Documentation
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Overview ¶
Package tun provides a TUN network interface for Linux.
It opens /dev/net/tun via ioctl and configures the resulting interface with an IP address, peer address, and MTU using the SIOCSIFADDR, SIOCSIFDSTADDR, SIOCSIFMTU, and SIOCSIFFLAGS ioctls — all without CGo.
Only Linux is supported (CGO_ENABLED=0, golang.org/x/sys/unix).
Typical usage:
dev, err := tun.Open("tun0") // allocate /dev/net/tun
if err != nil { ... }
defer dev.Close()
if err := dev.Configure(tun.Config{
LocalIP: net.ParseIP("10.8.0.6"),
PeerIP: net.ParseIP("10.8.0.5"),
MTU: 1500,
}); err != nil { ... }
// dev.File() is an *os.File; read/write raw IPv4 packets from it.
Index ¶
Constants ¶
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Variables ¶
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Functions ¶
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Types ¶
type Config ¶
type Config struct {
// LocalIP is the IP address assigned to this end of the tunnel.
LocalIP net.IP
// PeerIP is the P2P peer address for net30 topology.
// Mutually exclusive with Mask — set one or the other.
PeerIP net.IP
// Mask is the subnet mask for subnet topology.
// When set, the interface is configured as a regular (non-P2P) subnet
// rather than point-to-point, where the platform supports the difference.
Mask net.IPMask
// MTU is the maximum transmission unit for the interface (default 1500).
MTU int
}
Config is the addressing to give a TUN interface.
type Device ¶
type Device struct {
// contains filtered or unexported fields
}
Device represents an open TUN interface.
func Open ¶
Open allocates a TUN interface.
If ifaceName is empty, the kernel assigns a name (e.g. "tun0"). The interface is unconfigured; call Configure before writing packets.
Opening sequence (mirrors wireguard-go tun/tun_linux.go):
- Open /dev/net/tun with unix.Open (O_RDWR|O_CLOEXEC) — raw syscall, no Go runtime involvement yet.
- Issue TUNSETIFF directly on the raw fd.
- Set O_NONBLOCK on the raw fd so Go's runtime poller can use epoll.
- Wrap with os.NewFile — this registers the fd with epoll and enables deadline-based reads.
os.OpenFile instead of unix.Open registers the fd with epoll before TUNSETIFF runs. On some kernels /dev/net/tun is not epoll-able until a TUN interface is attached; epoll registration then fails silently and every os.File.Read returns poll.ErrNotPollable ("read /dev/net/tun: not pollable") at once.
func (*Device) Configure ¶
Configure sets the local IP, peer IP, MTU, and brings the interface up. It must be called after Open and before writing packets.
Source Files