dnet(3) 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 provided 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 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 occurrence in blob b of the
specified buf of length len, or -1 on failure.
blob_rindex() returns the offset of the last occurrence 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 according 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 following 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 specified 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 network 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 accommodate 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 number 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 values, 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 failure.
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 values, respectively.
All other dnet routines return 0 on success, or -1 on failure.
SEE ALSO
pcap(3)
AUTHORS
Dug Song <dugsong@monkey.org>
Oliver Falk <oliver@linux-kernel.at>
macOS 13.5 August 21, 2001 macOS 13.5
libdnet 1.17.0 - Generated Sat Nov 18 09:27:58 CST 2023