SHMIF(4) | Kernel Interfaces Manual | SHMIF(4)

# NAME

shmif — rump shared memory network interface

# SYNOPSIS

#include <rump/rump.h>

int
rump_pub_shmif_create(const char *path, int *ifnum);

# DESCRIPTION

The shmif interface uses a memory mapped regular file as a virtual Ethernet bus. All interfaces connected to the same bus see each others' traffic.

Using a memory mapped regular file as a bus has two implications:

1. The bus identifier is not in flat global namespace.
2. Configuring and using the interface is possible without superuser privileges on the host (normal host file access permissions for the bus hold).

It is not possible to directly access the host networking facilities from a rump virtual kernel using purely shmif. However, traffic can be routed to another rump kernel instance which provides both shmif and virt(4) networking.

An shmif interface can be created in two ways:

- Programmatically by calling rump_pub_shmif_create(). The bus pathname is passed in path. The number of the newly created interface is available after a successful call by dereferencing ifnum.
- Dynamically at runtime with ifconfig(8) or equivalent using the create command. In this case the bus path must be configured with ifconfig(8) linkstr before the interface address can be configured.

Destroying an shmif interface is possible only via ifconfig(8) destroy.

# SEE ALSO

rump(3), virt(4), ifconfig(8)

November 17, 2010 | NetBSD 6.0