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ETHER(3)ETHER(3)

NAME

ether – Ethernet device

SYNOPSIS

bind -a #ln /net

/net/ethern/clone /net/ethern/addr /net/ethern/ifstats /net/ethern/stats /net/ethern/[0-7] /net/ethern/[0-7]/data /net/ethern/[0-7]/ctl /net/ethern/[0-7]/ifstats /net/ethern/[0-7]/stats /net/ethern/[0-7]/type

DESCRIPTION

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.

The following control messages are supported:

Enable bridging (see bridge(3)).  

Set the interface into promiscuous mode, which makes it accept all incoming packets, whether addressed to it or not.  

marks the Ethernet packet type as being in use, if not already in use on this interface. A type of -1 means ‘all’ but appears to be a no-op.  

Treat the multicast Media-addr on this interface as a local address.  

Delete the multicast address Media-addr from this interface.  

Make the wireless interface scan for base stations.  

Set the interface to pass only packet headers, not data too.  

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).

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.

Writing packets to the data file automatically fills the source address before sending. To allow implementations of layer 2 bridges like bridge(3), connections can be set to bridge mode by writing bridge to the ctl file.

For bridge(3) and ethermultilink(8), the physical interface can be bypassed by writing bypass to the ctl file. This means that packets transmitted on the interface are not physically sent out but looped back to the bypass data file and packets received on the physical interface are ignored. Writing a packet to the bypass data file loops it back as if it was received on the physical interface.

SEE ALSO

ip(3), bridge(3), plan9.ini(8), ethermultilink(8)

SOURCE

/sys/src/9/port/devether.c
/sys/src/9/port/netif.c