The network configuration database, /etc/netconfig, is a system file used to store information about networks that are connected to the system. The netconfig database and the routines that access it (see getnetconfig(3NSL)) are part of the Network Selection component. The Network Selection component also includes getnetpath(3NSL) routines to provide application-specific network search paths. These routines access the netconfig database based on the environment variable NETPATH. See environ(5).
netconfig contains an entry for each network available on the system. Entries are separated by newlines. Fields are separated by whitespace and occur in the order in which they are described below. Whitespace can be embedded as ``\blank''
or ``\tab''. Backslashes may be embedded as ``\\''. Lines in /etc/netconfig that begin with a # (hash) in column 1 are treated as comments.
Each of the valid lines in the netconfig database correspond to an available transport. Each entry is of the form:
network ID semantics flag protocol-family protocol-name \
- A string used to uniquely identify a network. network ID consists of non-null characters, and has a length of at least 1. No maximum length is specified.
This namespace is locally significant and the local system administrator is the naming authority. All network IDs on a system must be unique.
- The semantics field is a string identifying the ``semantics'' of the network, that is, the set of services it supports, by identifying the service interface it provides. The semantics field is mandatory. The following semantics are recognized.
- Transport Provider Interface, connectionless
- Transport Provider Interface, connection oriented
- Transport Provider Interface, connection oriented, supports orderly release.
- The flag field records certain two-valued (``true'' and ``false'') attributes of networks. flag is a string composed of a combination of characters, each of which indicates
the value of the corresponding attribute. If the character is present, the attribute is ``true.'' If the character is absent, the attribute is ``false.'' ``-'' indicates that none of the attributes are present. Only one character is currently recognized:
- Visible (``default'') network. Used when the environment variable NETPATH is unset.
- The protocol family and protocol name fields are provided for protocol-specific applications. The protocol family field contains a string
that identifies a protocol family. The protocol family identifier follows the same rules as those for network IDs; the string consists of non-null characters, it has a length of at least 1, and there is no maximum length specified.
A ``-'' in the protocol family field indicates that no protocol family identifier applies (the network is experimental). The following are examples:
- Loopback (local to host).
- Internetwork: UDP, TCP, and the like.
- Internetwork over IPv6: UDP, TCP, and the like.
- ARPANET imp addresses
- PUP protocols: for example, BSP
- MIT CHAOS protocols
- XEROX NS protocols
- NBS protocols
- European Computer Manufacturers Association
- DATAKIT protocols
- CCITT protocols, X.25, and the like.
- IBM SNA
- Direct data link interface
- NSC Hyperchannel
- Apple Talk
- Network Interface Tap
- IEEE 802.2; also ISO 8802
- Umbrella for all families used by OSI (for example, protosw lookup)
- CCITT X.25 in particular
- AFI = 47, IDI = 4
- U.S. Government OSI
- The protocol name field contains a string that identifies a protocol. The protocol name identifier follows the same rules as those for network IDs;
that is, the string consists of non-NULL characters, it has a length of at least 1, and there is no maximum length specified. A ``-'' indicates that none of the names listed apply. The following protocol names are recognized.
- Transmission Control Protocol
- User Datagram Protocol
- Internet Control Message Protocol
- The network device is the full pathname of the device used to connect to the transport provider. Typically, this device will be in the /dev directory. The network
device must be specified.
- The name-to-address translation libraries support a ``directory service'' (a name-to-address mapping service) for the network. A ``-'' in this field indicates
the absence of any translation libraries. This has a special meaning for networks of the protocol family inet : its name-to-address mapping is provided by the name service switch based on the entries for hosts and services
in nsswitch.conf(4). For networks of other families, a ``-'' indicates non-functional name-to-address mapping. Otherwise, this field consists of a comma-separated
list of pathnames to dynamically linked libraries. The pathname of the library can be either absolute or relative. See dlopen(3DL).
Each field corresponds to an element in the struct netconfig structure. struct netconfig and the identifiers described on this manual page are defined in <netconfig.h>. This structure includes the following members:
- Network ID, including NULL terminator.
unsigned long nc_semantics
unsigned long nc_flag
- Protocol family.
- Protocol name.
- Full pathname of the network device.
unsigned long nc_nlookups
- Number of directory lookup libraries.
- Names of the name-to-address translation libraries.
unsigned long nc_unused
- Reserved for future expansion.
The nc_semantics field takes the following values, corresponding to the semantics identified above:
The nc_flag field is a bitfield. The following bit, corresponding to the attribute identified above, is currently recognized. NC_NOFLAG indicates
the absence of any attributes.