ip.4

操作系统设计与实现源码

.B NWTO_SND_URG
option causes bytes written to the channel to be send out as urgent data.
On receiving an
.B EURG
error the
.B NWTO_RCV_URG
option must be set to switch over to reading urgent data.  When all urgent
data has been read an
.B ENOURG
error will follow,
indicating that the option must be cleared with
.BR NWTO_RCV_NOTURG .
Alas the BSD implementation of urgent data disagrees with the RFC's, so to
be BSD compatible one must set the
.B 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
.B 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.
.SS "UDP Functions"
.PP
.ft B
ioctl(\fIfd\fP, NWIOGUDPOPT, &struct nwio_udpopt)
.ft R
.PP
The
.B NWIOGUDPOPT
ioctl returns the current options that result from the default options
and the options set with
.BR NWIOSUDPOPT .
When
.B NWUO_LP_SEL
or
.B NWUO_LP_SET
is selected the local port is returned in
.BR nwuo_locport .
When
.B NWUO_RP_SET
is selected the remote port is returned in
.BR nwuo_remport .
The local address is always returned in
.BR nwuo_locaddr ,
and when
.B NWUO_RA_SET
is selected the remote address is returned in
.BR nwuo_remaddr .
.PP
.ft B
ioctl(\fIfd\fP, NWIOSUDPOPT, &struct nwio_udpopt)
.ft R
.PP
A UDP channel must be configured using the
.B NWIOSUDPOPT
ioctl before any data can be read or written.
.B NWIOSUDPOPT
takes two parameters, a file descriptor to an open UDP device and
pointer to a
.B nwio_udpopt
structure that describes the requested configuration.
The
.B nwio_udpopt
structure is defined in <net/gen/udp_io.h> as:
.PP
.RS
.nf
.if t .ft C
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;
.SP
#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
.if t .ft R
.fi
.RE
.PP
A UDP channel is considered configured when one flag in each category has been
selected.
Thus one of
.BR NWUO_EXCL ,
.B NWUO_SHARED
or
.BR NWUO_COPY ,
one of
.BR NWUO_LP_SEL ,
.B NWUO_LP_SET
or
.BR NWUO_LP_ANY ,
one of
.B NWUO_EN_LOC
or
.BR NWUO_DI_LOC ,
one of
.BR NWUO_EN_BROAD ,
or
.BR NWUO_DI_BROAD ,
one of
.BR NWUO_RP_SET ,
or
.BR NWUO_RP_ANY ,
one of
.BR NWUO_RA_SET ,
or
.BR NWUO_RA_ANY ,
one of
.BR NWUO_RWDATONLY ,
or
.BR NWUO_RWDATALL ,
and one of
.BR NWUO_EN_IPOPT ,
or
.BR NWUO_DI_IPOPT .
The acc flags control the access to a certain UDP port.
.B NWUO_EXCL
means exclusive access:
no other channel can use this port.
.B 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.
.B NWUO_COPY
imposes no access restriction and all channels get a copy of every received
packet for that port.
.PP
The
.B locport
flags control the selection of the UDP port for this channel.
.B 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.
.B NWUO_LP_SET
sets the local port to the value of the
.B nwuo_locport
field.
.B NWUO_LP_ANY
does not select a port.
Reception of data is therefore not possible but it is
possible to send data.
(See
.BR tcpip_read ,
and
.B tcpip_write
above).
.PP
The
.B locaddr
flags control the reception of packets.
.B NWUO_EN_LOC
enables the reception of packets with the local IP address as destination.
.B NWUO_DI_LOC
disables the reception of packet for the local IP address.
.PP
The
.B broad
flags control the reception of broadcast packets.
.B NWUO_EN_BROAD
enables the reception of broadcast packets and
.B NWUO_DI_BROAD
disables the reception of broadcast packets.
.PP
The
.B remport
flags let the client to specify one specific remote UDP port or
to allow any remote port.
.B NWUO_RP_SET
sets the remote UDP port to the value of
.BR nwuo_remport .
Only packets with a matching remote port will be delivered
and all packets will be sent to that port.
.B NWUO_RP_ANY
allows reception of packets form any port and when transmitting packets the
remote port has to be specified.
.PP
The
.B remaddr
flags control the remote IP address.
.B NWUO_RA_SET
sets the remote IP address the value of
.BR nwuo_remaddr .
Only packets from that address will be delivered and all packets will be sent
to that address.
.B NWUO_RA_ANY
allows reception of packets from any host and when transmitting packets the
remote host has to be specified.
.PP
The
.B rw
flags control the format of the data to be sent or received.
With
.B 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
.B 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.
.ig \" Some for Philip to explain properly:
The header is defined in <net/gen/udp_hdr.h> and looks like this:
.PP
.RS
.nf
.if t .ft C
typedef struct udp_io_hdr
{
	ipaddr_t uih_src_addr;
	ipaddr_t uih_dst_addr;
	udpport_t uih_src_port;
	udpport_t uih_dst_port;
	u16_t uih_ip_opt_len;
	u16_t uih_data_len;
} udp_io_hdr_t;
.if t .ft R
.fi
.RE
.PP
The first four fields are the source and destination IP addresses and
ports.
.B Uih_ip_opt_len
is ???.
.B Uih_data_len
should equal the length of the packet data (packet lenght minus the
header.) ???
..
.PP
The
.B ipopt
flags control the delivery and transmission of IP options.
When
.B NWUO_EN_IPOPT
is set IP, options will be delivered and sent.
When
.B NWUO_DI_IPOPT
is set IP option will be stripped from received packets and no IP options will
be sent.
.ig \" Minix doesn't have this stuff (yet? ever?)
.SS "UDP Library Functions"
.PP
The following routines provide an somewhat easier to use interface to UDP than
the routines described above (\fBtcpip_open\fP, \fBudp_ioc_setopt\fP,
\fBtcpip_read\fP and \fBtcpip_write\fP).
.LP
.sC
errstat
udp_connect(udp_cap, chan_cap, srcport, dstport, dstaddr, flags)
capability *udp_cap;
capability *chan_cap;
udpport_t srcport;
udpport_t dstport;
ipaddr_t dstaddr;
int flags;
.eC
.kW "\fIudp_connect\fP"
\fIUdp_connect\fP combines the functionality of \fItcpip_open\fP and
\fIudp_ioc_setopt\fP.
A pointer to a UDP server capability should be passed in \fIudp_cap\fP, and
the channel capability will be returned in the capability pointed to by
\fIchan_cap\fP.
If \fIsrcport\fP is 0 then an unused port will be selected, otherwise the local
port will be set to \fIsrcport\fP.
If \fIdstport\fP is non-zero then communication will be restricted to remote ports
that equal to \fIdstport\fP, otherwise any data can be sent to or received from
any remote port.
The same thing applies to \fIdstaddr\fP; if \fIdstaddr\fP is non-zero then
only \fIdstaddr\fP can be reached.
Currently no flags are defined so \fIflags\fP should be 0.
.sH
udp_reconnect
.LP
.sC
errstat
udp_reconnect(chan_cap, srcport, dstport, dstaddr, flags)
capability *chan_cap;
udpport_t srcport;
udpport_t dstport;
ipaddr_t dstaddr;
int flags;
.eC
.kW "\fIudp_reconnect\fP"
\fIUdp_reconnect\fP is the same as \fIudp_connect\fP except that an existing
channel capability is (re)used.
.sH
udp_read_msg
.LP
.sC
errstat
udp_read_msg(chan_cap, msg, msglen, actlen, flags)
capability *chan_cap;
char *msg;
int msglen;
int *actlen;
int flags;
.eC
.kW "\fIudp_read_msg\fP"
\fIUdp_read_msg\fP delivers a UDP packet.
The data part of the UDP packet is
prepended with an \fIudp_io_hdr\fP.
The actual length of the possibly truncated packet is returned in \fIactlen\fP.
No flags are defined so \fIflags\fP should be 0.
.sH
udp_write_msg
.LP
.sC
errstat
udp_write_msg(chan_cap, msg, msglen, flags)
capability *chan_cap;
char *msg;
int msglen;
int flags;
.eC
.kW "\fIudp_write_msg\fP"
A UDP packet can be sent with \fIudp_write_msg\fP.
\fIMsg\fP should point to a \fIudp_io_hdr\fP followed by the data part of the
UDP packet.
The \fIuih_dst_addr\fP and \fIuih_dst_port\fP fields of the \fIudp_io_hdr\fP
should be filled in if no values are specified in the \fIudp_connect\fP,
or \fIudp_reconnect\fP.
.sH
udp_close
.LP
.sC
errstat
udp_close(chan_cap, flags)
capability *chan_cap;
int flags;
.eC
.kW "\fIudp_close\fP"
\fIUdp_close\fP cleans up the administration kept by the UDP library but does
not destroy the capability.
The function should be used if the capability is passed to another process
and should continue to exist.
No flags are defined so \fIflags\fP should be 0.
.sH
udp_destroy
.LP
.sC
errstat
udp_destroy(chan_cap, flags)
capability *chan_cap;
int flags;
.eC
.kW "\fIudp_destroy\fP"
\fIUdp_destroy\fP not only cleans up the administration kept by the UDP library
but also destroys the channel capability.
..
.SH FILES
.IP /dev/eth[01] 18n
First and second raw ethernet.
.IP /dev/psip[01]
First and second Pseudo IP network.
.IP /dev/ip[0123]
IP devices for two ethernets and two Pseudo IP networks.
.IP /dev/tcp[0123]
TCP devices for same four networks.
.IP /dev/udp[0123]
UDP devices.
.IP "/dev/eth, /dev/psip, /dev/ip, /dev/tcp, /dev/udp"
Devices for the default network, links to the devices above.
.B Eth
is only present if ethernet is the default,
.B psip
only for pseudo IP.
.SH "SEE ALSO"
.BR hton (3),
.BR oneC_sum (3),
.BR set_net_default (8),
.BR boot (8).
.SH DIAGNOSTICS
Several errors may be returned by the TCP/IP server.  The error code
is found in the
.B errno
variable if the
.BR read ,
.BR write ,
or
.B ioctl
call returns -1.  The TCP/IP error codes defined in <errno.h> are:
.IP EPACKSIZE 5c
This indicates an attempt to read or write with a buffer that is too
large or too small.
.IP EOUTOFBUFS
The TCP/IP server has insufficient memory to execute the request.
.IP EBADIOCTL
This indicates an attempt to execute a command the particular server
does not understand.
For example, a
.B NWIOGTCPCONF
on an ETH channel.
.IP EBADMODE
The request is refused because the channel is not fully configured, in the
wrong state or the parameters are invalid.
.IP EBADDEST
This indicates an illegal destination address for a packet.
.IP EDSTNORCH
The destination is not reachable.
.IP EISCONN
The channel is already connected so a second request is refused.
.IP EADDRINUSE
This address is in use.
.IP ECONNREFUSED
The connection is refused by the other side.
.IP ECONNRESET
The connection is reset (non-gracefully terminated) by the other side.
.IP ETIMEDOUT
The connection is terminated due to an expired timer.
.IP EURG
Urgent data is present and the current receive mode does not allow urgent data
to be transferred.
.IP ENOURG
No urgent data is present and a request came for urgent data.
.IP ENOTCONN
The request requires a connected channel and the channel is not connected.
.IP ESHUTDOWN
The connection is shut down.
That is, a
.B NWIOTCPSHUTDOWN
has been executed so no more data can be transmitted.
.IP ENOCONN
The connection does not exist.
.IP EGENERIC
A generic error code for extremely weird cases.
.SH AUTHOR
Philip Homburg ([e-mail])