How to Specify a Network Interface for Dialing in Go?

Setting Source Interface in Dialing with Go

In a network with multiple interfaces, it may be desired to dial a connection using a specific one. Despite Go's low-level nature, the standard library does not inherently support this.

To attempt this, we retrieve the target interface, eth1, using InterfaceByName, extract the first address using Addrs, and configure a Dialer with the acquired address as the LocalAddr. However, we encounter a "mismatched local address type" error.

The issue arises because the address obtained from the interface is of type *net.IPnet, which represents both the address and netmask. To dial, we require a *net.TCPAddr, which is an address and port.

To resolve the issue, we create a *net.TCPAddr explicitly after asserting the interface address as a *net.IPnet:

    ief, err := net.InterfaceByName("eth1")
    if err !=nil{
            log.Fatal(err)
    }
    addrs, err := ief.Addrs()
    if err !=nil{
            log.Fatal(err)
    }

    tcpAddr := &net.TCPAddr{
        IP: addrs[0].(*net.IPNet).IP,
    }

With this configuration, the Dialer can now establish a connection using the specified interface.

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