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

Example:

package main
import (
    "fmt"
    "github.com/jackpal/gateway"
)
func main() {
    gateway, err := gateway.DiscoverGateway()
    if err != nil {
        fmt.Println(err)
    } else {
        fmt.Println("Gateway:", gateway.String())
   }
}

Provides implementations for:

• Darwin (macOS)
• Dragonfly
• FreeBSD
• Linux
• NetBSD
• OpenBSD
• Solaris and illumos
• Windows

Other platforms use an implementation that always returns an error.

Pull requests for other OSs happily considered!

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

• 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.)

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

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.

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

• 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.

• 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.

• Implement DiscoverInterface for BSD-like OSes.

• Fix non-BSD-based builds.

• 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.

• 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.