gateway

A simple library for discovering the IP address of the default gateway.

Supports both IPv4 and IPv6.

Maintenance status: ✅ Maintained (stable). This library is feature-complete — I accept bug fixes and security patches, but am not adding new features. See SECURITY.md for how to report vulnerabilities.

IPv4 Example

package main

import (
    "fmt"

    "github.com/jackpal/gateway"
)

func main() {
    gw, err := gateway.DiscoverGateway()
    if err != nil {
        fmt.Println(err)
    } else {
        fmt.Println("IPv4 Gateway:", gw.String())
   }
}

IPv6 Example

package main

import (
    "fmt"

    "github.com/jackpal/gateway"
)

func main() {
    gw, err := gateway.DiscoverGatewayIPv6()
    if err != nil {
        fmt.Println(err)
    } else {
        fmt.Println("IPv6 Gateway:", gw.String())
   }
}

IPv4 and IPv6 Platform Support

Other platforms return an error.

Pull requests for other OSs happily considered!

Versions

v1.2.0

• Add IPv6 gateway discovery: DiscoverGatewayIPv6(), DiscoverGatewaysIPv6(), DiscoverInterfaceIPv6().
  • Supported on Darwin, BSD variants, Linux, Windows, and Solaris/illumos.
  • Note: IPv6 support has been verified on real devices for Linux and Darwin. Other platforms are implemented based on unit tests with synthetic route table data and are considered "best-effort".
• Deduplicate results from DiscoverGateways() and DiscoverGatewaysIPv6().

v1.1.2

• Fix metric parsing in localized Windows versions (e.g., Spanish).
• Standardize test file naming (use _test.go suffix).
• Update dependencies and Go version to 1.26.2.

v1.1.1

• Filter out On-link gateways. This is a Windows-specific feature. On-link gateways aren't currently connected to the Internet.

v1.1.0

• Add func DiscoverGateways() ([]net.IP, error). This func returns an array of gateways that contains at least one gateway. Otherwise returns an error.
• Update to go version 1.24.2
• Update dependencies to latest versions. (There was an x/net security warning.)

v1.0.16

Update x/net dependency. This was done to squelch a github security alert caused by depending upon an old version of x/net.

v1.0.15

Update dependencies to latest versions. This was done to squelch a github security alert caused by depending upon an old version of x/net. This is the first time I've updated module versions, the tests pass, so hopefully everything's good.

v1.0.14

• Fix panic when interface not set in Solaris netstat -rn output.

v1.0.13

• Add tools/check-cross-compile.sh to check that the code compiles for various OSs.
• Fix compilation errors exposed by tools/check-cross-compile.sh.

v1.0.12

• If there are multiple default gateways, Windows now returns the gateway with the lowest metric.
• Fix solaris build break. (In theory, IDK how to test this easily.)
• Upgrade to golang 1.21
• Upgrade golang.org/x/net version, makes dependabot happy. Probably was not any actual security issue because gateway doesn't use any of the APIs of golang.org/x/net that had security issues.

v1.0.11

• Implement DiscoverInterface for BSD-like OSes.

v1.0.10

• Fix non-BSD-based builds.

v1.0.9

• Add go.mod and go.sum files.
• Use "golang.org/x/net/route" to implement all BSD variants.
  • As a side effect this adds support for Dragonfly and NetBSD.
• Add example to README.
• Remove broken continuous integration.

v1.0.8

• Add support for OpenBSD
• Linux parser now supports gateways with an IP address of 0.0.0.0
• Fall back to netstat on darwin systems if route fails.
• Simplify Linux /proc/net/route parsers.