Provided by: libdumbnet-dev_1.12-9build1_amd64 
NAME
dumbnet — dumb networking library
SYNOPSIS
#include <dumbnet.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
dumbnet 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, dumbnet 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
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 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
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 dumbnet routines return 0 on success, or -1 on failure.
COMPATIBILITY
The library was originally named dnet but was renamed to dumbnet due to a conflict with the
DECnet library. This decision affects not only the filename of the shared library, but also
the header file names and the library's SONAME tag, which means that software built on a
non-Debian-derived distribution will not run with this library and recompiling the software
will only work if some adjustments to header include directives and compiler/linker flags
are made.
SEE ALSO
pcap(3)
AUTHORS
Dug Song ⟨dugsong@monkey.org⟩