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Manual Reference Pages  -  DNET (3)

NAME

dnet - dumb networking library

CONTENTS

Synopsis
     Network addressing
     Address Resolution Protocol
     Binary buffers
     Ethernet
     Firewalling
     Network interfaces
     Internet Protocol
     Internet Protocol Version 6
     Random number generation
     Routing
     Tunnel interface
Description
     Network addressing
     Address Resolution Protocol
     Binary buffers
     Ethernet
     Firewalling
     Network interfaces
     Internet Protocol
     Internet Protocol Version 6
     Random number generation
     Routing
     Tunnel interface
Return Values
See Also
Authors

SYNOPSIS


.Fd #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 (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 dnet routines return 0 on success, or -1 on failure.

SEE ALSO

pcap(3)

AUTHORS

Dug Song <dugsong@monkey.org>
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