Transcript 12. Networking

Networking
12.1 Introduction
VxWorks Network Configuration
Routing Protocols
Remote Access Services
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Network Protocols

Machines on a network must agree to exchange data in
some standard way.

Internet protocol suite (also called TCP/IP) provides
system independent protocols.

VxWorks provides an implementation of TCP/IP protocol
suite based on the 4.4BSD release

Features include:
– Increased configurability and scalability
– MUX layer
– Support for contemporary Internet features
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Network Components
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Network Scalability

Selective inclusion of core TCP/IP networking protocols
is provided.

TCP/IP parameters can be set by setting properties of
individual components. Examples: TCP Connection
Timeout, IP Time-to-Live value, TCP/UDP receive and
send buffer sizes, and tuning of internal buffers. (See
VxWorks Network Programmer’s Guide.)
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Network Services

VxWorks network services include:
– DHCP/BOOTP
– Simple Network Time Protocol (SNTP)
– DNS resolver
– Dynamic Routing (RIPv1/RIPv2/OSPF)
– rlogin/telnet
– Remote command execution
– Remote file access
– Multicasting, including IGMP

User can build other network services as needed.
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Networking
Introduction
12.2 VxWorks Network Configuration
Routing Protocols
Remote Access Services
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Host Names

To associate a name with an internet address:
hostAdd (hostName, hostAddr)

To display host name table use:
hostShow ()

The name of the boot host is automatically added to the
table from the boot parameters.
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Domain Name System

Domain Name System (DNS) is a distributed client/server
application supporting host names being stored in a
distributed database.

DNS requires a name server and, on the client side, a
resolver. VxWorks supports resolver functionality in
resolvLib.

resolvLib includes the following routines:
– resolvGetHostByName() -- send a DNS query to the name server
for the IP address of a host.
– resolvGetHostByAddr() -- send a DNS query to the name server
for the host name of an IP address.
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DNS Resolver Configuration

The DNS resolver component (/network components/networking
applications/DNS resolver) must be added to VxWorks.

The resolver must be initialized before use. Required
information includes RESOLVER_DOMAIN and
RESOLVER_DOMAIN_SERVER. This can be done
through the project facility or by calling resolvInit().
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DHCP Basics

Dynamic Host Configuration Protocol (DHCP) allows a
host to acquire an IP address, and possibly boot
parameters, from a remote host.

A DHCP client can obtain a temporary lease of an IP
address from a DHCP server, which maintains a database
of available addresses and other parameters. A DHCP
relay agent is necessary to support DHCP operation
across subnet boundaries.
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DHCP Configuration
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Networking
Introduction
VxWorks Network Configuration
12.3 Routing Protocols
Remote Access Services
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Routing Overview

Internet Protocol (IP) routing algorithm:
if (destination on a directly attached network)
send data to destination
else
use routing table to find correct router
send data to router

The target routing table can be built in two ways:
– Statically, by adding routes to a local routing table using
mRouteAdd() or routeAdd( ).
– Or dynamically, where hosts exchange routing information using
a routing protocol.

VxWorks supports two routing protocols: Routing
Information Protocol (RIP) and Open Shortest Path First
(OSPF).
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Adding Static Routes in VxWorks

To add multiple routes to the same location, use
mRouteAdd (dest, gateway, mask, tos, flags)
Can use a destination/gateway internet address in dot notation.
Specify destination subnet mask and IP type-of-service. See
routeLib help page for details.

To add a route to the 90.0.0.0 /24 network through the
router gatehost:
mRouteAdd (“90.0.0.0”, “gatehost”, 0xffffff00, 0, 0)

Routing table show routines, mRouteShow() or
routeShow() require the component /network
components/networking protocols/network debugging/ Network
show routines.
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Network Show Routines

Are used to display network statistics and debugging
information. Configuration information and statistics can
be shown for protocols (IP, ICMP, TCP, etc.) , buffering,
network interfaces, etc.

Example (ARP table entries):
->arptabShow
LINK LEVEL ARP TABLE
destination
gateway
flags Refcnt Use
Interface
-------------------------------------------------------------------------147.11.12.14
08:00:20:7b:06:fb
405
0
45
ei0
147.11.12.165
00:60:97:4f:d5:16
405
0
0
ei0
-------------------------------------------------------------------------value = 75 = 0x4b = ‘K’
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Dynamic Routing Overview

Dynamic routing protocols allow hosts (typically routers)
to exchange routing information. Advantages over
statically created routing tables include:
– Faster update as link states change
– Ability to calculate the most efficient route if there are multiple
routes to a destination
– Easier maintenance

These protocols do not affect the Internet routing
algorithm, but instead impose a routing policy when
constructing the routing table.

VxWorks supports RIP versions 1 and 2 and OSPF (an
optional component).
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Routing Internet Protocol

RIP uses UDP to exchange routing information.

RIP is a distance vector protocol -- each route includes a
number of hop counts. If multiple paths to a destination
exist, RIP chooses the most efficient route by minimizing
this count.

RIPv2 updates RIPv1 by including:
– support for classless addressing
– ability to use multicasting and broadcasting
– support for authentication

use ping( ) for testing routes

See ripLib in the VxWorks Reference Manual for details.
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Networking
Introduction
VxWorks Network Configuration
Routing Protocols
12.4 Remote Access Services
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VxWorks Remote Services
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Remote Login and Telnet

rlogin and telnet offer an alternative to crossdevelopment using the Tornado target server.
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NFS Server Overview

Allows remote hosts to access a target’s DOS file
systems using NFS protocol.

By default no authentication is performed.

Add the component /network components/networking
protocols/network filesystems/NFS server.

NFS server configuration supports:
1. Create a mountable DOS file system:
dosFsDevInitOptionsSet (DOS_OPT_EXPORT);
2. Export DOS file system:
nfsExport (name, fsId, rdOnly, notUsed);
3. Mount file system on remote host.
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VxWorks FTP Server

The FTP server component is included by configuring
/network components/networking protocols/network filesystems/FTP
server.

When target is booted, should see tFtpdTask (server
daemon) running.

FTP security, which will require a valid user name and
password from clients, can be included by configuring
/network components/networking protocols/network filesystems/FTP
server security.

The RLOGIN/TELNET password protection component allows a
single user name and encrypted password. Additional
users can be added by calling loginUserAdd() in
application initialization code.
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NFS vs. FTP Server

NFS Advantages:
– Efficient file access.
– Configurable number of servers pre-spawned.

FTP Advantages:
– Can access file systems other than DOS.
– All network hosts have FTP client.
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NFS Client Service

Network File System (NFS) was developed by Sun
Microsystems.

Allows efficient access to files. NFS transfers and buffers
files in pieces (usually 8 Kbytes).

Remote file systems are mounted, then accessed as if
they were local file systems.

VxWorks provides NFS client and server.

The NFS client component can be found under /network
components/networking protocols/network filesystems/NFS client.
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NFS Client Configuration

To access files on a remote machine using NFS:
0. Export server’s file system:
Makes the local file system available to remote host with appropriate
access permissions
1.
Mount the file system on the client.
nfsMount (host, fileSystem, localName)
2. Set the client’s authentication parameters:
nfsAuthUnixSet (hostName, uid, gid, ngids,aup_gids)
Defaults (NFS_GROUP_ID = 100 and NFS_USER_ID = 2001) will need
to be changed. UNIX users can get the required values using:
% id
uid=219(marc) gid=700(training)
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netDrv File Access Clients

netDrv allows access to remote files:
– Entire file read into target memory on open( ).
– read( )/write( ) act on copy of file in memory.
– File not written to remote host until close( ).

Can’t access large files (constrained by available
memory).

ioctl (fd, FIOSYNC, 0) is not supported.

dirLib routines opendir / readdir do not work on netDrv
directories. stat / fstat are only partially implemented.
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Creating network Devices
STATUS netDevCreate (devName, host,
protocol)
devName
host
protocol

Local name of device to create. By convention,
ends with ‘:’.
Name of remote machine (from previous
hostAdd( )).
Protocol to transfer files to/from
VxWorks (0= RSH or 1= FTP).
Example
-> netDevCreate (“ohio:”, “ohio”, 1)
-> fd = open (“ohio:/u/teamN”, 2)
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Executing Remote Commands

VxWorks programs can invoke remote shell (RSH)
commands on a UNIX host.

A file descriptor called a socket is created. Can read( )
from this socket to get command output.
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UNIX: Remote Command Execution
int rcmd (host, remotePort, localUser,
remoteUser, cmd, pFd2)
host
remotePort
localUser
remoteUser
cmd
pFd2

Host name or inet number.
Remote port number to connect to, typically
514 (RSH server).
Name of local user.
User name on remote host.
Shell command string to execute.
If non-zero, a socket for stderr is foreach I
(*.o)returned through this pointer.
Returns a socket file descriptor or ERROR.
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netDrv Client Services Comparison

Advantages of FTP over RSH:
– FTP is part of the TCP/IP protocol suite, so it is available on all
networked hosts.
– FTP is faster on open/close, since there is no shell delay.
– FTP server is supplied with VxWorks.

Advantages of RSH over FTP:
– FTP clear text password goes over the network on each open( )
and close( ).
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netDrv vs. nfsDrv

Advantages of nfsDrv over netDrv:
– Reads and writes only needed parts of the file.
– Can access arbitrarily large files.
– open( )/close( ) much faster.
– Can use dirLib routines.
– Can flush file changes with FIOSYNC.

Advantages of netDrv over nfsDrv:
– All networked hosts have an FTP server.
– Easier to configure.
– read( )/write( ) slightly faster.
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Summary

Internet Protocol for node-to-node routing.

MUX layer decouples link-layer driver and network
protocol.

Configuring the network
– Configure host name table using hostAdd() or use DNS resolver.
– Configure host’s routing table using mRouteAdd() or use
RIP/OSPF.

Show routines are available to troubleshoot network
configuration.
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Summary

DHCP allows a host to obtain IP address leases and boot
parameters from a remote server.

DHCP components:
– DHCP Server
– DHCP Relay Agent
– DHCP Client

rlogin (UNIX Host) and telnet support.

FTP and NFS servers allows local VxWorks files to be
accessed by a remote machine.
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Summary

nfsDrv mounts remote file systems with nfsMount( )
– Reads and writes portion of remote file.
– File system must be exported by remote host.

netDrv devices created with netDevCreate( ).
– Entire file is read into VxWorks on open( ), and not updated until
close( ).
– Uses either RSH (UNIX Host) or FTP for file transfer.
– RSH requires name and entry in .rhosts. (UNIX Host)
– FTP requires name and password.

rcmd ( ) and rlogin() (UNIX Host)
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