ether – Ethernet device
bind –a #ln /net
The Ethernet interface, /net/ethern, is a directory containing
subdirectories, one for each distinct Ethernet packet type, and
clone, addr, ifstats, and stats files. stats and ifstats are the
same as in the subdirectories (see below). Reading addr returns
the MAC address of this interface in hex with no
punctuation and no trailing newline. The number n (optional in
the bind) is the device number of the card, permitting multiple
cards to be used on a single machine.
Each directory contains files to control the associated connection, receive and send data, and supply statistics. Incoming Ethernet packets are demultiplexed by packet type and passed up the corresponding open connection. Reading from the data file reads packets of that type arriving from the network. A read will terminate at packet boundaries. Each write to the data file causes a packet to be sent. The Ethernet address of the interface is inserted into the packet header as the source address.
A connection is assigned to a packet type by opening its ctl file and writing connect n where n is a decimal integer constant identifying the Ethernet packet type. A type of –1 enables the connection to receive copies of packets of all types. A type of –2 enables the connection to receive copies of the first 64 bytes of packets of all types. If multiple connections are assigned to a given packet type a copy of each packet is passed up each connection.
Some interfaces also accept unique options when written to the ctl (or clone) file; see the description of wavelan in plan9.ini(8). The control messages described in ip(3) under Configuring interfaces from bridge to headersonly are understood. The additional control message nonblocking makes write systems calls to this interface non–blocking iff followed by nothing or a non–zero integer; a following 0 makes writes block on a full output queue.
Reading the ctl file returns the decimal index of the associated connection, 0 through 7. Reading the type file returns the decimal value of the assigned Ethernet packet type. Reading the stats file returns status information such as the Ethernet address of the card and general statistics, independent of the interface; ifstats contains device–specific data and statistics about the card.
An interface normally receives only those packets whose destination
address is that of the interface or is the broadcast address,
ff:ff:ff:ff:ff:ff. The interface can be made to receive all packets
on the network by writing the string promiscuous to the ctl file.
The interface remains promiscuous until the
control file is closed. The extra packets are passed up connections
only of types –1 and –2.