockaddr *sa);

     int
     addr_stob(const struct sockaddr *sa, uint16_t *bits);

     int
     addr_btom(uint16_t bits, void *mask, size_t size);

     int
     addr_mtob(const void *mask, size_t size, uint16_t *bits);

   Address Resolution Protocol
     typedef int

     (*arp_handler)(const struct arp_entry *entry, void *arg);

     arp_t *
     arp_open(void);

     int
     arp_add(arp_t *a, const struct arp_entry *entry);

     int
     arp_delete(arp_t *a, const struct arp_entry *entry);

     int
     arp_get(arp_t *a, struct arp_entry *entry);

     int
     arp_loop(arp_t *a, arp_handler callback, void *arg);

     arp_t *
     arp_close(arp_t *a);

   Binary buffers
     blob_t *
     blob_new(void);

     int
     blob_read(blob_t *b, void *buf, int len);

     int
     blob_write(blob_t *b, const void *buf, int len);

     int
     blob_seek(blob_t *b, int off, int whence);

     int
     blob_index(blob_t *b, const void *buf, int len);

     int
     blob_rindex(blob_t *b, const void *buf, int len);

     int
     blob_pack(blob_t *b, const void *fmt, ...);

     int
     blob_unpack(blob_t *b, const void *fmt, ...);

     int
     blob_print(blob_t *b, char *style, int len);

     blob_t *
     blob_free(blob_t *b);

   Ethernet
     eth_t *
     eth_open(const char *device);

     int
     eth_get(eth_t *e, eth_addr_t *ea);

     int
     eth_set(eth_t *e, const eth_addr_t *ea);

     ssize_t
     eth_send(eth_t *e, const void *buf, size_t len);

     eth_t *
     eth_close(eth_t *e);

   Firewalling
     typedef int

     (*fw_handler)(const struct fw_rule *rule, void *arg);

     fw_t *
     fw_open(void);

     int
     fw_add(fw_t *f, const struct fw_rule *rule);

     int
     fw_delete(fw_t *f, const struct fw_rule *rule);

     int
     fw_loop(fw_t *f, fw_handler callback, void *arg);

     fw_t *
     fw_close(fw_t *f);

   Network interfaces
     typedef int

     (*intf_handler)(const struct intf_entry *entry, void *arg);

     intf_t *
     intf_open(void);

     int
     intf_get(intf_t *i, struct intf_entry *entry);

     int
     intf_get_src(intf_t *i, struct intf_entry *entry, struct addr *src);

     int
     intf_get_dst(intf_t *i, struct intf_entry *entry, struct addr *dst);

     int
     intf_set(intf_t *i, const struct intf_entry *entry);

     int
     intf_loop(intf_t *i, intf_handler callback, void *arg);

     intf_t *
     intf_close(intf_t *i);

   Internet Protocol
     ip_t *
     ip_open(void);

     ssize_t
     ip_add_option(void *buf, size_t len, int proto, const void *optbuf, size_t optlen);

     void
     ip_checksum(void *buf, size_t len);

     ssize_t
     ip_send(ip_t *i, const void *buf, size_t len);

     ip_t *
     ip_close(ip_t *i);

   Internet Protocol Version 6
     void
     ip6_checksum(void *buf, size_t len);

   Random number generation
     rand_t *
     rand_open(void);

     int
     rand_get(rand_t *r, void *buf, size_t len);

     int
     rand_set(rand_t *r, const void *seed, size_t len);

     int
     rand_add(rand_t *r, const void *buf, size_t len);

     uint8_t
     rand_uint8(rand_t *r);

     uint16_t
     rand_uint16(rand_t *r);

     uint32_t
     rand_uint32(rand_t *r);

     int
     rand_shuffle(rand_t *r, void *base, size_t nmemb, size_t size);

     rand_t *
     rand_close(rand_t *r);

   Routing
     typedef int

     (*route_handler)(const struct route_entry *entry, void *arg);

     route_t *
     route_open(void);

     int
     route_add(route_t *r, const struct route_entry *entry);

     int
     route_delete(route_t *r, const struct route_entry *entry);

     int
     route_get(route_t *r, struct route_entry *entry);

     int
     route_loop(route_t *r, route_handler callback, void *arg);

     route_t *
     route_close(route_t *r);

   Tunnel interface
     tun_t *
     tun_open(struct addr *src, struct addr *dst, int mtu);

     int
     tun_fileno(tun_t *t);

     const char *
     tun_name(tun_t *t);

     ssize_t
     tun_send(tun_t *t, const void *buf, size_t size);

     ssize_t
     tun_recv(tun_t *t, void *buf, size_t size);

     tun_t *
     tun_close(tun_t *t);

DESCRIPTION
     dnet provides a simplified, portable interface to several low-level networking routines,
     including network address manipulation, kernel arp(4) cache and route(4) table lookup and
     manipulation, network firewalling, network interface lookup and manipulation, and raw IP
     packet and Ethernet frame transmission. It is intended to complement the functionality pro-
     vided by pcap(3).

     In addition, dnet also provides platform-independent definitions of various network protocol
     formats and values for portable low-level network programming, as well as a simple binary
     buffer handling API.

   Network addressing
     Network addresses are described by the following structure:

     struct addr {
	     uint16_t		     addr_type;
	     uint16_t		     addr_bits;
	     union {
		     eth_addr_t      __eth;
		     ip_addr_t	     __ip;
		     ip6_addr_t      __ip6;

		     uint8_t	     __data8[16];
		     uint16_t	     __data16[8];
		     uint32_t	     __data32[4];
	     } __addr_u;
     };
     #define addr_eth	     __addr_u.__eth
     #define addr_ip	     __addr_u.__ip
     #define addr_ip6	     __addr_u.__ip6
     #define addr_data8      __addr_u.__data8
     #define addr_data16     __addr_u.__data16
     #define addr_data32     __addr_u.__data32

     The following values are defined for addr_type:

     #define ADDR_TYPE_NONE	     0	     /* No address set */
     #define ADDR_TYPE_ETH	     1	     /* Ethernet */
     #define ADDR_TYPE_IP	     2	     /* Internet Protocol v4 */
     #define ADDR_TYPE_IP6	     3	     /* Internet Protocol v6 */

     The field addr_bits denotes the length of the network mask in bits.

     addr_cmp() compares network addresses a and b, returning an integer less than, equal to, or
     greater than zero if a is found, respectively, to be less than, equal to, or greater than b.
     Both addresses must be of the same address type.

     addr_bcast() computes the broadcast address for the network specified in a and writes it
     into b.

     addr_net() computes the network address for the network specified in a and writes it into b.

     addr_ntop() converts an address from network format to a string.

     addr_pton() converts an address (or hostname) from a string to network format.

     addr_ntoa() converts an address from network format to a string, returning a pointer to the
     result in static memory.

     addr_aton() is a synonym for addr_pton().

     addr_ntos() converts an address from network format to the appropriate struct sockaddr.

     addr_ston() converts an address from a struct sockaddr to network format.

     addr_btos() converts a network mask length to a network mask specified as a struct sockaddr.

     addr_stob() converts a network mask specified in a struct sockaddr to a network mask length.

     addr_btom() converts a network mask length to a network mask in network byte order.

     addr_mtob() converts a network mask in network byte order to a network mask length.

   Address Resolution Protocol
     ARP cache entries are described by the following structure:

     struct arp_entry {
	     struct addr     arp_pa;	     /* protocol address */
	     struct addr     arp_ha;	     /* hardware address */
     };

     arp_open() is used to obtain a handle to access the kernel arp(4) cache.

     arp_add() adds a new ARP entry.

     arp_delete() deletes the ARP entry for the protocol address specified by arp_pa.

     arp_get() retrieves the ARP entry for the protocol address specified by arp_pa.

     arp_loop() iterates over the kernel arp(4) cache, invoking the specified callback with each
     entry and the context arg passed to arp_loop().

     arp_close() closes the specified handle.

   Binary buffers
     Binary buffers are described by the following structure:

     typedef struct blob {
	     u_char	     *base;	     /* start of data */
	     int	      off;	     /* offset into data */
	     int	      end;	     /* end of data */
	     int	      size;	     /* size of allocation */
     } blob_t;

     blob_new() is used to allocate a new dynamic binary buffer, returning NULL on failure.

     blob_read() reads len bytes from the current offset in blob b into buf, returning the total
     number of bytes read, or -1 on failure.

     blob_write() writes len bytes from buf to blob b, advancing the current offset. It returns
     the number of bytes written, or -1 on failure.

     blob_seek() repositions the offset within blob b to off, according to the directive whence
     (see lseek(2) for details), returning the new absolute offset, or -1 on failure.

     blob_index() returns the offset of the first occurence in blob b of the specified buf of
     length len, or -1 on failure.

     blob_rindex() returns the offset of the last occurence in blob b of the specified buf of
     length len, or -1 on failure.

     blob_pack() converts and writes, and blob_unpack() reads and converts data in blob b accord-
     ing to the given format fmt as described below, returning 0 on success, and -1 on failure.

     The format string is composed of zero or more directives: ordinary characters (not % ),
     which are copied to / read from the blob, and conversion specifications, each of which
     results in reading / writing zero or more subsequent arguments.

     Each conversion specification is introduced by the character %, and may be prefixed by
     length specifier. The arguments must correspond properly (after type promotion) with the
     length and conversion specifiers.

     The length specifier is either a a decimal digit string specifying the length of the follow-
     ing argument, or the literal character * indicating that the length should be read from an
     integer argument for the argument following it.

     The conversion specifiers and their meanings are:

     D	     An unsigned 32-bit integer in network byte order.

     H	     An unsigned 16-bit integer in network byte order.

     b	     A binary buffer (length specifier required).

     c	     An unsigned character.

     d	     An unsigned 32-bit integer in host byte order.

     h	     An unsigned 16-bit integer in host byte order.

     s	     A C-style null-terminated string, whose maximum length must be specified when
	     unpacking.

     Custom conversion routines and their specifiers may be registered via blob_register_pack(),
     currently undocumented.

     blob_print() prints len bytes of the contents of blob b from the current offset in the spec-
     ified style; currently only ``hexl'' is available.

     blob_free() deallocates the memory associated with blob b and returns NULL.

   Ethernet
     eth_open() is used to obtain a handle to transmit raw Ethernet frames via the specified net-
     work device.

     eth_get() retrieves the hardware MAC address for the interface specified by e.

     eth_set() configures the hardware MAC address for the interface specified by e.

     eth_send() transmits len bytes of the Ethernet frame pointed to by buf.

     eth_close() closes the specified handle.

   Firewalling
     Firewall rules are described by the following structure:

     struct fw_rule {
	     char	     fw_device[INTF_NAME_LEN]; /* interface name */
	     uint8_t	     fw_op;		       /* operation */
	     uint8_t	     fw_dir;		       /* direction */
	     uint8_t	     fw_proto;		       /* IP protocol */
	     struct addr     fw_src;		       /* src address / net */
	     struct addr     fw_dst;		       /* dst address / net */
	     uint16_t	     fw_sport[2];	       /* range / ICMP type */
	     uint16_t	     fw_dport[2];	       /* range / ICMP code */
     };

     The following values are defined for fw_op:

     #define FW_OP_ALLOW     1
     #define FW_OP_BLOCK     2

     The following values are defined for fw_dir:

     #define FW_DIR_IN	     1
     #define FW_DIR_OUT      2

     fw_open() is used to obtain a handle to access the local network firewall configuration.

     fw_add() adds the specified firewall rule.

     fw_delete() deletes the specified firewall rule.

     fw_loop() iterates over the active firewall ruleset, invoking the specified callback with
     each rule and the context arg passed to fw_loop().

     fw_close() closes the specified handle.

   Network interfaces
     Network interface information is described by the following structure:

     #define INTF_NAME_LEN   16

     struct intf_entry {
	     u_int	     intf_len;			 /* length of entry */
	     char	     intf_name[INTF_NAME_LEN];	 /* interface name */
	     u_short	     intf_type; 		 /* interface type (r/o) */
	     u_short	     intf_flags;		 /* interface flags */
	     u_int	     intf_mtu;			 /* interface MTU */
	     struct addr     intf_addr; 		 /* interface address */
	     struct addr     intf_dst_addr;		 /* point-to-point dst */
	     struct addr     intf_link_addr;		 /* link-layer address */
	     u_int	     intf_alias_num;		 /* number of aliases */
	     struct addr     intf_alias_addrs __flexarr; /* array of aliases */
     };

     The following bitmask values are defined for intf_type:

     #define INTF_TYPE_OTHER	     1	     /* other */
     #define INTF_TYPE_ETH	     6	     /* Ethernet */
     #define INTF_TYPE_LOOPBACK      24      /* software loopback */
     #define INTF_TYPE_TUN	     53      /* proprietary virtual/internal */

     The following bitmask values are defined for intf_flags:

     #define INTF_FLAG_UP	     0x01    /* enable interface */
     #define INTF_FLAG_LOOPBACK      0x02    /* is a loopback net (r/o) */
     #define INTF_FLAG_POINTOPOINT   0x04    /* point-to-point link (r/o) */
     #define INTF_FLAG_NOARP	     0x08    /* disable ARP */
     #define INTF_FLAG_BROADCAST     0x10    /* supports broadcast (r/o) */
     #define INTF_FLAG_MULTICAST     0x20    /* supports multicast (r/o) */

     intf_open() is used to obtain a handle to access the network interface configuration.

     intf_get() retrieves an interface configuration entry, keyed on intf_name.  For all
     intf_get() functions, intf_len should be set to the size of the buffer pointed to by entry
     (usually sizeof(struct intf_entry), but should be larger to accomodate any interface alias
     addresses.

     intf_get_src() retrieves the configuration for the interface whose primary address matches
     the specified src.

     intf_get_dst() retrieves the configuration for the best interface with which to reach the
     specified dst.

     intf_set() sets the interface configuration entry.

     intf_loop() iterates over all network interfaces, invoking the specified callback with each
     interface configuration entry and the context arg passed to intf_loop().

     intf_close() closes the specified handle.

   Internet Protocol
     ip_open() is used to obtain a handle to transmit raw IP packets, routed by the kernel.

     ip_add_option() adds the header option for the protocol proto specified by optbuf of length
     optlen and appends it to the appropriate header of the IP packet contained in buf of size
     len, shifting any existing payload and adding NOPs to pad the option to a word boundary if
     necessary.

     ip_checksum() sets the IP checksum and any appropriate transport protocol checksum for the
     IP packet pointed to by buf of length len.

     ip_send() transmits len bytes of the IP packet pointed to by buf.

     ip_close() closes the specified handle.

   Internet Protocol Version 6
     ip6_checksum() sets the appropriate transport protocol checksum for the IPv6 packet pointed
     to by buf of length len.

   Random number generation
     rand_open() is used to obtain a handle for fast, cryptographically strong pseudo-random num-
     ber generation. The starting seed is derived from the system random data source device (if
     one exists), or from the current time and random stack contents.

     rand_set() re-initializes the PRNG to start from a known seed value, useful in generating
     repeatable sequences.

     rand_get() writes len random bytes into buf.

     rand_add() adds len bytes of entropy data from buf into the random mix.

     rand_uint8(), rand_uint16(), and rand_uint32() return 8, 16, and 32-bit unsigned random val-
     ues, respectively.

     rand_shuffle() randomly shuffles an array of nmemb elements of size bytes, starting at base.

     rand_close() closes the specified handle.

   Routing
     Routing table entries are described by the following structure:

     struct route_entry {
	     struct addr     route_dst;      /* destination address */
	     struct addr     route_gw;	     /* gateway address */
     };

     route_open() is used to obtain a handle to access the kernel route(4) table.

     route_add() adds a new routing table entry.

     route_delete() deletes the routing table entry for the destination prefix specified by
     route_dst.

     route_get() retrieves the routing table entry for the destination prefix specified by
     route_dst.

     route_loop() iterates over the kernel route(4) table, invoking the specified callback with
     each entry and the context arg passed to route_loop().

     route_close() closes the specified handle.

   Tunnel interface
     tun_open() is used to obtain a handle to a network tunnel interface, to which IP packets
     destined for dst are delivered (with source addresses rewritten to src ), where they may be
     read by a userland process and processed as desired. IP packets written back to the handle
     are injected into the kernel networking subsystem.

     tun_fileno() returns a file descriptor associated with the tunnel handle, suitable for
     select(2).

     tun_name() returns a pointer to the tunnel interface name.

     tun_send() submits a packet to the kernel networking subsystem for delivery.

     tun_recv() reads the next packet delivered to the tunnel interface.

     tun_close() closes the specified handle.

RETURN VALUES
     addr_ntop() returns a pointer to the dst argument, or NULL on failure.

     addr_ntoa() returns a pointer to a static memory area containing the printable address, or
     NULL on failure.

     arp_open(), eth_open(), fw_open(), intf_open(), ip_open(), rand_open(), and route_open()
     return a valid handle on success, or NULL on failure.

     arp_close(), eth_close(), fw_close(), intf_close(), ip_close(), rand_close(), and
     route_close() always return NULL.

     eth_send() and ip_send() return the length of the datagram successfully sent, or -1 on fail-
     ure.

     arp_loop(), fw_loop(), intf_loop(), and route_loop() return the status of their callback
     routines. Any non-zero return from a callback will cause the loop to exit immediately.

     ip_add_option() returns the length of the inserted option (which may have been padded with
     NOPs for memory alignment) or -1 on failure.

     rand_uint8(), rand_uint16(), and rand_uint32() return 8, 16, and 32-bit unsigned random val-
     ues, respectively.

     All other dnet routines return 0 on success, or -1 on failure.

SEE ALSO
     pcap(3)

AUTHORS
     Dug Song <dugsong@monkey.org>

BSD					 August 21, 2001				      BSD
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