IP(4)

NAME
ip, eth, psip, udp, tcp - Internet Protocol server devices and definitions

DESCRIPTION
The ip*, eth*, psip*, tcp*, and udp* devices give access to the Internet Protocol (IP) services in MINIX 3. There can be up to 16 different networks, with 4 network devices each (a network has either an eth* or a psip* device, not both.) The * in the device names is a decimal number, so one may see names from ip0 to ip15. A program scanning all networks must try all 16, and not stop if one in between is missing. One network is the default network. Its devices are linked to names without numbers.

The eth* and psip* devices give direct access to the network packets at the lowest level. The ip*, tcp*, and udp* devices give access to IP, TCP, or UDP services.

Most programs that use TCP/IP use code like the following to access the proper devices:

    if ((tcp_device= getenv("TCP_DEVICE")) == NULL)
    	tcp_device= "/dev/tcp";

The low level networking programs such as ifconfig(8) also have options to select the device they are working with. The convention is:

    ETH_DEVICE=device
    -E device
        Device to use as raw ethernet device instead of the default /dev/eth.
    PSIP_DEVICE=device
    -P device
        Pseudo IP device to use instead of /dev/psip.
    IP_DEVICE=device
    -I device
        IP device to use instead of /dev/ip.
    TCP_DEVICE=device
    -T device
        TCP device to use instead of /dev/tcp.
    UDP_DEVICE=device
    -U device
        UDP device to use instead of /dev/udp.

  Programming
Access to the IP services is provided using filedescriptors to open IP devices. These open IP channels can be configured with ioctl(2) calls, and data can be transferred by calls to read(2), and write(2).

  Types (general)

<sys/types.h>
    Defines u8_t, u16_t, u32_t and i32_t (and U8_t, U16_t, U32_t and I32_t for use in prototypes).

  Types (eth)

<net/gen/ether.h>
    Defines struct ether_addr (ether_addr_t) and ether_type_t and Ether_type_t for use in prototypes.

<net/gen/eth_io.h>
    Defines struct nwio_ethopt (nwio_ethopt_t) and struct nwio_ethstat (nwio_ethstat_t)

<net/gen/eth_hdr.h>
    Defines struct eth_hdr (eth_hdr_t)

  Types (psip)

<net/gen/psip_hdr.h>
    [[[No description available yet.]]]

<net/gen/psip_io.h>
    [[[No description available yet.]]]

  Types (ip)

<net/gen/in.h>
    Defines ipaddr_t, ipproto_t and struct ip_hdropt (ip_hdropt_t).

<net/gen/ip_io.h>
    Defines struct nwio_ipconf (nwio_ipconf_t) and struct nwio_ipopt (nwio_ipopt_t)

<net/gen/ip_hdr.h>
    Defines struct ip_hdr (ip_hdr_t)

<net/gen/route.h>
    Defines struct nwio_route (nwio_route_t)

  Types (tcp)

<net/gen/tcp.h>
    Defines tcpport_t and Tcpport_t for use in prototypes.

<net/gen/tcp_io.h>
    Defines struct nwio_tcpconf (nwio_tcpconf_t), struct nwio_tcpcl (nwio_tcpcl_t), struct nwio_tcpatt (nwio_tcpatt_t) and struct nwio_tcpopt (nwio_tcpopt_t).

<net/gen/tcp_hdr.h>
    Defines struct tcp_hdr (tcp_hdr_t) and struct tcp_hdropt (tcp_hdropt_t).

  Types (udp)

<net/gen/udp.h>
    Defines udpport_t and Udpport_t for use in prototypes.

<net/gen/udp_io.h>
    Defines struct nwio_udpopt (nwio_udpopt_t).

<net/gen/udp_hdr.h>
    Defines struct udp_hdr (udp_hdr_t) and struct udp_io_hdr (udp_io_hdr_t).

  Byte Order Conversion
All 16-bit and 32-bit quantities in IP headers must be in network byte order. The macros described in hton(3) can be used to convert these values to and from the byte order used by the host machine.

  The Internet Checksum
The oneC_sum function (see oneC_sum(3)) is used to calculate the one's complement checksum needed for IP network packets.

  General Functions

fd = open(tcpip_device, O_RDWR)

This is how one normally obtains a filedescriptor for a new TCP/IP channel. tcpip_device names one of the TCP/IP devices. The channel may be used both to send or to receive data.

n = read(fd, buf, size)

Receives one packet (low level devices) or a number of bytes (TCP stream). Returns the the number of bytes placed into buf, or returns -1 with an error code placed into errno.

n = write(fd, buf, size)

Sends one packet (low level devices) or a number of bytes (TCP stream). Returns size or -1 with the error code placed into errno. The TCP/IP read and write functions behave like reads and writes on pipes when it comes to signals.

  ETH Functions

ioctl(fd, NWIOGETHSTAT, &struct nwio_ethstat)

The NWIOGETHSTAT ioctl returns the Ethernet address and some statistics of the Ethernet server of the channel fd. The result is returned in the nwio_ethstat structure. The struct nwio_ethstat is defined in <net/gen/eth_io.h>:

    typedef struct nwio_ethstat
    {
            ether_addr_t nwes_addr;
            eth_stat_t nwes_stat;
    } nwio_ethstat_t;
    typedef struct eth_stat
    {
        unsigned long ets_recvErr,  /* # receive errors */
    	ets_sendErr,            /* # send error */
    	ets_OVW,                /* # buffer overwrite warnings,
                                       (packets arrive faster than
                                        can be processed) */
    	ets_CRCerr,             /* # crc errors of read */
    	ets_frameAll,           /* # frames not aligned (# bits
                                       not a multiple of 8) */
    	ets_missedP,            /* # packets missed due to too
                                       slow packet processing */
    	ets_packetR,            /* # packets received */
    	ets_packetT,            /* # packets transmitted */
    	ets_transDef,           /* # transmission deferred (there
                                       was a transmission of an
                                       other station in progress */
    	ets_collision,          /* # collisions */
    	ets_transAb,            /* # transmissions aborted due
                                       to excessive collisions */
    	ets_carrSense,          /* # carrier sense lost */
    	ets_fifoUnder,          /* # fifo underruns (processor
                                       is too busy) */
    	ets_fifoOver,           /* # fifo overruns (processor is
                                       too busy) */
    	ets_CDheartbeat,        /* # times unable to transmit
                                       collision signal */
    	ets_OWC;                /* # times out of window
                                       collision */
    } eth_stat_t;

ioctl(fd, NWIOSETHOPT, &struct nwio_ethopt)

Before an Ethernet channel can be used to send or receive Ethernet packets, it has to be configured using the NWIOSETHOPT ioctl. The structure nwio_ethopt is defined in <net/gen/eth_io.h>:

    typedef struct nwio_ethopt
    {
    	u32_t nweo_flags;
    	ether_addr_t nweo_multi, nweo_rem;
    	ether_type_t nweo_type;
    } nwio_ethopt_t;
    #define NWEO_NOFLAGS    0x0000L
    #define NWEO_ACC_MASK   0x0003L
    #       define NWEO_EXCL        0x00000001L
    #       define NWEO_SHARED      0x00000002L
    #       define NWEO_COPY        0x00000003L
    #define NWEO_LOC_MASK   0x0010L
    #       define NWEO_EN_LOC      0x00000010L
    #       define NWEO_DI_LOC      0x00100000L
    #define NWEO_BROAD_MASK 0x0020L
    #       define NWEO_EN_BROAD    0x00000020L
    #       define NWEO_DI_BROAD    0x00200000L
    #define NWEO_MULTI_MASK 0x0040L
    #       define NWEO_EN_MULTI    0x00000040L
    #       define NWEO_DI_MULTI    0x00400000L
    #define NWEO_PROMISC_MASK 0x0080L
    #       define NWEO_EN_PROMISC  0x00000080L
    #       define NWEO_DI_PROMISC  0x00800000L
    #define NWEO_REM_MASK   0x0100L
    #       define NWEO_REMSPEC     0x00000100L
    #       define NWEO_REMANY      0x01000000L
    #define NWEO_TYPE_MASK  0x0200L
    #       define NWEO_TYPESPEC    0x00000200L
    #       define NWEO_TYPEANY     0x02000000L
    #define NWEO_RW_MASK    0x1000L
    #       define NWEO_RWDATONLY   0x00001000L
    #       define NWEO_RWDATALL    0x10000000L

The configuration is divided in a number of section (covered by the xx_MASK macros). Options can be set in the nweo_flags field. The first section (NWEO_ACC_MASK) controls the access to a certain Ethernet packet type. If NWEO_EXCL is selected then this is the only channel that can send or receive Ethernet packets of the selected type. If NWEO_SHARED is selected then multiple channels (which all have to select NWEO_SHARED) can use the same Ethernet type, they all can send packets but incoming packets will be delivered to at most one of them. If NWEO_COPY is selected then multiple channels have access to the same Ethernet type and all receive a copy of an incoming packet.

The NWEO_LOC_MASK flags control the delivery of packets with a destination address equal to the Ethernet address of the machine. If NWEO_EN_LOC is selected then these packets will be delivered and with NWEO_DI_LOC they will be discarded.

NWEO_BROAD_MASK, NWEO_MULTI_MASK, and NWEO_PROMISC_MASK do the same to broadcast packets, multicast packets and promiscuous mode packets as NWEO_LOC_MASK does for local packets. Except that the precise multicast address is taken from the nweo_multi field.

The NWEO_REM_MASK flags control whether communication is restricted to single destination or not. NWEO_REMSPEC restricts sending and receiving of packets to the single remote computer specified in the nweo_rem field. NWEO_REMANY allows sending to and receiving from any remote computer.

NWEO_TYPESPEC restricts sending and receiving of packets to the type specified in nweo_type. The type has to be in network byte order (using hton(3)). NWEO_TYPEANY allows any type.

If the Ethernet header is completely specified by the nweo_flags i.e., all of NWEO_EN_LOC, NWEO_DI_BROAD, NWEO_DI_MULTI, NWEO_DI_PROMISC, NWEO_REMSPEC and NWEO_TYPESPEC are specified, then NWEO_RWDATONLY can be used to send and receive only the data part of an Ethernet packet. If NWEO_RWDATALL is specified then both Ethernet header and data are used.

  PSIP Functions

[[[No description available yet.]]]

  IP Functions

ioctl(fd, NWIOGIPCONF, &struct nwio_ipconf)

The NWIOGIPCONF ioctl reports the Internet Address and the netmask. For the nwio_ipconf structure see the NWIOSIPCONF ioctl below.

ioctl(fd, NWIOGIPOROUTE, &struct nwio_route)

The NWIOGIPOROUTE ioctl can be used to query an IP server about its routing table. [[[NWIODIPOROUTE, NWIOGIPIROUTE, NWIODIPIROUTE?]]] The structure nwio_route is defined in <net/gen/route.h>:

    typedef struct nwio_route
    {
            u32_t nwr_ent_no;
            u32_t nwr_ent_count;
            ipaddr_t nwr_dest;
            ipaddr_t nwr_netmask;
            ipaddr_t nwr_gateway;
            u32_t nwr_dist;
            u32_t nwr_flags;
            u32_t nwr_pref;
    } nwio_route_t;
    #define NWRF_EMPTY      0
    #define NWRF_INUSE      1
    #define NWRF_FIXED      2

The requested entry is taken from nwr_ent_no. Entries are counted from 0, so the value 0 can be used for an initial query. The size of the routing table is returned in nwr_ent_count. The nwr_flags indicates if the entry is in use (NWRF_INUSE) and if the entry was inserted manually (using NWIOSIPOROUTE) or generated by the IP server itself. The route is described by nwr_dest, nwr_netmask, nwr_gateway, nwr_dist, and nwr_pref. Nwr_dest and nwr_netmask select the destination addresses. A value of 0.0.0.0 (0x0) in both nwr_dest and nwr_netmask means every host. A value of 255.255.255.255 (0xffffffff) in nwr_netmask means a single host. Other values of nwr_netmask are netmasks for the network specified by nwr_dest. Nwr_gateway is gateway that should be used. Nwr_dist is a minimal distance. Packets with a time to live smaller than nwr_dist will not reach the destination. If two routes have equal netmask and distance fields but different gateways then the gateway with highest value in nwr_pref is used.

ioctl(fd, NWIOSIPCONF, &struct nwio_ipconf)

The NWIOSIPCONF ioctl can be used to inform the IP server about its Internet Address and/or its netmask. Normally an IP server will discover its Internet Address using the RARP protocol. NWIOSIPCONF can be used in the case that the RARP failed, or the netmask has to be changed. Note that higher level protocols (TCP and UDP) assume that the Internet Address of an IP device does not change, therefore TCP and UDP stop functioning if the Internet Address is changed.

The structure nwio_ipconf is defined in <net/gen/ip_io.h>:

    typedef struct nwio_ipconf
    {
    	u32_t   nwic_flags;
    	ipaddr_t nwic_ipaddr;
    	ipaddr_t nwic_netmask;
    } nwio_ipconf_t;
    #define NWIC_NOFLAGS            0x0
    #define NWIC_FLAGS              0x3
    #       define NWIC_IPADDR_SET          0x1
    #       define NWIC_NETMASK_SET         0x2

The function of nwio_ipconf depends on the value of nwic_flags. If NWIC_IPADDR_SET is set then the Internet Address will be set to nwic_ipaddr. If NWIC_NETMASK_SET is set then the Internet Address will be set to nwic_netmask.

ioctl(fd, NWIOSIPOPT, &struct nwio_ipopt)

Before an IP channel can be used, it has to be configured using the NWIOSIPOPT ioctl. The structure nwio_ipopt is defined in <net/gen/ip_io.h>:

    typedef struct nwio_ipopt
    {
            u32_t nwio_flags;
            ipaddr_t nwio_rem;
            ip_hdropt_t nwio_hdropt;
            u8_t nwio_tos;
            u8_t nwio_ttl;
            u8_t nwio_df;
            ipproto_t nwio_proto;
    } nwio_ipopt_t;
    #define NWIO_NOFLAGS    0x0000L
    #define NWIO_ACC_MASK   0x0003L
    #       define NWIO_EXCL        0x00000001L
    #       define NWIO_SHARED      0x00000002L
    #       define NWIO_COPY        0x00000003L
    #define NWIO_LOC_MASK   0x0010L
    #       define NWIO_EN_LOC      0x00000010L
    #       define NWIO_DI_LOC      0x00100000L
    #define NWIO_BROAD_MASK 0x0020L
    #       define NWIO_EN_BROAD    0x00000020L
    #       define NWIO_DI_BROAD    0x00200000L
    #define NWIO_REM_MASK   0x0100L
    #       define NWIO_REMSPEC     0x00000100L
    #       define NWIO_REMANY      0x01000000L
    #define NWIO_PROTO_MASK 0x0200L
    #       define NWIO_PROTOSPEC   0x00000200L
    #       define NWIO_PROTOANY    0x02000000L
    #define NWIO_HDR_O_MASK 0x0400L
    #       define NWIO_HDR_O_SPEC  0x00000400L
    #       define NWIO_HDR_O_ANY   0x04000000L
    #define NWIO_RW_MASK    0x1000L
    #       define NWIO_RWDATONLY   0x00001000L
    #       define NWIO_RWDATALL    0x10000000L

The options are divided in several categories: NWIO_ACC_MASK, NWIO_LOC_MASK, NWIO_BROAD_MASK, NWIO_REM_MASK, NWIO_PROTO_MASK, NWIO_HDR_O_MASK and NWIO_RW_MASK. A channel is configured when one option of each category is set.

The options covered by NWIO_ACC_MASK control the number of channels that can use one IP protocol. If NWIO_EXCL is specified then only that channel can use a certain IP protocol. If NWIO_SHARED then multiple channels that all have to specify NWIO_SHARED can use the same IP protocol, but incoming packets will be delivered to a most one channel. NWIO_COPY does not impose any restrictions. Every channel gets a copy of an incoming packet.

NWIO_LOC_MASK and NWIO_BROAD_MASK control the delivery of packets. If NWIO_EN_LOC is specified then packets that are explicitly send to the IP server are delivered. If NWIO_EN_BROAD is specified then broadcast packets are delivered. Either one or both of them can be disabled with NWIO_DI_LOC and NWIO_DI_BROAD.

NWIO_REMSPEC can be used to restrict communication to one remote host. This host is taken from the nwio_rem field. If any remote host is to be allowed then NWIO_REMANY can be used.

NWIO_PROTOSPEC restricts communication to one IP protocol, specified in nwio_proto. NWIO_PROTOANY allows any protocol to be sent or received.

NWIO_HDR_O_SPEC specifies all IP header options in advance. The values are taken from nwio_hdropt, nwio_tos, nwio_ttl, and nwio_df. Nwio_hdropt specifies the IP options that should be present in an outgoing packet. Ip_hdropt_t is defined in <net/gen/in.h>:

    typedef struct ip_hdropt
    {
            u8_t iho_opt_siz;
            u8_t iho_data[IP_MAX_HDR_SIZE-IP_MIN_HDR_SIZE];
    } ip_hdropt_t;

The bytes of size iho_opt_siz in iho_data are appended to the IP header. Nwio_tos specifies the value of the ``type of service'' bits, nwio_ttl gives the value of the ``time to live'' field and nwio_df specifies whether fragmentation is disallowed or not. NWIO_HDR_O_ANY specifies that the header options should be specified at each write request.

NWIO_RWDATONLY specifies that the header should be omitted from a write request. This option can only be used when all header fields are specified in previous options: NWIO_EN_LOC, NWIO_DI_BROAD, NWIO_REMSPEC, NWIO_PROTOSPEC and NWIO_HDR_O_SPEC. A read operation will also only return the data part, so the IP options will be lost.

ioctl(fd, NWIOSIPOROUTE, &struct nwio_route)

The NWIOSIPOROUTE ioctl adds a route to the routing table. See NWIOGIPOROUTE above for a description of the nwio_route structure. The fields nwr_ent_no and nwr_ent_count are ignored.

  TCP Functions

ioctl(fd, NWIOTCPCONN, &struct nwio_tcpcl)

The NWIOTCPCONN ioctl tries to setup a connection with a remote TCP/IP server. The channel must be fully configured (see NWIOSTCPCONF) and values for the local port, the remote port and the remote address have be specified using NWTC_LP_SET or NWTC_LP_SEL, NWTC_SET_RA and NWTC_SET_RP. The struct nwio_tcpcl is defined in <net/gen/tcp_io.h> as:

    typedef struct nwio_tcpcl
    {
    	long nwtcl_flags;
    	long nwtcl_ttl;
    } nwio_tcpcl_t;

Set the nwtcl_flags field to zero before the connect or listen call. [[[Further explanation of nwio_tcpcl?]]]

ioctl(fd, NWIOGTCPCONF, &struct nwio_tcpconf)

This call reports the current configuration of a TCP channel. The nwtc_flags field shows the status of the access, locport, remaddr and remport fields. Nwtc_locaddr contains the Internet address of the TCP/IP server. Remaddr contains the Internet address of the remote TCP/IP server when set with NWTC_SET_RA or after a successful connect or listen (see NWIOTCPCONN or NWIOTCPLISTEN). Nwio_locport contains the local TCP/IP port set with NWTC_LP_SET or the selected port set with NWTC_LP_SEL. Nwtc_remport contains the TCP port of the remote TCP/IP server as set with NWIO_SET_RP or after a successful connect or listen.

A value of 0 (zero) is reported for nwtc_remaddr, nwtc_locport or nwtc_remport when no value is set either explicitly or implicitly.

ioctl(fd, NWIOTCPLISTEN, &struct nwio_tcpcl)

The NWIOTCPLISTEN ioctl waits until a remote TCP/IP server tries to connect to this channel. The channel has to be configured (see NWIOSTCPCONF). An additional restriction is that the local port must be set (with NWTC_LP_SET) or selected (with NWTC_LP_SEL). When a remote address is set only connections for that host are accepted, and when a remote port is set only connections from that port are accepted. After a successful listen NWIOGTCPCONF can be used to find out what the address and port of the other side are.

ioctl(fd, NWIOSTCPCONF, &struct nwio_tcpconf)

Before a TCP channel can be used it must configured using the NWIOSTCPCONF ioctl. The parameters to NWIOSTCPCONF are the channel file descriptor and a struct nwio_tcpconf as defined in <net/gen/tcp_io.h>:

    typedef struct nwio_tcpconf
    {
    	u32_t nwtc_flags;
    	ipaddr_t nwtc_locaddr;
    	ipaddr_t nwtc_remaddr;
    	tcpport_t nwtc_locport;
    	tcpport_t nwtc_remport;
    } nwio_tcpconf_t;
    #define NWTC_NOFLAGS    0x0000L
    #define NWTC_ACC_MASK   0x0003L
    #       define NWTC_EXCL        0x00000001L
    #       define NWTC_SHARED      0x00000002L
    #       define NWTC_COPY        0x00000003L
    #define NWTC_LOCPORT_MASK       0x0030L
    #       define NWTC_LP_UNSET    0x00000010L
    #       define NWTC_LP_SET      0x00000020L
    #       define NWTC_LP_SEL      0x00000030L
    #define NWTC_REMADDR_MASK       0x0100L
    #       define NWTC_SET_RA      0x00000100L
    #       define NWTC_UNSET_RA    0x01000000L
    #define NWTC_REMPORT_MASK       0x0200L
    #       define NWTC_SET_RP      0x00000200L
    #       define NWTC_UNSET_RP    0x02000000L

A tcp channel is considered configured when one flag in each category has been selected. Thus one of NWTC_EXCL, NWTC_SHARED or NWTC_COPY, one of NWTC_LP_UNSET, NWTC_LP_SET or NWTC_LP_SEL, one of NWTC_SET_RA or NWTC_UNSET_RA, and one of NWTC_SET_RP or NWTC_UNSET_RP.

The acc flags control the access to a certain TCP port. NWTC_EXCL means exclusive access. An attempt to configure a channel will be denied if the same port is specified as that of a channel that requested exclusive access. NWTC_SHARED indicates that several channels use the same port but cooperate. If the shared mode is specified for one channel than all other channel that use the same port should also be configured with the NWTC_SHARED flag. NWTC_COPY is specified when the programmer does not care about other channels. This is the default.

The locport flags control which TCP port is used for communication. NWTC_LP_UNSET indicates the absence of a local port. This is the default. NWTC_LP_SET means that the nwtc_locport field contains the local port to be used by TCP. This value must be in network byte order (see hton(3).) NWTC_LP_SEL requests the TCP server to pick a port. This port will be in the range from 32768 to 65535 and will be unique.

The remaddr flags specify which hosts are acceptable for connections. NWTC_SET_RA indicates that only connection to the host specified in nwtc_remaddr are acceptable. Nwtc_remaddr should be in network byte order (see hton(3).) NWTC_UNSET_RA allows every host on the other side of a connection. This is the default.

The remport flags specify which remote ports are acceptable for connections. NWTC_SET_RP indicates that only the port specified in nwtc_remport is acceptable. NWTC_UNSET_RP allows every port on the other side of a connection. This is the default.

ioctl(fd, NWIOTCPSHUTDOWN)

The NWIOTCPSHUTDOWN tells the TCP/IP server that no more data will be sent over the channel specified by fd. This command can be issued when the channel is connected to a remote TCP/IP server. The TCP/IP server will tell the remote TCP/IP server and the client of the remote TCP/IP server will receive an end-of-file indication.

ioctl(fd, NWIOGTCPOPT, &struct nwio_tcpopt)
ioctl(fd, NWIOSTCPOPT, &struct nwio_tcpopt)

The behaviour of a TCP channel may be changed by setting a number of options. The TCP options can be obtained with the NWIOGTCPOPT ioctl and set with the NWIOSTCPOPT ioctl. The options are passed in a struct nwio_tcpopt as defined in <net/gen/tcp_io.h>:

    typedef struct nwio_tcpopt
    {
    	u32_t nwto_flags;
    } nwio_tcpopt_t;
    #define NWTO_NOFLAG     0x0000L
    #define NWTO_SND_URG_MASK       0x0001L
    #       define NWTO_SND_URG     0x00000001L
    #       define NWTO_SND_NOTURG  0x00010000L
    #define NWTO_RCV_URG_MASK       0x0002L
    #       define NWTO_RCV_URG     0x00000002L
    #       define NWTO_RCV_NOTURG  0x00020000L
    #define NWTO_BSD_URG_MASK       0x0004L
    #       define NWTO_BSD_URG     0x00000004L
    #define NWTO_DEL_RST_MASK       0x0008L
    #       define NWTO_DEL_RST     0x00000008L

The NWTO_SND_URG option causes bytes written to the channel to be send out as urgent data. On receiving an EURG error the NWTO_RCV_URG option must be set to switch over to reading urgent data. When all urgent data has been read an ENOURG error will follow, indicating that the option must be cleared with NWTO_RCV_NOTURG. Alas the BSD implementation of urgent data disagrees with the RFC's, so to be BSD compatible one must set the NWTO_BSD_URG option beforehand on a channel that is to send or receive urgent data. Given that the BSD implementation is the regarded as the TCP/IP standard one should always use the BSD style. The NWTO_DEL_RST option delays a failure response on a connect to the same port as the current open connection. Without this option a connect would fail if a server is not yet listening. With this option a connect will linger on until the server starts listening. This option is useful for a server that opens a connection, tells the remote end the local port number and then listens (FTP), or for a program that forks off servers for incoming connections (TELNET). A new connection may come in before a new listen can be started, so it is nice if the new connect doesn't fail. Use this option only when it is clearly needed.

  UDP Functions

ioctl(fd, NWIOGUDPOPT, &struct nwio_udpopt)

The NWIOGUDPOPT ioctl returns the current options that result from the default options and the options set with NWIOSUDPOPT. When NWUO_LP_SEL or NWUO_LP_SET is selected the local port is returned in nwuo_locport. When NWUO_RP_SET is selected the remote port is returned in nwuo_remport. The local address is always returned in nwuo_locaddr, and when NWUO_RA_SET is selected the remote address is returned in nwuo_remaddr.

ioctl(fd, NWIOSUDPOPT, &struct nwio_udpopt)

A UDP channel must be configured using the NWIOSUDPOPT ioctl before any data can be read or written. NWIOSUDPOPT takes two parameters, a file descriptor to an open UDP device and pointer to a nwio_udpopt structure that describes the requested configuration. The nwio_udpopt structure is defined in <net/gen/udp_io.h> as:

    typedef struct nwio_udpopt
    {
    	unsigned long nwuo_flags;
    	udpport_t nwuo_locport;
    	udpport_t nwuo_remport;
    	ipaddr_t nwuo_locaddr;
    	ipaddr_t nwuo_remaddr;
    } nwio_udpopt_t;
    #define NWUO_NOFLAGS            0x0000L
    #define NWUO_ACC_MASK           0x0003L
    #define         NWUO_EXCL               0x00000001L
    #define         NWUO_SHARED             0x00000002L
    #define         NWUO_COPY               0x00000003L
    #define NWUO_LOCPORT_MASK       0x000CL
    #define         NWUO_LP_SEL             0x00000004L
    #define         NWUO_LP_SET             0x00000008L
    #define         NWUO_LP_ANY             0x0000000CL
    #define NWUO_LOCADDR_MASK       0x0010L
    #define         NWUO_EN_LOC             0x00000010L
    #define         NWUO_DI_LOC             0x00100000L
    #define NWUO_BROAD_MASK         0x0020L
    #define         NWUO_EN_BROAD           0x00000020L
    #define         NWUO_DI_BROAD           0x00200000L
    #define NWUO_REMPORT_MASK       0x0100L
    #define         NWUO_RP_SET             0x00000100L
    #define         NWUO_RP_ANY             0x01000000L
    #define NWUO_REMADDR_MASK       0x0200L
    #define         NWUO_RA_SET             0x00000200L
    #define         NWUO_RA_ANY             0x02000000L
    #define NWUO_RW_MASK            0x1000L
    #define         NWUO_RWDATONLY          0x00001000L
    #define         NWUO_RWDATALL           0x10000000L
    #define NWUO_IPOPT_MASK         0x2000L
    #define         NWUO_EN_IPOPT           0x00002000L
    #define         NWUO_DI_IPOPT           0x20000000L

A UDP channel is considered configured when one flag in each category has been selected. Thus one of NWUO_EXCL, NWUO_SHARED or NWUO_COPY, one of NWUO_LP_SEL, NWUO_LP_SET or NWUO_LP_ANY, one of NWUO_EN_LOC or NWUO_DI_LOC, one of NWUO_EN_BROAD, or NWUO_DI_BROAD, one of NWUO_RP_SET, or NWUO_RP_ANY, one of NWUO_RA_SET, or NWUO_RA_ANY, one of NWUO_RWDATONLY, or NWUO_RWDATALL, and one of NWUO_EN_IPOPT, or NWUO_DI_IPOPT. The acc flags control the access to a certain UDP port. NWUO_EXCL means exclusive access: no other channel can use this port. NWUO_SHARED means shared access: only channels that specify shared access can use this port and all packets that are received are handed to at most one channel. NWUO_COPY imposes no access restriction and all channels get a copy of every received packet for that port.

The locport flags control the selection of the UDP port for this channel. NWUO_LP_SEL requests the server to pick a port. This port will be in the range from 32768 to 65535 and it will be unique. NWUO_LP_SET sets the local port to the value of the nwuo_locport field. NWUO_LP_ANY does not select a port. Reception of data is therefore not possible but it is possible to send data.

The locaddr flags control the reception of packets. NWUO_EN_LOC enables the reception of packets with the local IP address as destination. NWUO_DI_LOC disables the reception of packet for the local IP address.

The broad flags control the reception of broadcast packets. NWUO_EN_BROAD enables the reception of broadcast packets and NWUO_DI_BROAD disables the reception of broadcast packets.

The remport flags let the client to specify one specific remote UDP port or to allow any remote port. NWUO_RP_SET sets the remote UDP port to the value of nwuo_remport. Only packets with a matching remote port will be delivered and all packets will be sent to that port. NWUO_RP_ANY allows reception of packets form any port and when transmitting packets the remote port has to be specified.

The remaddr flags control the remote IP address. NWUO_RA_SET sets the remote IP address the value of nwuo_remaddr. Only packets from that address will be delivered and all packets will be sent to that address. NWUO_RA_ANY allows reception of packets from any host and when transmitting packets the remote host has to be specified.

The rw flags control the format of the data to be sent or received. With NWUO_RWDATONLY only the data part of a UDP packet is sent to the server and only the data part is received from the server. The NWUO_RWDATALL mode presents the data part of a UDP packet with a header that contains the source and destination IP address, source and destination UDP ports, the IP options, etc. The server expects such a header in front of the data to be transmitted.

The ipopt flags control the delivery and transmission of IP options. When NWUO_EN_IPOPT is set IP, options will be delivered and sent. When NWUO_DI_IPOPT is set IP option will be stripped from received packets and no IP options will be sent.

FILES

/dev/eth*
    Raw ethernet. The numbers in the device names are decimal, so one may see names from eth0 to eth15.

/dev/psip*
    First and second Pseudo IP network.

/dev/ip*
    IP devices for two ethernets and two Pseudo IP networks.

/dev/tcp*
    TCP devices for same four networks.

/dev/udp*
    UDP devices.

/dev/eth, /dev/psip, /dev/ip, /dev/tcp, /dev/udp
    Devices for the default network, links to the devices above. Eth is only present if ethernet is the default, psip only for pseudo IP.

SEE ALSO
hton(3), oneC_sum(3), inet(8), boot(8).

DIAGNOSTICS
Several errors may be returned by the TCP/IP server. The error code is found in the errno variable if the read, write, or ioctl call returns -1. The TCP/IP error codes defined in <errno.h> are, among others:

EPACKSIZE
    This indicates an attempt to read or write with a buffer that is too large or too small.

ENOBUFS
    The TCP/IP server has insufficient memory to execute the request.

EBADIOCTL
    This indicates an attempt to execute a command the particular server does not understand. For example, a NWIOGTCPCONF on an ETH channel.

EBADMODE
    The request is refused because the channel is not fully configured, in the wrong state or the parameters are invalid.

ENETUNREACH
    The destination network is not reachable.

EHOSTUNREACH
    The destination host is not reachable.

EISCONN
    The channel is already connected so a second request is refused.

EADDRINUSE
    This address is in use.

ECONNREFUSED
    The connection is refused by the other side.

ECONNRESET
    The connection is reset (non-gracefully terminated) by the other side.

ETIMEDOUT
    The connection is terminated due to an expired timer.

EURG
    Urgent data is present and the current receive mode does not allow urgent data to be transferred.

ENOURG
    No urgent data is present and a request came for urgent data.

ENOTCONN
    The request requires a connected channel and the channel is not connected.

ESHUTDOWN
    The connection is shut down. That is, a NWIOTCPSHUTDOWN has been executed so no more data can be transmitted.

ENOCONN
    The connection does not exist.

EGENERIC
    A generic error code for extremely weird cases.

AUTHOR
Philip Homburg (philip@cs.vu.nl)